[PATCH 0/3] mm: improve proportional memcg protection

[PATCH 0/3] mm: improve proportional memcg protection

[Yafang Shao]

Since proportional memory.{min, low} reclaim is introduced in
commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
it have been proved that the proportional reclaim is hard to understand and
the issues caused by it is harder to understand.[1]. That dilemma faced by
us is caused by that the proportional reclaim mixed up memcg and the
reclaim context.

In proportional reclaim, the whole reclaim context - includes the memcg
to be reclaimed and the reclaimer, should be considered, rather than
memcg only.

To make it clear, a new member 'protection' is introduced in the reclaim
context (struct shrink_control) to replace mem_cgroup_protection(). This
one is set when we check whether the memcg is protected or not.

After this change, the issue pointed by me[1] - a really old left-over
value can slow down target reclaim - can be fixed, and I think it could
also avoid some potential race.

Patch #1 and patch #2 is the preparation of patch #3.

[1]. https://lore.kernel.org/linux-mm/20200423061629.24185-1-laoar.shao@gmail.com

Yafang Shao (3):
  mm: move struct scan_control into internal.h
  mm: add reclaim context as a new parameter in mem_cgroup_protected()
  mm: improvements on memcg protection functions

 include/linux/memcontrol.h |  34 -----------
 mm/internal.h              | 101 +++++++++++++++++++++++++++++++
 mm/memcontrol.c            |  66 +++++++++++++++------
 mm/vmscan.c                | 118 ++-----------------------------------
 4 files changed, 152 insertions(+), 167 deletions(-)

-- 
2.18.2

[PATCH 1/3] mm: move struct scan_control into internal.h

[Yafang Shao]

This struct will be used in multiple source file under mm/, so move the
definition of it into mm/internal.h.

Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Chris Down <chris@chrisdown.name>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 mm/internal.h | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++
 mm/vmscan.c   | 83 --------------------------------------------------
 2 files changed, 84 insertions(+), 83 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index b5634e78f01d..a0b3bdd933b9 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -11,6 +11,7 @@
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include <linux/tracepoint-defs.h>
+#include <linux/swap.h>
 
 /*
  * The set of flags that only affect watermark checking and reclaim
@@ -254,6 +255,89 @@ int find_suitable_fallback(struct free_area *area, unsigned int order,
 
 #endif
 
+struct scan_control {
+	/* How many pages shrink_list() should reclaim */
+	unsigned long nr_to_reclaim;
+
+	/*
+	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
+	 * are scanned.
+	 */
+	nodemask_t	*nodemask;
+
+	/*
+	 * The memory cgroup that hit its limit and as a result is the
+	 * primary target of this reclaim invocation.
+	 */
+	struct mem_cgroup *target_mem_cgroup;
+
+	/* Can active pages be deactivated as part of reclaim? */
+#define DEACTIVATE_ANON 1
+#define DEACTIVATE_FILE 2
+	unsigned int may_deactivate:2;
+	unsigned int force_deactivate:1;
+	unsigned int skipped_deactivate:1;
+
+	/* Writepage batching in laptop mode; RECLAIM_WRITE */
+	unsigned int may_writepage:1;
+
+	/* Can mapped pages be reclaimed? */
+	unsigned int may_unmap:1;
+
+	/* Can pages be swapped as part of reclaim? */
+	unsigned int may_swap:1;
+
+	/*
+	 * Cgroups are not reclaimed below their configured memory.low,
+	 * unless we threaten to OOM. If any cgroups are skipped due to
+	 * memory.low and nothing was reclaimed, go back for memory.low.
+	 */
+	unsigned int memcg_low_reclaim:1;
+	unsigned int memcg_low_skipped:1;
+
+	unsigned int hibernation_mode:1;
+
+	/* One of the zones is ready for compaction */
+	unsigned int compaction_ready:1;
+
+	/* There is easily reclaimable cold cache in the current node */
+	unsigned int cache_trim_mode:1;
+
+	/* The file pages on the current node are dangerously low */
+	unsigned int file_is_tiny:1;
+
+	/* Allocation order */
+	s8 order;
+
+	/* Scan (total_size >> priority) pages at once */
+	s8 priority;
+
+	/* The highest zone to isolate pages for reclaim from */
+	s8 reclaim_idx;
+
+	/* This context's GFP mask */
+	gfp_t gfp_mask;
+
+	/* Incremented by the number of inactive pages that were scanned */
+	unsigned long nr_scanned;
+
+	/* Number of pages freed so far during a call to shrink_zones() */
+	unsigned long nr_reclaimed;
+
+	struct {
+		unsigned int dirty;
+		unsigned int unqueued_dirty;
+		unsigned int congested;
+		unsigned int writeback;
+		unsigned int immediate;
+		unsigned int file_taken;
+		unsigned int taken;
+	} nr;
+
+	/* for recording the reclaimed slab by now */
+	struct reclaim_state reclaim_state;
+};
+
 /*
  * This function returns the order of a free page in the buddy system. In
  * general, page_zone(page)->lock must be held by the caller to prevent the
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b06868fc4926..4c98512e2c9f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -63,89 +63,6 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/vmscan.h>
 
-struct scan_control {
-	/* How many pages shrink_list() should reclaim */
-	unsigned long nr_to_reclaim;
-
-	/*
-	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
-	 * are scanned.
-	 */
-	nodemask_t	*nodemask;
-
-	/*
-	 * The memory cgroup that hit its limit and as a result is the
-	 * primary target of this reclaim invocation.
-	 */
-	struct mem_cgroup *target_mem_cgroup;
-
-	/* Can active pages be deactivated as part of reclaim? */
-#define DEACTIVATE_ANON 1
-#define DEACTIVATE_FILE 2
-	unsigned int may_deactivate:2;
-	unsigned int force_deactivate:1;
-	unsigned int skipped_deactivate:1;
-
-	/* Writepage batching in laptop mode; RECLAIM_WRITE */
-	unsigned int may_writepage:1;
-
-	/* Can mapped pages be reclaimed? */
-	unsigned int may_unmap:1;
-
-	/* Can pages be swapped as part of reclaim? */
-	unsigned int may_swap:1;
-
-	/*
-	 * Cgroups are not reclaimed below their configured memory.low,
-	 * unless we threaten to OOM. If any cgroups are skipped due to
-	 * memory.low and nothing was reclaimed, go back for memory.low.
-	 */
-	unsigned int memcg_low_reclaim:1;
-	unsigned int memcg_low_skipped:1;
-
-	unsigned int hibernation_mode:1;
-
-	/* One of the zones is ready for compaction */
-	unsigned int compaction_ready:1;
-
-	/* There is easily reclaimable cold cache in the current node */
-	unsigned int cache_trim_mode:1;
-
-	/* The file pages on the current node are dangerously low */
-	unsigned int file_is_tiny:1;
-
-	/* Allocation order */
-	s8 order;
-
-	/* Scan (total_size >> priority) pages at once */
-	s8 priority;
-
-	/* The highest zone to isolate pages for reclaim from */
-	s8 reclaim_idx;
-
-	/* This context's GFP mask */
-	gfp_t gfp_mask;
-
-	/* Incremented by the number of inactive pages that were scanned */
-	unsigned long nr_scanned;
-
-	/* Number of pages freed so far during a call to shrink_zones() */
-	unsigned long nr_reclaimed;
-
-	struct {
-		unsigned int dirty;
-		unsigned int unqueued_dirty;
-		unsigned int congested;
-		unsigned int writeback;
-		unsigned int immediate;
-		unsigned int file_taken;
-		unsigned int taken;
-	} nr;
-
-	/* for recording the reclaimed slab by now */
-	struct reclaim_state reclaim_state;
-};
-
 #ifdef ARCH_HAS_PREFETCHW
 #define prefetchw_prev_lru_page(_page, _base, _field)			\
 	do {								\
-- 
2.18.2

[PATCH 2/3] mm: add reclaim context as a new parameter in mem_cgroup_protected()

[Yafang Shao]

Add the reclaim context 'struct scan_control *sc' as a new parameter in
the function mem_cgroup_protected(), which will be used later. Change
the name of 'root' to 'target' for better understanding as this is a
targeted reclaim.
Also move the declaration and definition of the changed function into
mm/internal.h.

Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Chris Down <chris@chrisdown.name>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/linux/memcontrol.h |  9 ---------
 mm/memcontrol.c            | 14 ++++++++------
 mm/vmscan.c                |  2 +-
 3 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index d275c72c4f8e..b327857a1e7e 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -357,9 +357,6 @@ static inline unsigned long mem_cgroup_protection(struct mem_cgroup *memcg,
 		   READ_ONCE(memcg->memory.elow));
 }
 
-enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
-						struct mem_cgroup *memcg);
-
 int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
 			  gfp_t gfp_mask, struct mem_cgroup **memcgp,
 			  bool compound);
@@ -841,12 +838,6 @@ static inline unsigned long mem_cgroup_protection(struct mem_cgroup *memcg,
 	return 0;
 }
 
-static inline enum mem_cgroup_protection mem_cgroup_protected(
-	struct mem_cgroup *root, struct mem_cgroup *memcg)
-{
-	return MEMCG_PROT_NONE;
-}
-
 static inline int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
 					gfp_t gfp_mask,
 					struct mem_cgroup **memcgp,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5beea03dd58a..51dab7f2e714 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6367,6 +6367,7 @@ static unsigned long effective_protection(unsigned long usage,
  * mem_cgroup_protected - check if memory consumption is in the normal range
  * @root: the top ancestor of the sub-tree being checked
  * @memcg: the memory cgroup to check
+ * @sc: the reclaim context
  *
  * WARNING: This function is not stateless! It can only be used as part
  *          of a top-down tree iteration, not for isolated queries.
@@ -6377,8 +6378,9 @@ static unsigned long effective_protection(unsigned long usage,
  *     an unprotected supply of reclaimable memory from other cgroups.
  *   MEMCG_PROT_MIN: cgroup memory is protected
  */
-enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
-						struct mem_cgroup *memcg)
+enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *target,
+						struct mem_cgroup *memcg,
+						struct scan_control *sc)
 {
 	unsigned long usage, parent_usage;
 	struct mem_cgroup *parent;
@@ -6386,9 +6388,9 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
 	if (mem_cgroup_disabled())
 		return MEMCG_PROT_NONE;
 
-	if (!root)
-		root = root_mem_cgroup;
-	if (memcg == root)
+	if (!target)
+		target = root_mem_cgroup;
+	if (memcg == target)
 		return MEMCG_PROT_NONE;
 
 	usage = page_counter_read(&memcg->memory);
@@ -6400,7 +6402,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
 	if (!parent)
 		return MEMCG_PROT_NONE;
 
-	if (parent == root) {
+	if (parent == target) {
 		memcg->memory.emin = READ_ONCE(memcg->memory.min);
 		memcg->memory.elow = memcg->memory.low;
 		goto out;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4c98512e2c9f..61c944e7f587 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2551,7 +2551,7 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
 		unsigned long reclaimed;
 		unsigned long scanned;
 
-		switch (mem_cgroup_protected(target_memcg, memcg)) {
+		switch (mem_cgroup_protected(target_memcg, memcg, sc)) {
 		case MEMCG_PROT_MIN:
 			/*
 			 * Hard protection.
-- 
2.18.2

[PATCH 3/3] mm: improvements on memcg protection functions

[Yafang Shao]

Since proportional memory.{min, low} reclaim is introduced in
commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
it have been proved that the proportional reclaim is hard to understand and
the issues caused by it is harder to understand.[1]. That dilemma faced by
us is caused by that the proportional reclaim mixed up memcg and the
reclaim context.

In proportional reclaim, the whole reclaim context - includes the memcg
to be reclaimed and the reclaimer, should be considered, rather than
memcg only.

To make it clear, a new member 'protection' is introduced in the reclaim
context (struct shrink_control) to replace mem_cgroup_protection(). This
one is set when we check whether the memcg is protected or not.

After this change, the issue pointed by me[1] - a really old left-over
value can slow donw target reclaim - can be fixed, and I think it could
also avoid some potential race.

[1]. https://lore.kernel.org/linux-mm/20200423061629.24185-1-laoar.shao@gmail.com

Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Chris Down <chris@chrisdown.name>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/linux/memcontrol.h | 25 ----------------
 mm/internal.h              | 17 +++++++++++
 mm/memcontrol.c            | 58 +++++++++++++++++++++++++++-----------
 mm/vmscan.c                | 35 +++--------------------
 4 files changed, 63 insertions(+), 72 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index b327857a1e7e..9d5ceeba3b31 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -50,12 +50,6 @@ enum memcg_memory_event {
 	MEMCG_NR_MEMORY_EVENTS,
 };
 
-enum mem_cgroup_protection {
-	MEMCG_PROT_NONE,
-	MEMCG_PROT_LOW,
-	MEMCG_PROT_MIN,
-};
-
 struct mem_cgroup_reclaim_cookie {
 	pg_data_t *pgdat;
 	unsigned int generation;
@@ -344,19 +338,6 @@ static inline bool mem_cgroup_disabled(void)
 	return !cgroup_subsys_enabled(memory_cgrp_subsys);
 }
 
-static inline unsigned long mem_cgroup_protection(struct mem_cgroup *memcg,
-						  bool in_low_reclaim)
-{
-	if (mem_cgroup_disabled())
-		return 0;
-
-	if (in_low_reclaim)
-		return READ_ONCE(memcg->memory.emin);
-
-	return max(READ_ONCE(memcg->memory.emin),
-		   READ_ONCE(memcg->memory.elow));
-}
-
 int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
 			  gfp_t gfp_mask, struct mem_cgroup **memcgp,
 			  bool compound);
@@ -832,12 +813,6 @@ static inline void memcg_memory_event_mm(struct mm_struct *mm,
 {
 }
 
-static inline unsigned long mem_cgroup_protection(struct mem_cgroup *memcg,
-						  bool in_low_reclaim)
-{
-	return 0;
-}
-
 static inline int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
 					gfp_t gfp_mask,
 					struct mem_cgroup **memcgp,
diff --git a/mm/internal.h b/mm/internal.h
index a0b3bdd933b9..10c762a79c0c 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -271,6 +271,9 @@ struct scan_control {
 	 */
 	struct mem_cgroup *target_mem_cgroup;
 
+	/* Memcg protection in this reclaim context */
+	unsigned long protection;
+
 	/* Can active pages be deactivated as part of reclaim? */
 #define DEACTIVATE_ANON 1
 #define DEACTIVATE_FILE 2
@@ -338,6 +341,20 @@ struct scan_control {
 	struct reclaim_state reclaim_state;
 };
 
+#ifdef CONFIG_MEMCG
+bool mem_cgroup_protected(struct mem_cgroup *target,
+			  struct mem_cgroup *memcg,
+			  struct scan_control *sc);
+
+#else
+static inline bool mem_cgroup_protected(struct mem_cgroup *target,
+					struct mem_cgroup *memcg,
+					struct scan_control *sc)
+{
+	return false;
+}
+#endif
+
 /*
  * This function returns the order of a free page in the buddy system. In
  * general, page_zone(page)->lock must be held by the caller to prevent the
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 51dab7f2e714..f2f191898f2b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6372,35 +6372,30 @@ static unsigned long effective_protection(unsigned long usage,
  * WARNING: This function is not stateless! It can only be used as part
  *          of a top-down tree iteration, not for isolated queries.
  *
- * Returns one of the following:
- *   MEMCG_PROT_NONE: cgroup memory is not protected
- *   MEMCG_PROT_LOW: cgroup memory is protected as long there is
- *     an unprotected supply of reclaimable memory from other cgroups.
- *   MEMCG_PROT_MIN: cgroup memory is protected
  */
-enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *target,
-						struct mem_cgroup *memcg,
-						struct scan_control *sc)
+bool mem_cgroup_protected(struct mem_cgroup *target,
+			  struct mem_cgroup *memcg,
+			  struct scan_control *sc)
 {
 	unsigned long usage, parent_usage;
 	struct mem_cgroup *parent;
 
 	if (mem_cgroup_disabled())
-		return MEMCG_PROT_NONE;
+		return false;
 
 	if (!target)
 		target = root_mem_cgroup;
 	if (memcg == target)
-		return MEMCG_PROT_NONE;
+		return false;
 
 	usage = page_counter_read(&memcg->memory);
 	if (!usage)
-		return MEMCG_PROT_NONE;
+		return false;
 
 	parent = parent_mem_cgroup(memcg);
 	/* No parent means a non-hierarchical mode on v1 memcg */
 	if (!parent)
-		return MEMCG_PROT_NONE;
+		return false;
 
 	if (parent == target) {
 		memcg->memory.emin = READ_ONCE(memcg->memory.min);
@@ -6420,12 +6415,43 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *target,
 			atomic_long_read(&parent->memory.children_low_usage)));
 
 out:
+	/*
+	 * Hard protection.
+	 * If there is no reclaimable memory, OOM.
+	 */
 	if (usage <= memcg->memory.emin)
-		return MEMCG_PROT_MIN;
-	else if (usage <= memcg->memory.elow)
-		return MEMCG_PROT_LOW;
+		return true;
+
+	/* The protection takes effect when false is returned. */
+	if (sc->memcg_low_reclaim)
+		sc->protection = memcg->memory.emin;
 	else
-		return MEMCG_PROT_NONE;
+		sc->protection = max(memcg->memory.emin, memcg->memory.elow);
+
+	if (usage <= memcg->memory.elow) {
+		/*
+		 * Soft protection.
+		 * Respect the protection only as long as there is an
+		 * unprotected supply of reclaimable memory from other
+		 * cgroups.
+		 */
+		if (!sc->memcg_low_reclaim) {
+			sc->memcg_low_skipped = 1;
+			return true;
+		}
+
+		memcg_memory_event(memcg, MEMCG_LOW);
+
+		return false;
+	}
+
+	/*
+	 * All protection thresholds breached. We may still choose to vary
+	 * the scan pressure applied based on by how much the cgroup in
+	 * question has exceeded its protection thresholds
+	 * (see get_scan_count).
+	 */
+	return false;
 }
 
 /**
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 61c944e7f587..a81bf736ac11 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2263,8 +2263,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
 		unsigned long protection;
 
 		lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
-		protection = mem_cgroup_protection(memcg,
-						   sc->memcg_low_reclaim);
+		protection = sc->protection;
 
 		if (protection) {
 			/*
@@ -2551,36 +2550,10 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
 		unsigned long reclaimed;
 		unsigned long scanned;
 
-		switch (mem_cgroup_protected(target_memcg, memcg, sc)) {
-		case MEMCG_PROT_MIN:
-			/*
-			 * Hard protection.
-			 * If there is no reclaimable memory, OOM.
-			 */
+		sc->protection = 0;
+
+		if (mem_cgroup_protected(target_memcg, memcg, sc))
 			continue;
-		case MEMCG_PROT_LOW:
-			/*
-			 * Soft protection.
-			 * Respect the protection only as long as
-			 * there is an unprotected supply
-			 * of reclaimable memory from other cgroups.
-			 */
-			if (!sc->memcg_low_reclaim) {
-				sc->memcg_low_skipped = 1;
-				continue;
-			}
-			memcg_memory_event(memcg, MEMCG_LOW);
-			break;
-		case MEMCG_PROT_NONE:
-			/*
-			 * All protection thresholds breached. We may
-			 * still choose to vary the scan pressure
-			 * applied based on by how much the cgroup in
-			 * question has exceeded its protection
-			 * thresholds (see get_scan_count).
-			 */
-			break;
-		}
 
 		reclaimed = sc->nr_reclaimed;
 		scanned = sc->nr_scanned;
-- 
2.18.2

Re: [PATCH 3/3] mm: improvements on memcg protection functions

[Michal Hocko]

On Sat 25-04-20 11:24:18, Yafang Shao wrote:
> Since proportional memory.{min, low} reclaim is introduced in
> commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
> it have been proved that the proportional reclaim is hard to understand and
> the issues caused by it is harder to understand.[1]. That dilemma faced by
> us is caused by that the proportional reclaim mixed up memcg and the
> reclaim context.
> 
> In proportional reclaim, the whole reclaim context - includes the memcg
> to be reclaimed and the reclaimer, should be considered, rather than
> memcg only.
> 
> To make it clear, a new member 'protection' is introduced in the reclaim
> context (struct shrink_control) to replace mem_cgroup_protection(). This

s@shrink_control@scan_control@

> one is set when we check whether the memcg is protected or not.
> 
> After this change, the issue pointed by me[1] - a really old left-over
> value can slow donw target reclaim - can be fixed, and I think it could
> also avoid some potential race.

The patch would have been much esier to review if you only focused on
the effective protection value caching. I really fail to see why you had
to make mem_cgroup_protected even more convoluted with more side effects
(e.g. sc->memcg_low_skipped). This goes directly opposite to what
Johannes was proposing in other email AFAICS.

Your changelog doesn't explain why double caching the effective value is
an improvement. I believe your goal was to drop the special casing for
the reclaim targets which are the only to ignore protection as they are
clearly violating the consumption constraints. This makes some sense
to me because it makes the special case have a local effect.

But I really dislike your patch. Please follow up on Johannes'
suggestion to split up the mem_cgroup_protected into parts
http://lkml.kernel.org/r/20200424134438.GA496852@cmpxchg.org

-- 
Michal Hocko
SUSE Labs

Re: [PATCH 3/3] mm: improvements on memcg protection functions

[Yafang Shao]

On Mon, Apr 27, 2020 at 5:40 PM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Sat 25-04-20 11:24:18, Yafang Shao wrote:
> > Since proportional memory.{min, low} reclaim is introduced in
> > commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
> > it have been proved that the proportional reclaim is hard to understand and
> > the issues caused by it is harder to understand.[1]. That dilemma faced by
> > us is caused by that the proportional reclaim mixed up memcg and the
> > reclaim context.
> >
> > In proportional reclaim, the whole reclaim context - includes the memcg
> > to be reclaimed and the reclaimer, should be considered, rather than
> > memcg only.
> >
> > To make it clear, a new member 'protection' is introduced in the reclaim
> > context (struct shrink_control) to replace mem_cgroup_protection(). This
>
> s@shrink_control@scan_control@
>

Thanks for pointing this out.

> > one is set when we check whether the memcg is protected or not.
> >
> > After this change, the issue pointed by me[1] - a really old left-over
> > value can slow donw target reclaim - can be fixed, and I think it could
> > also avoid some potential race.
>
> The patch would have been much esier to review if you only focused on
> the effective protection value caching. I really fail to see why you had
> to make mem_cgroup_protected even more convoluted with more side effects
> (e.g. sc->memcg_low_skipped). This goes directly opposite to what
> Johannes was proposing in other email AFAICS.
>

Sorry, I failed to see what the advantage of Johannes's proposal
except the better naming.

> Your changelog doesn't explain why double caching the effective value is
> an improvement.

The improvement is, to avoid getting an wrong value calculated by
other reclaimers and avoid issues in mem_cgroup_protection() that we
haven't noticed.

> I believe your goal was to drop the special casing for
> the reclaim targets which are the only to ignore protection as they are
> clearly violating the consumption constraints. This makes some sense
> to me because it makes the special case have a local effect.
>

> But I really dislike your patch. Please follow up on Johannes'
> suggestion to split up the mem_cgroup_protected into parts
> http://lkml.kernel.org/r/20200424134438.GA496852@cmpxchg.org
>

As I said above, I failed to see the advantage of this proposal.
Maybe we can wait until Johannes can show his code.

Hi Johannes,

Would you pls. show a simple implementation on your proposal ASAP ?


-- 
Thanks
Yafang

Re: [PATCH 3/3] mm: improvements on memcg protection functions

[Michal Hocko]

On Mon 27-04-20 18:09:27, Yafang Shao wrote:
> On Mon, Apr 27, 2020 at 5:40 PM Michal Hocko <mhocko@kernel.org> wrote:
> >
> > On Sat 25-04-20 11:24:18, Yafang Shao wrote:
> > > Since proportional memory.{min, low} reclaim is introduced in
> > > commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
> > > it have been proved that the proportional reclaim is hard to understand and
> > > the issues caused by it is harder to understand.[1]. That dilemma faced by
> > > us is caused by that the proportional reclaim mixed up memcg and the
> > > reclaim context.
> > >
> > > In proportional reclaim, the whole reclaim context - includes the memcg
> > > to be reclaimed and the reclaimer, should be considered, rather than
> > > memcg only.
> > >
> > > To make it clear, a new member 'protection' is introduced in the reclaim
> > > context (struct shrink_control) to replace mem_cgroup_protection(). This
> >
> > s@shrink_control@scan_control@
> >
> 
> Thanks for pointing this out.
> 
> > > one is set when we check whether the memcg is protected or not.
> > >
> > > After this change, the issue pointed by me[1] - a really old left-over
> > > value can slow donw target reclaim - can be fixed, and I think it could
> > > also avoid some potential race.
> >
> > The patch would have been much esier to review if you only focused on
> > the effective protection value caching. I really fail to see why you had
> > to make mem_cgroup_protected even more convoluted with more side effects
> > (e.g. sc->memcg_low_skipped). This goes directly opposite to what
> > Johannes was proposing in other email AFAICS.
> >
> 
> Sorry, I failed to see what the advantage of Johannes's proposal
> except the better naming.

The immediate advantage is that predicate should better not have any
side effect. So splitting into the calculation part which has clearly
defined side effects and having a simple predicate that consults
pre-calculated values makes a lot of sense to me.

> > Your changelog doesn't explain why double caching the effective value is
> > an improvement.
> 
> The improvement is, to avoid getting an wrong value calculated by
> other reclaimers and avoid issues in mem_cgroup_protection() that we
> haven't noticed.

This is not true in general. There is still parallel calculation done
and so parallel reclaimers might affect each other. Your patch only
makes a real difference for leaf memcgs which are the reclaim target as
well. All intermediate nodes really do not care about the cached values
because they do not have any pages on the LRU lists.

-- 
Michal Hocko
SUSE Labs

Re: [PATCH 3/3] mm: improvements on memcg protection functions

[Yafang Shao]

On Mon, Apr 27, 2020 at 6:50 PM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Mon 27-04-20 18:09:27, Yafang Shao wrote:
> > On Mon, Apr 27, 2020 at 5:40 PM Michal Hocko <mhocko@kernel.org> wrote:
> > >
> > > On Sat 25-04-20 11:24:18, Yafang Shao wrote:
> > > > Since proportional memory.{min, low} reclaim is introduced in
> > > > commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
> > > > it have been proved that the proportional reclaim is hard to understand and
> > > > the issues caused by it is harder to understand.[1]. That dilemma faced by
> > > > us is caused by that the proportional reclaim mixed up memcg and the
> > > > reclaim context.
> > > >
> > > > In proportional reclaim, the whole reclaim context - includes the memcg
> > > > to be reclaimed and the reclaimer, should be considered, rather than
> > > > memcg only.
> > > >
> > > > To make it clear, a new member 'protection' is introduced in the reclaim
> > > > context (struct shrink_control) to replace mem_cgroup_protection(). This
> > >
> > > s@shrink_control@scan_control@
> > >
> >
> > Thanks for pointing this out.
> >
> > > > one is set when we check whether the memcg is protected or not.
> > > >
> > > > After this change, the issue pointed by me[1] - a really old left-over
> > > > value can slow donw target reclaim - can be fixed, and I think it could
> > > > also avoid some potential race.
> > >
> > > The patch would have been much esier to review if you only focused on
> > > the effective protection value caching. I really fail to see why you had
> > > to make mem_cgroup_protected even more convoluted with more side effects
> > > (e.g. sc->memcg_low_skipped). This goes directly opposite to what
> > > Johannes was proposing in other email AFAICS.
> > >
> >
> > Sorry, I failed to see what the advantage of Johannes's proposal
> > except the better naming.
>
> The immediate advantage is that predicate should better not have any
> side effect.

No, it still has side effect. That is not an immediate advantage neither.
See bellow,

> So splitting into the calculation part which has clearly
> defined side effects and having a simple predicate that consults
> pre-calculated values makes a lot of sense to me.
>

When you calculate the effective values,  the source values to
calculate it  may be changed with these values when you do the
predicate.
IOW, this proposal greatly increase the race window.

> > > Your changelog doesn't explain why double caching the effective value is
> > > an improvement.
> >
> > The improvement is, to avoid getting an wrong value calculated by
> > other reclaimers and avoid issues in mem_cgroup_protection() that we
> > haven't noticed.
>
> This is not true in general. There is still parallel calculation done
> and so parallel reclaimers might affect each other. Your patch only
> makes a real difference for leaf memcgs which are the reclaim target as
> well.

The race between  parallel reclaimers is fundamentally exist, and we
can do now is reducing the race window as far as possible.

> All intermediate nodes really do not care about the cached values
> because they do not have any pages on the LRU lists.
>

But read these cached values can save lot of time against the existing
code, as the existing code still calculates them even if they are
useless.
If you think that is a issue, I think why not skip scanning these
intermediate nodes because they don't have any pages on the LRU lists
?

-- 
Thanks
Yafang

Re: [PATCH 3/3] mm: improvements on memcg protection functions

[Michal Hocko]

On Mon 27-04-20 19:06:52, Yafang Shao wrote:
> On Mon, Apr 27, 2020 at 6:50 PM Michal Hocko <mhocko@kernel.org> wrote:
> >
> > On Mon 27-04-20 18:09:27, Yafang Shao wrote:
> > > On Mon, Apr 27, 2020 at 5:40 PM Michal Hocko <mhocko@kernel.org> wrote:
> > > >
> > > > On Sat 25-04-20 11:24:18, Yafang Shao wrote:
> > > > > Since proportional memory.{min, low} reclaim is introduced in
> > > > > commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
> > > > > it have been proved that the proportional reclaim is hard to understand and
> > > > > the issues caused by it is harder to understand.[1]. That dilemma faced by
> > > > > us is caused by that the proportional reclaim mixed up memcg and the
> > > > > reclaim context.
> > > > >
> > > > > In proportional reclaim, the whole reclaim context - includes the memcg
> > > > > to be reclaimed and the reclaimer, should be considered, rather than
> > > > > memcg only.
> > > > >
> > > > > To make it clear, a new member 'protection' is introduced in the reclaim
> > > > > context (struct shrink_control) to replace mem_cgroup_protection(). This
> > > >
> > > > s@shrink_control@scan_control@
> > > >
> > >
> > > Thanks for pointing this out.
> > >
> > > > > one is set when we check whether the memcg is protected or not.
> > > > >
> > > > > After this change, the issue pointed by me[1] - a really old left-over
> > > > > value can slow donw target reclaim - can be fixed, and I think it could
> > > > > also avoid some potential race.
> > > >
> > > > The patch would have been much esier to review if you only focused on
> > > > the effective protection value caching. I really fail to see why you had
> > > > to make mem_cgroup_protected even more convoluted with more side effects
> > > > (e.g. sc->memcg_low_skipped). This goes directly opposite to what
> > > > Johannes was proposing in other email AFAICS.
> > > >
> > >
> > > Sorry, I failed to see what the advantage of Johannes's proposal
> > > except the better naming.
> >
> > The immediate advantage is that predicate should better not have any
> > side effect.
> 
> No, it still has side effect. That is not an immediate advantage neither.
> See bellow,

I believe you have misunderstood the proposal.
mem_cgroup_below_{min,low,protection} won't have any side effect on the
memcg. It would be only mem_cgroup_calculate_protection which updates
the cached state. So there won't be any predicate to have side effect.

> > So splitting into the calculation part which has clearly
> > defined side effects and having a simple predicate that consults
> > pre-calculated values makes a lot of sense to me.
> >
> 
> When you calculate the effective values,  the source values to
> calculate it  may be changed with these values when you do the
> predicate.
> IOW, this proposal greatly increase the race window.

Why do you think so?

> > > > Your changelog doesn't explain why double caching the effective value is
> > > > an improvement.
> > >
> > > The improvement is, to avoid getting an wrong value calculated by
> > > other reclaimers and avoid issues in mem_cgroup_protection() that we
> > > haven't noticed.
> >
> > This is not true in general. There is still parallel calculation done
> > and so parallel reclaimers might affect each other. Your patch only
> > makes a real difference for leaf memcgs which are the reclaim target as
> > well.
> 
> The race between  parallel reclaimers is fundamentally exist, and we
> can do now is reducing the race window as far as possible.

Reducing the race window is futile. The situation changes after each
reclaim attempt. All we need is to keep a protection consistent
regardless of where the reclaim root. That means that hierarchies deeper
in the tree cannot override the protection from those which are higher.

> > All intermediate nodes really do not care about the cached values
> > because they do not have any pages on the LRU lists.
> >
> 
> But read these cached values can save lot of time against the existing
> code, as the existing code still calculates them even if they are
> useless.

They are not useless. Intermediate values are necessary for the
protection distribution for lower level memcgs.

-- 
Michal Hocko
SUSE Labs

Re: [PATCH 3/3] mm: improvements on memcg protection functions

[Yafang Shao]

On Mon, Apr 27, 2020 at 7:24 PM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Mon 27-04-20 19:06:52, Yafang Shao wrote:
> > On Mon, Apr 27, 2020 at 6:50 PM Michal Hocko <mhocko@kernel.org> wrote:
> > >
> > > On Mon 27-04-20 18:09:27, Yafang Shao wrote:
> > > > On Mon, Apr 27, 2020 at 5:40 PM Michal Hocko <mhocko@kernel.org> wrote:
> > > > >
> > > > > On Sat 25-04-20 11:24:18, Yafang Shao wrote:
> > > > > > Since proportional memory.{min, low} reclaim is introduced in
> > > > > > commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
> > > > > > it have been proved that the proportional reclaim is hard to understand and
> > > > > > the issues caused by it is harder to understand.[1]. That dilemma faced by
> > > > > > us is caused by that the proportional reclaim mixed up memcg and the
> > > > > > reclaim context.
> > > > > >
> > > > > > In proportional reclaim, the whole reclaim context - includes the memcg
> > > > > > to be reclaimed and the reclaimer, should be considered, rather than
> > > > > > memcg only.
> > > > > >
> > > > > > To make it clear, a new member 'protection' is introduced in the reclaim
> > > > > > context (struct shrink_control) to replace mem_cgroup_protection(). This
> > > > >
> > > > > s@shrink_control@scan_control@
> > > > >
> > > >
> > > > Thanks for pointing this out.
> > > >
> > > > > > one is set when we check whether the memcg is protected or not.
> > > > > >
> > > > > > After this change, the issue pointed by me[1] - a really old left-over
> > > > > > value can slow donw target reclaim - can be fixed, and I think it could
> > > > > > also avoid some potential race.
> > > > >
> > > > > The patch would have been much esier to review if you only focused on
> > > > > the effective protection value caching. I really fail to see why you had
> > > > > to make mem_cgroup_protected even more convoluted with more side effects
> > > > > (e.g. sc->memcg_low_skipped). This goes directly opposite to what
> > > > > Johannes was proposing in other email AFAICS.
> > > > >
> > > >
> > > > Sorry, I failed to see what the advantage of Johannes's proposal
> > > > except the better naming.
> > >
> > > The immediate advantage is that predicate should better not have any
> > > side effect.
> >
> > No, it still has side effect. That is not an immediate advantage neither.
> > See bellow,
>
> I believe you have misunderstood the proposal.
> mem_cgroup_below_{min,low,protection} won't have any side effect on the
> memcg. It would be only mem_cgroup_calculate_protection which updates
> the cached state. So there won't be any predicate to have side effect.
>

Maybe  I misunderstood this porposal, or both of us misunderstood this
proposal.

> > > So splitting into the calculation part which has clearly
> > > defined side effects and having a simple predicate that consults
> > > pre-calculated values makes a lot of sense to me.
> > >
> >
> > When you calculate the effective values,  the source values to
> > calculate it  may be changed with these values when you do the
> > predicate.
> > IOW, this proposal greatly increase the race window.
>
> Why do you think so?
>

See above, I don't think it is proper to disccuss it any more until we
see the code.

> > > > > Your changelog doesn't explain why double caching the effective value is
> > > > > an improvement.
> > > >
> > > > The improvement is, to avoid getting an wrong value calculated by
> > > > other reclaimers and avoid issues in mem_cgroup_protection() that we
> > > > haven't noticed.
> > >
> > > This is not true in general. There is still parallel calculation done
> > > and so parallel reclaimers might affect each other. Your patch only
> > > makes a real difference for leaf memcgs which are the reclaim target as
> > > well.
> >
> > The race between  parallel reclaimers is fundamentally exist, and we
> > can do now is reducing the race window as far as possible.
>
> Reducing the race window is futile. The situation changes after each
> reclaim attempt. All we need is to keep a protection consistent
> regardless of where the reclaim root. That means that hierarchies deeper
> in the tree cannot override the protection from those which are higher.
>

That is what I have implemented in this patchset.

> > > All intermediate nodes really do not care about the cached values
> > > because they do not have any pages on the LRU lists.
> > >
> >
> > But read these cached values can save lot of time against the existing
> > code, as the existing code still calculates them even if they are
> > useless.
>
> They are not useless. Intermediate values are necessary for the
> protection distribution for lower level memcgs.
>



-- 
Thanks
Yafang

Re: [PATCH 0/3] mm: improve proportional memcg protection

[Johannes Weiner]

On Sat, Apr 25, 2020 at 11:24:15AM -0400, Yafang Shao wrote:
> Since proportional memory.{min, low} reclaim is introduced in
> commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
> it have been proved that the proportional reclaim is hard to understand and
> the issues caused by it is harder to understand.[1]. That dilemma faced by
> us is caused by that the proportional reclaim mixed up memcg and the
> reclaim context.
> 
> In proportional reclaim, the whole reclaim context - includes the memcg
> to be reclaimed and the reclaimer, should be considered, rather than
> memcg only.
> 
> To make it clear, a new member 'protection' is introduced in the reclaim
> context (struct shrink_control) to replace mem_cgroup_protection(). This
> one is set when we check whether the memcg is protected or not.

This patch series makes the code harder to understand.

It's already tricky to understand ownership and lifetime/validity of
struct scan_control members when it's just vmscan.c functions touching
them. Expanding the scope to the entire MM is a bad idea.

Splitting up sc->memcg_low_reclaim handling and the associated restart
logic makes control flow harder to follow as well.

The problem with the current code is a suboptimal interface between
the memcg protection calculation and the reclaim control flow. We need
to clean that up, not remove the interface and thereby all clarity on
who handles which information.

Re: [PATCH 0/3] mm: improve proportional memcg protection

[Yafang Shao]

On Tue, Apr 28, 2020 at 1:05 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Sat, Apr 25, 2020 at 11:24:15AM -0400, Yafang Shao wrote:
> > Since proportional memory.{min, low} reclaim is introduced in
> > commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
> > it have been proved that the proportional reclaim is hard to understand and
> > the issues caused by it is harder to understand.[1]. That dilemma faced by
> > us is caused by that the proportional reclaim mixed up memcg and the
> > reclaim context.
> >
> > In proportional reclaim, the whole reclaim context - includes the memcg
> > to be reclaimed and the reclaimer, should be considered, rather than
> > memcg only.
> >
> > To make it clear, a new member 'protection' is introduced in the reclaim
> > context (struct shrink_control) to replace mem_cgroup_protection(). This
> > one is set when we check whether the memcg is protected or not.
>
> This patch series makes the code harder to understand.
>

I don't think so.
With this  patchset, you don't need to care about what the emin of this
memcg and its parent should be when you calculate the scan count.
Furthermore, you don't need to worry about the potential race when you
are getting the scan count.
'Protection' is calculated when we check whether the memcg is
'protected' or not, that is really easy to understand.

> It's already tricky to understand ownership and lifetime/validity of
> struct scan_control members when it's just vmscan.c functions touching
> them.

Note that the reclaimers can call the funtions existing in vmscan.c,
compaction.c, slub.c, filemap.c, oom_kill.c, workingset.c,
page-writeback.c, swap.c, khugepaged.c and etc. IOW, it may be used in
these functions sooner or later.

> Expanding the scope to the entire MM is a bad idea.
>

Well, mem_cgroup_protection() is only used in memcontrol.c and vmscan.c.
So expanding the scope to the entire LINUX is a MORE bad idea.
There may be some other functions doing this as well.

> Splitting up sc->memcg_low_reclaim handling and the associated restart
> logic makes control flow harder to follow as well.
>

Placing sc->memcg_low_reclaim in lots of callsites make the control
flow more than harder to follow.

> The problem with the current code is a suboptimal interface between
> the memcg protection calculation and the reclaim control flow. We need
> to clean that up, not remove the interface and thereby all clarity on
> who handles which information.

'remove the interface ' in the CURRENT CALLSITE is really a good 'clean up'.

Seems we can't get an agreement on how to improve current code.
So I will submit a patch to revert the commit 9783aa9917f8 ("mm,
memcg: proportional memory.{low,min} reclaim") first.
Then let's talk about the good solution to implement it.

BTW, I can't image why such a bad  and ugly implementation got merged
in the first place.
The quantity of memory cgroup is becoming more and more bad.


--
Thanks
Yafang

Re: [PATCH 0/3] mm: improve proportional memcg protection

[Johannes Weiner]

On Tue, Apr 28, 2020 at 09:45:27AM +0800, Yafang Shao wrote:
> On Tue, Apr 28, 2020 at 1:05 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
> > On Sat, Apr 25, 2020 at 11:24:15AM -0400, Yafang Shao wrote:
> > > Since proportional memory.{min, low} reclaim is introduced in
> > > commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
> > > it have been proved that the proportional reclaim is hard to understand and
> > > the issues caused by it is harder to understand.[1]. That dilemma faced by
> > > us is caused by that the proportional reclaim mixed up memcg and the
> > > reclaim context.
> > >
> > > In proportional reclaim, the whole reclaim context - includes the memcg
> > > to be reclaimed and the reclaimer, should be considered, rather than
> > > memcg only.
> > >
> > > To make it clear, a new member 'protection' is introduced in the reclaim
> > > context (struct shrink_control) to replace mem_cgroup_protection(). This
> > > one is set when we check whether the memcg is protected or not.
> >
> > This patch series makes the code harder to understand.
> >
> 
> I don't think so.
> With this  patchset, you don't need to care about what the emin of this
> memcg and its parent should be when you calculate the scan count.
> Furthermore, you don't need to worry about the potential race when you
> are getting the scan count.
> 'Protection' is calculated when we check whether the memcg is
> 'protected' or not, that is really easy to understand.

If we could calculate emin and elow in one go at the beginning of the
reclaim walk and then operate on private copies inside scan_control, I
would agree with you. It would be better. But that would require
replicating the entire cgroup tree structure, which isn't practical.

After your patch we're still building and propagating shared
hierarchical state as we iterate through the cgroup tree. I'm not sure
why handing off scan_control and having somebody else write the racy
state in there is supposed to make it better.

> > It's already tricky to understand ownership and lifetime/validity of
> > struct scan_control members when it's just vmscan.c functions touching
> > them.
> 
> Note that the reclaimers can call the funtions existing in vmscan.c,
> compaction.c, slub.c, filemap.c, oom_kill.c, workingset.c,
> page-writeback.c, swap.c, khugepaged.c and etc. IOW, it may be used in
> these functions sooner or later.

Right, but in general we try to make helper functions and predicates
operate on very specific pieces of data, with clearly delineated side
effects.

Your patch is handing off a huge collection of private data that
drives the reclaim algorithm and gives it to an external function for
non-obvious manipulation.

> > Expanding the scope to the entire MM is a bad idea.
> >
> 
> Well, mem_cgroup_protection() is only used in memcontrol.c and vmscan.c.
> So expanding the scope to the entire LINUX is a MORE bad idea.
> There may be some other functions doing this as well.

That's a /much/ less exposed interface.

> > Splitting up sc->memcg_low_reclaim handling and the associated restart
> > logic makes control flow harder to follow as well.
> >
> 
> Placing sc->memcg_low_reclaim in lots of callsites make the control
> flow more than harder to follow.

Those are the places where the control flow decisions are actually
made. You didn't change that, you just obscured how those decisions
are being made and who owns which parts of the state machine.

> Seems we can't get an agreement on how to improve current code.
> So I will submit a patch to revert the commit 9783aa9917f8 ("mm,
> memcg: proportional memory.{low,min} reclaim") first.

What do you think that will accomplish?

> BTW, I can't image why such a bad  and ugly implementation got merged
> in the first place.
> The quantity of memory cgroup is becoming more and more bad.

I'm sorry you feel that way. However, it's always possible to use an
earlier version of the memory controller. Here is a good one from 2011:

/* memcontrol.c - Memory Controller
 *
 * Copyright IBM Corporation, 2007
 * Author Balbir Singh <balbir@linux.vnet.ibm.com>
 *
 * Copyright 2007 OpenVZ SWsoft Inc
 * Author: Pavel Emelianov <xemul@openvz.org>
 *
 * Memory thresholds
 * Copyright (C) 2009 Nokia Corporation
 * Author: Kirill A. Shutemov
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/res_counter.h>
#include <linux/memcontrol.h>
#include <linux/cgroup.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/pagemap.h>
#include <linux/smp.h>
#include <linux/page-flags.h>
#include <linux/backing-dev.h>
#include <linux/bit_spinlock.h>
#include <linux/rcupdate.h>
#include <linux/limits.h>
#include <linux/mutex.h>
#include <linux/rbtree.h>
#include <linux/shmem_fs.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/spinlock.h>
#include <linux/eventfd.h>
#include <linux/sort.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/vmalloc.h>
#include <linux/mm_inline.h>
#include <linux/page_cgroup.h>
#include <linux/cpu.h>
#include <linux/oom.h>
#include "internal.h"

#include <asm/uaccess.h>

#include <trace/events/vmscan.h>

struct cgroup_subsys mem_cgroup_subsys __read_mostly;
#define MEM_CGROUP_RECLAIM_RETRIES	5
struct mem_cgroup *root_mem_cgroup __read_mostly;

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
/* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
int do_swap_account __read_mostly;

/* for remember boot option*/
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED
static int really_do_swap_account __initdata = 1;
#else
static int really_do_swap_account __initdata = 0;
#endif

#else
#define do_swap_account		(0)
#endif


/*
 * Statistics for memory cgroup.
 */
enum mem_cgroup_stat_index {
	/*
	 * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
	 */
	MEM_CGROUP_STAT_CACHE, 	   /* # of pages charged as cache */
	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as anon rss */
	MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
	MEM_CGROUP_STAT_DATA, /* end of data requires synchronization */
	MEM_CGROUP_ON_MOVE,	/* someone is moving account between groups */
	MEM_CGROUP_STAT_NSTATS,
};

enum mem_cgroup_events_index {
	MEM_CGROUP_EVENTS_PGPGIN,	/* # of pages paged in */
	MEM_CGROUP_EVENTS_PGPGOUT,	/* # of pages paged out */
	MEM_CGROUP_EVENTS_COUNT,	/* # of pages paged in/out */
	MEM_CGROUP_EVENTS_PGFAULT,	/* # of page-faults */
	MEM_CGROUP_EVENTS_PGMAJFAULT,	/* # of major page-faults */
	MEM_CGROUP_EVENTS_NSTATS,
};
/*
 * Per memcg event counter is incremented at every pagein/pageout. With THP,
 * it will be incremated by the number of pages. This counter is used for
 * for trigger some periodic events. This is straightforward and better
 * than using jiffies etc. to handle periodic memcg event.
 */
enum mem_cgroup_events_target {
	MEM_CGROUP_TARGET_THRESH,
	MEM_CGROUP_TARGET_SOFTLIMIT,
	MEM_CGROUP_TARGET_NUMAINFO,
	MEM_CGROUP_NTARGETS,
};
#define THRESHOLDS_EVENTS_TARGET (128)
#define SOFTLIMIT_EVENTS_TARGET (1024)
#define NUMAINFO_EVENTS_TARGET	(1024)

struct mem_cgroup_stat_cpu {
	long count[MEM_CGROUP_STAT_NSTATS];
	unsigned long events[MEM_CGROUP_EVENTS_NSTATS];
	unsigned long targets[MEM_CGROUP_NTARGETS];
};

/*
 * per-zone information in memory controller.
 */
struct mem_cgroup_per_zone {
	/*
	 * spin_lock to protect the per cgroup LRU
	 */
	struct list_head	lists[NR_LRU_LISTS];
	unsigned long		count[NR_LRU_LISTS];

	struct zone_reclaim_stat reclaim_stat;
	struct rb_node		tree_node;	/* RB tree node */
	unsigned long long	usage_in_excess;/* Set to the value by which */
						/* the soft limit is exceeded*/
	bool			on_tree;
	struct mem_cgroup	*mem;		/* Back pointer, we cannot */
						/* use container_of	   */
};
/* Macro for accessing counter */
#define MEM_CGROUP_ZSTAT(mz, idx)	((mz)->count[(idx)])

struct mem_cgroup_per_node {
	struct mem_cgroup_per_zone zoneinfo[MAX_NR_ZONES];
};

struct mem_cgroup_lru_info {
	struct mem_cgroup_per_node *nodeinfo[MAX_NUMNODES];
};

/*
 * Cgroups above their limits are maintained in a RB-Tree, independent of
 * their hierarchy representation
 */

struct mem_cgroup_tree_per_zone {
	struct rb_root rb_root;
	spinlock_t lock;
};

struct mem_cgroup_tree_per_node {
	struct mem_cgroup_tree_per_zone rb_tree_per_zone[MAX_NR_ZONES];
};

struct mem_cgroup_tree {
	struct mem_cgroup_tree_per_node *rb_tree_per_node[MAX_NUMNODES];
};

static struct mem_cgroup_tree soft_limit_tree __read_mostly;

struct mem_cgroup_threshold {
	struct eventfd_ctx *eventfd;
	u64 threshold;
};

/* For threshold */
struct mem_cgroup_threshold_ary {
	/* An array index points to threshold just below usage. */
	int current_threshold;
	/* Size of entries[] */
	unsigned int size;
	/* Array of thresholds */
	struct mem_cgroup_threshold entries[0];
};

struct mem_cgroup_thresholds {
	/* Primary thresholds array */
	struct mem_cgroup_threshold_ary *primary;
	/*
	 * Spare threshold array.
	 * This is needed to make mem_cgroup_unregister_event() "never fail".
	 * It must be able to store at least primary->size - 1 entries.
	 */
	struct mem_cgroup_threshold_ary *spare;
};

/* for OOM */
struct mem_cgroup_eventfd_list {
	struct list_head list;
	struct eventfd_ctx *eventfd;
};

static void mem_cgroup_threshold(struct mem_cgroup *mem);
static void mem_cgroup_oom_notify(struct mem_cgroup *mem);

/*
 * The memory controller data structure. The memory controller controls both
 * page cache and RSS per cgroup. We would eventually like to provide
 * statistics based on the statistics developed by Rik Van Riel for clock-pro,
 * to help the administrator determine what knobs to tune.
 *
 * TODO: Add a water mark for the memory controller. Reclaim will begin when
 * we hit the water mark. May be even add a low water mark, such that
 * no reclaim occurs from a cgroup at it's low water mark, this is
 * a feature that will be implemented much later in the future.
 */
struct mem_cgroup {
	struct cgroup_subsys_state css;
	/*
	 * the counter to account for memory usage
	 */
	struct res_counter res;
	/*
	 * the counter to account for mem+swap usage.
	 */
	struct res_counter memsw;
	/*
	 * Per cgroup active and inactive list, similar to the
	 * per zone LRU lists.
	 */
	struct mem_cgroup_lru_info info;
	/*
	 * While reclaiming in a hierarchy, we cache the last child we
	 * reclaimed from.
	 */
	int last_scanned_child;
	int last_scanned_node;
#if MAX_NUMNODES > 1
	nodemask_t	scan_nodes;
	atomic_t	numainfo_events;
	atomic_t	numainfo_updating;
#endif
	/*
	 * Should the accounting and control be hierarchical, per subtree?
	 */
	bool use_hierarchy;
	atomic_t	oom_lock;
	atomic_t	refcnt;

	unsigned int	swappiness;
	/* OOM-Killer disable */
	int		oom_kill_disable;

	/* set when res.limit == memsw.limit */
	bool		memsw_is_minimum;

	/* protect arrays of thresholds */
	struct mutex thresholds_lock;

	/* thresholds for memory usage. RCU-protected */
	struct mem_cgroup_thresholds thresholds;

	/* thresholds for mem+swap usage. RCU-protected */
	struct mem_cgroup_thresholds memsw_thresholds;

	/* For oom notifier event fd */
	struct list_head oom_notify;

	/*
	 * Should we move charges of a task when a task is moved into this
	 * mem_cgroup ? And what type of charges should we move ?
	 */
	unsigned long 	move_charge_at_immigrate;
	/*
	 * percpu counter.
	 */
	struct mem_cgroup_stat_cpu *stat;
	/*
	 * used when a cpu is offlined or other synchronizations
	 * See mem_cgroup_read_stat().
	 */
	struct mem_cgroup_stat_cpu nocpu_base;
	spinlock_t pcp_counter_lock;
};

/* Stuffs for move charges at task migration. */
/*
 * Types of charges to be moved. "move_charge_at_immitgrate" is treated as a
 * left-shifted bitmap of these types.
 */
enum move_type {
	MOVE_CHARGE_TYPE_ANON,	/* private anonymous page and swap of it */
	MOVE_CHARGE_TYPE_FILE,	/* file page(including tmpfs) and swap of it */
	NR_MOVE_TYPE,
};

/* "mc" and its members are protected by cgroup_mutex */
static struct move_charge_struct {
	spinlock_t	  lock; /* for from, to */
	struct mem_cgroup *from;
	struct mem_cgroup *to;
	unsigned long precharge;
	unsigned long moved_charge;
	unsigned long moved_swap;
	struct task_struct *moving_task;	/* a task moving charges */
	wait_queue_head_t waitq;		/* a waitq for other context */
} mc = {
	.lock = __SPIN_LOCK_UNLOCKED(mc.lock),
	.waitq = __WAIT_QUEUE_HEAD_INITIALIZER(mc.waitq),
};

static bool move_anon(void)
{
	return test_bit(MOVE_CHARGE_TYPE_ANON,
					&mc.to->move_charge_at_immigrate);
}

static bool move_file(void)
{
	return test_bit(MOVE_CHARGE_TYPE_FILE,
					&mc.to->move_charge_at_immigrate);
}

/*
 * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
 * limit reclaim to prevent infinite loops, if they ever occur.
 */
#define	MEM_CGROUP_MAX_RECLAIM_LOOPS		(100)
#define	MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS	(2)

enum charge_type {
	MEM_CGROUP_CHARGE_TYPE_CACHE = 0,
	MEM_CGROUP_CHARGE_TYPE_MAPPED,
	MEM_CGROUP_CHARGE_TYPE_SHMEM,	/* used by page migration of shmem */
	MEM_CGROUP_CHARGE_TYPE_FORCE,	/* used by force_empty */
	MEM_CGROUP_CHARGE_TYPE_SWAPOUT,	/* for accounting swapcache */
	MEM_CGROUP_CHARGE_TYPE_DROP,	/* a page was unused swap cache */
	NR_CHARGE_TYPE,
};

/* for encoding cft->private value on file */
#define _MEM			(0)
#define _MEMSWAP		(1)
#define _OOM_TYPE		(2)
#define MEMFILE_PRIVATE(x, val)	(((x) << 16) | (val))
#define MEMFILE_TYPE(val)	(((val) >> 16) & 0xffff)
#define MEMFILE_ATTR(val)	((val) & 0xffff)
/* Used for OOM nofiier */
#define OOM_CONTROL		(0)

/*
 * Reclaim flags for mem_cgroup_hierarchical_reclaim
 */
#define MEM_CGROUP_RECLAIM_NOSWAP_BIT	0x0
#define MEM_CGROUP_RECLAIM_NOSWAP	(1 << MEM_CGROUP_RECLAIM_NOSWAP_BIT)
#define MEM_CGROUP_RECLAIM_SHRINK_BIT	0x1
#define MEM_CGROUP_RECLAIM_SHRINK	(1 << MEM_CGROUP_RECLAIM_SHRINK_BIT)
#define MEM_CGROUP_RECLAIM_SOFT_BIT	0x2
#define MEM_CGROUP_RECLAIM_SOFT		(1 << MEM_CGROUP_RECLAIM_SOFT_BIT)

static void mem_cgroup_get(struct mem_cgroup *mem);
static void mem_cgroup_put(struct mem_cgroup *mem);
static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
static void drain_all_stock_async(struct mem_cgroup *mem);

static struct mem_cgroup_per_zone *
mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
{
	return &mem->info.nodeinfo[nid]->zoneinfo[zid];
}

struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *mem)
{
	return &mem->css;
}

static struct mem_cgroup_per_zone *
page_cgroup_zoneinfo(struct mem_cgroup *mem, struct page *page)
{
	int nid = page_to_nid(page);
	int zid = page_zonenum(page);

	return mem_cgroup_zoneinfo(mem, nid, zid);
}

static struct mem_cgroup_tree_per_zone *
soft_limit_tree_node_zone(int nid, int zid)
{
	return &soft_limit_tree.rb_tree_per_node[nid]->rb_tree_per_zone[zid];
}

static struct mem_cgroup_tree_per_zone *
soft_limit_tree_from_page(struct page *page)
{
	int nid = page_to_nid(page);
	int zid = page_zonenum(page);

	return &soft_limit_tree.rb_tree_per_node[nid]->rb_tree_per_zone[zid];
}

static void
__mem_cgroup_insert_exceeded(struct mem_cgroup *mem,
				struct mem_cgroup_per_zone *mz,
				struct mem_cgroup_tree_per_zone *mctz,
				unsigned long long new_usage_in_excess)
{
	struct rb_node **p = &mctz->rb_root.rb_node;
	struct rb_node *parent = NULL;
	struct mem_cgroup_per_zone *mz_node;

	if (mz->on_tree)
		return;

	mz->usage_in_excess = new_usage_in_excess;
	if (!mz->usage_in_excess)
		return;
	while (*p) {
		parent = *p;
		mz_node = rb_entry(parent, struct mem_cgroup_per_zone,
					tree_node);
		if (mz->usage_in_excess < mz_node->usage_in_excess)
			p = &(*p)->rb_left;
		/*
		 * We can't avoid mem cgroups that are over their soft
		 * limit by the same amount
		 */
		else if (mz->usage_in_excess >= mz_node->usage_in_excess)
			p = &(*p)->rb_right;
	}
	rb_link_node(&mz->tree_node, parent, p);
	rb_insert_color(&mz->tree_node, &mctz->rb_root);
	mz->on_tree = true;
}

static void
__mem_cgroup_remove_exceeded(struct mem_cgroup *mem,
				struct mem_cgroup_per_zone *mz,
				struct mem_cgroup_tree_per_zone *mctz)
{
	if (!mz->on_tree)
		return;
	rb_erase(&mz->tree_node, &mctz->rb_root);
	mz->on_tree = false;
}

static void
mem_cgroup_remove_exceeded(struct mem_cgroup *mem,
				struct mem_cgroup_per_zone *mz,
				struct mem_cgroup_tree_per_zone *mctz)
{
	spin_lock(&mctz->lock);
	__mem_cgroup_remove_exceeded(mem, mz, mctz);
	spin_unlock(&mctz->lock);
}


static void mem_cgroup_update_tree(struct mem_cgroup *mem, struct page *page)
{
	unsigned long long excess;
	struct mem_cgroup_per_zone *mz;
	struct mem_cgroup_tree_per_zone *mctz;
	int nid = page_to_nid(page);
	int zid = page_zonenum(page);
	mctz = soft_limit_tree_from_page(page);

	/*
	 * Necessary to update all ancestors when hierarchy is used.
	 * because their event counter is not touched.
	 */
	for (; mem; mem = parent_mem_cgroup(mem)) {
		mz = mem_cgroup_zoneinfo(mem, nid, zid);
		excess = res_counter_soft_limit_excess(&mem->res);
		/*
		 * We have to update the tree if mz is on RB-tree or
		 * mem is over its softlimit.
		 */
		if (excess || mz->on_tree) {
			spin_lock(&mctz->lock);
			/* if on-tree, remove it */
			if (mz->on_tree)
				__mem_cgroup_remove_exceeded(mem, mz, mctz);
			/*
			 * Insert again. mz->usage_in_excess will be updated.
			 * If excess is 0, no tree ops.
			 */
			__mem_cgroup_insert_exceeded(mem, mz, mctz, excess);
			spin_unlock(&mctz->lock);
		}
	}
}

static void mem_cgroup_remove_from_trees(struct mem_cgroup *mem)
{
	int node, zone;
	struct mem_cgroup_per_zone *mz;
	struct mem_cgroup_tree_per_zone *mctz;

	for_each_node_state(node, N_POSSIBLE) {
		for (zone = 0; zone < MAX_NR_ZONES; zone++) {
			mz = mem_cgroup_zoneinfo(mem, node, zone);
			mctz = soft_limit_tree_node_zone(node, zone);
			mem_cgroup_remove_exceeded(mem, mz, mctz);
		}
	}
}

static struct mem_cgroup_per_zone *
__mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
{
	struct rb_node *rightmost = NULL;
	struct mem_cgroup_per_zone *mz;

retry:
	mz = NULL;
	rightmost = rb_last(&mctz->rb_root);
	if (!rightmost)
		goto done;		/* Nothing to reclaim from */

	mz = rb_entry(rightmost, struct mem_cgroup_per_zone, tree_node);
	/*
	 * Remove the node now but someone else can add it back,
	 * we will to add it back at the end of reclaim to its correct
	 * position in the tree.
	 */
	__mem_cgroup_remove_exceeded(mz->mem, mz, mctz);
	if (!res_counter_soft_limit_excess(&mz->mem->res) ||
		!css_tryget(&mz->mem->css))
		goto retry;
done:
	return mz;
}

static struct mem_cgroup_per_zone *
mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
{
	struct mem_cgroup_per_zone *mz;

	spin_lock(&mctz->lock);
	mz = __mem_cgroup_largest_soft_limit_node(mctz);
	spin_unlock(&mctz->lock);
	return mz;
}

/*
 * Implementation Note: reading percpu statistics for memcg.
 *
 * Both of vmstat[] and percpu_counter has threshold and do periodic
 * synchronization to implement "quick" read. There are trade-off between
 * reading cost and precision of value. Then, we may have a chance to implement
 * a periodic synchronizion of counter in memcg's counter.
 *
 * But this _read() function is used for user interface now. The user accounts
 * memory usage by memory cgroup and he _always_ requires exact value because
 * he accounts memory. Even if we provide quick-and-fuzzy read, we always
 * have to visit all online cpus and make sum. So, for now, unnecessary
 * synchronization is not implemented. (just implemented for cpu hotplug)
 *
 * If there are kernel internal actions which can make use of some not-exact
 * value, and reading all cpu value can be performance bottleneck in some
 * common workload, threashold and synchonization as vmstat[] should be
 * implemented.
 */
static long mem_cgroup_read_stat(struct mem_cgroup *mem,
				 enum mem_cgroup_stat_index idx)
{
	long val = 0;
	int cpu;

	get_online_cpus();
	for_each_online_cpu(cpu)
		val += per_cpu(mem->stat->count[idx], cpu);
#ifdef CONFIG_HOTPLUG_CPU
	spin_lock(&mem->pcp_counter_lock);
	val += mem->nocpu_base.count[idx];
	spin_unlock(&mem->pcp_counter_lock);
#endif
	put_online_cpus();
	return val;
}

static void mem_cgroup_swap_statistics(struct mem_cgroup *mem,
					 bool charge)
{
	int val = (charge) ? 1 : -1;
	this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_SWAPOUT], val);
}

void mem_cgroup_pgfault(struct mem_cgroup *mem, int val)
{
	this_cpu_add(mem->stat->events[MEM_CGROUP_EVENTS_PGFAULT], val);
}

void mem_cgroup_pgmajfault(struct mem_cgroup *mem, int val)
{
	this_cpu_add(mem->stat->events[MEM_CGROUP_EVENTS_PGMAJFAULT], val);
}

static unsigned long mem_cgroup_read_events(struct mem_cgroup *mem,
					    enum mem_cgroup_events_index idx)
{
	unsigned long val = 0;
	int cpu;

	for_each_online_cpu(cpu)
		val += per_cpu(mem->stat->events[idx], cpu);
#ifdef CONFIG_HOTPLUG_CPU
	spin_lock(&mem->pcp_counter_lock);
	val += mem->nocpu_base.events[idx];
	spin_unlock(&mem->pcp_counter_lock);
#endif
	return val;
}

static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
					 bool file, int nr_pages)
{
	preempt_disable();

	if (file)
		__this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_CACHE], nr_pages);
	else
		__this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_RSS], nr_pages);

	/* pagein of a big page is an event. So, ignore page size */
	if (nr_pages > 0)
		__this_cpu_inc(mem->stat->events[MEM_CGROUP_EVENTS_PGPGIN]);
	else {
		__this_cpu_inc(mem->stat->events[MEM_CGROUP_EVENTS_PGPGOUT]);
		nr_pages = -nr_pages; /* for event */
	}

	__this_cpu_add(mem->stat->events[MEM_CGROUP_EVENTS_COUNT], nr_pages);

	preempt_enable();
}

static unsigned long
mem_cgroup_get_zonestat_node(struct mem_cgroup *mem, int nid, enum lru_list idx)
{
	struct mem_cgroup_per_zone *mz;
	u64 total = 0;
	int zid;

	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
		mz = mem_cgroup_zoneinfo(mem, nid, zid);
		total += MEM_CGROUP_ZSTAT(mz, idx);
	}
	return total;
}
static unsigned long mem_cgroup_get_local_zonestat(struct mem_cgroup *mem,
					enum lru_list idx)
{
	int nid;
	u64 total = 0;

	for_each_online_node(nid)
		total += mem_cgroup_get_zonestat_node(mem, nid, idx);
	return total;
}

static bool __memcg_event_check(struct mem_cgroup *mem, int target)
{
	unsigned long val, next;

	val = this_cpu_read(mem->stat->events[MEM_CGROUP_EVENTS_COUNT]);
	next = this_cpu_read(mem->stat->targets[target]);
	/* from time_after() in jiffies.h */
	return ((long)next - (long)val < 0);
}

static void __mem_cgroup_target_update(struct mem_cgroup *mem, int target)
{
	unsigned long val, next;

	val = this_cpu_read(mem->stat->events[MEM_CGROUP_EVENTS_COUNT]);

	switch (target) {
	case MEM_CGROUP_TARGET_THRESH:
		next = val + THRESHOLDS_EVENTS_TARGET;
		break;
	case MEM_CGROUP_TARGET_SOFTLIMIT:
		next = val + SOFTLIMIT_EVENTS_TARGET;
		break;
	case MEM_CGROUP_TARGET_NUMAINFO:
		next = val + NUMAINFO_EVENTS_TARGET;
		break;
	default:
		return;
	}

	this_cpu_write(mem->stat->targets[target], next);
}

/*
 * Check events in order.
 *
 */
static void memcg_check_events(struct mem_cgroup *mem, struct page *page)
{
	/* threshold event is triggered in finer grain than soft limit */
	if (unlikely(__memcg_event_check(mem, MEM_CGROUP_TARGET_THRESH))) {
		mem_cgroup_threshold(mem);
		__mem_cgroup_target_update(mem, MEM_CGROUP_TARGET_THRESH);
		if (unlikely(__memcg_event_check(mem,
			     MEM_CGROUP_TARGET_SOFTLIMIT))) {
			mem_cgroup_update_tree(mem, page);
			__mem_cgroup_target_update(mem,
						   MEM_CGROUP_TARGET_SOFTLIMIT);
		}
#if MAX_NUMNODES > 1
		if (unlikely(__memcg_event_check(mem,
			MEM_CGROUP_TARGET_NUMAINFO))) {
			atomic_inc(&mem->numainfo_events);
			__mem_cgroup_target_update(mem,
				MEM_CGROUP_TARGET_NUMAINFO);
		}
#endif
	}
}

static struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
{
	return container_of(cgroup_subsys_state(cont,
				mem_cgroup_subsys_id), struct mem_cgroup,
				css);
}

struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
{
	/*
	 * mm_update_next_owner() may clear mm->owner to NULL
	 * if it races with swapoff, page migration, etc.
	 * So this can be called with p == NULL.
	 */
	if (unlikely(!p))
		return NULL;

	return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
				struct mem_cgroup, css);
}

struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
{
	struct mem_cgroup *mem = NULL;

	if (!mm)
		return NULL;
	/*
	 * Because we have no locks, mm->owner's may be being moved to other
	 * cgroup. We use css_tryget() here even if this looks
	 * pessimistic (rather than adding locks here).
	 */
	rcu_read_lock();
	do {
		mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
		if (unlikely(!mem))
			break;
	} while (!css_tryget(&mem->css));
	rcu_read_unlock();
	return mem;
}

/* The caller has to guarantee "mem" exists before calling this */
static struct mem_cgroup *mem_cgroup_start_loop(struct mem_cgroup *mem)
{
	struct cgroup_subsys_state *css;
	int found;

	if (!mem) /* ROOT cgroup has the smallest ID */
		return root_mem_cgroup; /*css_put/get against root is ignored*/
	if (!mem->use_hierarchy) {
		if (css_tryget(&mem->css))
			return mem;
		return NULL;
	}
	rcu_read_lock();
	/*
	 * searching a memory cgroup which has the smallest ID under given
	 * ROOT cgroup. (ID >= 1)
	 */
	css = css_get_next(&mem_cgroup_subsys, 1, &mem->css, &found);
	if (css && css_tryget(css))
		mem = container_of(css, struct mem_cgroup, css);
	else
		mem = NULL;
	rcu_read_unlock();
	return mem;
}

static struct mem_cgroup *mem_cgroup_get_next(struct mem_cgroup *iter,
					struct mem_cgroup *root,
					bool cond)
{
	int nextid = css_id(&iter->css) + 1;
	int found;
	int hierarchy_used;
	struct cgroup_subsys_state *css;

	hierarchy_used = iter->use_hierarchy;

	css_put(&iter->css);
	/* If no ROOT, walk all, ignore hierarchy */
	if (!cond || (root && !hierarchy_used))
		return NULL;

	if (!root)
		root = root_mem_cgroup;

	do {
		iter = NULL;
		rcu_read_lock();

		css = css_get_next(&mem_cgroup_subsys, nextid,
				&root->css, &found);
		if (css && css_tryget(css))
			iter = container_of(css, struct mem_cgroup, css);
		rcu_read_unlock();
		/* If css is NULL, no more cgroups will be found */
		nextid = found + 1;
	} while (css && !iter);

	return iter;
}
/*
 * for_eacn_mem_cgroup_tree() for visiting all cgroup under tree. Please
 * be careful that "break" loop is not allowed. We have reference count.
 * Instead of that modify "cond" to be false and "continue" to exit the loop.
 */
#define for_each_mem_cgroup_tree_cond(iter, root, cond)	\
	for (iter = mem_cgroup_start_loop(root);\
	     iter != NULL;\
	     iter = mem_cgroup_get_next(iter, root, cond))

#define for_each_mem_cgroup_tree(iter, root) \
	for_each_mem_cgroup_tree_cond(iter, root, true)

#define for_each_mem_cgroup_all(iter) \
	for_each_mem_cgroup_tree_cond(iter, NULL, true)


static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
{
	return (mem == root_mem_cgroup);
}

void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
{
	struct mem_cgroup *mem;

	if (!mm)
		return;

	rcu_read_lock();
	mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
	if (unlikely(!mem))
		goto out;

	switch (idx) {
	case PGMAJFAULT:
		mem_cgroup_pgmajfault(mem, 1);
		break;
	case PGFAULT:
		mem_cgroup_pgfault(mem, 1);
		break;
	default:
		BUG();
	}
out:
	rcu_read_unlock();
}
EXPORT_SYMBOL(mem_cgroup_count_vm_event);

/*
 * Following LRU functions are allowed to be used without PCG_LOCK.
 * Operations are called by routine of global LRU independently from memcg.
 * What we have to take care of here is validness of pc->mem_cgroup.
 *
 * Changes to pc->mem_cgroup happens when
 * 1. charge
 * 2. moving account
 * In typical case, "charge" is done before add-to-lru. Exception is SwapCache.
 * It is added to LRU before charge.
 * If PCG_USED bit is not set, page_cgroup is not added to this private LRU.
 * When moving account, the page is not on LRU. It's isolated.
 */

void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
{
	struct page_cgroup *pc;
	struct mem_cgroup_per_zone *mz;

	if (mem_cgroup_disabled())
		return;
	pc = lookup_page_cgroup(page);
	/* can happen while we handle swapcache. */
	if (!TestClearPageCgroupAcctLRU(pc))
		return;
	VM_BUG_ON(!pc->mem_cgroup);
	/*
	 * We don't check PCG_USED bit. It's cleared when the "page" is finally
	 * removed from global LRU.
	 */
	mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
	/* huge page split is done under lru_lock. so, we have no races. */
	MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
	if (mem_cgroup_is_root(pc->mem_cgroup))
		return;
	VM_BUG_ON(list_empty(&pc->lru));
	list_del_init(&pc->lru);
}

void mem_cgroup_del_lru(struct page *page)
{
	mem_cgroup_del_lru_list(page, page_lru(page));
}

/*
 * Writeback is about to end against a page which has been marked for immediate
 * reclaim.  If it still appears to be reclaimable, move it to the tail of the
 * inactive list.
 */
void mem_cgroup_rotate_reclaimable_page(struct page *page)
{
	struct mem_cgroup_per_zone *mz;
	struct page_cgroup *pc;
	enum lru_list lru = page_lru(page);

	if (mem_cgroup_disabled())
		return;

	pc = lookup_page_cgroup(page);
	/* unused or root page is not rotated. */
	if (!PageCgroupUsed(pc))
		return;
	/* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
	smp_rmb();
	if (mem_cgroup_is_root(pc->mem_cgroup))
		return;
	mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
	list_move_tail(&pc->lru, &mz->lists[lru]);
}

void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru)
{
	struct mem_cgroup_per_zone *mz;
	struct page_cgroup *pc;

	if (mem_cgroup_disabled())
		return;

	pc = lookup_page_cgroup(page);
	/* unused or root page is not rotated. */
	if (!PageCgroupUsed(pc))
		return;
	/* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
	smp_rmb();
	if (mem_cgroup_is_root(pc->mem_cgroup))
		return;
	mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
	list_move(&pc->lru, &mz->lists[lru]);
}

void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
{
	struct page_cgroup *pc;
	struct mem_cgroup_per_zone *mz;

	if (mem_cgroup_disabled())
		return;
	pc = lookup_page_cgroup(page);
	VM_BUG_ON(PageCgroupAcctLRU(pc));
	if (!PageCgroupUsed(pc))
		return;
	/* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
	smp_rmb();
	mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
	/* huge page split is done under lru_lock. so, we have no races. */
	MEM_CGROUP_ZSTAT(mz, lru) += 1 << compound_order(page);
	SetPageCgroupAcctLRU(pc);
	if (mem_cgroup_is_root(pc->mem_cgroup))
		return;
	list_add(&pc->lru, &mz->lists[lru]);
}

/*
 * At handling SwapCache and other FUSE stuff, pc->mem_cgroup may be changed
 * while it's linked to lru because the page may be reused after it's fully
 * uncharged. To handle that, unlink page_cgroup from LRU when charge it again.
 * It's done under lock_page and expected that zone->lru_lock isnever held.
 */
static void mem_cgroup_lru_del_before_commit(struct page *page)
{
	unsigned long flags;
	struct zone *zone = page_zone(page);
	struct page_cgroup *pc = lookup_page_cgroup(page);

	/*
	 * Doing this check without taking ->lru_lock seems wrong but this
	 * is safe. Because if page_cgroup's USED bit is unset, the page
	 * will not be added to any memcg's LRU. If page_cgroup's USED bit is
	 * set, the commit after this will fail, anyway.
	 * This all charge/uncharge is done under some mutual execustion.
	 * So, we don't need to taking care of changes in USED bit.
	 */
	if (likely(!PageLRU(page)))
		return;

	spin_lock_irqsave(&zone->lru_lock, flags);
	/*
	 * Forget old LRU when this page_cgroup is *not* used. This Used bit
	 * is guarded by lock_page() because the page is SwapCache.
	 */
	if (!PageCgroupUsed(pc))
		mem_cgroup_del_lru_list(page, page_lru(page));
	spin_unlock_irqrestore(&zone->lru_lock, flags);
}

static void mem_cgroup_lru_add_after_commit(struct page *page)
{
	unsigned long flags;
	struct zone *zone = page_zone(page);
	struct page_cgroup *pc = lookup_page_cgroup(page);

	/* taking care of that the page is added to LRU while we commit it */
	if (likely(!PageLRU(page)))
		return;
	spin_lock_irqsave(&zone->lru_lock, flags);
	/* link when the page is linked to LRU but page_cgroup isn't */
	if (PageLRU(page) && !PageCgroupAcctLRU(pc))
		mem_cgroup_add_lru_list(page, page_lru(page));
	spin_unlock_irqrestore(&zone->lru_lock, flags);
}


void mem_cgroup_move_lists(struct page *page,
			   enum lru_list from, enum lru_list to)
{
	if (mem_cgroup_disabled())
		return;
	mem_cgroup_del_lru_list(page, from);
	mem_cgroup_add_lru_list(page, to);
}

int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
{
	int ret;
	struct mem_cgroup *curr = NULL;
	struct task_struct *p;

	p = find_lock_task_mm(task);
	if (!p)
		return 0;
	curr = try_get_mem_cgroup_from_mm(p->mm);
	task_unlock(p);
	if (!curr)
		return 0;
	/*
	 * We should check use_hierarchy of "mem" not "curr". Because checking
	 * use_hierarchy of "curr" here make this function true if hierarchy is
	 * enabled in "curr" and "curr" is a child of "mem" in *cgroup*
	 * hierarchy(even if use_hierarchy is disabled in "mem").
	 */
	if (mem->use_hierarchy)
		ret = css_is_ancestor(&curr->css, &mem->css);
	else
		ret = (curr == mem);
	css_put(&curr->css);
	return ret;
}

static int calc_inactive_ratio(struct mem_cgroup *memcg, unsigned long *present_pages)
{
	unsigned long active;
	unsigned long inactive;
	unsigned long gb;
	unsigned long inactive_ratio;

	inactive = mem_cgroup_get_local_zonestat(memcg, LRU_INACTIVE_ANON);
	active = mem_cgroup_get_local_zonestat(memcg, LRU_ACTIVE_ANON);

	gb = (inactive + active) >> (30 - PAGE_SHIFT);
	if (gb)
		inactive_ratio = int_sqrt(10 * gb);
	else
		inactive_ratio = 1;

	if (present_pages) {
		present_pages[0] = inactive;
		present_pages[1] = active;
	}

	return inactive_ratio;
}

int mem_cgroup_inactive_anon_is_low(struct mem_cgroup *memcg)
{
	unsigned long active;
	unsigned long inactive;
	unsigned long present_pages[2];
	unsigned long inactive_ratio;

	inactive_ratio = calc_inactive_ratio(memcg, present_pages);

	inactive = present_pages[0];
	active = present_pages[1];

	if (inactive * inactive_ratio < active)
		return 1;

	return 0;
}

int mem_cgroup_inactive_file_is_low(struct mem_cgroup *memcg)
{
	unsigned long active;
	unsigned long inactive;

	inactive = mem_cgroup_get_local_zonestat(memcg, LRU_INACTIVE_FILE);
	active = mem_cgroup_get_local_zonestat(memcg, LRU_ACTIVE_FILE);

	return (active > inactive);
}

unsigned long mem_cgroup_zone_nr_lru_pages(struct mem_cgroup *memcg,
						struct zone *zone,
						enum lru_list lru)
{
	int nid = zone_to_nid(zone);
	int zid = zone_idx(zone);
	struct mem_cgroup_per_zone *mz = mem_cgroup_zoneinfo(memcg, nid, zid);

	return MEM_CGROUP_ZSTAT(mz, lru);
}

static unsigned long mem_cgroup_node_nr_file_lru_pages(struct mem_cgroup *memcg,
							int nid)
{
	unsigned long ret;

	ret = mem_cgroup_get_zonestat_node(memcg, nid, LRU_INACTIVE_FILE) +
		mem_cgroup_get_zonestat_node(memcg, nid, LRU_ACTIVE_FILE);

	return ret;
}

static unsigned long mem_cgroup_node_nr_anon_lru_pages(struct mem_cgroup *memcg,
							int nid)
{
	unsigned long ret;

	ret = mem_cgroup_get_zonestat_node(memcg, nid, LRU_INACTIVE_ANON) +
		mem_cgroup_get_zonestat_node(memcg, nid, LRU_ACTIVE_ANON);
	return ret;
}

#if MAX_NUMNODES > 1
static unsigned long mem_cgroup_nr_file_lru_pages(struct mem_cgroup *memcg)
{
	u64 total = 0;
	int nid;

	for_each_node_state(nid, N_HIGH_MEMORY)
		total += mem_cgroup_node_nr_file_lru_pages(memcg, nid);

	return total;
}

static unsigned long mem_cgroup_nr_anon_lru_pages(struct mem_cgroup *memcg)
{
	u64 total = 0;
	int nid;

	for_each_node_state(nid, N_HIGH_MEMORY)
		total += mem_cgroup_node_nr_anon_lru_pages(memcg, nid);

	return total;
}

static unsigned long
mem_cgroup_node_nr_unevictable_lru_pages(struct mem_cgroup *memcg, int nid)
{
	return mem_cgroup_get_zonestat_node(memcg, nid, LRU_UNEVICTABLE);
}

static unsigned long
mem_cgroup_nr_unevictable_lru_pages(struct mem_cgroup *memcg)
{
	u64 total = 0;
	int nid;

	for_each_node_state(nid, N_HIGH_MEMORY)
		total += mem_cgroup_node_nr_unevictable_lru_pages(memcg, nid);

	return total;
}

static unsigned long mem_cgroup_node_nr_lru_pages(struct mem_cgroup *memcg,
							int nid)
{
	enum lru_list l;
	u64 total = 0;

	for_each_lru(l)
		total += mem_cgroup_get_zonestat_node(memcg, nid, l);

	return total;
}

static unsigned long mem_cgroup_nr_lru_pages(struct mem_cgroup *memcg)
{
	u64 total = 0;
	int nid;

	for_each_node_state(nid, N_HIGH_MEMORY)
		total += mem_cgroup_node_nr_lru_pages(memcg, nid);

	return total;
}
#endif /* CONFIG_NUMA */

struct zone_reclaim_stat *mem_cgroup_get_reclaim_stat(struct mem_cgroup *memcg,
						      struct zone *zone)
{
	int nid = zone_to_nid(zone);
	int zid = zone_idx(zone);
	struct mem_cgroup_per_zone *mz = mem_cgroup_zoneinfo(memcg, nid, zid);

	return &mz->reclaim_stat;
}

struct zone_reclaim_stat *
mem_cgroup_get_reclaim_stat_from_page(struct page *page)
{
	struct page_cgroup *pc;
	struct mem_cgroup_per_zone *mz;

	if (mem_cgroup_disabled())
		return NULL;

	pc = lookup_page_cgroup(page);
	if (!PageCgroupUsed(pc))
		return NULL;
	/* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
	smp_rmb();
	mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
	return &mz->reclaim_stat;
}

unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
					struct list_head *dst,
					unsigned long *scanned, int order,
					int mode, struct zone *z,
					struct mem_cgroup *mem_cont,
					int active, int file)
{
	unsigned long nr_taken = 0;
	struct page *page;
	unsigned long scan;
	LIST_HEAD(pc_list);
	struct list_head *src;
	struct page_cgroup *pc, *tmp;
	int nid = zone_to_nid(z);
	int zid = zone_idx(z);
	struct mem_cgroup_per_zone *mz;
	int lru = LRU_FILE * file + active;
	int ret;

	BUG_ON(!mem_cont);
	mz = mem_cgroup_zoneinfo(mem_cont, nid, zid);
	src = &mz->lists[lru];

	scan = 0;
	list_for_each_entry_safe_reverse(pc, tmp, src, lru) {
		if (scan >= nr_to_scan)
			break;

		if (unlikely(!PageCgroupUsed(pc)))
			continue;

		page = lookup_cgroup_page(pc);

		if (unlikely(!PageLRU(page)))
			continue;

		scan++;
		ret = __isolate_lru_page(page, mode, file);
		switch (ret) {
		case 0:
			list_move(&page->lru, dst);
			mem_cgroup_del_lru(page);
			nr_taken += hpage_nr_pages(page);
			break;
		case -EBUSY:
			/* we don't affect global LRU but rotate in our LRU */
			mem_cgroup_rotate_lru_list(page, page_lru(page));
			break;
		default:
			break;
		}
	}

	*scanned = scan;

	trace_mm_vmscan_memcg_isolate(0, nr_to_scan, scan, nr_taken,
				      0, 0, 0, mode);

	return nr_taken;
}

#define mem_cgroup_from_res_counter(counter, member)	\
	container_of(counter, struct mem_cgroup, member)

/**
 * mem_cgroup_margin - calculate chargeable space of a memory cgroup
 * @mem: the memory cgroup
 *
 * Returns the maximum amount of memory @mem can be charged with, in
 * pages.
 */
static unsigned long mem_cgroup_margin(struct mem_cgroup *mem)
{
	unsigned long long margin;

	margin = res_counter_margin(&mem->res);
	if (do_swap_account)
		margin = min(margin, res_counter_margin(&mem->memsw));
	return margin >> PAGE_SHIFT;
}

static unsigned int get_swappiness(struct mem_cgroup *memcg)
{
	struct cgroup *cgrp = memcg->css.cgroup;

	/* root ? */
	if (cgrp->parent == NULL)
		return vm_swappiness;

	return memcg->swappiness;
}

static void mem_cgroup_start_move(struct mem_cgroup *mem)
{
	int cpu;

	get_online_cpus();
	spin_lock(&mem->pcp_counter_lock);
	for_each_online_cpu(cpu)
		per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) += 1;
	mem->nocpu_base.count[MEM_CGROUP_ON_MOVE] += 1;
	spin_unlock(&mem->pcp_counter_lock);
	put_online_cpus();

	synchronize_rcu();
}

static void mem_cgroup_end_move(struct mem_cgroup *mem)
{
	int cpu;

	if (!mem)
		return;
	get_online_cpus();
	spin_lock(&mem->pcp_counter_lock);
	for_each_online_cpu(cpu)
		per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) -= 1;
	mem->nocpu_base.count[MEM_CGROUP_ON_MOVE] -= 1;
	spin_unlock(&mem->pcp_counter_lock);
	put_online_cpus();
}
/*
 * 2 routines for checking "mem" is under move_account() or not.
 *
 * mem_cgroup_stealed() - checking a cgroup is mc.from or not. This is used
 *			  for avoiding race in accounting. If true,
 *			  pc->mem_cgroup may be overwritten.
 *
 * mem_cgroup_under_move() - checking a cgroup is mc.from or mc.to or
 *			  under hierarchy of moving cgroups. This is for
 *			  waiting at hith-memory prressure caused by "move".
 */

static bool mem_cgroup_stealed(struct mem_cgroup *mem)
{
	VM_BUG_ON(!rcu_read_lock_held());
	return this_cpu_read(mem->stat->count[MEM_CGROUP_ON_MOVE]) > 0;
}

static bool mem_cgroup_under_move(struct mem_cgroup *mem)
{
	struct mem_cgroup *from;
	struct mem_cgroup *to;
	bool ret = false;
	/*
	 * Unlike task_move routines, we access mc.to, mc.from not under
	 * mutual exclusion by cgroup_mutex. Here, we take spinlock instead.
	 */
	spin_lock(&mc.lock);
	from = mc.from;
	to = mc.to;
	if (!from)
		goto unlock;
	if (from == mem || to == mem
	    || (mem->use_hierarchy && css_is_ancestor(&from->css, &mem->css))
	    || (mem->use_hierarchy && css_is_ancestor(&to->css,	&mem->css)))
		ret = true;
unlock:
	spin_unlock(&mc.lock);
	return ret;
}

static bool mem_cgroup_wait_acct_move(struct mem_cgroup *mem)
{
	if (mc.moving_task && current != mc.moving_task) {
		if (mem_cgroup_under_move(mem)) {
			DEFINE_WAIT(wait);
			prepare_to_wait(&mc.waitq, &wait, TASK_INTERRUPTIBLE);
			/* moving charge context might have finished. */
			if (mc.moving_task)
				schedule();
			finish_wait(&mc.waitq, &wait);
			return true;
		}
	}
	return false;
}

/**
 * mem_cgroup_print_oom_info: Called from OOM with tasklist_lock held in read mode.
 * @memcg: The memory cgroup that went over limit
 * @p: Task that is going to be killed
 *
 * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
 * enabled
 */
void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
{
	struct cgroup *task_cgrp;
	struct cgroup *mem_cgrp;
	/*
	 * Need a buffer in BSS, can't rely on allocations. The code relies
	 * on the assumption that OOM is serialized for memory controller.
	 * If this assumption is broken, revisit this code.
	 */
	static char memcg_name[PATH_MAX];
	int ret;

	if (!memcg || !p)
		return;


	rcu_read_lock();

	mem_cgrp = memcg->css.cgroup;
	task_cgrp = task_cgroup(p, mem_cgroup_subsys_id);

	ret = cgroup_path(task_cgrp, memcg_name, PATH_MAX);
	if (ret < 0) {
		/*
		 * Unfortunately, we are unable to convert to a useful name
		 * But we'll still print out the usage information
		 */
		rcu_read_unlock();
		goto done;
	}
	rcu_read_unlock();

	printk(KERN_INFO "Task in %s killed", memcg_name);

	rcu_read_lock();
	ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
	if (ret < 0) {
		rcu_read_unlock();
		goto done;
	}
	rcu_read_unlock();

	/*
	 * Continues from above, so we don't need an KERN_ level
	 */
	printk(KERN_CONT " as a result of limit of %s\n", memcg_name);
done:

	printk(KERN_INFO "memory: usage %llukB, limit %llukB, failcnt %llu\n",
		res_counter_read_u64(&memcg->res, RES_USAGE) >> 10,
		res_counter_read_u64(&memcg->res, RES_LIMIT) >> 10,
		res_counter_read_u64(&memcg->res, RES_FAILCNT));
	printk(KERN_INFO "memory+swap: usage %llukB, limit %llukB, "
		"failcnt %llu\n",
		res_counter_read_u64(&memcg->memsw, RES_USAGE) >> 10,
		res_counter_read_u64(&memcg->memsw, RES_LIMIT) >> 10,
		res_counter_read_u64(&memcg->memsw, RES_FAILCNT));
}

/*
 * This function returns the number of memcg under hierarchy tree. Returns
 * 1(self count) if no children.
 */
static int mem_cgroup_count_children(struct mem_cgroup *mem)
{
	int num = 0;
	struct mem_cgroup *iter;

	for_each_mem_cgroup_tree(iter, mem)
		num++;
	return num;
}

/*
 * Return the memory (and swap, if configured) limit for a memcg.
 */
u64 mem_cgroup_get_limit(struct mem_cgroup *memcg)
{
	u64 limit;
	u64 memsw;

	limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
	limit += total_swap_pages << PAGE_SHIFT;

	memsw = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
	/*
	 * If memsw is finite and limits the amount of swap space available
	 * to this memcg, return that limit.
	 */
	return min(limit, memsw);
}

/*
 * Visit the first child (need not be the first child as per the ordering
 * of the cgroup list, since we track last_scanned_child) of @mem and use
 * that to reclaim free pages from.
 */
static struct mem_cgroup *
mem_cgroup_select_victim(struct mem_cgroup *root_mem)
{
	struct mem_cgroup *ret = NULL;
	struct cgroup_subsys_state *css;
	int nextid, found;

	if (!root_mem->use_hierarchy) {
		css_get(&root_mem->css);
		ret = root_mem;
	}

	while (!ret) {
		rcu_read_lock();
		nextid = root_mem->last_scanned_child + 1;
		css = css_get_next(&mem_cgroup_subsys, nextid, &root_mem->css,
				   &found);
		if (css && css_tryget(css))
			ret = container_of(css, struct mem_cgroup, css);

		rcu_read_unlock();
		/* Updates scanning parameter */
		if (!css) {
			/* this means start scan from ID:1 */
			root_mem->last_scanned_child = 0;
		} else
			root_mem->last_scanned_child = found;
	}

	return ret;
}

/**
 * test_mem_cgroup_node_reclaimable
 * @mem: the target memcg
 * @nid: the node ID to be checked.
 * @noswap : specify true here if the user wants flle only information.
 *
 * This function returns whether the specified memcg contains any
 * reclaimable pages on a node. Returns true if there are any reclaimable
 * pages in the node.
 */
static bool test_mem_cgroup_node_reclaimable(struct mem_cgroup *mem,
		int nid, bool noswap)
{
	if (mem_cgroup_node_nr_file_lru_pages(mem, nid))
		return true;
	if (noswap || !total_swap_pages)
		return false;
	if (mem_cgroup_node_nr_anon_lru_pages(mem, nid))
		return true;
	return false;

}
#if MAX_NUMNODES > 1

/*
 * Always updating the nodemask is not very good - even if we have an empty
 * list or the wrong list here, we can start from some node and traverse all
 * nodes based on the zonelist. So update the list loosely once per 10 secs.
 *
 */
static void mem_cgroup_may_update_nodemask(struct mem_cgroup *mem)
{
	int nid;
	/*
	 * numainfo_events > 0 means there was at least NUMAINFO_EVENTS_TARGET
	 * pagein/pageout changes since the last update.
	 */
	if (!atomic_read(&mem->numainfo_events))
		return;
	if (atomic_inc_return(&mem->numainfo_updating) > 1)
		return;

	/* make a nodemask where this memcg uses memory from */
	mem->scan_nodes = node_states[N_HIGH_MEMORY];

	for_each_node_mask(nid, node_states[N_HIGH_MEMORY]) {

		if (!test_mem_cgroup_node_reclaimable(mem, nid, false))
			node_clear(nid, mem->scan_nodes);
	}

	atomic_set(&mem->numainfo_events, 0);
	atomic_set(&mem->numainfo_updating, 0);
}

/*
 * Selecting a node where we start reclaim from. Because what we need is just
 * reducing usage counter, start from anywhere is O,K. Considering
 * memory reclaim from current node, there are pros. and cons.
 *
 * Freeing memory from current node means freeing memory from a node which
 * we'll use or we've used. So, it may make LRU bad. And if several threads
 * hit limits, it will see a contention on a node. But freeing from remote
 * node means more costs for memory reclaim because of memory latency.
 *
 * Now, we use round-robin. Better algorithm is welcomed.
 */
int mem_cgroup_select_victim_node(struct mem_cgroup *mem)
{
	int node;

	mem_cgroup_may_update_nodemask(mem);
	node = mem->last_scanned_node;

	node = next_node(node, mem->scan_nodes);
	if (node == MAX_NUMNODES)
		node = first_node(mem->scan_nodes);
	/*
	 * We call this when we hit limit, not when pages are added to LRU.
	 * No LRU may hold pages because all pages are UNEVICTABLE or
	 * memcg is too small and all pages are not on LRU. In that case,
	 * we use curret node.
	 */
	if (unlikely(node == MAX_NUMNODES))
		node = numa_node_id();

	mem->last_scanned_node = node;
	return node;
}

/*
 * Check all nodes whether it contains reclaimable pages or not.
 * For quick scan, we make use of scan_nodes. This will allow us to skip
 * unused nodes. But scan_nodes is lazily updated and may not cotain
 * enough new information. We need to do double check.
 */
bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
{
	int nid;

	/*
	 * quick check...making use of scan_node.
	 * We can skip unused nodes.
	 */
	if (!nodes_empty(mem->scan_nodes)) {
		for (nid = first_node(mem->scan_nodes);
		     nid < MAX_NUMNODES;
		     nid = next_node(nid, mem->scan_nodes)) {

			if (test_mem_cgroup_node_reclaimable(mem, nid, noswap))
				return true;
		}
	}
	/*
	 * Check rest of nodes.
	 */
	for_each_node_state(nid, N_HIGH_MEMORY) {
		if (node_isset(nid, mem->scan_nodes))
			continue;
		if (test_mem_cgroup_node_reclaimable(mem, nid, noswap))
			return true;
	}
	return false;
}

#else
int mem_cgroup_select_victim_node(struct mem_cgroup *mem)
{
	return 0;
}

bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
{
	return test_mem_cgroup_node_reclaimable(mem, 0, noswap);
}
#endif

/*
 * Scan the hierarchy if needed to reclaim memory. We remember the last child
 * we reclaimed from, so that we don't end up penalizing one child extensively
 * based on its position in the children list.
 *
 * root_mem is the original ancestor that we've been reclaim from.
 *
 * We give up and return to the caller when we visit root_mem twice.
 * (other groups can be removed while we're walking....)
 *
 * If shrink==true, for avoiding to free too much, this returns immedieately.
 */
static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
						struct zone *zone,
						gfp_t gfp_mask,
						unsigned long reclaim_options,
						unsigned long *total_scanned)
{
	struct mem_cgroup *victim;
	int ret, total = 0;
	int loop = 0;
	bool noswap = reclaim_options & MEM_CGROUP_RECLAIM_NOSWAP;
	bool shrink = reclaim_options & MEM_CGROUP_RECLAIM_SHRINK;
	bool check_soft = reclaim_options & MEM_CGROUP_RECLAIM_SOFT;
	unsigned long excess;
	unsigned long nr_scanned;

	excess = res_counter_soft_limit_excess(&root_mem->res) >> PAGE_SHIFT;

	/* If memsw_is_minimum==1, swap-out is of-no-use. */
	if (!check_soft && root_mem->memsw_is_minimum)
		noswap = true;

	while (1) {
		victim = mem_cgroup_select_victim(root_mem);
		if (victim == root_mem) {
			loop++;
			/*
			 * We are not draining per cpu cached charges during
			 * soft limit reclaim  because global reclaim doesn't
			 * care about charges. It tries to free some memory and
			 * charges will not give any.
			 */
			if (!check_soft && loop >= 1)
				drain_all_stock_async(root_mem);
			if (loop >= 2) {
				/*
				 * If we have not been able to reclaim
				 * anything, it might because there are
				 * no reclaimable pages under this hierarchy
				 */
				if (!check_soft || !total) {
					css_put(&victim->css);
					break;
				}
				/*
				 * We want to do more targeted reclaim.
				 * excess >> 2 is not to excessive so as to
				 * reclaim too much, nor too less that we keep
				 * coming back to reclaim from this cgroup
				 */
				if (total >= (excess >> 2) ||
					(loop > MEM_CGROUP_MAX_RECLAIM_LOOPS)) {
					css_put(&victim->css);
					break;
				}
			}
		}
		if (!mem_cgroup_reclaimable(victim, noswap)) {
			/* this cgroup's local usage == 0 */
			css_put(&victim->css);
			continue;
		}
		/* we use swappiness of local cgroup */
		if (check_soft) {
			ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,
				noswap, get_swappiness(victim), zone,
				&nr_scanned);
			*total_scanned += nr_scanned;
		} else
			ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
						noswap, get_swappiness(victim));
		css_put(&victim->css);
		/*
		 * At shrinking usage, we can't check we should stop here or
		 * reclaim more. It's depends on callers. last_scanned_child
		 * will work enough for keeping fairness under tree.
		 */
		if (shrink)
			return ret;
		total += ret;
		if (check_soft) {
			if (!res_counter_soft_limit_excess(&root_mem->res))
				return total;
		} else if (mem_cgroup_margin(root_mem))
			return total;
	}
	return total;
}

/*
 * Check OOM-Killer is already running under our hierarchy.
 * If someone is running, return false.
 */
static bool mem_cgroup_oom_lock(struct mem_cgroup *mem)
{
	int x, lock_count = 0;
	struct mem_cgroup *iter;

	for_each_mem_cgroup_tree(iter, mem) {
		x = atomic_inc_return(&iter->oom_lock);
		lock_count = max(x, lock_count);
	}

	if (lock_count == 1)
		return true;
	return false;
}

static int mem_cgroup_oom_unlock(struct mem_cgroup *mem)
{
	struct mem_cgroup *iter;

	/*
	 * When a new child is created while the hierarchy is under oom,
	 * mem_cgroup_oom_lock() may not be called. We have to use
	 * atomic_add_unless() here.
	 */
	for_each_mem_cgroup_tree(iter, mem)
		atomic_add_unless(&iter->oom_lock, -1, 0);
	return 0;
}


static DEFINE_MUTEX(memcg_oom_mutex);
static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);

struct oom_wait_info {
	struct mem_cgroup *mem;
	wait_queue_t	wait;
};

static int memcg_oom_wake_function(wait_queue_t *wait,
	unsigned mode, int sync, void *arg)
{
	struct mem_cgroup *wake_mem = (struct mem_cgroup *)arg;
	struct oom_wait_info *oom_wait_info;

	oom_wait_info = container_of(wait, struct oom_wait_info, wait);

	if (oom_wait_info->mem == wake_mem)
		goto wakeup;
	/* if no hierarchy, no match */
	if (!oom_wait_info->mem->use_hierarchy || !wake_mem->use_hierarchy)
		return 0;
	/*
	 * Both of oom_wait_info->mem and wake_mem are stable under us.
	 * Then we can use css_is_ancestor without taking care of RCU.
	 */
	if (!css_is_ancestor(&oom_wait_info->mem->css, &wake_mem->css) &&
	    !css_is_ancestor(&wake_mem->css, &oom_wait_info->mem->css))
		return 0;

wakeup:
	return autoremove_wake_function(wait, mode, sync, arg);
}

static void memcg_wakeup_oom(struct mem_cgroup *mem)
{
	/* for filtering, pass "mem" as argument. */
	__wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, mem);
}

static void memcg_oom_recover(struct mem_cgroup *mem)
{
	if (mem && atomic_read(&mem->oom_lock))
		memcg_wakeup_oom(mem);
}

/*
 * try to call OOM killer. returns false if we should exit memory-reclaim loop.
 */
bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
{
	struct oom_wait_info owait;
	bool locked, need_to_kill;

	owait.mem = mem;
	owait.wait.flags = 0;
	owait.wait.func = memcg_oom_wake_function;
	owait.wait.private = current;
	INIT_LIST_HEAD(&owait.wait.task_list);
	need_to_kill = true;
	/* At first, try to OOM lock hierarchy under mem.*/
	mutex_lock(&memcg_oom_mutex);
	locked = mem_cgroup_oom_lock(mem);
	/*
	 * Even if signal_pending(), we can't quit charge() loop without
	 * accounting. So, UNINTERRUPTIBLE is appropriate. But SIGKILL
	 * under OOM is always welcomed, use TASK_KILLABLE here.
	 */
	prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
	if (!locked || mem->oom_kill_disable)
		need_to_kill = false;
	if (locked)
		mem_cgroup_oom_notify(mem);
	mutex_unlock(&memcg_oom_mutex);

	if (need_to_kill) {
		finish_wait(&memcg_oom_waitq, &owait.wait);
		mem_cgroup_out_of_memory(mem, mask);
	} else {
		schedule();
		finish_wait(&memcg_oom_waitq, &owait.wait);
	}
	mutex_lock(&memcg_oom_mutex);
	mem_cgroup_oom_unlock(mem);
	memcg_wakeup_oom(mem);
	mutex_unlock(&memcg_oom_mutex);

	if (test_thread_flag(TIF_MEMDIE) || fatal_signal_pending(current))
		return false;
	/* Give chance to dying process */
	schedule_timeout(1);
	return true;
}

/*
 * Currently used to update mapped file statistics, but the routine can be
 * generalized to update other statistics as well.
 *
 * Notes: Race condition
 *
 * We usually use page_cgroup_lock() for accessing page_cgroup member but
 * it tends to be costly. But considering some conditions, we doesn't need
 * to do so _always_.
 *
 * Considering "charge", lock_page_cgroup() is not required because all
 * file-stat operations happen after a page is attached to radix-tree. There
 * are no race with "charge".
 *
 * Considering "uncharge", we know that memcg doesn't clear pc->mem_cgroup
 * at "uncharge" intentionally. So, we always see valid pc->mem_cgroup even
 * if there are race with "uncharge". Statistics itself is properly handled
 * by flags.
 *
 * Considering "move", this is an only case we see a race. To make the race
 * small, we check MEM_CGROUP_ON_MOVE percpu value and detect there are
 * possibility of race condition. If there is, we take a lock.
 */

void mem_cgroup_update_page_stat(struct page *page,
				 enum mem_cgroup_page_stat_item idx, int val)
{
	struct mem_cgroup *mem;
	struct page_cgroup *pc = lookup_page_cgroup(page);
	bool need_unlock = false;
	unsigned long uninitialized_var(flags);

	if (unlikely(!pc))
		return;

	rcu_read_lock();
	mem = pc->mem_cgroup;
	if (unlikely(!mem || !PageCgroupUsed(pc)))
		goto out;
	/* pc->mem_cgroup is unstable ? */
	if (unlikely(mem_cgroup_stealed(mem)) || PageTransHuge(page)) {
		/* take a lock against to access pc->mem_cgroup */
		move_lock_page_cgroup(pc, &flags);
		need_unlock = true;
		mem = pc->mem_cgroup;
		if (!mem || !PageCgroupUsed(pc))
			goto out;
	}

	switch (idx) {
	case MEMCG_NR_FILE_MAPPED:
		if (val > 0)
			SetPageCgroupFileMapped(pc);
		else if (!page_mapped(page))
			ClearPageCgroupFileMapped(pc);
		idx = MEM_CGROUP_STAT_FILE_MAPPED;
		break;
	default:
		BUG();
	}

	this_cpu_add(mem->stat->count[idx], val);

out:
	if (unlikely(need_unlock))
		move_unlock_page_cgroup(pc, &flags);
	rcu_read_unlock();
	return;
}
EXPORT_SYMBOL(mem_cgroup_update_page_stat);

/*
 * size of first charge trial. "32" comes from vmscan.c's magic value.
 * TODO: maybe necessary to use big numbers in big irons.
 */
#define CHARGE_BATCH	32U
struct memcg_stock_pcp {
	struct mem_cgroup *cached; /* this never be root cgroup */
	unsigned int nr_pages;
	struct work_struct work;
	unsigned long flags;
#define FLUSHING_CACHED_CHARGE	(0)
};
static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
static DEFINE_MUTEX(percpu_charge_mutex);

/*
 * Try to consume stocked charge on this cpu. If success, one page is consumed
 * from local stock and true is returned. If the stock is 0 or charges from a
 * cgroup which is not current target, returns false. This stock will be
 * refilled.
 */
static bool consume_stock(struct mem_cgroup *mem)
{
	struct memcg_stock_pcp *stock;
	bool ret = true;

	stock = &get_cpu_var(memcg_stock);
	if (mem == stock->cached && stock->nr_pages)
		stock->nr_pages--;
	else /* need to call res_counter_charge */
		ret = false;
	put_cpu_var(memcg_stock);
	return ret;
}

/*
 * Returns stocks cached in percpu to res_counter and reset cached information.
 */
static void drain_stock(struct memcg_stock_pcp *stock)
{
	struct mem_cgroup *old = stock->cached;

	if (stock->nr_pages) {
		unsigned long bytes = stock->nr_pages * PAGE_SIZE;

		res_counter_uncharge(&old->res, bytes);
		if (do_swap_account)
			res_counter_uncharge(&old->memsw, bytes);
		stock->nr_pages = 0;
	}
	stock->cached = NULL;
}

/*
 * This must be called under preempt disabled or must be called by
 * a thread which is pinned to local cpu.
 */
static void drain_local_stock(struct work_struct *dummy)
{
	struct memcg_stock_pcp *stock = &__get_cpu_var(memcg_stock);
	drain_stock(stock);
	clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
}

/*
 * Cache charges(val) which is from res_counter, to local per_cpu area.
 * This will be consumed by consume_stock() function, later.
 */
static void refill_stock(struct mem_cgroup *mem, unsigned int nr_pages)
{
	struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock);

	if (stock->cached != mem) { /* reset if necessary */
		drain_stock(stock);
		stock->cached = mem;
	}
	stock->nr_pages += nr_pages;
	put_cpu_var(memcg_stock);
}

/*
 * Tries to drain stocked charges in other cpus. This function is asynchronous
 * and just put a work per cpu for draining localy on each cpu. Caller can
 * expects some charges will be back to res_counter later but cannot wait for
 * it.
 */
static void drain_all_stock_async(struct mem_cgroup *root_mem)
{
	int cpu, curcpu;
	/*
	 * If someone calls draining, avoid adding more kworker runs.
	 */
	if (!mutex_trylock(&percpu_charge_mutex))
		return;
	/* Notify other cpus that system-wide "drain" is running */
	get_online_cpus();
	/*
	 * Get a hint for avoiding draining charges on the current cpu,
	 * which must be exhausted by our charging.  It is not required that
	 * this be a precise check, so we use raw_smp_processor_id() instead of
	 * getcpu()/putcpu().
	 */
	curcpu = raw_smp_processor_id();
	for_each_online_cpu(cpu) {
		struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
		struct mem_cgroup *mem;

		if (cpu == curcpu)
			continue;

		mem = stock->cached;
		if (!mem)
			continue;
		if (mem != root_mem) {
			if (!root_mem->use_hierarchy)
				continue;
			/* check whether "mem" is under tree of "root_mem" */
			if (!css_is_ancestor(&mem->css, &root_mem->css))
				continue;
		}
		if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags))
			schedule_work_on(cpu, &stock->work);
	}
 	put_online_cpus();
	mutex_unlock(&percpu_charge_mutex);
	/* We don't wait for flush_work */
}

/* This is a synchronous drain interface. */
static void drain_all_stock_sync(void)
{
	/* called when force_empty is called */
	mutex_lock(&percpu_charge_mutex);
	schedule_on_each_cpu(drain_local_stock);
	mutex_unlock(&percpu_charge_mutex);
}

/*
 * This function drains percpu counter value from DEAD cpu and
 * move it to local cpu. Note that this function can be preempted.
 */
static void mem_cgroup_drain_pcp_counter(struct mem_cgroup *mem, int cpu)
{
	int i;

	spin_lock(&mem->pcp_counter_lock);
	for (i = 0; i < MEM_CGROUP_STAT_DATA; i++) {
		long x = per_cpu(mem->stat->count[i], cpu);

		per_cpu(mem->stat->count[i], cpu) = 0;
		mem->nocpu_base.count[i] += x;
	}
	for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++) {
		unsigned long x = per_cpu(mem->stat->events[i], cpu);

		per_cpu(mem->stat->events[i], cpu) = 0;
		mem->nocpu_base.events[i] += x;
	}
	/* need to clear ON_MOVE value, works as a kind of lock. */
	per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) = 0;
	spin_unlock(&mem->pcp_counter_lock);
}

static void synchronize_mem_cgroup_on_move(struct mem_cgroup *mem, int cpu)
{
	int idx = MEM_CGROUP_ON_MOVE;

	spin_lock(&mem->pcp_counter_lock);
	per_cpu(mem->stat->count[idx], cpu) = mem->nocpu_base.count[idx];
	spin_unlock(&mem->pcp_counter_lock);
}

static int __cpuinit memcg_cpu_hotplug_callback(struct notifier_block *nb,
					unsigned long action,
					void *hcpu)
{
	int cpu = (unsigned long)hcpu;
	struct memcg_stock_pcp *stock;
	struct mem_cgroup *iter;

	if ((action == CPU_ONLINE)) {
		for_each_mem_cgroup_all(iter)
			synchronize_mem_cgroup_on_move(iter, cpu);
		return NOTIFY_OK;
	}

	if ((action != CPU_DEAD) || action != CPU_DEAD_FROZEN)
		return NOTIFY_OK;

	for_each_mem_cgroup_all(iter)
		mem_cgroup_drain_pcp_counter(iter, cpu);

	stock = &per_cpu(memcg_stock, cpu);
	drain_stock(stock);
	return NOTIFY_OK;
}


/* See __mem_cgroup_try_charge() for details */
enum {
	CHARGE_OK,		/* success */
	CHARGE_RETRY,		/* need to retry but retry is not bad */
	CHARGE_NOMEM,		/* we can't do more. return -ENOMEM */
	CHARGE_WOULDBLOCK,	/* GFP_WAIT wasn't set and no enough res. */
	CHARGE_OOM_DIE,		/* the current is killed because of OOM */
};

static int mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,
				unsigned int nr_pages, bool oom_check)
{
	unsigned long csize = nr_pages * PAGE_SIZE;
	struct mem_cgroup *mem_over_limit;
	struct res_counter *fail_res;
	unsigned long flags = 0;
	int ret;

	ret = res_counter_charge(&mem->res, csize, &fail_res);

	if (likely(!ret)) {
		if (!do_swap_account)
			return CHARGE_OK;
		ret = res_counter_charge(&mem->memsw, csize, &fail_res);
		if (likely(!ret))
			return CHARGE_OK;

		res_counter_uncharge(&mem->res, csize);
		mem_over_limit = mem_cgroup_from_res_counter(fail_res, memsw);
		flags |= MEM_CGROUP_RECLAIM_NOSWAP;
	} else
		mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
	/*
	 * nr_pages can be either a huge page (HPAGE_PMD_NR), a batch
	 * of regular pages (CHARGE_BATCH), or a single regular page (1).
	 *
	 * Never reclaim on behalf of optional batching, retry with a
	 * single page instead.
	 */
	if (nr_pages == CHARGE_BATCH)
		return CHARGE_RETRY;

	if (!(gfp_mask & __GFP_WAIT))
		return CHARGE_WOULDBLOCK;

	ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, NULL,
					      gfp_mask, flags, NULL);
	if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
		return CHARGE_RETRY;
	/*
	 * Even though the limit is exceeded at this point, reclaim
	 * may have been able to free some pages.  Retry the charge
	 * before killing the task.
	 *
	 * Only for regular pages, though: huge pages are rather
	 * unlikely to succeed so close to the limit, and we fall back
	 * to regular pages anyway in case of failure.
	 */
	if (nr_pages == 1 && ret)
		return CHARGE_RETRY;

	/*
	 * At task move, charge accounts can be doubly counted. So, it's
	 * better to wait until the end of task_move if something is going on.
	 */
	if (mem_cgroup_wait_acct_move(mem_over_limit))
		return CHARGE_RETRY;

	/* If we don't need to call oom-killer at el, return immediately */
	if (!oom_check)
		return CHARGE_NOMEM;
	/* check OOM */
	if (!mem_cgroup_handle_oom(mem_over_limit, gfp_mask))
		return CHARGE_OOM_DIE;

	return CHARGE_RETRY;
}

/*
 * Unlike exported interface, "oom" parameter is added. if oom==true,
 * oom-killer can be invoked.
 */
static int __mem_cgroup_try_charge(struct mm_struct *mm,
				   gfp_t gfp_mask,
				   unsigned int nr_pages,
				   struct mem_cgroup **memcg,
				   bool oom)
{
	unsigned int batch = max(CHARGE_BATCH, nr_pages);
	int nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
	struct mem_cgroup *mem = NULL;
	int ret;

	/*
	 * Unlike gloval-vm's OOM-kill, we're not in memory shortage
	 * in system level. So, allow to go ahead dying process in addition to
	 * MEMDIE process.
	 */
	if (unlikely(test_thread_flag(TIF_MEMDIE)
		     || fatal_signal_pending(current)))
		goto bypass;

	/*
	 * We always charge the cgroup the mm_struct belongs to.
	 * The mm_struct's mem_cgroup changes on task migration if the
	 * thread group leader migrates. It's possible that mm is not
	 * set, if so charge the init_mm (happens for pagecache usage).
	 */
	if (!*memcg && !mm)
		goto bypass;
again:
	if (*memcg) { /* css should be a valid one */
		mem = *memcg;
		VM_BUG_ON(css_is_removed(&mem->css));
		if (mem_cgroup_is_root(mem))
			goto done;
		if (nr_pages == 1 && consume_stock(mem))
			goto done;
		css_get(&mem->css);
	} else {
		struct task_struct *p;

		rcu_read_lock();
		p = rcu_dereference(mm->owner);
		/*
		 * Because we don't have task_lock(), "p" can exit.
		 * In that case, "mem" can point to root or p can be NULL with
		 * race with swapoff. Then, we have small risk of mis-accouning.
		 * But such kind of mis-account by race always happens because
		 * we don't have cgroup_mutex(). It's overkill and we allo that
		 * small race, here.
		 * (*) swapoff at el will charge against mm-struct not against
		 * task-struct. So, mm->owner can be NULL.
		 */
		mem = mem_cgroup_from_task(p);
		if (!mem || mem_cgroup_is_root(mem)) {
			rcu_read_unlock();
			goto done;
		}
		if (nr_pages == 1 && consume_stock(mem)) {
			/*
			 * It seems dagerous to access memcg without css_get().
			 * But considering how consume_stok works, it's not
			 * necessary. If consume_stock success, some charges
			 * from this memcg are cached on this cpu. So, we
			 * don't need to call css_get()/css_tryget() before
			 * calling consume_stock().
			 */
			rcu_read_unlock();
			goto done;
		}
		/* after here, we may be blocked. we need to get refcnt */
		if (!css_tryget(&mem->css)) {
			rcu_read_unlock();
			goto again;
		}
		rcu_read_unlock();
	}

	do {
		bool oom_check;

		/* If killed, bypass charge */
		if (fatal_signal_pending(current)) {
			css_put(&mem->css);
			goto bypass;
		}

		oom_check = false;
		if (oom && !nr_oom_retries) {
			oom_check = true;
			nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
		}

		ret = mem_cgroup_do_charge(mem, gfp_mask, batch, oom_check);
		switch (ret) {
		case CHARGE_OK:
			break;
		case CHARGE_RETRY: /* not in OOM situation but retry */
			batch = nr_pages;
			css_put(&mem->css);
			mem = NULL;
			goto again;
		case CHARGE_WOULDBLOCK: /* !__GFP_WAIT */
			css_put(&mem->css);
			goto nomem;
		case CHARGE_NOMEM: /* OOM routine works */
			if (!oom) {
				css_put(&mem->css);
				goto nomem;
			}
			/* If oom, we never return -ENOMEM */
			nr_oom_retries--;
			break;
		case CHARGE_OOM_DIE: /* Killed by OOM Killer */
			css_put(&mem->css);
			goto bypass;
		}
	} while (ret != CHARGE_OK);

	if (batch > nr_pages)
		refill_stock(mem, batch - nr_pages);
	css_put(&mem->css);
done:
	*memcg = mem;
	return 0;
nomem:
	*memcg = NULL;
	return -ENOMEM;
bypass:
	*memcg = NULL;
	return 0;
}

/*
 * Somemtimes we have to undo a charge we got by try_charge().
 * This function is for that and do uncharge, put css's refcnt.
 * gotten by try_charge().
 */
static void __mem_cgroup_cancel_charge(struct mem_cgroup *mem,
				       unsigned int nr_pages)
{
	if (!mem_cgroup_is_root(mem)) {
		unsigned long bytes = nr_pages * PAGE_SIZE;

		res_counter_uncharge(&mem->res, bytes);
		if (do_swap_account)
			res_counter_uncharge(&mem->memsw, bytes);
	}
}

/*
 * A helper function to get mem_cgroup from ID. must be called under
 * rcu_read_lock(). The caller must check css_is_removed() or some if
 * it's concern. (dropping refcnt from swap can be called against removed
 * memcg.)
 */
static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
{
	struct cgroup_subsys_state *css;

	/* ID 0 is unused ID */
	if (!id)
		return NULL;
	css = css_lookup(&mem_cgroup_subsys, id);
	if (!css)
		return NULL;
	return container_of(css, struct mem_cgroup, css);
}

struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
{
	struct mem_cgroup *mem = NULL;
	struct page_cgroup *pc;
	unsigned short id;
	swp_entry_t ent;

	VM_BUG_ON(!PageLocked(page));

	pc = lookup_page_cgroup(page);
	lock_page_cgroup(pc);
	if (PageCgroupUsed(pc)) {
		mem = pc->mem_cgroup;
		if (mem && !css_tryget(&mem->css))
			mem = NULL;
	} else if (PageSwapCache(page)) {
		ent.val = page_private(page);
		id = lookup_swap_cgroup(ent);
		rcu_read_lock();
		mem = mem_cgroup_lookup(id);
		if (mem && !css_tryget(&mem->css))
			mem = NULL;
		rcu_read_unlock();
	}
	unlock_page_cgroup(pc);
	return mem;
}

static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
				       struct page *page,
				       unsigned int nr_pages,
				       struct page_cgroup *pc,
				       enum charge_type ctype)
{
	lock_page_cgroup(pc);
	if (unlikely(PageCgroupUsed(pc))) {
		unlock_page_cgroup(pc);
		__mem_cgroup_cancel_charge(mem, nr_pages);
		return;
	}
	/*
	 * we don't need page_cgroup_lock about tail pages, becase they are not
	 * accessed by any other context at this point.
	 */
	pc->mem_cgroup = mem;
	/*
	 * We access a page_cgroup asynchronously without lock_page_cgroup().
	 * Especially when a page_cgroup is taken from a page, pc->mem_cgroup
	 * is accessed after testing USED bit. To make pc->mem_cgroup visible
	 * before USED bit, we need memory barrier here.
	 * See mem_cgroup_add_lru_list(), etc.
 	 */
	smp_wmb();
	switch (ctype) {
	case MEM_CGROUP_CHARGE_TYPE_CACHE:
	case MEM_CGROUP_CHARGE_TYPE_SHMEM:
		SetPageCgroupCache(pc);
		SetPageCgroupUsed(pc);
		break;
	case MEM_CGROUP_CHARGE_TYPE_MAPPED:
		ClearPageCgroupCache(pc);
		SetPageCgroupUsed(pc);
		break;
	default:
		break;
	}

	mem_cgroup_charge_statistics(mem, PageCgroupCache(pc), nr_pages);
	unlock_page_cgroup(pc);
	/*
	 * "charge_statistics" updated event counter. Then, check it.
	 * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
	 * if they exceeds softlimit.
	 */
	memcg_check_events(mem, page);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE

#define PCGF_NOCOPY_AT_SPLIT ((1 << PCG_LOCK) | (1 << PCG_MOVE_LOCK) |\
			(1 << PCG_ACCT_LRU) | (1 << PCG_MIGRATION))
/*
 * Because tail pages are not marked as "used", set it. We're under
 * zone->lru_lock, 'splitting on pmd' and compund_lock.
 */
void mem_cgroup_split_huge_fixup(struct page *head, struct page *tail)
{
	struct page_cgroup *head_pc = lookup_page_cgroup(head);
	struct page_cgroup *tail_pc = lookup_page_cgroup(tail);
	unsigned long flags;

	if (mem_cgroup_disabled())
		return;
	/*
	 * We have no races with charge/uncharge but will have races with
	 * page state accounting.
	 */
	move_lock_page_cgroup(head_pc, &flags);

	tail_pc->mem_cgroup = head_pc->mem_cgroup;
	smp_wmb(); /* see __commit_charge() */
	if (PageCgroupAcctLRU(head_pc)) {
		enum lru_list lru;
		struct mem_cgroup_per_zone *mz;

		/*
		 * LRU flags cannot be copied because we need to add tail
		 *.page to LRU by generic call and our hook will be called.
		 * We hold lru_lock, then, reduce counter directly.
		 */
		lru = page_lru(head);
		mz = page_cgroup_zoneinfo(head_pc->mem_cgroup, head);
		MEM_CGROUP_ZSTAT(mz, lru) -= 1;
	}
	tail_pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
	move_unlock_page_cgroup(head_pc, &flags);
}
#endif

/**
 * mem_cgroup_move_account - move account of the page
 * @page: the page
 * @nr_pages: number of regular pages (>1 for huge pages)
 * @pc:	page_cgroup of the page.
 * @from: mem_cgroup which the page is moved from.
 * @to:	mem_cgroup which the page is moved to. @from != @to.
 * @uncharge: whether we should call uncharge and css_put against @from.
 *
 * The caller must confirm following.
 * - page is not on LRU (isolate_page() is useful.)
 * - compound_lock is held when nr_pages > 1
 *
 * This function doesn't do "charge" nor css_get to new cgroup. It should be
 * done by a caller(__mem_cgroup_try_charge would be useful). If @uncharge is
 * true, this function does "uncharge" from old cgroup, but it doesn't if
 * @uncharge is false, so a caller should do "uncharge".
 */
static int mem_cgroup_move_account(struct page *page,
				   unsigned int nr_pages,
				   struct page_cgroup *pc,
				   struct mem_cgroup *from,
				   struct mem_cgroup *to,
				   bool uncharge)
{
	unsigned long flags;
	int ret;

	VM_BUG_ON(from == to);
	VM_BUG_ON(PageLRU(page));
	/*
	 * The page is isolated from LRU. So, collapse function
	 * will not handle this page. But page splitting can happen.
	 * Do this check under compound_page_lock(). The caller should
	 * hold it.
	 */
	ret = -EBUSY;
	if (nr_pages > 1 && !PageTransHuge(page))
		goto out;

	lock_page_cgroup(pc);

	ret = -EINVAL;
	if (!PageCgroupUsed(pc) || pc->mem_cgroup != from)
		goto unlock;

	move_lock_page_cgroup(pc, &flags);

	if (PageCgroupFileMapped(pc)) {
		/* Update mapped_file data for mem_cgroup */
		preempt_disable();
		__this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
		__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
		preempt_enable();
	}
	mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -nr_pages);
	if (uncharge)
		/* This is not "cancel", but cancel_charge does all we need. */
		__mem_cgroup_cancel_charge(from, nr_pages);

	/* caller should have done css_get */
	pc->mem_cgroup = to;
	mem_cgroup_charge_statistics(to, PageCgroupCache(pc), nr_pages);
	/*
	 * We charges against "to" which may not have any tasks. Then, "to"
	 * can be under rmdir(). But in current implementation, caller of
	 * this function is just force_empty() and move charge, so it's
	 * guaranteed that "to" is never removed. So, we don't check rmdir
	 * status here.
	 */
	move_unlock_page_cgroup(pc, &flags);
	ret = 0;
unlock:
	unlock_page_cgroup(pc);
	/*
	 * check events
	 */
	memcg_check_events(to, page);
	memcg_check_events(from, page);
out:
	return ret;
}

/*
 * move charges to its parent.
 */

static int mem_cgroup_move_parent(struct page *page,
				  struct page_cgroup *pc,
				  struct mem_cgroup *child,
				  gfp_t gfp_mask)
{
	struct cgroup *cg = child->css.cgroup;
	struct cgroup *pcg = cg->parent;
	struct mem_cgroup *parent;
	unsigned int nr_pages;
	unsigned long uninitialized_var(flags);
	int ret;

	/* Is ROOT ? */
	if (!pcg)
		return -EINVAL;

	ret = -EBUSY;
	if (!get_page_unless_zero(page))
		goto out;
	if (isolate_lru_page(page))
		goto put;

	nr_pages = hpage_nr_pages(page);

	parent = mem_cgroup_from_cont(pcg);
	ret = __mem_cgroup_try_charge(NULL, gfp_mask, nr_pages, &parent, false);
	if (ret || !parent)
		goto put_back;

	if (nr_pages > 1)
		flags = compound_lock_irqsave(page);

	ret = mem_cgroup_move_account(page, nr_pages, pc, child, parent, true);
	if (ret)
		__mem_cgroup_cancel_charge(parent, nr_pages);

	if (nr_pages > 1)
		compound_unlock_irqrestore(page, flags);
put_back:
	putback_lru_page(page);
put:
	put_page(page);
out:
	return ret;
}

/*
 * Charge the memory controller for page usage.
 * Return
 * 0 if the charge was successful
 * < 0 if the cgroup is over its limit
 */
static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
				gfp_t gfp_mask, enum charge_type ctype)
{
	struct mem_cgroup *mem = NULL;
	unsigned int nr_pages = 1;
	struct page_cgroup *pc;
	bool oom = true;
	int ret;

	if (PageTransHuge(page)) {
		nr_pages <<= compound_order(page);
		VM_BUG_ON(!PageTransHuge(page));
		/*
		 * Never OOM-kill a process for a huge page.  The
		 * fault handler will fall back to regular pages.
		 */
		oom = false;
	}

	pc = lookup_page_cgroup(page);
	BUG_ON(!pc); /* XXX: remove this and move pc lookup into commit */

	ret = __mem_cgroup_try_charge(mm, gfp_mask, nr_pages, &mem, oom);
	if (ret || !mem)
		return ret;

	__mem_cgroup_commit_charge(mem, page, nr_pages, pc, ctype);
	return 0;
}

int mem_cgroup_newpage_charge(struct page *page,
			      struct mm_struct *mm, gfp_t gfp_mask)
{
	if (mem_cgroup_disabled())
		return 0;
	/*
	 * If already mapped, we don't have to account.
	 * If page cache, page->mapping has address_space.
	 * But page->mapping may have out-of-use anon_vma pointer,
	 * detecit it by PageAnon() check. newly-mapped-anon's page->mapping
	 * is NULL.
  	 */
	if (page_mapped(page) || (page->mapping && !PageAnon(page)))
		return 0;
	if (unlikely(!mm))
		mm = &init_mm;
	return mem_cgroup_charge_common(page, mm, gfp_mask,
				MEM_CGROUP_CHARGE_TYPE_MAPPED);
}

static void
__mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
					enum charge_type ctype);

static void
__mem_cgroup_commit_charge_lrucare(struct page *page, struct mem_cgroup *mem,
					enum charge_type ctype)
{
	struct page_cgroup *pc = lookup_page_cgroup(page);
	/*
	 * In some case, SwapCache, FUSE(splice_buf->radixtree), the page
	 * is already on LRU. It means the page may on some other page_cgroup's
	 * LRU. Take care of it.
	 */
	mem_cgroup_lru_del_before_commit(page);
	__mem_cgroup_commit_charge(mem, page, 1, pc, ctype);
	mem_cgroup_lru_add_after_commit(page);
	return;
}

int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
				gfp_t gfp_mask)
{
	struct mem_cgroup *mem = NULL;
	int ret;

	if (mem_cgroup_disabled())
		return 0;
	if (PageCompound(page))
		return 0;
	/*
	 * Corner case handling. This is called from add_to_page_cache()
	 * in usual. But some FS (shmem) precharges this page before calling it
	 * and call add_to_page_cache() with GFP_NOWAIT.
	 *
	 * For GFP_NOWAIT case, the page may be pre-charged before calling
	 * add_to_page_cache(). (See shmem.c) check it here and avoid to call
	 * charge twice. (It works but has to pay a bit larger cost.)
	 * And when the page is SwapCache, it should take swap information
	 * into account. This is under lock_page() now.
	 */
	if (!(gfp_mask & __GFP_WAIT)) {
		struct page_cgroup *pc;

		pc = lookup_page_cgroup(page);
		if (!pc)
			return 0;
		lock_page_cgroup(pc);
		if (PageCgroupUsed(pc)) {
			unlock_page_cgroup(pc);
			return 0;
		}
		unlock_page_cgroup(pc);
	}

	if (unlikely(!mm))
		mm = &init_mm;

	if (page_is_file_cache(page)) {
		ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, &mem, true);
		if (ret || !mem)
			return ret;

		/*
		 * FUSE reuses pages without going through the final
		 * put that would remove them from the LRU list, make
		 * sure that they get relinked properly.
		 */
		__mem_cgroup_commit_charge_lrucare(page, mem,
					MEM_CGROUP_CHARGE_TYPE_CACHE);
		return ret;
	}
	/* shmem */
	if (PageSwapCache(page)) {
		ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem);
		if (!ret)
			__mem_cgroup_commit_charge_swapin(page, mem,
					MEM_CGROUP_CHARGE_TYPE_SHMEM);
	} else
		ret = mem_cgroup_charge_common(page, mm, gfp_mask,
					MEM_CGROUP_CHARGE_TYPE_SHMEM);

	return ret;
}

/*
 * While swap-in, try_charge -> commit or cancel, the page is locked.
 * And when try_charge() successfully returns, one refcnt to memcg without
 * struct page_cgroup is acquired. This refcnt will be consumed by
 * "commit()" or removed by "cancel()"
 */
int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
				 struct page *page,
				 gfp_t mask, struct mem_cgroup **ptr)
{
	struct mem_cgroup *mem;
	int ret;

	*ptr = NULL;

	if (mem_cgroup_disabled())
		return 0;

	if (!do_swap_account)
		goto charge_cur_mm;
	/*
	 * A racing thread's fault, or swapoff, may have already updated
	 * the pte, and even removed page from swap cache: in those cases
	 * do_swap_page()'s pte_same() test will fail; but there's also a
	 * KSM case which does need to charge the page.
	 */
	if (!PageSwapCache(page))
		goto charge_cur_mm;
	mem = try_get_mem_cgroup_from_page(page);
	if (!mem)
		goto charge_cur_mm;
	*ptr = mem;
	ret = __mem_cgroup_try_charge(NULL, mask, 1, ptr, true);
	css_put(&mem->css);
	return ret;
charge_cur_mm:
	if (unlikely(!mm))
		mm = &init_mm;
	return __mem_cgroup_try_charge(mm, mask, 1, ptr, true);
}

static void
__mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
					enum charge_type ctype)
{
	if (mem_cgroup_disabled())
		return;
	if (!ptr)
		return;
	cgroup_exclude_rmdir(&ptr->css);

	__mem_cgroup_commit_charge_lrucare(page, ptr, ctype);
	/*
	 * Now swap is on-memory. This means this page may be
	 * counted both as mem and swap....double count.
	 * Fix it by uncharging from memsw. Basically, this SwapCache is stable
	 * under lock_page(). But in do_swap_page()::memory.c, reuse_swap_page()
	 * may call delete_from_swap_cache() before reach here.
	 */
	if (do_swap_account && PageSwapCache(page)) {
		swp_entry_t ent = {.val = page_private(page)};
		unsigned short id;
		struct mem_cgroup *memcg;

		id = swap_cgroup_record(ent, 0);
		rcu_read_lock();
		memcg = mem_cgroup_lookup(id);
		if (memcg) {
			/*
			 * This recorded memcg can be obsolete one. So, avoid
			 * calling css_tryget
			 */
			if (!mem_cgroup_is_root(memcg))
				res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
			mem_cgroup_swap_statistics(memcg, false);
			mem_cgroup_put(memcg);
		}
		rcu_read_unlock();
	}
	/*
	 * At swapin, we may charge account against cgroup which has no tasks.
	 * So, rmdir()->pre_destroy() can be called while we do this charge.
	 * In that case, we need to call pre_destroy() again. check it here.
	 */
	cgroup_release_and_wakeup_rmdir(&ptr->css);
}

void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr)
{
	__mem_cgroup_commit_charge_swapin(page, ptr,
					MEM_CGROUP_CHARGE_TYPE_MAPPED);
}

void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *mem)
{
	if (mem_cgroup_disabled())
		return;
	if (!mem)
		return;
	__mem_cgroup_cancel_charge(mem, 1);
}

static void mem_cgroup_do_uncharge(struct mem_cgroup *mem,
				   unsigned int nr_pages,
				   const enum charge_type ctype)
{
	struct memcg_batch_info *batch = NULL;
	bool uncharge_memsw = true;

	/* If swapout, usage of swap doesn't decrease */
	if (!do_swap_account || ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
		uncharge_memsw = false;

	batch = &current->memcg_batch;
	/*
	 * In usual, we do css_get() when we remember memcg pointer.
	 * But in this case, we keep res->usage until end of a series of
	 * uncharges. Then, it's ok to ignore memcg's refcnt.
	 */
	if (!batch->memcg)
		batch->memcg = mem;
	/*
	 * do_batch > 0 when unmapping pages or inode invalidate/truncate.
	 * In those cases, all pages freed continuously can be expected to be in
	 * the same cgroup and we have chance to coalesce uncharges.
	 * But we do uncharge one by one if this is killed by OOM(TIF_MEMDIE)
	 * because we want to do uncharge as soon as possible.
	 */

	if (!batch->do_batch || test_thread_flag(TIF_MEMDIE))
		goto direct_uncharge;

	if (nr_pages > 1)
		goto direct_uncharge;

	/*
	 * In typical case, batch->memcg == mem. This means we can
	 * merge a series of uncharges to an uncharge of res_counter.
	 * If not, we uncharge res_counter ony by one.
	 */
	if (batch->memcg != mem)
		goto direct_uncharge;
	/* remember freed charge and uncharge it later */
	batch->nr_pages++;
	if (uncharge_memsw)
		batch->memsw_nr_pages++;
	return;
direct_uncharge:
	res_counter_uncharge(&mem->res, nr_pages * PAGE_SIZE);
	if (uncharge_memsw)
		res_counter_uncharge(&mem->memsw, nr_pages * PAGE_SIZE);
	if (unlikely(batch->memcg != mem))
		memcg_oom_recover(mem);
	return;
}

/*
 * uncharge if !page_mapped(page)
 */
static struct mem_cgroup *
__mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
{
	struct mem_cgroup *mem = NULL;
	unsigned int nr_pages = 1;
	struct page_cgroup *pc;

	if (mem_cgroup_disabled())
		return NULL;

	if (PageSwapCache(page))
		return NULL;

	if (PageTransHuge(page)) {
		nr_pages <<= compound_order(page);
		VM_BUG_ON(!PageTransHuge(page));
	}
	/*
	 * Check if our page_cgroup is valid
	 */
	pc = lookup_page_cgroup(page);
	if (unlikely(!pc || !PageCgroupUsed(pc)))
		return NULL;

	lock_page_cgroup(pc);

	mem = pc->mem_cgroup;

	if (!PageCgroupUsed(pc))
		goto unlock_out;

	switch (ctype) {
	case MEM_CGROUP_CHARGE_TYPE_MAPPED:
	case MEM_CGROUP_CHARGE_TYPE_DROP:
		/* See mem_cgroup_prepare_migration() */
		if (page_mapped(page) || PageCgroupMigration(pc))
			goto unlock_out;
		break;
	case MEM_CGROUP_CHARGE_TYPE_SWAPOUT:
		if (!PageAnon(page)) {	/* Shared memory */
			if (page->mapping && !page_is_file_cache(page))
				goto unlock_out;
		} else if (page_mapped(page)) /* Anon */
				goto unlock_out;
		break;
	default:
		break;
	}

	mem_cgroup_charge_statistics(mem, PageCgroupCache(pc), -nr_pages);

	ClearPageCgroupUsed(pc);
	/*
	 * pc->mem_cgroup is not cleared here. It will be accessed when it's
	 * freed from LRU. This is safe because uncharged page is expected not
	 * to be reused (freed soon). Exception is SwapCache, it's handled by
	 * special functions.
	 */

	unlock_page_cgroup(pc);
	/*
	 * even after unlock, we have mem->res.usage here and this memcg
	 * will never be freed.
	 */
	memcg_check_events(mem, page);
	if (do_swap_account && ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT) {
		mem_cgroup_swap_statistics(mem, true);
		mem_cgroup_get(mem);
	}
	if (!mem_cgroup_is_root(mem))
		mem_cgroup_do_uncharge(mem, nr_pages, ctype);

	return mem;

unlock_out:
	unlock_page_cgroup(pc);
	return NULL;
}

void mem_cgroup_uncharge_page(struct page *page)
{
	/* early check. */
	if (page_mapped(page))
		return;
	if (page->mapping && !PageAnon(page))
		return;
	__mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_MAPPED);
}

void mem_cgroup_uncharge_cache_page(struct page *page)
{
	VM_BUG_ON(page_mapped(page));
	VM_BUG_ON(page->mapping);
	__mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE);
}

/*
 * Batch_start/batch_end is called in unmap_page_range/invlidate/trucate.
 * In that cases, pages are freed continuously and we can expect pages
 * are in the same memcg. All these calls itself limits the number of
 * pages freed at once, then uncharge_start/end() is called properly.
 * This may be called prural(2) times in a context,
 */

void mem_cgroup_uncharge_start(void)
{
	current->memcg_batch.do_batch++;
	/* We can do nest. */
	if (current->memcg_batch.do_batch == 1) {
		current->memcg_batch.memcg = NULL;
		current->memcg_batch.nr_pages = 0;
		current->memcg_batch.memsw_nr_pages = 0;
	}
}

void mem_cgroup_uncharge_end(void)
{
	struct memcg_batch_info *batch = &current->memcg_batch;

	if (!batch->do_batch)
		return;

	batch->do_batch--;
	if (batch->do_batch) /* If stacked, do nothing. */
		return;

	if (!batch->memcg)
		return;
	/*
	 * This "batch->memcg" is valid without any css_get/put etc...
	 * bacause we hide charges behind us.
	 */
	if (batch->nr_pages)
		res_counter_uncharge(&batch->memcg->res,
				     batch->nr_pages * PAGE_SIZE);
	if (batch->memsw_nr_pages)
		res_counter_uncharge(&batch->memcg->memsw,
				     batch->memsw_nr_pages * PAGE_SIZE);
	memcg_oom_recover(batch->memcg);
	/* forget this pointer (for sanity check) */
	batch->memcg = NULL;
}

#ifdef CONFIG_SWAP
/*
 * called after __delete_from_swap_cache() and drop "page" account.
 * memcg information is recorded to swap_cgroup of "ent"
 */
void
mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
{
	struct mem_cgroup *memcg;
	int ctype = MEM_CGROUP_CHARGE_TYPE_SWAPOUT;

	if (!swapout) /* this was a swap cache but the swap is unused ! */
		ctype = MEM_CGROUP_CHARGE_TYPE_DROP;

	memcg = __mem_cgroup_uncharge_common(page, ctype);

	/*
	 * record memcg information,  if swapout && memcg != NULL,
	 * mem_cgroup_get() was called in uncharge().
	 */
	if (do_swap_account && swapout && memcg)
		swap_cgroup_record(ent, css_id(&memcg->css));
}
#endif

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
/*
 * called from swap_entry_free(). remove record in swap_cgroup and
 * uncharge "memsw" account.
 */
void mem_cgroup_uncharge_swap(swp_entry_t ent)
{
	struct mem_cgroup *memcg;
	unsigned short id;

	if (!do_swap_account)
		return;

	id = swap_cgroup_record(ent, 0);
	rcu_read_lock();
	memcg = mem_cgroup_lookup(id);
	if (memcg) {
		/*
		 * We uncharge this because swap is freed.
		 * This memcg can be obsolete one. We avoid calling css_tryget
		 */
		if (!mem_cgroup_is_root(memcg))
			res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
		mem_cgroup_swap_statistics(memcg, false);
		mem_cgroup_put(memcg);
	}
	rcu_read_unlock();
}

/**
 * mem_cgroup_move_swap_account - move swap charge and swap_cgroup's record.
 * @entry: swap entry to be moved
 * @from:  mem_cgroup which the entry is moved from
 * @to:  mem_cgroup which the entry is moved to
 * @need_fixup: whether we should fixup res_counters and refcounts.
 *
 * It succeeds only when the swap_cgroup's record for this entry is the same
 * as the mem_cgroup's id of @from.
 *
 * Returns 0 on success, -EINVAL on failure.
 *
 * The caller must have charged to @to, IOW, called res_counter_charge() about
 * both res and memsw, and called css_get().
 */
static int mem_cgroup_move_swap_account(swp_entry_t entry,
		struct mem_cgroup *from, struct mem_cgroup *to, bool need_fixup)
{
	unsigned short old_id, new_id;

	old_id = css_id(&from->css);
	new_id = css_id(&to->css);

	if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
		mem_cgroup_swap_statistics(from, false);
		mem_cgroup_swap_statistics(to, true);
		/*
		 * This function is only called from task migration context now.
		 * It postpones res_counter and refcount handling till the end
		 * of task migration(mem_cgroup_clear_mc()) for performance
		 * improvement. But we cannot postpone mem_cgroup_get(to)
		 * because if the process that has been moved to @to does
		 * swap-in, the refcount of @to might be decreased to 0.
		 */
		mem_cgroup_get(to);
		if (need_fixup) {
			if (!mem_cgroup_is_root(from))
				res_counter_uncharge(&from->memsw, PAGE_SIZE);
			mem_cgroup_put(from);
			/*
			 * we charged both to->res and to->memsw, so we should
			 * uncharge to->res.
			 */
			if (!mem_cgroup_is_root(to))
				res_counter_uncharge(&to->res, PAGE_SIZE);
		}
		return 0;
	}
	return -EINVAL;
}
#else
static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
		struct mem_cgroup *from, struct mem_cgroup *to, bool need_fixup)
{
	return -EINVAL;
}
#endif

/*
 * Before starting migration, account PAGE_SIZE to mem_cgroup that the old
 * page belongs to.
 */
int mem_cgroup_prepare_migration(struct page *page,
	struct page *newpage, struct mem_cgroup **ptr, gfp_t gfp_mask)
{
	struct mem_cgroup *mem = NULL;
	struct page_cgroup *pc;
	enum charge_type ctype;
	int ret = 0;

	*ptr = NULL;

	VM_BUG_ON(PageTransHuge(page));
	if (mem_cgroup_disabled())
		return 0;

	pc = lookup_page_cgroup(page);
	lock_page_cgroup(pc);
	if (PageCgroupUsed(pc)) {
		mem = pc->mem_cgroup;
		css_get(&mem->css);
		/*
		 * At migrating an anonymous page, its mapcount goes down
		 * to 0 and uncharge() will be called. But, even if it's fully
		 * unmapped, migration may fail and this page has to be
		 * charged again. We set MIGRATION flag here and delay uncharge
		 * until end_migration() is called
		 *
		 * Corner Case Thinking
		 * A)
		 * When the old page was mapped as Anon and it's unmap-and-freed
		 * while migration was ongoing.
		 * If unmap finds the old page, uncharge() of it will be delayed
		 * until end_migration(). If unmap finds a new page, it's
		 * uncharged when it make mapcount to be 1->0. If unmap code
		 * finds swap_migration_entry, the new page will not be mapped
		 * and end_migration() will find it(mapcount==0).
		 *
		 * B)
		 * When the old page was mapped but migraion fails, the kernel
		 * remaps it. A charge for it is kept by MIGRATION flag even
		 * if mapcount goes down to 0. We can do remap successfully
		 * without charging it again.
		 *
		 * C)
		 * The "old" page is under lock_page() until the end of
		 * migration, so, the old page itself will not be swapped-out.
		 * If the new page is swapped out before end_migraton, our
		 * hook to usual swap-out path will catch the event.
		 */
		if (PageAnon(page))
			SetPageCgroupMigration(pc);
	}
	unlock_page_cgroup(pc);
	/*
	 * If the page is not charged at this point,
	 * we return here.
	 */
	if (!mem)
		return 0;

	*ptr = mem;
	ret = __mem_cgroup_try_charge(NULL, gfp_mask, 1, ptr, false);
	css_put(&mem->css);/* drop extra refcnt */
	if (ret || *ptr == NULL) {
		if (PageAnon(page)) {
			lock_page_cgroup(pc);
			ClearPageCgroupMigration(pc);
			unlock_page_cgroup(pc);
			/*
			 * The old page may be fully unmapped while we kept it.
			 */
			mem_cgroup_uncharge_page(page);
		}
		return -ENOMEM;
	}
	/*
	 * We charge new page before it's used/mapped. So, even if unlock_page()
	 * is called before end_migration, we can catch all events on this new
	 * page. In the case new page is migrated but not remapped, new page's
	 * mapcount will be finally 0 and we call uncharge in end_migration().
	 */
	pc = lookup_page_cgroup(newpage);
	if (PageAnon(page))
		ctype = MEM_CGROUP_CHARGE_TYPE_MAPPED;
	else if (page_is_file_cache(page))
		ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
	else
		ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;
	__mem_cgroup_commit_charge(mem, page, 1, pc, ctype);
	return ret;
}

/* remove redundant charge if migration failed*/
void mem_cgroup_end_migration(struct mem_cgroup *mem,
	struct page *oldpage, struct page *newpage, bool migration_ok)
{
	struct page *used, *unused;
	struct page_cgroup *pc;

	if (!mem)
		return;
	/* blocks rmdir() */
	cgroup_exclude_rmdir(&mem->css);
	if (!migration_ok) {
		used = oldpage;
		unused = newpage;
	} else {
		used = newpage;
		unused = oldpage;
	}
	/*
	 * We disallowed uncharge of pages under migration because mapcount
	 * of the page goes down to zero, temporarly.
	 * Clear the flag and check the page should be charged.
	 */
	pc = lookup_page_cgroup(oldpage);
	lock_page_cgroup(pc);
	ClearPageCgroupMigration(pc);
	unlock_page_cgroup(pc);

	__mem_cgroup_uncharge_common(unused, MEM_CGROUP_CHARGE_TYPE_FORCE);

	/*
	 * If a page is a file cache, radix-tree replacement is very atomic
	 * and we can skip this check. When it was an Anon page, its mapcount
	 * goes down to 0. But because we added MIGRATION flage, it's not
	 * uncharged yet. There are several case but page->mapcount check
	 * and USED bit check in mem_cgroup_uncharge_page() will do enough
	 * check. (see prepare_charge() also)
	 */
	if (PageAnon(used))
		mem_cgroup_uncharge_page(used);
	/*
	 * At migration, we may charge account against cgroup which has no
	 * tasks.
	 * So, rmdir()->pre_destroy() can be called while we do this charge.
	 * In that case, we need to call pre_destroy() again. check it here.
	 */
	cgroup_release_and_wakeup_rmdir(&mem->css);
}

/*
 * A call to try to shrink memory usage on charge failure at shmem's swapin.
 * Calling hierarchical_reclaim is not enough because we should update
 * last_oom_jiffies to prevent pagefault_out_of_memory from invoking global OOM.
 * Moreover considering hierarchy, we should reclaim from the mem_over_limit,
 * not from the memcg which this page would be charged to.
 * try_charge_swapin does all of these works properly.
 */
int mem_cgroup_shmem_charge_fallback(struct page *page,
			    struct mm_struct *mm,
			    gfp_t gfp_mask)
{
	struct mem_cgroup *mem;
	int ret;

	if (mem_cgroup_disabled())
		return 0;

	ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem);
	if (!ret)
		mem_cgroup_cancel_charge_swapin(mem); /* it does !mem check */

	return ret;
}

#ifdef CONFIG_DEBUG_VM
static struct page_cgroup *lookup_page_cgroup_used(struct page *page)
{
	struct page_cgroup *pc;

	pc = lookup_page_cgroup(page);
	if (likely(pc) && PageCgroupUsed(pc))
		return pc;
	return NULL;
}

bool mem_cgroup_bad_page_check(struct page *page)
{
	if (mem_cgroup_disabled())
		return false;

	return lookup_page_cgroup_used(page) != NULL;
}

void mem_cgroup_print_bad_page(struct page *page)
{
	struct page_cgroup *pc;

	pc = lookup_page_cgroup_used(page);
	if (pc) {
		int ret = -1;
		char *path;

		printk(KERN_ALERT "pc:%p pc->flags:%lx pc->mem_cgroup:%p",
		       pc, pc->flags, pc->mem_cgroup);

		path = kmalloc(PATH_MAX, GFP_KERNEL);
		if (path) {
			rcu_read_lock();
			ret = cgroup_path(pc->mem_cgroup->css.cgroup,
							path, PATH_MAX);
			rcu_read_unlock();
		}

		printk(KERN_CONT "(%s)\n",
				(ret < 0) ? "cannot get the path" : path);
		kfree(path);
	}
}
#endif

static DEFINE_MUTEX(set_limit_mutex);

static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
				unsigned long long val)
{
	int retry_count;
	u64 memswlimit, memlimit;
	int ret = 0;
	int children = mem_cgroup_count_children(memcg);
	u64 curusage, oldusage;
	int enlarge;

	/*
	 * For keeping hierarchical_reclaim simple, how long we should retry
	 * is depends on callers. We set our retry-count to be function
	 * of # of children which we should visit in this loop.
	 */
	retry_count = MEM_CGROUP_RECLAIM_RETRIES * children;

	oldusage = res_counter_read_u64(&memcg->res, RES_USAGE);

	enlarge = 0;
	while (retry_count) {
		if (signal_pending(current)) {
			ret = -EINTR;
			break;
		}
		/*
		 * Rather than hide all in some function, I do this in
		 * open coded manner. You see what this really does.
		 * We have to guarantee mem->res.limit < mem->memsw.limit.
		 */
		mutex_lock(&set_limit_mutex);
		memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
		if (memswlimit < val) {
			ret = -EINVAL;
			mutex_unlock(&set_limit_mutex);
			break;
		}

		memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
		if (memlimit < val)
			enlarge = 1;

		ret = res_counter_set_limit(&memcg->res, val);
		if (!ret) {
			if (memswlimit == val)
				memcg->memsw_is_minimum = true;
			else
				memcg->memsw_is_minimum = false;
		}
		mutex_unlock(&set_limit_mutex);

		if (!ret)
			break;

		mem_cgroup_hierarchical_reclaim(memcg, NULL, GFP_KERNEL,
						MEM_CGROUP_RECLAIM_SHRINK,
						NULL);
		curusage = res_counter_read_u64(&memcg->res, RES_USAGE);
		/* Usage is reduced ? */
  		if (curusage >= oldusage)
			retry_count--;
		else
			oldusage = curusage;
	}
	if (!ret && enlarge)
		memcg_oom_recover(memcg);

	return ret;
}

static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
					unsigned long long val)
{
	int retry_count;
	u64 memlimit, memswlimit, oldusage, curusage;
	int children = mem_cgroup_count_children(memcg);
	int ret = -EBUSY;
	int enlarge = 0;

	/* see mem_cgroup_resize_res_limit */
 	retry_count = children * MEM_CGROUP_RECLAIM_RETRIES;
	oldusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
	while (retry_count) {
		if (signal_pending(current)) {
			ret = -EINTR;
			break;
		}
		/*
		 * Rather than hide all in some function, I do this in
		 * open coded manner. You see what this really does.
		 * We have to guarantee mem->res.limit < mem->memsw.limit.
		 */
		mutex_lock(&set_limit_mutex);
		memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
		if (memlimit > val) {
			ret = -EINVAL;
			mutex_unlock(&set_limit_mutex);
			break;
		}
		memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
		if (memswlimit < val)
			enlarge = 1;
		ret = res_counter_set_limit(&memcg->memsw, val);
		if (!ret) {
			if (memlimit == val)
				memcg->memsw_is_minimum = true;
			else
				memcg->memsw_is_minimum = false;
		}
		mutex_unlock(&set_limit_mutex);

		if (!ret)
			break;

		mem_cgroup_hierarchical_reclaim(memcg, NULL, GFP_KERNEL,
						MEM_CGROUP_RECLAIM_NOSWAP |
						MEM_CGROUP_RECLAIM_SHRINK,
						NULL);
		curusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
		/* Usage is reduced ? */
		if (curusage >= oldusage)
			retry_count--;
		else
			oldusage = curusage;
	}
	if (!ret && enlarge)
		memcg_oom_recover(memcg);
	return ret;
}

unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
					    gfp_t gfp_mask,
					    unsigned long *total_scanned)
{
	unsigned long nr_reclaimed = 0;
	struct mem_cgroup_per_zone *mz, *next_mz = NULL;
	unsigned long reclaimed;
	int loop = 0;
	struct mem_cgroup_tree_per_zone *mctz;
	unsigned long long excess;
	unsigned long nr_scanned;

	if (order > 0)
		return 0;

	mctz = soft_limit_tree_node_zone(zone_to_nid(zone), zone_idx(zone));
	/*
	 * This loop can run a while, specially if mem_cgroup's continuously
	 * keep exceeding their soft limit and putting the system under
	 * pressure
	 */
	do {
		if (next_mz)
			mz = next_mz;
		else
			mz = mem_cgroup_largest_soft_limit_node(mctz);
		if (!mz)
			break;

		nr_scanned = 0;
		reclaimed = mem_cgroup_hierarchical_reclaim(mz->mem, zone,
						gfp_mask,
						MEM_CGROUP_RECLAIM_SOFT,
						&nr_scanned);
		nr_reclaimed += reclaimed;
		*total_scanned += nr_scanned;
		spin_lock(&mctz->lock);

		/*
		 * If we failed to reclaim anything from this memory cgroup
		 * it is time to move on to the next cgroup
		 */
		next_mz = NULL;
		if (!reclaimed) {
			do {
				/*
				 * Loop until we find yet another one.
				 *
				 * By the time we get the soft_limit lock
				 * again, someone might have aded the
				 * group back on the RB tree. Iterate to
				 * make sure we get a different mem.
				 * mem_cgroup_largest_soft_limit_node returns
				 * NULL if no other cgroup is present on
				 * the tree
				 */
				next_mz =
				__mem_cgroup_largest_soft_limit_node(mctz);
				if (next_mz == mz)
					css_put(&next_mz->mem->css);
				else /* next_mz == NULL or other memcg */
					break;
			} while (1);
		}
		__mem_cgroup_remove_exceeded(mz->mem, mz, mctz);
		excess = res_counter_soft_limit_excess(&mz->mem->res);
		/*
		 * One school of thought says that we should not add
		 * back the node to the tree if reclaim returns 0.
		 * But our reclaim could return 0, simply because due
		 * to priority we are exposing a smaller subset of
		 * memory to reclaim from. Consider this as a longer
		 * term TODO.
		 */
		/* If excess == 0, no tree ops */
		__mem_cgroup_insert_exceeded(mz->mem, mz, mctz, excess);
		spin_unlock(&mctz->lock);
		css_put(&mz->mem->css);
		loop++;
		/*
		 * Could not reclaim anything and there are no more
		 * mem cgroups to try or we seem to be looping without
		 * reclaiming anything.
		 */
		if (!nr_reclaimed &&
			(next_mz == NULL ||
			loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS))
			break;
	} while (!nr_reclaimed);
	if (next_mz)
		css_put(&next_mz->mem->css);
	return nr_reclaimed;
}

/*
 * This routine traverse page_cgroup in given list and drop them all.
 * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
 */
static int mem_cgroup_force_empty_list(struct mem_cgroup *mem,
				int node, int zid, enum lru_list lru)
{
	struct zone *zone;
	struct mem_cgroup_per_zone *mz;
	struct page_cgroup *pc, *busy;
	unsigned long flags, loop;
	struct list_head *list;
	int ret = 0;

	zone = &NODE_DATA(node)->node_zones[zid];
	mz = mem_cgroup_zoneinfo(mem, node, zid);
	list = &mz->lists[lru];

	loop = MEM_CGROUP_ZSTAT(mz, lru);
	/* give some margin against EBUSY etc...*/
	loop += 256;
	busy = NULL;
	while (loop--) {
		struct page *page;

		ret = 0;
		spin_lock_irqsave(&zone->lru_lock, flags);
		if (list_empty(list)) {
			spin_unlock_irqrestore(&zone->lru_lock, flags);
			break;
		}
		pc = list_entry(list->prev, struct page_cgroup, lru);
		if (busy == pc) {
			list_move(&pc->lru, list);
			busy = NULL;
			spin_unlock_irqrestore(&zone->lru_lock, flags);
			continue;
		}
		spin_unlock_irqrestore(&zone->lru_lock, flags);

		page = lookup_cgroup_page(pc);

		ret = mem_cgroup_move_parent(page, pc, mem, GFP_KERNEL);
		if (ret == -ENOMEM)
			break;

		if (ret == -EBUSY || ret == -EINVAL) {
			/* found lock contention or "pc" is obsolete. */
			busy = pc;
			cond_resched();
		} else
			busy = NULL;
	}

	if (!ret && !list_empty(list))
		return -EBUSY;
	return ret;
}

/*
 * make mem_cgroup's charge to be 0 if there is no task.
 * This enables deleting this mem_cgroup.
 */
static int mem_cgroup_force_empty(struct mem_cgroup *mem, bool free_all)
{
	int ret;
	int node, zid, shrink;
	int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
	struct cgroup *cgrp = mem->css.cgroup;

	css_get(&mem->css);

	shrink = 0;
	/* should free all ? */
	if (free_all)
		goto try_to_free;
move_account:
	do {
		ret = -EBUSY;
		if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
			goto out;
		ret = -EINTR;
		if (signal_pending(current))
			goto out;
		/* This is for making all *used* pages to be on LRU. */
		lru_add_drain_all();
		drain_all_stock_sync();
		ret = 0;
		mem_cgroup_start_move(mem);
		for_each_node_state(node, N_HIGH_MEMORY) {
			for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
				enum lru_list l;
				for_each_lru(l) {
					ret = mem_cgroup_force_empty_list(mem,
							node, zid, l);
					if (ret)
						break;
				}
			}
			if (ret)
				break;
		}
		mem_cgroup_end_move(mem);
		memcg_oom_recover(mem);
		/* it seems parent cgroup doesn't have enough mem */
		if (ret == -ENOMEM)
			goto try_to_free;
		cond_resched();
	/* "ret" should also be checked to ensure all lists are empty. */
	} while (mem->res.usage > 0 || ret);
out:
	css_put(&mem->css);
	return ret;

try_to_free:
	/* returns EBUSY if there is a task or if we come here twice. */
	if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children) || shrink) {
		ret = -EBUSY;
		goto out;
	}
	/* we call try-to-free pages for make this cgroup empty */
	lru_add_drain_all();
	/* try to free all pages in this cgroup */
	shrink = 1;
	while (nr_retries && mem->res.usage > 0) {
		int progress;

		if (signal_pending(current)) {
			ret = -EINTR;
			goto out;
		}
		progress = try_to_free_mem_cgroup_pages(mem, GFP_KERNEL,
						false, get_swappiness(mem));
		if (!progress) {
			nr_retries--;
			/* maybe some writeback is necessary */
			congestion_wait(BLK_RW_ASYNC, HZ/10);
		}

	}
	lru_add_drain();
	/* try move_account...there may be some *locked* pages. */
	goto move_account;
}

int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event)
{
	return mem_cgroup_force_empty(mem_cgroup_from_cont(cont), true);
}


static u64 mem_cgroup_hierarchy_read(struct cgroup *cont, struct cftype *cft)
{
	return mem_cgroup_from_cont(cont)->use_hierarchy;
}

static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
					u64 val)
{
	int retval = 0;
	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
	struct cgroup *parent = cont->parent;
	struct mem_cgroup *parent_mem = NULL;

	if (parent)
		parent_mem = mem_cgroup_from_cont(parent);

	cgroup_lock();
	/*
	 * If parent's use_hierarchy is set, we can't make any modifications
	 * in the child subtrees. If it is unset, then the change can
	 * occur, provided the current cgroup has no children.
	 *
	 * For the root cgroup, parent_mem is NULL, we allow value to be
	 * set if there are no children.
	 */
	if ((!parent_mem || !parent_mem->use_hierarchy) &&
				(val == 1 || val == 0)) {
		if (list_empty(&cont->children))
			mem->use_hierarchy = val;
		else
			retval = -EBUSY;
	} else
		retval = -EINVAL;
	cgroup_unlock();

	return retval;
}


static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *mem,
					       enum mem_cgroup_stat_index idx)
{
	struct mem_cgroup *iter;
	long val = 0;

	/* Per-cpu values can be negative, use a signed accumulator */
	for_each_mem_cgroup_tree(iter, mem)
		val += mem_cgroup_read_stat(iter, idx);

	if (val < 0) /* race ? */
		val = 0;
	return val;
}

static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
{
	u64 val;

	if (!mem_cgroup_is_root(mem)) {
		if (!swap)
			return res_counter_read_u64(&mem->res, RES_USAGE);
		else
			return res_counter_read_u64(&mem->memsw, RES_USAGE);
	}

	val = mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_CACHE);
	val += mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_RSS);

	if (swap)
		val += mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_SWAPOUT);

	return val << PAGE_SHIFT;
}

static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
{
	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
	u64 val;
	int type, name;

	type = MEMFILE_TYPE(cft->private);
	name = MEMFILE_ATTR(cft->private);
	switch (type) {
	case _MEM:
		if (name == RES_USAGE)
			val = mem_cgroup_usage(mem, false);
		else
			val = res_counter_read_u64(&mem->res, name);
		break;
	case _MEMSWAP:
		if (name == RES_USAGE)
			val = mem_cgroup_usage(mem, true);
		else
			val = res_counter_read_u64(&mem->memsw, name);
		break;
	default:
		BUG();
		break;
	}
	return val;
}
/*
 * The user of this function is...
 * RES_LIMIT.
 */
static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
			    const char *buffer)
{
	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
	int type, name;
	unsigned long long val;
	int ret;

	type = MEMFILE_TYPE(cft->private);
	name = MEMFILE_ATTR(cft->private);
	switch (name) {
	case RES_LIMIT:
		if (mem_cgroup_is_root(memcg)) { /* Can't set limit on root */
			ret = -EINVAL;
			break;
		}
		/* This function does all necessary parse...reuse it */
		ret = res_counter_memparse_write_strategy(buffer, &val);
		if (ret)
			break;
		if (type == _MEM)
			ret = mem_cgroup_resize_limit(memcg, val);
		else
			ret = mem_cgroup_resize_memsw_limit(memcg, val);
		break;
	case RES_SOFT_LIMIT:
		ret = res_counter_memparse_write_strategy(buffer, &val);
		if (ret)
			break;
		/*
		 * For memsw, soft limits are hard to implement in terms
		 * of semantics, for now, we support soft limits for
		 * control without swap
		 */
		if (type == _MEM)
			ret = res_counter_set_soft_limit(&memcg->res, val);
		else
			ret = -EINVAL;
		break;
	default:
		ret = -EINVAL; /* should be BUG() ? */
		break;
	}
	return ret;
}

static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
		unsigned long long *mem_limit, unsigned long long *memsw_limit)
{
	struct cgroup *cgroup;
	unsigned long long min_limit, min_memsw_limit, tmp;

	min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
	min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
	cgroup = memcg->css.cgroup;
	if (!memcg->use_hierarchy)
		goto out;

	while (cgroup->parent) {
		cgroup = cgroup->parent;
		memcg = mem_cgroup_from_cont(cgroup);
		if (!memcg->use_hierarchy)
			break;
		tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
		min_limit = min(min_limit, tmp);
		tmp = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
		min_memsw_limit = min(min_memsw_limit, tmp);
	}
out:
	*mem_limit = min_limit;
	*memsw_limit = min_memsw_limit;
	return;
}

static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
{
	struct mem_cgroup *mem;
	int type, name;

	mem = mem_cgroup_from_cont(cont);
	type = MEMFILE_TYPE(event);
	name = MEMFILE_ATTR(event);
	switch (name) {
	case RES_MAX_USAGE:
		if (type == _MEM)
			res_counter_reset_max(&mem->res);
		else
			res_counter_reset_max(&mem->memsw);
		break;
	case RES_FAILCNT:
		if (type == _MEM)
			res_counter_reset_failcnt(&mem->res);
		else
			res_counter_reset_failcnt(&mem->memsw);
		break;
	}

	return 0;
}

static u64 mem_cgroup_move_charge_read(struct cgroup *cgrp,
					struct cftype *cft)
{
	return mem_cgroup_from_cont(cgrp)->move_charge_at_immigrate;
}

#ifdef CONFIG_MMU
static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
					struct cftype *cft, u64 val)
{
	struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);

	if (val >= (1 << NR_MOVE_TYPE))
		return -EINVAL;
	/*
	 * We check this value several times in both in can_attach() and
	 * attach(), so we need cgroup lock to prevent this value from being
	 * inconsistent.
	 */
	cgroup_lock();
	mem->move_charge_at_immigrate = val;
	cgroup_unlock();

	return 0;
}
#else
static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
					struct cftype *cft, u64 val)
{
	return -ENOSYS;
}
#endif


/* For read statistics */
enum {
	MCS_CACHE,
	MCS_RSS,
	MCS_FILE_MAPPED,
	MCS_PGPGIN,
	MCS_PGPGOUT,
	MCS_SWAP,
	MCS_PGFAULT,
	MCS_PGMAJFAULT,
	MCS_INACTIVE_ANON,
	MCS_ACTIVE_ANON,
	MCS_INACTIVE_FILE,
	MCS_ACTIVE_FILE,
	MCS_UNEVICTABLE,
	NR_MCS_STAT,
};

struct mcs_total_stat {
	s64 stat[NR_MCS_STAT];
};

struct {
	char *local_name;
	char *total_name;
} memcg_stat_strings[NR_MCS_STAT] = {
	{"cache", "total_cache"},
	{"rss", "total_rss"},
	{"mapped_file", "total_mapped_file"},
	{"pgpgin", "total_pgpgin"},
	{"pgpgout", "total_pgpgout"},
	{"swap", "total_swap"},
	{"pgfault", "total_pgfault"},
	{"pgmajfault", "total_pgmajfault"},
	{"inactive_anon", "total_inactive_anon"},
	{"active_anon", "total_active_anon"},
	{"inactive_file", "total_inactive_file"},
	{"active_file", "total_active_file"},
	{"unevictable", "total_unevictable"}
};


static void
mem_cgroup_get_local_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
{
	s64 val;

	/* per cpu stat */
	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
	s->stat[MCS_CACHE] += val * PAGE_SIZE;
	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
	s->stat[MCS_RSS] += val * PAGE_SIZE;
	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_MAPPED);
	s->stat[MCS_FILE_MAPPED] += val * PAGE_SIZE;
	val = mem_cgroup_read_events(mem, MEM_CGROUP_EVENTS_PGPGIN);
	s->stat[MCS_PGPGIN] += val;
	val = mem_cgroup_read_events(mem, MEM_CGROUP_EVENTS_PGPGOUT);
	s->stat[MCS_PGPGOUT] += val;
	if (do_swap_account) {
		val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_SWAPOUT);
		s->stat[MCS_SWAP] += val * PAGE_SIZE;
	}
	val = mem_cgroup_read_events(mem, MEM_CGROUP_EVENTS_PGFAULT);
	s->stat[MCS_PGFAULT] += val;
	val = mem_cgroup_read_events(mem, MEM_CGROUP_EVENTS_PGMAJFAULT);
	s->stat[MCS_PGMAJFAULT] += val;

	/* per zone stat */
	val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON);
	s->stat[MCS_INACTIVE_ANON] += val * PAGE_SIZE;
	val = mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_ANON);
	s->stat[MCS_ACTIVE_ANON] += val * PAGE_SIZE;
	val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_FILE);
	s->stat[MCS_INACTIVE_FILE] += val * PAGE_SIZE;
	val = mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_FILE);
	s->stat[MCS_ACTIVE_FILE] += val * PAGE_SIZE;
	val = mem_cgroup_get_local_zonestat(mem, LRU_UNEVICTABLE);
	s->stat[MCS_UNEVICTABLE] += val * PAGE_SIZE;
}

static void
mem_cgroup_get_total_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
{
	struct mem_cgroup *iter;

	for_each_mem_cgroup_tree(iter, mem)
		mem_cgroup_get_local_stat(iter, s);
}

#ifdef CONFIG_NUMA
static int mem_control_numa_stat_show(struct seq_file *m, void *arg)
{
	int nid;
	unsigned long total_nr, file_nr, anon_nr, unevictable_nr;
	unsigned long node_nr;
	struct cgroup *cont = m->private;
	struct mem_cgroup *mem_cont = mem_cgroup_from_cont(cont);

	total_nr = mem_cgroup_nr_lru_pages(mem_cont);
	seq_printf(m, "total=%lu", total_nr);
	for_each_node_state(nid, N_HIGH_MEMORY) {
		node_nr = mem_cgroup_node_nr_lru_pages(mem_cont, nid);
		seq_printf(m, " N%d=%lu", nid, node_nr);
	}
	seq_putc(m, '\n');

	file_nr = mem_cgroup_nr_file_lru_pages(mem_cont);
	seq_printf(m, "file=%lu", file_nr);
	for_each_node_state(nid, N_HIGH_MEMORY) {
		node_nr = mem_cgroup_node_nr_file_lru_pages(mem_cont, nid);
		seq_printf(m, " N%d=%lu", nid, node_nr);
	}
	seq_putc(m, '\n');

	anon_nr = mem_cgroup_nr_anon_lru_pages(mem_cont);
	seq_printf(m, "anon=%lu", anon_nr);
	for_each_node_state(nid, N_HIGH_MEMORY) {
		node_nr = mem_cgroup_node_nr_anon_lru_pages(mem_cont, nid);
		seq_printf(m, " N%d=%lu", nid, node_nr);
	}
	seq_putc(m, '\n');

	unevictable_nr = mem_cgroup_nr_unevictable_lru_pages(mem_cont);
	seq_printf(m, "unevictable=%lu", unevictable_nr);
	for_each_node_state(nid, N_HIGH_MEMORY) {
		node_nr = mem_cgroup_node_nr_unevictable_lru_pages(mem_cont,
									nid);
		seq_printf(m, " N%d=%lu", nid, node_nr);
	}
	seq_putc(m, '\n');
	return 0;
}
#endif /* CONFIG_NUMA */

static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
				 struct cgroup_map_cb *cb)
{
	struct mem_cgroup *mem_cont = mem_cgroup_from_cont(cont);
	struct mcs_total_stat mystat;
	int i;

	memset(&mystat, 0, sizeof(mystat));
	mem_cgroup_get_local_stat(mem_cont, &mystat);


	for (i = 0; i < NR_MCS_STAT; i++) {
		if (i == MCS_SWAP && !do_swap_account)
			continue;
		cb->fill(cb, memcg_stat_strings[i].local_name, mystat.stat[i]);
	}

	/* Hierarchical information */
	{
		unsigned long long limit, memsw_limit;
		memcg_get_hierarchical_limit(mem_cont, &limit, &memsw_limit);
		cb->fill(cb, "hierarchical_memory_limit", limit);
		if (do_swap_account)
			cb->fill(cb, "hierarchical_memsw_limit", memsw_limit);
	}

	memset(&mystat, 0, sizeof(mystat));
	mem_cgroup_get_total_stat(mem_cont, &mystat);
	for (i = 0; i < NR_MCS_STAT; i++) {
		if (i == MCS_SWAP && !do_swap_account)
			continue;
		cb->fill(cb, memcg_stat_strings[i].total_name, mystat.stat[i]);
	}

#ifdef CONFIG_DEBUG_VM
	cb->fill(cb, "inactive_ratio", calc_inactive_ratio(mem_cont, NULL));

	{
		int nid, zid;
		struct mem_cgroup_per_zone *mz;
		unsigned long recent_rotated[2] = {0, 0};
		unsigned long recent_scanned[2] = {0, 0};

		for_each_online_node(nid)
			for (zid = 0; zid < MAX_NR_ZONES; zid++) {
				mz = mem_cgroup_zoneinfo(mem_cont, nid, zid);

				recent_rotated[0] +=
					mz->reclaim_stat.recent_rotated[0];
				recent_rotated[1] +=
					mz->reclaim_stat.recent_rotated[1];
				recent_scanned[0] +=
					mz->reclaim_stat.recent_scanned[0];
				recent_scanned[1] +=
					mz->reclaim_stat.recent_scanned[1];
			}
		cb->fill(cb, "recent_rotated_anon", recent_rotated[0]);
		cb->fill(cb, "recent_rotated_file", recent_rotated[1]);
		cb->fill(cb, "recent_scanned_anon", recent_scanned[0]);
		cb->fill(cb, "recent_scanned_file", recent_scanned[1]);
	}
#endif

	return 0;
}

static u64 mem_cgroup_swappiness_read(struct cgroup *cgrp, struct cftype *cft)
{
	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);

	return get_swappiness(memcg);
}

static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
				       u64 val)
{
	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
	struct mem_cgroup *parent;

	if (val > 100)
		return -EINVAL;

	if (cgrp->parent == NULL)
		return -EINVAL;

	parent = mem_cgroup_from_cont(cgrp->parent);

	cgroup_lock();

	/* If under hierarchy, only empty-root can set this value */
	if ((parent->use_hierarchy) ||
	    (memcg->use_hierarchy && !list_empty(&cgrp->children))) {
		cgroup_unlock();
		return -EINVAL;
	}

	memcg->swappiness = val;

	cgroup_unlock();

	return 0;
}

static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
{
	struct mem_cgroup_threshold_ary *t;
	u64 usage;
	int i;

	rcu_read_lock();
	if (!swap)
		t = rcu_dereference(memcg->thresholds.primary);
	else
		t = rcu_dereference(memcg->memsw_thresholds.primary);

	if (!t)
		goto unlock;

	usage = mem_cgroup_usage(memcg, swap);

	/*
	 * current_threshold points to threshold just below usage.
	 * If it's not true, a threshold was crossed after last
	 * call of __mem_cgroup_threshold().
	 */
	i = t->current_threshold;

	/*
	 * Iterate backward over array of thresholds starting from
	 * current_threshold and check if a threshold is crossed.
	 * If none of thresholds below usage is crossed, we read
	 * only one element of the array here.
	 */
	for (; i >= 0 && unlikely(t->entries[i].threshold > usage); i--)
		eventfd_signal(t->entries[i].eventfd, 1);

	/* i = current_threshold + 1 */
	i++;

	/*
	 * Iterate forward over array of thresholds starting from
	 * current_threshold+1 and check if a threshold is crossed.
	 * If none of thresholds above usage is crossed, we read
	 * only one element of the array here.
	 */
	for (; i < t->size && unlikely(t->entries[i].threshold <= usage); i++)
		eventfd_signal(t->entries[i].eventfd, 1);

	/* Update current_threshold */
	t->current_threshold = i - 1;
unlock:
	rcu_read_unlock();
}

static void mem_cgroup_threshold(struct mem_cgroup *memcg)
{
	while (memcg) {
		__mem_cgroup_threshold(memcg, false);
		if (do_swap_account)
			__mem_cgroup_threshold(memcg, true);

		memcg = parent_mem_cgroup(memcg);
	}
}

static int compare_thresholds(const void *a, const void *b)
{
	const struct mem_cgroup_threshold *_a = a;
	const struct mem_cgroup_threshold *_b = b;

	return _a->threshold - _b->threshold;
}

static int mem_cgroup_oom_notify_cb(struct mem_cgroup *mem)
{
	struct mem_cgroup_eventfd_list *ev;

	list_for_each_entry(ev, &mem->oom_notify, list)
		eventfd_signal(ev->eventfd, 1);
	return 0;
}

static void mem_cgroup_oom_notify(struct mem_cgroup *mem)
{
	struct mem_cgroup *iter;

	for_each_mem_cgroup_tree(iter, mem)
		mem_cgroup_oom_notify_cb(iter);
}

static int mem_cgroup_usage_register_event(struct cgroup *cgrp,
	struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
{
	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
	struct mem_cgroup_thresholds *thresholds;
	struct mem_cgroup_threshold_ary *new;
	int type = MEMFILE_TYPE(cft->private);
	u64 threshold, usage;
	int i, size, ret;

	ret = res_counter_memparse_write_strategy(args, &threshold);
	if (ret)
		return ret;

	mutex_lock(&memcg->thresholds_lock);

	if (type == _MEM)
		thresholds = &memcg->thresholds;
	else if (type == _MEMSWAP)
		thresholds = &memcg->memsw_thresholds;
	else
		BUG();

	usage = mem_cgroup_usage(memcg, type == _MEMSWAP);

	/* Check if a threshold crossed before adding a new one */
	if (thresholds->primary)
		__mem_cgroup_threshold(memcg, type == _MEMSWAP);

	size = thresholds->primary ? thresholds->primary->size + 1 : 1;

	/* Allocate memory for new array of thresholds */
	new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold),
			GFP_KERNEL);
	if (!new) {
		ret = -ENOMEM;
		goto unlock;
	}
	new->size = size;

	/* Copy thresholds (if any) to new array */
	if (thresholds->primary) {
		memcpy(new->entries, thresholds->primary->entries, (size - 1) *
				sizeof(struct mem_cgroup_threshold));
	}

	/* Add new threshold */
	new->entries[size - 1].eventfd = eventfd;
	new->entries[size - 1].threshold = threshold;

	/* Sort thresholds. Registering of new threshold isn't time-critical */
	sort(new->entries, size, sizeof(struct mem_cgroup_threshold),
			compare_thresholds, NULL);

	/* Find current threshold */
	new->current_threshold = -1;
	for (i = 0; i < size; i++) {
		if (new->entries[i].threshold < usage) {
			/*
			 * new->current_threshold will not be used until
			 * rcu_assign_pointer(), so it's safe to increment
			 * it here.
			 */
			++new->current_threshold;
		}
	}

	/* Free old spare buffer and save old primary buffer as spare */
	kfree(thresholds->spare);
	thresholds->spare = thresholds->primary;

	rcu_assign_pointer(thresholds->primary, new);

	/* To be sure that nobody uses thresholds */
	synchronize_rcu();

unlock:
	mutex_unlock(&memcg->thresholds_lock);

	return ret;
}

static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp,
	struct cftype *cft, struct eventfd_ctx *eventfd)
{
	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
	struct mem_cgroup_thresholds *thresholds;
	struct mem_cgroup_threshold_ary *new;
	int type = MEMFILE_TYPE(cft->private);
	u64 usage;
	int i, j, size;

	mutex_lock(&memcg->thresholds_lock);
	if (type == _MEM)
		thresholds = &memcg->thresholds;
	else if (type == _MEMSWAP)
		thresholds = &memcg->memsw_thresholds;
	else
		BUG();

	/*
	 * Something went wrong if we trying to unregister a threshold
	 * if we don't have thresholds
	 */
	BUG_ON(!thresholds);

	usage = mem_cgroup_usage(memcg, type == _MEMSWAP);

	/* Check if a threshold crossed before removing */
	__mem_cgroup_threshold(memcg, type == _MEMSWAP);

	/* Calculate new number of threshold */
	size = 0;
	for (i = 0; i < thresholds->primary->size; i++) {
		if (thresholds->primary->entries[i].eventfd != eventfd)
			size++;
	}

	new = thresholds->spare;

	/* Set thresholds array to NULL if we don't have thresholds */
	if (!size) {
		kfree(new);
		new = NULL;
		goto swap_buffers;
	}

	new->size = size;

	/* Copy thresholds and find current threshold */
	new->current_threshold = -1;
	for (i = 0, j = 0; i < thresholds->primary->size; i++) {
		if (thresholds->primary->entries[i].eventfd == eventfd)
			continue;

		new->entries[j] = thresholds->primary->entries[i];
		if (new->entries[j].threshold < usage) {
			/*
			 * new->current_threshold will not be used
			 * until rcu_assign_pointer(), so it's safe to increment
			 * it here.
			 */
			++new->current_threshold;
		}
		j++;
	}

swap_buffers:
	/* Swap primary and spare array */
	thresholds->spare = thresholds->primary;
	rcu_assign_pointer(thresholds->primary, new);

	/* To be sure that nobody uses thresholds */
	synchronize_rcu();

	mutex_unlock(&memcg->thresholds_lock);
}

static int mem_cgroup_oom_register_event(struct cgroup *cgrp,
	struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
{
	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
	struct mem_cgroup_eventfd_list *event;
	int type = MEMFILE_TYPE(cft->private);

	BUG_ON(type != _OOM_TYPE);
	event = kmalloc(sizeof(*event),	GFP_KERNEL);
	if (!event)
		return -ENOMEM;

	mutex_lock(&memcg_oom_mutex);

	event->eventfd = eventfd;
	list_add(&event->list, &memcg->oom_notify);

	/* already in OOM ? */
	if (atomic_read(&memcg->oom_lock))
		eventfd_signal(eventfd, 1);
	mutex_unlock(&memcg_oom_mutex);

	return 0;
}

static void mem_cgroup_oom_unregister_event(struct cgroup *cgrp,
	struct cftype *cft, struct eventfd_ctx *eventfd)
{
	struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
	struct mem_cgroup_eventfd_list *ev, *tmp;
	int type = MEMFILE_TYPE(cft->private);

	BUG_ON(type != _OOM_TYPE);

	mutex_lock(&memcg_oom_mutex);

	list_for_each_entry_safe(ev, tmp, &mem->oom_notify, list) {
		if (ev->eventfd == eventfd) {
			list_del(&ev->list);
			kfree(ev);
		}
	}

	mutex_unlock(&memcg_oom_mutex);
}

static int mem_cgroup_oom_control_read(struct cgroup *cgrp,
	struct cftype *cft,  struct cgroup_map_cb *cb)
{
	struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);

	cb->fill(cb, "oom_kill_disable", mem->oom_kill_disable);

	if (atomic_read(&mem->oom_lock))
		cb->fill(cb, "under_oom", 1);
	else
		cb->fill(cb, "under_oom", 0);
	return 0;
}

static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
	struct cftype *cft, u64 val)
{
	struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
	struct mem_cgroup *parent;

	/* cannot set to root cgroup and only 0 and 1 are allowed */
	if (!cgrp->parent || !((val == 0) || (val == 1)))
		return -EINVAL;

	parent = mem_cgroup_from_cont(cgrp->parent);

	cgroup_lock();
	/* oom-kill-disable is a flag for subhierarchy. */
	if ((parent->use_hierarchy) ||
	    (mem->use_hierarchy && !list_empty(&cgrp->children))) {
		cgroup_unlock();
		return -EINVAL;
	}
	mem->oom_kill_disable = val;
	if (!val)
		memcg_oom_recover(mem);
	cgroup_unlock();
	return 0;
}

#ifdef CONFIG_NUMA
static const struct file_operations mem_control_numa_stat_file_operations = {
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

static int mem_control_numa_stat_open(struct inode *unused, struct file *file)
{
	struct cgroup *cont = file->f_dentry->d_parent->d_fsdata;

	file->f_op = &mem_control_numa_stat_file_operations;
	return single_open(file, mem_control_numa_stat_show, cont);
}
#endif /* CONFIG_NUMA */

static struct cftype mem_cgroup_files[] = {
	{
		.name = "usage_in_bytes",
		.private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
		.read_u64 = mem_cgroup_read,
		.register_event = mem_cgroup_usage_register_event,
		.unregister_event = mem_cgroup_usage_unregister_event,
	},
	{
		.name = "max_usage_in_bytes",
		.private = MEMFILE_PRIVATE(_MEM, RES_MAX_USAGE),
		.trigger = mem_cgroup_reset,
		.read_u64 = mem_cgroup_read,
	},
	{
		.name = "limit_in_bytes",
		.private = MEMFILE_PRIVATE(_MEM, RES_LIMIT),
		.write_string = mem_cgroup_write,
		.read_u64 = mem_cgroup_read,
	},
	{
		.name = "soft_limit_in_bytes",
		.private = MEMFILE_PRIVATE(_MEM, RES_SOFT_LIMIT),
		.write_string = mem_cgroup_write,
		.read_u64 = mem_cgroup_read,
	},
	{
		.name = "failcnt",
		.private = MEMFILE_PRIVATE(_MEM, RES_FAILCNT),
		.trigger = mem_cgroup_reset,
		.read_u64 = mem_cgroup_read,
	},
	{
		.name = "stat",
		.read_map = mem_control_stat_show,
	},
	{
		.name = "force_empty",
		.trigger = mem_cgroup_force_empty_write,
	},
	{
		.name = "use_hierarchy",
		.write_u64 = mem_cgroup_hierarchy_write,
		.read_u64 = mem_cgroup_hierarchy_read,
	},
	{
		.name = "swappiness",
		.read_u64 = mem_cgroup_swappiness_read,
		.write_u64 = mem_cgroup_swappiness_write,
	},
	{
		.name = "move_charge_at_immigrate",
		.read_u64 = mem_cgroup_move_charge_read,
		.write_u64 = mem_cgroup_move_charge_write,
	},
	{
		.name = "oom_control",
		.read_map = mem_cgroup_oom_control_read,
		.write_u64 = mem_cgroup_oom_control_write,
		.register_event = mem_cgroup_oom_register_event,
		.unregister_event = mem_cgroup_oom_unregister_event,
		.private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
	},
#ifdef CONFIG_NUMA
	{
		.name = "numa_stat",
		.open = mem_control_numa_stat_open,
		.mode = S_IRUGO,
	},
#endif
};

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
static struct cftype memsw_cgroup_files[] = {
	{
		.name = "memsw.usage_in_bytes",
		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
		.read_u64 = mem_cgroup_read,
		.register_event = mem_cgroup_usage_register_event,
		.unregister_event = mem_cgroup_usage_unregister_event,
	},
	{
		.name = "memsw.max_usage_in_bytes",
		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_MAX_USAGE),
		.trigger = mem_cgroup_reset,
		.read_u64 = mem_cgroup_read,
	},
	{
		.name = "memsw.limit_in_bytes",
		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_LIMIT),
		.write_string = mem_cgroup_write,
		.read_u64 = mem_cgroup_read,
	},
	{
		.name = "memsw.failcnt",
		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_FAILCNT),
		.trigger = mem_cgroup_reset,
		.read_u64 = mem_cgroup_read,
	},
};

static int register_memsw_files(struct cgroup *cont, struct cgroup_subsys *ss)
{
	if (!do_swap_account)
		return 0;
	return cgroup_add_files(cont, ss, memsw_cgroup_files,
				ARRAY_SIZE(memsw_cgroup_files));
};
#else
static int register_memsw_files(struct cgroup *cont, struct cgroup_subsys *ss)
{
	return 0;
}
#endif

static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
{
	struct mem_cgroup_per_node *pn;
	struct mem_cgroup_per_zone *mz;
	enum lru_list l;
	int zone, tmp = node;
	/*
	 * This routine is called against possible nodes.
	 * But it's BUG to call kmalloc() against offline node.
	 *
	 * TODO: this routine can waste much memory for nodes which will
	 *       never be onlined. It's better to use memory hotplug callback
	 *       function.
	 */
	if (!node_state(node, N_NORMAL_MEMORY))
		tmp = -1;
	pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, tmp);
	if (!pn)
		return 1;

	mem->info.nodeinfo[node] = pn;
	for (zone = 0; zone < MAX_NR_ZONES; zone++) {
		mz = &pn->zoneinfo[zone];
		for_each_lru(l)
			INIT_LIST_HEAD(&mz->lists[l]);
		mz->usage_in_excess = 0;
		mz->on_tree = false;
		mz->mem = mem;
	}
	return 0;
}

static void free_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
{
	kfree(mem->info.nodeinfo[node]);
}

static struct mem_cgroup *mem_cgroup_alloc(void)
{
	struct mem_cgroup *mem;
	int size = sizeof(struct mem_cgroup);

	/* Can be very big if MAX_NUMNODES is very big */
	if (size < PAGE_SIZE)
		mem = kzalloc(size, GFP_KERNEL);
	else
		mem = vzalloc(size);

	if (!mem)
		return NULL;

	mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
	if (!mem->stat)
		goto out_free;
	spin_lock_init(&mem->pcp_counter_lock);
	return mem;

out_free:
	if (size < PAGE_SIZE)
		kfree(mem);
	else
		vfree(mem);
	return NULL;
}

/*
 * At destroying mem_cgroup, references from swap_cgroup can remain.
 * (scanning all at force_empty is too costly...)
 *
 * Instead of clearing all references at force_empty, we remember
 * the number of reference from swap_cgroup and free mem_cgroup when
 * it goes down to 0.
 *
 * Removal of cgroup itself succeeds regardless of refs from swap.
 */

static void __mem_cgroup_free(struct mem_cgroup *mem)
{
	int node;

	mem_cgroup_remove_from_trees(mem);
	free_css_id(&mem_cgroup_subsys, &mem->css);

	for_each_node_state(node, N_POSSIBLE)
		free_mem_cgroup_per_zone_info(mem, node);

	free_percpu(mem->stat);
	if (sizeof(struct mem_cgroup) < PAGE_SIZE)
		kfree(mem);
	else
		vfree(mem);
}

static void mem_cgroup_get(struct mem_cgroup *mem)
{
	atomic_inc(&mem->refcnt);
}

static void __mem_cgroup_put(struct mem_cgroup *mem, int count)
{
	if (atomic_sub_and_test(count, &mem->refcnt)) {
		struct mem_cgroup *parent = parent_mem_cgroup(mem);
		__mem_cgroup_free(mem);
		if (parent)
			mem_cgroup_put(parent);
	}
}

static void mem_cgroup_put(struct mem_cgroup *mem)
{
	__mem_cgroup_put(mem, 1);
}

/*
 * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled.
 */
static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem)
{
	if (!mem->res.parent)
		return NULL;
	return mem_cgroup_from_res_counter(mem->res.parent, res);
}

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
static void __init enable_swap_cgroup(void)
{
	if (!mem_cgroup_disabled() && really_do_swap_account)
		do_swap_account = 1;
}
#else
static void __init enable_swap_cgroup(void)
{
}
#endif

static int mem_cgroup_soft_limit_tree_init(void)
{
	struct mem_cgroup_tree_per_node *rtpn;
	struct mem_cgroup_tree_per_zone *rtpz;
	int tmp, node, zone;

	for_each_node_state(node, N_POSSIBLE) {
		tmp = node;
		if (!node_state(node, N_NORMAL_MEMORY))
			tmp = -1;
		rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, tmp);
		if (!rtpn)
			return 1;

		soft_limit_tree.rb_tree_per_node[node] = rtpn;

		for (zone = 0; zone < MAX_NR_ZONES; zone++) {
			rtpz = &rtpn->rb_tree_per_zone[zone];
			rtpz->rb_root = RB_ROOT;
			spin_lock_init(&rtpz->lock);
		}
	}
	return 0;
}

static struct cgroup_subsys_state * __ref
mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
{
	struct mem_cgroup *mem, *parent;
	long error = -ENOMEM;
	int node;

	mem = mem_cgroup_alloc();
	if (!mem)
		return ERR_PTR(error);

	for_each_node_state(node, N_POSSIBLE)
		if (alloc_mem_cgroup_per_zone_info(mem, node))
			goto free_out;

	/* root ? */
	if (cont->parent == NULL) {
		int cpu;
		enable_swap_cgroup();
		parent = NULL;
		root_mem_cgroup = mem;
		if (mem_cgroup_soft_limit_tree_init())
			goto free_out;
		for_each_possible_cpu(cpu) {
			struct memcg_stock_pcp *stock =
						&per_cpu(memcg_stock, cpu);
			INIT_WORK(&stock->work, drain_local_stock);
		}
		hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
	} else {
		parent = mem_cgroup_from_cont(cont->parent);
		mem->use_hierarchy = parent->use_hierarchy;
		mem->oom_kill_disable = parent->oom_kill_disable;
	}

	if (parent && parent->use_hierarchy) {
		res_counter_init(&mem->res, &parent->res);
		res_counter_init(&mem->memsw, &parent->memsw);
		/*
		 * We increment refcnt of the parent to ensure that we can
		 * safely access it on res_counter_charge/uncharge.
		 * This refcnt will be decremented when freeing this
		 * mem_cgroup(see mem_cgroup_put).
		 */
		mem_cgroup_get(parent);
	} else {
		res_counter_init(&mem->res, NULL);
		res_counter_init(&mem->memsw, NULL);
	}
	mem->last_scanned_child = 0;
	mem->last_scanned_node = MAX_NUMNODES;
	INIT_LIST_HEAD(&mem->oom_notify);

	if (parent)
		mem->swappiness = get_swappiness(parent);
	atomic_set(&mem->refcnt, 1);
	mem->move_charge_at_immigrate = 0;
	mutex_init(&mem->thresholds_lock);
	return &mem->css;
free_out:
	__mem_cgroup_free(mem);
	root_mem_cgroup = NULL;
	return ERR_PTR(error);
}

static int mem_cgroup_pre_destroy(struct cgroup_subsys *ss,
					struct cgroup *cont)
{
	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);

	return mem_cgroup_force_empty(mem, false);
}

static void mem_cgroup_destroy(struct cgroup_subsys *ss,
				struct cgroup *cont)
{
	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);

	mem_cgroup_put(mem);
}

static int mem_cgroup_populate(struct cgroup_subsys *ss,
				struct cgroup *cont)
{
	int ret;

	ret = cgroup_add_files(cont, ss, mem_cgroup_files,
				ARRAY_SIZE(mem_cgroup_files));

	if (!ret)
		ret = register_memsw_files(cont, ss);
	return ret;
}

#ifdef CONFIG_MMU
/* Handlers for move charge at task migration. */
#define PRECHARGE_COUNT_AT_ONCE	256
static int mem_cgroup_do_precharge(unsigned long count)
{
	int ret = 0;
	int batch_count = PRECHARGE_COUNT_AT_ONCE;
	struct mem_cgroup *mem = mc.to;

	if (mem_cgroup_is_root(mem)) {
		mc.precharge += count;
		/* we don't need css_get for root */
		return ret;
	}
	/* try to charge at once */
	if (count > 1) {
		struct res_counter *dummy;
		/*
		 * "mem" cannot be under rmdir() because we've already checked
		 * by cgroup_lock_live_cgroup() that it is not removed and we
		 * are still under the same cgroup_mutex. So we can postpone
		 * css_get().
		 */
		if (res_counter_charge(&mem->res, PAGE_SIZE * count, &dummy))
			goto one_by_one;
		if (do_swap_account && res_counter_charge(&mem->memsw,
						PAGE_SIZE * count, &dummy)) {
			res_counter_uncharge(&mem->res, PAGE_SIZE * count);
			goto one_by_one;
		}
		mc.precharge += count;
		return ret;
	}
one_by_one:
	/* fall back to one by one charge */
	while (count--) {
		if (signal_pending(current)) {
			ret = -EINTR;
			break;
		}
		if (!batch_count--) {
			batch_count = PRECHARGE_COUNT_AT_ONCE;
			cond_resched();
		}
		ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, 1, &mem, false);
		if (ret || !mem)
			/* mem_cgroup_clear_mc() will do uncharge later */
			return -ENOMEM;
		mc.precharge++;
	}
	return ret;
}

/**
 * is_target_pte_for_mc - check a pte whether it is valid for move charge
 * @vma: the vma the pte to be checked belongs
 * @addr: the address corresponding to the pte to be checked
 * @ptent: the pte to be checked
 * @target: the pointer the target page or swap ent will be stored(can be NULL)
 *
 * Returns
 *   0(MC_TARGET_NONE): if the pte is not a target for move charge.
 *   1(MC_TARGET_PAGE): if the page corresponding to this pte is a target for
 *     move charge. if @target is not NULL, the page is stored in target->page
 *     with extra refcnt got(Callers should handle it).
 *   2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
 *     target for charge migration. if @target is not NULL, the entry is stored
 *     in target->ent.
 *
 * Called with pte lock held.
 */
union mc_target {
	struct page	*page;
	swp_entry_t	ent;
};

enum mc_target_type {
	MC_TARGET_NONE,	/* not used */
	MC_TARGET_PAGE,
	MC_TARGET_SWAP,
};

static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
						unsigned long addr, pte_t ptent)
{
	struct page *page = vm_normal_page(vma, addr, ptent);

	if (!page || !page_mapped(page))
		return NULL;
	if (PageAnon(page)) {
		/* we don't move shared anon */
		if (!move_anon() || page_mapcount(page) > 2)
			return NULL;
	} else if (!move_file())
		/* we ignore mapcount for file pages */
		return NULL;
	if (!get_page_unless_zero(page))
		return NULL;

	return page;
}

static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
			unsigned long addr, pte_t ptent, swp_entry_t *entry)
{
	int usage_count;
	struct page *page = NULL;
	swp_entry_t ent = pte_to_swp_entry(ptent);

	if (!move_anon() || non_swap_entry(ent))
		return NULL;
	usage_count = mem_cgroup_count_swap_user(ent, &page);
	if (usage_count > 1) { /* we don't move shared anon */
		if (page)
			put_page(page);
		return NULL;
	}
	if (do_swap_account)
		entry->val = ent.val;

	return page;
}

static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
			unsigned long addr, pte_t ptent, swp_entry_t *entry)
{
	struct page *page = NULL;
	struct inode *inode;
	struct address_space *mapping;
	pgoff_t pgoff;

	if (!vma->vm_file) /* anonymous vma */
		return NULL;
	if (!move_file())
		return NULL;

	inode = vma->vm_file->f_path.dentry->d_inode;
	mapping = vma->vm_file->f_mapping;
	if (pte_none(ptent))
		pgoff = linear_page_index(vma, addr);
	else /* pte_file(ptent) is true */
		pgoff = pte_to_pgoff(ptent);

	/* page is moved even if it's not RSS of this task(page-faulted). */
	if (!mapping_cap_swap_backed(mapping)) { /* normal file */
		page = find_get_page(mapping, pgoff);
	} else { /* shmem/tmpfs file. we should take account of swap too. */
		swp_entry_t ent;
		mem_cgroup_get_shmem_target(inode, pgoff, &page, &ent);
		if (do_swap_account)
			entry->val = ent.val;
	}

	return page;
}

static int is_target_pte_for_mc(struct vm_area_struct *vma,
		unsigned long addr, pte_t ptent, union mc_target *target)
{
	struct page *page = NULL;
	struct page_cgroup *pc;
	int ret = 0;
	swp_entry_t ent = { .val = 0 };

	if (pte_present(ptent))
		page = mc_handle_present_pte(vma, addr, ptent);
	else if (is_swap_pte(ptent))
		page = mc_handle_swap_pte(vma, addr, ptent, &ent);
	else if (pte_none(ptent) || pte_file(ptent))
		page = mc_handle_file_pte(vma, addr, ptent, &ent);

	if (!page && !ent.val)
		return 0;
	if (page) {
		pc = lookup_page_cgroup(page);
		/*
		 * Do only loose check w/o page_cgroup lock.
		 * mem_cgroup_move_account() checks the pc is valid or not under
		 * the lock.
		 */
		if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
			ret = MC_TARGET_PAGE;
			if (target)
				target->page = page;
		}
		if (!ret || !target)
			put_page(page);
	}
	/* There is a swap entry and a page doesn't exist or isn't charged */
	if (ent.val && !ret &&
			css_id(&mc.from->css) == lookup_swap_cgroup(ent)) {
		ret = MC_TARGET_SWAP;
		if (target)
			target->ent = ent;
	}
	return ret;
}

static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
					unsigned long addr, unsigned long end,
					struct mm_walk *walk)
{
	struct vm_area_struct *vma = walk->private;
	pte_t *pte;
	spinlock_t *ptl;

	split_huge_page_pmd(walk->mm, pmd);

	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
	for (; addr != end; pte++, addr += PAGE_SIZE)
		if (is_target_pte_for_mc(vma, addr, *pte, NULL))
			mc.precharge++;	/* increment precharge temporarily */
	pte_unmap_unlock(pte - 1, ptl);
	cond_resched();

	return 0;
}

static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
{
	unsigned long precharge;
	struct vm_area_struct *vma;

	down_read(&mm->mmap_sem);
	for (vma = mm->mmap; vma; vma = vma->vm_next) {
		struct mm_walk mem_cgroup_count_precharge_walk = {
			.pmd_entry = mem_cgroup_count_precharge_pte_range,
			.mm = mm,
			.private = vma,
		};
		if (is_vm_hugetlb_page(vma))
			continue;
		walk_page_range(vma->vm_start, vma->vm_end,
					&mem_cgroup_count_precharge_walk);
	}
	up_read(&mm->mmap_sem);

	precharge = mc.precharge;
	mc.precharge = 0;

	return precharge;
}

static int mem_cgroup_precharge_mc(struct mm_struct *mm)
{
	unsigned long precharge = mem_cgroup_count_precharge(mm);

	VM_BUG_ON(mc.moving_task);
	mc.moving_task = current;
	return mem_cgroup_do_precharge(precharge);
}

/* cancels all extra charges on mc.from and mc.to, and wakes up all waiters. */
static void __mem_cgroup_clear_mc(void)
{
	struct mem_cgroup *from = mc.from;
	struct mem_cgroup *to = mc.to;

	/* we must uncharge all the leftover precharges from mc.to */
	if (mc.precharge) {
		__mem_cgroup_cancel_charge(mc.to, mc.precharge);
		mc.precharge = 0;
	}
	/*
	 * we didn't uncharge from mc.from at mem_cgroup_move_account(), so
	 * we must uncharge here.
	 */
	if (mc.moved_charge) {
		__mem_cgroup_cancel_charge(mc.from, mc.moved_charge);
		mc.moved_charge = 0;
	}
	/* we must fixup refcnts and charges */
	if (mc.moved_swap) {
		/* uncharge swap account from the old cgroup */
		if (!mem_cgroup_is_root(mc.from))
			res_counter_uncharge(&mc.from->memsw,
						PAGE_SIZE * mc.moved_swap);
		__mem_cgroup_put(mc.from, mc.moved_swap);

		if (!mem_cgroup_is_root(mc.to)) {
			/*
			 * we charged both to->res and to->memsw, so we should
			 * uncharge to->res.
			 */
			res_counter_uncharge(&mc.to->res,
						PAGE_SIZE * mc.moved_swap);
		}
		/* we've already done mem_cgroup_get(mc.to) */
		mc.moved_swap = 0;
	}
	memcg_oom_recover(from);
	memcg_oom_recover(to);
	wake_up_all(&mc.waitq);
}

static void mem_cgroup_clear_mc(void)
{
	struct mem_cgroup *from = mc.from;

	/*
	 * we must clear moving_task before waking up waiters at the end of
	 * task migration.
	 */
	mc.moving_task = NULL;
	__mem_cgroup_clear_mc();
	spin_lock(&mc.lock);
	mc.from = NULL;
	mc.to = NULL;
	spin_unlock(&mc.lock);
	mem_cgroup_end_move(from);
}

static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
				struct cgroup *cgroup,
				struct task_struct *p)
{
	int ret = 0;
	struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);

	if (mem->move_charge_at_immigrate) {
		struct mm_struct *mm;
		struct mem_cgroup *from = mem_cgroup_from_task(p);

		VM_BUG_ON(from == mem);

		mm = get_task_mm(p);
		if (!mm)
			return 0;
		/* We move charges only when we move a owner of the mm */
		if (mm->owner == p) {
			VM_BUG_ON(mc.from);
			VM_BUG_ON(mc.to);
			VM_BUG_ON(mc.precharge);
			VM_BUG_ON(mc.moved_charge);
			VM_BUG_ON(mc.moved_swap);
			mem_cgroup_start_move(from);
			spin_lock(&mc.lock);
			mc.from = from;
			mc.to = mem;
			spin_unlock(&mc.lock);
			/* We set mc.moving_task later */

			ret = mem_cgroup_precharge_mc(mm);
			if (ret)
				mem_cgroup_clear_mc();
		}
		mmput(mm);
	}
	return ret;
}

static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
				struct cgroup *cgroup,
				struct task_struct *p)
{
	mem_cgroup_clear_mc();
}

static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
				unsigned long addr, unsigned long end,
				struct mm_walk *walk)
{
	int ret = 0;
	struct vm_area_struct *vma = walk->private;
	pte_t *pte;
	spinlock_t *ptl;

	split_huge_page_pmd(walk->mm, pmd);
retry:
	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
	for (; addr != end; addr += PAGE_SIZE) {
		pte_t ptent = *(pte++);
		union mc_target target;
		int type;
		struct page *page;
		struct page_cgroup *pc;
		swp_entry_t ent;

		if (!mc.precharge)
			break;

		type = is_target_pte_for_mc(vma, addr, ptent, &target);
		switch (type) {
		case MC_TARGET_PAGE:
			page = target.page;
			if (isolate_lru_page(page))
				goto put;
			pc = lookup_page_cgroup(page);
			if (!mem_cgroup_move_account(page, 1, pc,
						     mc.from, mc.to, false)) {
				mc.precharge--;
				/* we uncharge from mc.from later. */
				mc.moved_charge++;
			}
			putback_lru_page(page);
put:			/* is_target_pte_for_mc() gets the page */
			put_page(page);
			break;
		case MC_TARGET_SWAP:
			ent = target.ent;
			if (!mem_cgroup_move_swap_account(ent,
						mc.from, mc.to, false)) {
				mc.precharge--;
				/* we fixup refcnts and charges later. */
				mc.moved_swap++;
			}
			break;
		default:
			break;
		}
	}
	pte_unmap_unlock(pte - 1, ptl);
	cond_resched();

	if (addr != end) {
		/*
		 * We have consumed all precharges we got in can_attach().
		 * We try charge one by one, but don't do any additional
		 * charges to mc.to if we have failed in charge once in attach()
		 * phase.
		 */
		ret = mem_cgroup_do_precharge(1);
		if (!ret)
			goto retry;
	}

	return ret;
}

static void mem_cgroup_move_charge(struct mm_struct *mm)
{
	struct vm_area_struct *vma;

	lru_add_drain_all();
retry:
	if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
		/*
		 * Someone who are holding the mmap_sem might be waiting in
		 * waitq. So we cancel all extra charges, wake up all waiters,
		 * and retry. Because we cancel precharges, we might not be able
		 * to move enough charges, but moving charge is a best-effort
		 * feature anyway, so it wouldn't be a big problem.
		 */
		__mem_cgroup_clear_mc();
		cond_resched();
		goto retry;
	}
	for (vma = mm->mmap; vma; vma = vma->vm_next) {
		int ret;
		struct mm_walk mem_cgroup_move_charge_walk = {
			.pmd_entry = mem_cgroup_move_charge_pte_range,
			.mm = mm,
			.private = vma,
		};
		if (is_vm_hugetlb_page(vma))
			continue;
		ret = walk_page_range(vma->vm_start, vma->vm_end,
						&mem_cgroup_move_charge_walk);
		if (ret)
			/*
			 * means we have consumed all precharges and failed in
			 * doing additional charge. Just abandon here.
			 */
			break;
	}
	up_read(&mm->mmap_sem);
}

static void mem_cgroup_move_task(struct cgroup_subsys *ss,
				struct cgroup *cont,
				struct cgroup *old_cont,
				struct task_struct *p)
{
	struct mm_struct *mm = get_task_mm(p);

	if (mm) {
		if (mc.to)
			mem_cgroup_move_charge(mm);
		put_swap_token(mm);
		mmput(mm);
	}
	if (mc.to)
		mem_cgroup_clear_mc();
}
#else	/* !CONFIG_MMU */
static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
				struct cgroup *cgroup,
				struct task_struct *p)
{
	return 0;
}
static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
				struct cgroup *cgroup,
				struct task_struct *p)
{
}
static void mem_cgroup_move_task(struct cgroup_subsys *ss,
				struct cgroup *cont,
				struct cgroup *old_cont,
				struct task_struct *p)
{
}
#endif

struct cgroup_subsys mem_cgroup_subsys = {
	.name = "memory",
	.subsys_id = mem_cgroup_subsys_id,
	.create = mem_cgroup_create,
	.pre_destroy = mem_cgroup_pre_destroy,
	.destroy = mem_cgroup_destroy,
	.populate = mem_cgroup_populate,
	.can_attach = mem_cgroup_can_attach,
	.cancel_attach = mem_cgroup_cancel_attach,
	.attach = mem_cgroup_move_task,
	.early_init = 0,
	.use_id = 1,
};

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
static int __init enable_swap_account(char *s)
{
	/* consider enabled if no parameter or 1 is given */
	if (!strcmp(s, "1"))
		really_do_swap_account = 1;
	else if (!strcmp(s, "0"))
		really_do_swap_account = 0;
	return 1;
}
__setup("swapaccount=", enable_swap_account);

#endif

Re: [PATCH 0/3] mm: improve proportional memcg protection

[Yafang Shao]

On Tue, Apr 28, 2020 at 11:38 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Tue, Apr 28, 2020 at 09:45:27AM +0800, Yafang Shao wrote:
> > On Tue, Apr 28, 2020 at 1:05 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
> > > On Sat, Apr 25, 2020 at 11:24:15AM -0400, Yafang Shao wrote:
> > > > Since proportional memory.{min, low} reclaim is introduced in
> > > > commit 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim"),
> > > > it have been proved that the proportional reclaim is hard to understand and
> > > > the issues caused by it is harder to understand.[1]. That dilemma faced by
> > > > us is caused by that the proportional reclaim mixed up memcg and the
> > > > reclaim context.
> > > >
> > > > In proportional reclaim, the whole reclaim context - includes the memcg
> > > > to be reclaimed and the reclaimer, should be considered, rather than
> > > > memcg only.
> > > >
> > > > To make it clear, a new member 'protection' is introduced in the reclaim
> > > > context (struct shrink_control) to replace mem_cgroup_protection(). This
> > > > one is set when we check whether the memcg is protected or not.
> > >
> > > This patch series makes the code harder to understand.
> > >
> >
> > I don't think so.
> > With this  patchset, you don't need to care about what the emin of this
> > memcg and its parent should be when you calculate the scan count.
> > Furthermore, you don't need to worry about the potential race when you
> > are getting the scan count.
> > 'Protection' is calculated when we check whether the memcg is
> > 'protected' or not, that is really easy to understand.
>
> If we could calculate emin and elow in one go at the beginning of the
> reclaim walk and then operate on private copies inside scan_control, I
> would agree with you. It would be better. But that would require
> replicating the entire cgroup tree structure, which isn't practical.
>

Note that we have to scan the entire cgroup tree when we are reclaiming pages.
Each scanned memcg has to check mem_cgroup_protection(), so why do you
think this is practical ?

> After your patch we're still building and propagating shared
> hierarchical state as we iterate through the cgroup tree.

I'm waiting your patch, with the expectation that you can fix this
issue perfectly.

> I'm not sure
> why handing off scan_control and having somebody else write the racy
> state in there is supposed to make it better.
>
> > > It's already tricky to understand ownership and lifetime/validity of
> > > struct scan_control members when it's just vmscan.c functions touching
> > > them.
> >
> > Note that the reclaimers can call the funtions existing in vmscan.c,
> > compaction.c, slub.c, filemap.c, oom_kill.c, workingset.c,
> > page-writeback.c, swap.c, khugepaged.c and etc. IOW, it may be used in
> > these functions sooner or later.
>
> Right, but in general we try to make helper functions and predicates
> operate on very specific pieces of data, with clearly delineated side
> effects.
>

I'm sorry that I can't find any "clearly delineated side effects" on
the helper mem_cgroup_protection() when they are operating on the
"very specific pieces of data" emin and elow.
I'm not sure whether there is double standard here.


> Your patch is handing off a huge collection of private data that
> drives the reclaim algorithm and gives it to an external function for
> non-obvious manipulation.
>

However,  mem_cgroup_protection() is doing the same thing.

> > > Expanding the scope to the entire MM is a bad idea.
> > >
> >
> > Well, mem_cgroup_protection() is only used in memcontrol.c and vmscan.c.
> > So expanding the scope to the entire LINUX is a MORE bad idea.
> > There may be some other functions doing this as well.
>
> That's a /much/ less exposed interface.
>

There're many structs in memcontrol.h which are only used in
memcontrol.c but exposed to the entire linux.
I'm not sure whether they are /much/ less exposed or not.

> > > Splitting up sc->memcg_low_reclaim handling and the associated restart
> > > logic makes control flow harder to follow as well.
> > >
> >
> > Placing sc->memcg_low_reclaim in lots of callsites make the control
> > flow more than harder to follow.
>
> Those are the places where the control flow decisions are actually
> made. You didn't change that, you just obscured how those decisions
> are being made and who owns which parts of the state machine.
>

I can't agree with you.
The callsite in get_can_count() really don't care about whether it is
memcg_low_reclaim or not, while it really cares is how many pages can
be scanned.  The control flow should be made when you check the memcg,
and then the others only need to care about the result of this
decision.

> > Seems we can't get an agreement on how to improve current code.
> > So I will submit a patch to revert the commit 9783aa9917f8 ("mm,
> > memcg: proportional memory.{low,min} reclaim") first.
>
> What do you think that will accomplish?
>

I think that there will be perfromance regression in target reclaim,
however, I hope my understanding is wrong.
But I haven't done more performance regression test to verify my
understanding, as I'm really busy currently to explain to our users
that why the result of memcg protection is not expected. I will do
some verification once I'm escaped from my current bad situation.

> > BTW, I can't image why such a bad  and ugly implementation got merged
> > in the first place.
> > The quantity of memory cgroup is becoming more and more bad.
>
> I'm sorry you feel that way. However, it's always possible to use an
> earlier version of the memory controller. Here is a good one from 2011:
>

Thanks for you suggestion, but I'm not sure whether it cooperates well
with the other parts of the entire linux kernel.

> /* memcontrol.c - Memory Controller
>  *
>  * Copyright IBM Corporation, 2007
>  * Author Balbir Singh <balbir@linux.vnet.ibm.com>
>  *
>  * Copyright 2007 OpenVZ SWsoft Inc
>  * Author: Pavel Emelianov <xemul@openvz.org>
>  *
>  * Memory thresholds
>  * Copyright (C) 2009 Nokia Corporation
>  * Author: Kirill A. Shutemov
>  *
>  * This program is free software; you can redistribute it and/or modify
>  * it under the terms of the GNU General Public License as published by
>  * the Free Software Foundation; either version 2 of the License, or
>  * (at your option) any later version.
>  *
>  * This program is distributed in the hope that it will be useful,
>  * but WITHOUT ANY WARRANTY; without even the implied warranty of
>  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>  * GNU General Public License for more details.
>  */
>
> #include <linux/res_counter.h>
> #include <linux/memcontrol.h>
> #include <linux/cgroup.h>
> #include <linux/mm.h>
> #include <linux/hugetlb.h>
> #include <linux/pagemap.h>
> #include <linux/smp.h>
> #include <linux/page-flags.h>
> #include <linux/backing-dev.h>
> #include <linux/bit_spinlock.h>
> #include <linux/rcupdate.h>
> #include <linux/limits.h>
> #include <linux/mutex.h>
> #include <linux/rbtree.h>
> #include <linux/shmem_fs.h>
> #include <linux/slab.h>
> #include <linux/swap.h>
> #include <linux/swapops.h>
> #include <linux/spinlock.h>
> #include <linux/eventfd.h>
> #include <linux/sort.h>
> #include <linux/fs.h>
> #include <linux/seq_file.h>
> #include <linux/vmalloc.h>
> #include <linux/mm_inline.h>
> #include <linux/page_cgroup.h>
> #include <linux/cpu.h>
> #include <linux/oom.h>
> #include "internal.h"
>
> #include <asm/uaccess.h>
>
> #include <trace/events/vmscan.h>
>
> struct cgroup_subsys mem_cgroup_subsys __read_mostly;
> #define MEM_CGROUP_RECLAIM_RETRIES      5
> struct mem_cgroup *root_mem_cgroup __read_mostly;
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> /* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
> int do_swap_account __read_mostly;
>
> /* for remember boot option*/
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED
> static int really_do_swap_account __initdata = 1;
> #else
> static int really_do_swap_account __initdata = 0;
> #endif
>
> #else
> #define do_swap_account         (0)
> #endif
>
>
> /*
>  * Statistics for memory cgroup.
>  */
> enum mem_cgroup_stat_index {
>         /*
>          * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
>          */
>         MEM_CGROUP_STAT_CACHE,     /* # of pages charged as cache */
>         MEM_CGROUP_STAT_RSS,       /* # of pages charged as anon rss */
>         MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
>         MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
>         MEM_CGROUP_STAT_DATA, /* end of data requires synchronization */
>         MEM_CGROUP_ON_MOVE,     /* someone is moving account between groups */
>         MEM_CGROUP_STAT_NSTATS,
> };
>
> enum mem_cgroup_events_index {
>         MEM_CGROUP_EVENTS_PGPGIN,       /* # of pages paged in */
>         MEM_CGROUP_EVENTS_PGPGOUT,      /* # of pages paged out */
>         MEM_CGROUP_EVENTS_COUNT,        /* # of pages paged in/out */
>         MEM_CGROUP_EVENTS_PGFAULT,      /* # of page-faults */
>         MEM_CGROUP_EVENTS_PGMAJFAULT,   /* # of major page-faults */
>         MEM_CGROUP_EVENTS_NSTATS,
> };
> /*
>  * Per memcg event counter is incremented at every pagein/pageout. With THP,
>  * it will be incremated by the number of pages. This counter is used for
>  * for trigger some periodic events. This is straightforward and better
>  * than using jiffies etc. to handle periodic memcg event.
>  */
> enum mem_cgroup_events_target {
>         MEM_CGROUP_TARGET_THRESH,
>         MEM_CGROUP_TARGET_SOFTLIMIT,
>         MEM_CGROUP_TARGET_NUMAINFO,
>         MEM_CGROUP_NTARGETS,
> };
> #define THRESHOLDS_EVENTS_TARGET (128)
> #define SOFTLIMIT_EVENTS_TARGET (1024)
> #define NUMAINFO_EVENTS_TARGET  (1024)
>
> struct mem_cgroup_stat_cpu {
>         long count[MEM_CGROUP_STAT_NSTATS];
>         unsigned long events[MEM_CGROUP_EVENTS_NSTATS];
>         unsigned long targets[MEM_CGROUP_NTARGETS];
> };
>
> /*
>  * per-zone information in memory controller.
>  */
> struct mem_cgroup_per_zone {
>         /*
>          * spin_lock to protect the per cgroup LRU
>          */
>         struct list_head        lists[NR_LRU_LISTS];
>         unsigned long           count[NR_LRU_LISTS];
>
>         struct zone_reclaim_stat reclaim_stat;
>         struct rb_node          tree_node;      /* RB tree node */
>         unsigned long long      usage_in_excess;/* Set to the value by which */
>                                                 /* the soft limit is exceeded*/
>         bool                    on_tree;
>         struct mem_cgroup       *mem;           /* Back pointer, we cannot */
>                                                 /* use container_of        */
> };
> /* Macro for accessing counter */
> #define MEM_CGROUP_ZSTAT(mz, idx)       ((mz)->count[(idx)])
>
> struct mem_cgroup_per_node {
>         struct mem_cgroup_per_zone zoneinfo[MAX_NR_ZONES];
> };
>
> struct mem_cgroup_lru_info {
>         struct mem_cgroup_per_node *nodeinfo[MAX_NUMNODES];
> };
>
> /*
>  * Cgroups above their limits are maintained in a RB-Tree, independent of
>  * their hierarchy representation
>  */
>
> struct mem_cgroup_tree_per_zone {
>         struct rb_root rb_root;
>         spinlock_t lock;
> };
>
> struct mem_cgroup_tree_per_node {
>         struct mem_cgroup_tree_per_zone rb_tree_per_zone[MAX_NR_ZONES];
> };
>
> struct mem_cgroup_tree {
>         struct mem_cgroup_tree_per_node *rb_tree_per_node[MAX_NUMNODES];
> };
>
> static struct mem_cgroup_tree soft_limit_tree __read_mostly;
>
> struct mem_cgroup_threshold {
>         struct eventfd_ctx *eventfd;
>         u64 threshold;
> };
>
> /* For threshold */
> struct mem_cgroup_threshold_ary {
>         /* An array index points to threshold just below usage. */
>         int current_threshold;
>         /* Size of entries[] */
>         unsigned int size;
>         /* Array of thresholds */
>         struct mem_cgroup_threshold entries[0];
> };
>
> struct mem_cgroup_thresholds {
>         /* Primary thresholds array */
>         struct mem_cgroup_threshold_ary *primary;
>         /*
>          * Spare threshold array.
>          * This is needed to make mem_cgroup_unregister_event() "never fail".
>          * It must be able to store at least primary->size - 1 entries.
>          */
>         struct mem_cgroup_threshold_ary *spare;
> };
>
> /* for OOM */
> struct mem_cgroup_eventfd_list {
>         struct list_head list;
>         struct eventfd_ctx *eventfd;
> };
>
> static void mem_cgroup_threshold(struct mem_cgroup *mem);
> static void mem_cgroup_oom_notify(struct mem_cgroup *mem);
>
> /*
>  * The memory controller data structure. The memory controller controls both
>  * page cache and RSS per cgroup. We would eventually like to provide
>  * statistics based on the statistics developed by Rik Van Riel for clock-pro,
>  * to help the administrator determine what knobs to tune.
>  *
>  * TODO: Add a water mark for the memory controller. Reclaim will begin when
>  * we hit the water mark. May be even add a low water mark, such that
>  * no reclaim occurs from a cgroup at it's low water mark, this is
>  * a feature that will be implemented much later in the future.
>  */
> struct mem_cgroup {
>         struct cgroup_subsys_state css;
>         /*
>          * the counter to account for memory usage
>          */
>         struct res_counter res;
>         /*
>          * the counter to account for mem+swap usage.
>          */
>         struct res_counter memsw;
>         /*
>          * Per cgroup active and inactive list, similar to the
>          * per zone LRU lists.
>          */
>         struct mem_cgroup_lru_info info;
>         /*
>          * While reclaiming in a hierarchy, we cache the last child we
>          * reclaimed from.
>          */
>         int last_scanned_child;
>         int last_scanned_node;
> #if MAX_NUMNODES > 1
>         nodemask_t      scan_nodes;
>         atomic_t        numainfo_events;
>         atomic_t        numainfo_updating;
> #endif
>         /*
>          * Should the accounting and control be hierarchical, per subtree?
>          */
>         bool use_hierarchy;
>         atomic_t        oom_lock;
>         atomic_t        refcnt;
>
>         unsigned int    swappiness;
>         /* OOM-Killer disable */
>         int             oom_kill_disable;
>
>         /* set when res.limit == memsw.limit */
>         bool            memsw_is_minimum;
>
>         /* protect arrays of thresholds */
>         struct mutex thresholds_lock;
>
>         /* thresholds for memory usage. RCU-protected */
>         struct mem_cgroup_thresholds thresholds;
>
>         /* thresholds for mem+swap usage. RCU-protected */
>         struct mem_cgroup_thresholds memsw_thresholds;
>
>         /* For oom notifier event fd */
>         struct list_head oom_notify;
>
>         /*
>          * Should we move charges of a task when a task is moved into this
>          * mem_cgroup ? And what type of charges should we move ?
>          */
>         unsigned long   move_charge_at_immigrate;
>         /*
>          * percpu counter.
>          */
>         struct mem_cgroup_stat_cpu *stat;
>         /*
>          * used when a cpu is offlined or other synchronizations
>          * See mem_cgroup_read_stat().
>          */
>         struct mem_cgroup_stat_cpu nocpu_base;
>         spinlock_t pcp_counter_lock;
> };
>
> /* Stuffs for move charges at task migration. */
> /*
>  * Types of charges to be moved. "move_charge_at_immitgrate" is treated as a
>  * left-shifted bitmap of these types.
>  */
> enum move_type {
>         MOVE_CHARGE_TYPE_ANON,  /* private anonymous page and swap of it */
>         MOVE_CHARGE_TYPE_FILE,  /* file page(including tmpfs) and swap of it */
>         NR_MOVE_TYPE,
> };
>
> /* "mc" and its members are protected by cgroup_mutex */
> static struct move_charge_struct {
>         spinlock_t        lock; /* for from, to */
>         struct mem_cgroup *from;
>         struct mem_cgroup *to;
>         unsigned long precharge;
>         unsigned long moved_charge;
>         unsigned long moved_swap;
>         struct task_struct *moving_task;        /* a task moving charges */
>         wait_queue_head_t waitq;                /* a waitq for other context */
> } mc = {
>         .lock = __SPIN_LOCK_UNLOCKED(mc.lock),
>         .waitq = __WAIT_QUEUE_HEAD_INITIALIZER(mc.waitq),
> };
>
> static bool move_anon(void)
> {
>         return test_bit(MOVE_CHARGE_TYPE_ANON,
>                                         &mc.to->move_charge_at_immigrate);
> }
>
> static bool move_file(void)
> {
>         return test_bit(MOVE_CHARGE_TYPE_FILE,
>                                         &mc.to->move_charge_at_immigrate);
> }
>
> /*
>  * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
>  * limit reclaim to prevent infinite loops, if they ever occur.
>  */
> #define MEM_CGROUP_MAX_RECLAIM_LOOPS            (100)
> #define MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS (2)
>
> enum charge_type {
>         MEM_CGROUP_CHARGE_TYPE_CACHE = 0,
>         MEM_CGROUP_CHARGE_TYPE_MAPPED,
>         MEM_CGROUP_CHARGE_TYPE_SHMEM,   /* used by page migration of shmem */
>         MEM_CGROUP_CHARGE_TYPE_FORCE,   /* used by force_empty */
>         MEM_CGROUP_CHARGE_TYPE_SWAPOUT, /* for accounting swapcache */
>         MEM_CGROUP_CHARGE_TYPE_DROP,    /* a page was unused swap cache */
>         NR_CHARGE_TYPE,
> };
>
> /* for encoding cft->private value on file */
> #define _MEM                    (0)
> #define _MEMSWAP                (1)
> #define _OOM_TYPE               (2)
> #define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val))
> #define MEMFILE_TYPE(val)       (((val) >> 16) & 0xffff)
> #define MEMFILE_ATTR(val)       ((val) & 0xffff)
> /* Used for OOM nofiier */
> #define OOM_CONTROL             (0)
>
> /*
>  * Reclaim flags for mem_cgroup_hierarchical_reclaim
>  */
> #define MEM_CGROUP_RECLAIM_NOSWAP_BIT   0x0
> #define MEM_CGROUP_RECLAIM_NOSWAP       (1 << MEM_CGROUP_RECLAIM_NOSWAP_BIT)
> #define MEM_CGROUP_RECLAIM_SHRINK_BIT   0x1
> #define MEM_CGROUP_RECLAIM_SHRINK       (1 << MEM_CGROUP_RECLAIM_SHRINK_BIT)
> #define MEM_CGROUP_RECLAIM_SOFT_BIT     0x2
> #define MEM_CGROUP_RECLAIM_SOFT         (1 << MEM_CGROUP_RECLAIM_SOFT_BIT)
>
> static void mem_cgroup_get(struct mem_cgroup *mem);
> static void mem_cgroup_put(struct mem_cgroup *mem);
> static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
> static void drain_all_stock_async(struct mem_cgroup *mem);
>
> static struct mem_cgroup_per_zone *
> mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
> {
>         return &mem->info.nodeinfo[nid]->zoneinfo[zid];
> }
>
> struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *mem)
> {
>         return &mem->css;
> }
>
> static struct mem_cgroup_per_zone *
> page_cgroup_zoneinfo(struct mem_cgroup *mem, struct page *page)
> {
>         int nid = page_to_nid(page);
>         int zid = page_zonenum(page);
>
>         return mem_cgroup_zoneinfo(mem, nid, zid);
> }
>
> static struct mem_cgroup_tree_per_zone *
> soft_limit_tree_node_zone(int nid, int zid)
> {
>         return &soft_limit_tree.rb_tree_per_node[nid]->rb_tree_per_zone[zid];
> }
>
> static struct mem_cgroup_tree_per_zone *
> soft_limit_tree_from_page(struct page *page)
> {
>         int nid = page_to_nid(page);
>         int zid = page_zonenum(page);
>
>         return &soft_limit_tree.rb_tree_per_node[nid]->rb_tree_per_zone[zid];
> }
>
> static void
> __mem_cgroup_insert_exceeded(struct mem_cgroup *mem,
>                                 struct mem_cgroup_per_zone *mz,
>                                 struct mem_cgroup_tree_per_zone *mctz,
>                                 unsigned long long new_usage_in_excess)
> {
>         struct rb_node **p = &mctz->rb_root.rb_node;
>         struct rb_node *parent = NULL;
>         struct mem_cgroup_per_zone *mz_node;
>
>         if (mz->on_tree)
>                 return;
>
>         mz->usage_in_excess = new_usage_in_excess;
>         if (!mz->usage_in_excess)
>                 return;
>         while (*p) {
>                 parent = *p;
>                 mz_node = rb_entry(parent, struct mem_cgroup_per_zone,
>                                         tree_node);
>                 if (mz->usage_in_excess < mz_node->usage_in_excess)
>                         p = &(*p)->rb_left;
>                 /*
>                  * We can't avoid mem cgroups that are over their soft
>                  * limit by the same amount
>                  */
>                 else if (mz->usage_in_excess >= mz_node->usage_in_excess)
>                         p = &(*p)->rb_right;
>         }
>         rb_link_node(&mz->tree_node, parent, p);
>         rb_insert_color(&mz->tree_node, &mctz->rb_root);
>         mz->on_tree = true;
> }
>
> static void
> __mem_cgroup_remove_exceeded(struct mem_cgroup *mem,
>                                 struct mem_cgroup_per_zone *mz,
>                                 struct mem_cgroup_tree_per_zone *mctz)
> {
>         if (!mz->on_tree)
>                 return;
>         rb_erase(&mz->tree_node, &mctz->rb_root);
>         mz->on_tree = false;
> }
>
> static void
> mem_cgroup_remove_exceeded(struct mem_cgroup *mem,
>                                 struct mem_cgroup_per_zone *mz,
>                                 struct mem_cgroup_tree_per_zone *mctz)
> {
>         spin_lock(&mctz->lock);
>         __mem_cgroup_remove_exceeded(mem, mz, mctz);
>         spin_unlock(&mctz->lock);
> }
>
>
> static void mem_cgroup_update_tree(struct mem_cgroup *mem, struct page *page)
> {
>         unsigned long long excess;
>         struct mem_cgroup_per_zone *mz;
>         struct mem_cgroup_tree_per_zone *mctz;
>         int nid = page_to_nid(page);
>         int zid = page_zonenum(page);
>         mctz = soft_limit_tree_from_page(page);
>
>         /*
>          * Necessary to update all ancestors when hierarchy is used.
>          * because their event counter is not touched.
>          */
>         for (; mem; mem = parent_mem_cgroup(mem)) {
>                 mz = mem_cgroup_zoneinfo(mem, nid, zid);
>                 excess = res_counter_soft_limit_excess(&mem->res);
>                 /*
>                  * We have to update the tree if mz is on RB-tree or
>                  * mem is over its softlimit.
>                  */
>                 if (excess || mz->on_tree) {
>                         spin_lock(&mctz->lock);
>                         /* if on-tree, remove it */
>                         if (mz->on_tree)
>                                 __mem_cgroup_remove_exceeded(mem, mz, mctz);
>                         /*
>                          * Insert again. mz->usage_in_excess will be updated.
>                          * If excess is 0, no tree ops.
>                          */
>                         __mem_cgroup_insert_exceeded(mem, mz, mctz, excess);
>                         spin_unlock(&mctz->lock);
>                 }
>         }
> }
>
> static void mem_cgroup_remove_from_trees(struct mem_cgroup *mem)
> {
>         int node, zone;
>         struct mem_cgroup_per_zone *mz;
>         struct mem_cgroup_tree_per_zone *mctz;
>
>         for_each_node_state(node, N_POSSIBLE) {
>                 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
>                         mz = mem_cgroup_zoneinfo(mem, node, zone);
>                         mctz = soft_limit_tree_node_zone(node, zone);
>                         mem_cgroup_remove_exceeded(mem, mz, mctz);
>                 }
>         }
> }
>
> static struct mem_cgroup_per_zone *
> __mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
> {
>         struct rb_node *rightmost = NULL;
>         struct mem_cgroup_per_zone *mz;
>
> retry:
>         mz = NULL;
>         rightmost = rb_last(&mctz->rb_root);
>         if (!rightmost)
>                 goto done;              /* Nothing to reclaim from */
>
>         mz = rb_entry(rightmost, struct mem_cgroup_per_zone, tree_node);
>         /*
>          * Remove the node now but someone else can add it back,
>          * we will to add it back at the end of reclaim to its correct
>          * position in the tree.
>          */
>         __mem_cgroup_remove_exceeded(mz->mem, mz, mctz);
>         if (!res_counter_soft_limit_excess(&mz->mem->res) ||
>                 !css_tryget(&mz->mem->css))
>                 goto retry;
> done:
>         return mz;
> }
>
> static struct mem_cgroup_per_zone *
> mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
> {
>         struct mem_cgroup_per_zone *mz;
>
>         spin_lock(&mctz->lock);
>         mz = __mem_cgroup_largest_soft_limit_node(mctz);
>         spin_unlock(&mctz->lock);
>         return mz;
> }
>
> /*
>  * Implementation Note: reading percpu statistics for memcg.
>  *
>  * Both of vmstat[] and percpu_counter has threshold and do periodic
>  * synchronization to implement "quick" read. There are trade-off between
>  * reading cost and precision of value. Then, we may have a chance to implement
>  * a periodic synchronizion of counter in memcg's counter.
>  *
>  * But this _read() function is used for user interface now. The user accounts
>  * memory usage by memory cgroup and he _always_ requires exact value because
>  * he accounts memory. Even if we provide quick-and-fuzzy read, we always
>  * have to visit all online cpus and make sum. So, for now, unnecessary
>  * synchronization is not implemented. (just implemented for cpu hotplug)
>  *
>  * If there are kernel internal actions which can make use of some not-exact
>  * value, and reading all cpu value can be performance bottleneck in some
>  * common workload, threashold and synchonization as vmstat[] should be
>  * implemented.
>  */
> static long mem_cgroup_read_stat(struct mem_cgroup *mem,
>                                  enum mem_cgroup_stat_index idx)
> {
>         long val = 0;
>         int cpu;
>
>         get_online_cpus();
>         for_each_online_cpu(cpu)
>                 val += per_cpu(mem->stat->count[idx], cpu);
> #ifdef CONFIG_HOTPLUG_CPU
>         spin_lock(&mem->pcp_counter_lock);
>         val += mem->nocpu_base.count[idx];
>         spin_unlock(&mem->pcp_counter_lock);
> #endif
>         put_online_cpus();
>         return val;
> }
>
> static void mem_cgroup_swap_statistics(struct mem_cgroup *mem,
>                                          bool charge)
> {
>         int val = (charge) ? 1 : -1;
>         this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_SWAPOUT], val);
> }
>
> void mem_cgroup_pgfault(struct mem_cgroup *mem, int val)
> {
>         this_cpu_add(mem->stat->events[MEM_CGROUP_EVENTS_PGFAULT], val);
> }
>
> void mem_cgroup_pgmajfault(struct mem_cgroup *mem, int val)
> {
>         this_cpu_add(mem->stat->events[MEM_CGROUP_EVENTS_PGMAJFAULT], val);
> }
>
> static unsigned long mem_cgroup_read_events(struct mem_cgroup *mem,
>                                             enum mem_cgroup_events_index idx)
> {
>         unsigned long val = 0;
>         int cpu;
>
>         for_each_online_cpu(cpu)
>                 val += per_cpu(mem->stat->events[idx], cpu);
> #ifdef CONFIG_HOTPLUG_CPU
>         spin_lock(&mem->pcp_counter_lock);
>         val += mem->nocpu_base.events[idx];
>         spin_unlock(&mem->pcp_counter_lock);
> #endif
>         return val;
> }
>
> static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
>                                          bool file, int nr_pages)
> {
>         preempt_disable();
>
>         if (file)
>                 __this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_CACHE], nr_pages);
>         else
>                 __this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_RSS], nr_pages);
>
>         /* pagein of a big page is an event. So, ignore page size */
>         if (nr_pages > 0)
>                 __this_cpu_inc(mem->stat->events[MEM_CGROUP_EVENTS_PGPGIN]);
>         else {
>                 __this_cpu_inc(mem->stat->events[MEM_CGROUP_EVENTS_PGPGOUT]);
>                 nr_pages = -nr_pages; /* for event */
>         }
>
>         __this_cpu_add(mem->stat->events[MEM_CGROUP_EVENTS_COUNT], nr_pages);
>
>         preempt_enable();
> }
>
> static unsigned long
> mem_cgroup_get_zonestat_node(struct mem_cgroup *mem, int nid, enum lru_list idx)
> {
>         struct mem_cgroup_per_zone *mz;
>         u64 total = 0;
>         int zid;
>
>         for (zid = 0; zid < MAX_NR_ZONES; zid++) {
>                 mz = mem_cgroup_zoneinfo(mem, nid, zid);
>                 total += MEM_CGROUP_ZSTAT(mz, idx);
>         }
>         return total;
> }
> static unsigned long mem_cgroup_get_local_zonestat(struct mem_cgroup *mem,
>                                         enum lru_list idx)
> {
>         int nid;
>         u64 total = 0;
>
>         for_each_online_node(nid)
>                 total += mem_cgroup_get_zonestat_node(mem, nid, idx);
>         return total;
> }
>
> static bool __memcg_event_check(struct mem_cgroup *mem, int target)
> {
>         unsigned long val, next;
>
>         val = this_cpu_read(mem->stat->events[MEM_CGROUP_EVENTS_COUNT]);
>         next = this_cpu_read(mem->stat->targets[target]);
>         /* from time_after() in jiffies.h */
>         return ((long)next - (long)val < 0);
> }
>
> static void __mem_cgroup_target_update(struct mem_cgroup *mem, int target)
> {
>         unsigned long val, next;
>
>         val = this_cpu_read(mem->stat->events[MEM_CGROUP_EVENTS_COUNT]);
>
>         switch (target) {
>         case MEM_CGROUP_TARGET_THRESH:
>                 next = val + THRESHOLDS_EVENTS_TARGET;
>                 break;
>         case MEM_CGROUP_TARGET_SOFTLIMIT:
>                 next = val + SOFTLIMIT_EVENTS_TARGET;
>                 break;
>         case MEM_CGROUP_TARGET_NUMAINFO:
>                 next = val + NUMAINFO_EVENTS_TARGET;
>                 break;
>         default:
>                 return;
>         }
>
>         this_cpu_write(mem->stat->targets[target], next);
> }
>
> /*
>  * Check events in order.
>  *
>  */
> static void memcg_check_events(struct mem_cgroup *mem, struct page *page)
> {
>         /* threshold event is triggered in finer grain than soft limit */
>         if (unlikely(__memcg_event_check(mem, MEM_CGROUP_TARGET_THRESH))) {
>                 mem_cgroup_threshold(mem);
>                 __mem_cgroup_target_update(mem, MEM_CGROUP_TARGET_THRESH);
>                 if (unlikely(__memcg_event_check(mem,
>                              MEM_CGROUP_TARGET_SOFTLIMIT))) {
>                         mem_cgroup_update_tree(mem, page);
>                         __mem_cgroup_target_update(mem,
>                                                    MEM_CGROUP_TARGET_SOFTLIMIT);
>                 }
> #if MAX_NUMNODES > 1
>                 if (unlikely(__memcg_event_check(mem,
>                         MEM_CGROUP_TARGET_NUMAINFO))) {
>                         atomic_inc(&mem->numainfo_events);
>                         __mem_cgroup_target_update(mem,
>                                 MEM_CGROUP_TARGET_NUMAINFO);
>                 }
> #endif
>         }
> }
>
> static struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
> {
>         return container_of(cgroup_subsys_state(cont,
>                                 mem_cgroup_subsys_id), struct mem_cgroup,
>                                 css);
> }
>
> struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
> {
>         /*
>          * mm_update_next_owner() may clear mm->owner to NULL
>          * if it races with swapoff, page migration, etc.
>          * So this can be called with p == NULL.
>          */
>         if (unlikely(!p))
>                 return NULL;
>
>         return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
>                                 struct mem_cgroup, css);
> }
>
> struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
> {
>         struct mem_cgroup *mem = NULL;
>
>         if (!mm)
>                 return NULL;
>         /*
>          * Because we have no locks, mm->owner's may be being moved to other
>          * cgroup. We use css_tryget() here even if this looks
>          * pessimistic (rather than adding locks here).
>          */
>         rcu_read_lock();
>         do {
>                 mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
>                 if (unlikely(!mem))
>                         break;
>         } while (!css_tryget(&mem->css));
>         rcu_read_unlock();
>         return mem;
> }
>
> /* The caller has to guarantee "mem" exists before calling this */
> static struct mem_cgroup *mem_cgroup_start_loop(struct mem_cgroup *mem)
> {
>         struct cgroup_subsys_state *css;
>         int found;
>
>         if (!mem) /* ROOT cgroup has the smallest ID */
>                 return root_mem_cgroup; /*css_put/get against root is ignored*/
>         if (!mem->use_hierarchy) {
>                 if (css_tryget(&mem->css))
>                         return mem;
>                 return NULL;
>         }
>         rcu_read_lock();
>         /*
>          * searching a memory cgroup which has the smallest ID under given
>          * ROOT cgroup. (ID >= 1)
>          */
>         css = css_get_next(&mem_cgroup_subsys, 1, &mem->css, &found);
>         if (css && css_tryget(css))
>                 mem = container_of(css, struct mem_cgroup, css);
>         else
>                 mem = NULL;
>         rcu_read_unlock();
>         return mem;
> }
>
> static struct mem_cgroup *mem_cgroup_get_next(struct mem_cgroup *iter,
>                                         struct mem_cgroup *root,
>                                         bool cond)
> {
>         int nextid = css_id(&iter->css) + 1;
>         int found;
>         int hierarchy_used;
>         struct cgroup_subsys_state *css;
>
>         hierarchy_used = iter->use_hierarchy;
>
>         css_put(&iter->css);
>         /* If no ROOT, walk all, ignore hierarchy */
>         if (!cond || (root && !hierarchy_used))
>                 return NULL;
>
>         if (!root)
>                 root = root_mem_cgroup;
>
>         do {
>                 iter = NULL;
>                 rcu_read_lock();
>
>                 css = css_get_next(&mem_cgroup_subsys, nextid,
>                                 &root->css, &found);
>                 if (css && css_tryget(css))
>                         iter = container_of(css, struct mem_cgroup, css);
>                 rcu_read_unlock();
>                 /* If css is NULL, no more cgroups will be found */
>                 nextid = found + 1;
>         } while (css && !iter);
>
>         return iter;
> }
> /*
>  * for_eacn_mem_cgroup_tree() for visiting all cgroup under tree. Please
>  * be careful that "break" loop is not allowed. We have reference count.
>  * Instead of that modify "cond" to be false and "continue" to exit the loop.
>  */
> #define for_each_mem_cgroup_tree_cond(iter, root, cond) \
>         for (iter = mem_cgroup_start_loop(root);\
>              iter != NULL;\
>              iter = mem_cgroup_get_next(iter, root, cond))
>
> #define for_each_mem_cgroup_tree(iter, root) \
>         for_each_mem_cgroup_tree_cond(iter, root, true)
>
> #define for_each_mem_cgroup_all(iter) \
>         for_each_mem_cgroup_tree_cond(iter, NULL, true)
>
>
> static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
> {
>         return (mem == root_mem_cgroup);
> }
>
> void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
> {
>         struct mem_cgroup *mem;
>
>         if (!mm)
>                 return;
>
>         rcu_read_lock();
>         mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
>         if (unlikely(!mem))
>                 goto out;
>
>         switch (idx) {
>         case PGMAJFAULT:
>                 mem_cgroup_pgmajfault(mem, 1);
>                 break;
>         case PGFAULT:
>                 mem_cgroup_pgfault(mem, 1);
>                 break;
>         default:
>                 BUG();
>         }
> out:
>         rcu_read_unlock();
> }
> EXPORT_SYMBOL(mem_cgroup_count_vm_event);
>
> /*
>  * Following LRU functions are allowed to be used without PCG_LOCK.
>  * Operations are called by routine of global LRU independently from memcg.
>  * What we have to take care of here is validness of pc->mem_cgroup.
>  *
>  * Changes to pc->mem_cgroup happens when
>  * 1. charge
>  * 2. moving account
>  * In typical case, "charge" is done before add-to-lru. Exception is SwapCache.
>  * It is added to LRU before charge.
>  * If PCG_USED bit is not set, page_cgroup is not added to this private LRU.
>  * When moving account, the page is not on LRU. It's isolated.
>  */
>
> void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
> {
>         struct page_cgroup *pc;
>         struct mem_cgroup_per_zone *mz;
>
>         if (mem_cgroup_disabled())
>                 return;
>         pc = lookup_page_cgroup(page);
>         /* can happen while we handle swapcache. */
>         if (!TestClearPageCgroupAcctLRU(pc))
>                 return;
>         VM_BUG_ON(!pc->mem_cgroup);
>         /*
>          * We don't check PCG_USED bit. It's cleared when the "page" is finally
>          * removed from global LRU.
>          */
>         mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
>         /* huge page split is done under lru_lock. so, we have no races. */
>         MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
>         if (mem_cgroup_is_root(pc->mem_cgroup))
>                 return;
>         VM_BUG_ON(list_empty(&pc->lru));
>         list_del_init(&pc->lru);
> }
>
> void mem_cgroup_del_lru(struct page *page)
> {
>         mem_cgroup_del_lru_list(page, page_lru(page));
> }
>
> /*
>  * Writeback is about to end against a page which has been marked for immediate
>  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
>  * inactive list.
>  */
> void mem_cgroup_rotate_reclaimable_page(struct page *page)
> {
>         struct mem_cgroup_per_zone *mz;
>         struct page_cgroup *pc;
>         enum lru_list lru = page_lru(page);
>
>         if (mem_cgroup_disabled())
>                 return;
>
>         pc = lookup_page_cgroup(page);
>         /* unused or root page is not rotated. */
>         if (!PageCgroupUsed(pc))
>                 return;
>         /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
>         smp_rmb();
>         if (mem_cgroup_is_root(pc->mem_cgroup))
>                 return;
>         mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
>         list_move_tail(&pc->lru, &mz->lists[lru]);
> }
>
> void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru)
> {
>         struct mem_cgroup_per_zone *mz;
>         struct page_cgroup *pc;
>
>         if (mem_cgroup_disabled())
>                 return;
>
>         pc = lookup_page_cgroup(page);
>         /* unused or root page is not rotated. */
>         if (!PageCgroupUsed(pc))
>                 return;
>         /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
>         smp_rmb();
>         if (mem_cgroup_is_root(pc->mem_cgroup))
>                 return;
>         mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
>         list_move(&pc->lru, &mz->lists[lru]);
> }
>
> void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
> {
>         struct page_cgroup *pc;
>         struct mem_cgroup_per_zone *mz;
>
>         if (mem_cgroup_disabled())
>                 return;
>         pc = lookup_page_cgroup(page);
>         VM_BUG_ON(PageCgroupAcctLRU(pc));
>         if (!PageCgroupUsed(pc))
>                 return;
>         /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
>         smp_rmb();
>         mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
>         /* huge page split is done under lru_lock. so, we have no races. */
>         MEM_CGROUP_ZSTAT(mz, lru) += 1 << compound_order(page);
>         SetPageCgroupAcctLRU(pc);
>         if (mem_cgroup_is_root(pc->mem_cgroup))
>                 return;
>         list_add(&pc->lru, &mz->lists[lru]);
> }
>
> /*
>  * At handling SwapCache and other FUSE stuff, pc->mem_cgroup may be changed
>  * while it's linked to lru because the page may be reused after it's fully
>  * uncharged. To handle that, unlink page_cgroup from LRU when charge it again.
>  * It's done under lock_page and expected that zone->lru_lock isnever held.
>  */
> static void mem_cgroup_lru_del_before_commit(struct page *page)
> {
>         unsigned long flags;
>         struct zone *zone = page_zone(page);
>         struct page_cgroup *pc = lookup_page_cgroup(page);
>
>         /*
>          * Doing this check without taking ->lru_lock seems wrong but this
>          * is safe. Because if page_cgroup's USED bit is unset, the page
>          * will not be added to any memcg's LRU. If page_cgroup's USED bit is
>          * set, the commit after this will fail, anyway.
>          * This all charge/uncharge is done under some mutual execustion.
>          * So, we don't need to taking care of changes in USED bit.
>          */
>         if (likely(!PageLRU(page)))
>                 return;
>
>         spin_lock_irqsave(&zone->lru_lock, flags);
>         /*
>          * Forget old LRU when this page_cgroup is *not* used. This Used bit
>          * is guarded by lock_page() because the page is SwapCache.
>          */
>         if (!PageCgroupUsed(pc))
>                 mem_cgroup_del_lru_list(page, page_lru(page));
>         spin_unlock_irqrestore(&zone->lru_lock, flags);
> }
>
> static void mem_cgroup_lru_add_after_commit(struct page *page)
> {
>         unsigned long flags;
>         struct zone *zone = page_zone(page);
>         struct page_cgroup *pc = lookup_page_cgroup(page);
>
>         /* taking care of that the page is added to LRU while we commit it */
>         if (likely(!PageLRU(page)))
>                 return;
>         spin_lock_irqsave(&zone->lru_lock, flags);
>         /* link when the page is linked to LRU but page_cgroup isn't */
>         if (PageLRU(page) && !PageCgroupAcctLRU(pc))
>                 mem_cgroup_add_lru_list(page, page_lru(page));
>         spin_unlock_irqrestore(&zone->lru_lock, flags);
> }
>
>
> void mem_cgroup_move_lists(struct page *page,
>                            enum lru_list from, enum lru_list to)
> {
>         if (mem_cgroup_disabled())
>                 return;
>         mem_cgroup_del_lru_list(page, from);
>         mem_cgroup_add_lru_list(page, to);
> }
>
> int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
> {
>         int ret;
>         struct mem_cgroup *curr = NULL;
>         struct task_struct *p;
>
>         p = find_lock_task_mm(task);
>         if (!p)
>                 return 0;
>         curr = try_get_mem_cgroup_from_mm(p->mm);
>         task_unlock(p);
>         if (!curr)
>                 return 0;
>         /*
>          * We should check use_hierarchy of "mem" not "curr". Because checking
>          * use_hierarchy of "curr" here make this function true if hierarchy is
>          * enabled in "curr" and "curr" is a child of "mem" in *cgroup*
>          * hierarchy(even if use_hierarchy is disabled in "mem").
>          */
>         if (mem->use_hierarchy)
>                 ret = css_is_ancestor(&curr->css, &mem->css);
>         else
>                 ret = (curr == mem);
>         css_put(&curr->css);
>         return ret;
> }
>
> static int calc_inactive_ratio(struct mem_cgroup *memcg, unsigned long *present_pages)
> {
>         unsigned long active;
>         unsigned long inactive;
>         unsigned long gb;
>         unsigned long inactive_ratio;
>
>         inactive = mem_cgroup_get_local_zonestat(memcg, LRU_INACTIVE_ANON);
>         active = mem_cgroup_get_local_zonestat(memcg, LRU_ACTIVE_ANON);
>
>         gb = (inactive + active) >> (30 - PAGE_SHIFT);
>         if (gb)
>                 inactive_ratio = int_sqrt(10 * gb);
>         else
>                 inactive_ratio = 1;
>
>         if (present_pages) {
>                 present_pages[0] = inactive;
>                 present_pages[1] = active;
>         }
>
>         return inactive_ratio;
> }
>
> int mem_cgroup_inactive_anon_is_low(struct mem_cgroup *memcg)
> {
>         unsigned long active;
>         unsigned long inactive;
>         unsigned long present_pages[2];
>         unsigned long inactive_ratio;
>
>         inactive_ratio = calc_inactive_ratio(memcg, present_pages);
>
>         inactive = present_pages[0];
>         active = present_pages[1];
>
>         if (inactive * inactive_ratio < active)
>                 return 1;
>
>         return 0;
> }
>
> int mem_cgroup_inactive_file_is_low(struct mem_cgroup *memcg)
> {
>         unsigned long active;
>         unsigned long inactive;
>
>         inactive = mem_cgroup_get_local_zonestat(memcg, LRU_INACTIVE_FILE);
>         active = mem_cgroup_get_local_zonestat(memcg, LRU_ACTIVE_FILE);
>
>         return (active > inactive);
> }
>
> unsigned long mem_cgroup_zone_nr_lru_pages(struct mem_cgroup *memcg,
>                                                 struct zone *zone,
>                                                 enum lru_list lru)
> {
>         int nid = zone_to_nid(zone);
>         int zid = zone_idx(zone);
>         struct mem_cgroup_per_zone *mz = mem_cgroup_zoneinfo(memcg, nid, zid);
>
>         return MEM_CGROUP_ZSTAT(mz, lru);
> }
>
> static unsigned long mem_cgroup_node_nr_file_lru_pages(struct mem_cgroup *memcg,
>                                                         int nid)
> {
>         unsigned long ret;
>
>         ret = mem_cgroup_get_zonestat_node(memcg, nid, LRU_INACTIVE_FILE) +
>                 mem_cgroup_get_zonestat_node(memcg, nid, LRU_ACTIVE_FILE);
>
>         return ret;
> }
>
> static unsigned long mem_cgroup_node_nr_anon_lru_pages(struct mem_cgroup *memcg,
>                                                         int nid)
> {
>         unsigned long ret;
>
>         ret = mem_cgroup_get_zonestat_node(memcg, nid, LRU_INACTIVE_ANON) +
>                 mem_cgroup_get_zonestat_node(memcg, nid, LRU_ACTIVE_ANON);
>         return ret;
> }
>
> #if MAX_NUMNODES > 1
> static unsigned long mem_cgroup_nr_file_lru_pages(struct mem_cgroup *memcg)
> {
>         u64 total = 0;
>         int nid;
>
>         for_each_node_state(nid, N_HIGH_MEMORY)
>                 total += mem_cgroup_node_nr_file_lru_pages(memcg, nid);
>
>         return total;
> }
>
> static unsigned long mem_cgroup_nr_anon_lru_pages(struct mem_cgroup *memcg)
> {
>         u64 total = 0;
>         int nid;
>
>         for_each_node_state(nid, N_HIGH_MEMORY)
>                 total += mem_cgroup_node_nr_anon_lru_pages(memcg, nid);
>
>         return total;
> }
>
> static unsigned long
> mem_cgroup_node_nr_unevictable_lru_pages(struct mem_cgroup *memcg, int nid)
> {
>         return mem_cgroup_get_zonestat_node(memcg, nid, LRU_UNEVICTABLE);
> }
>
> static unsigned long
> mem_cgroup_nr_unevictable_lru_pages(struct mem_cgroup *memcg)
> {
>         u64 total = 0;
>         int nid;
>
>         for_each_node_state(nid, N_HIGH_MEMORY)
>                 total += mem_cgroup_node_nr_unevictable_lru_pages(memcg, nid);
>
>         return total;
> }
>
> static unsigned long mem_cgroup_node_nr_lru_pages(struct mem_cgroup *memcg,
>                                                         int nid)
> {
>         enum lru_list l;
>         u64 total = 0;
>
>         for_each_lru(l)
>                 total += mem_cgroup_get_zonestat_node(memcg, nid, l);
>
>         return total;
> }
>
> static unsigned long mem_cgroup_nr_lru_pages(struct mem_cgroup *memcg)
> {
>         u64 total = 0;
>         int nid;
>
>         for_each_node_state(nid, N_HIGH_MEMORY)
>                 total += mem_cgroup_node_nr_lru_pages(memcg, nid);
>
>         return total;
> }
> #endif /* CONFIG_NUMA */
>
> struct zone_reclaim_stat *mem_cgroup_get_reclaim_stat(struct mem_cgroup *memcg,
>                                                       struct zone *zone)
> {
>         int nid = zone_to_nid(zone);
>         int zid = zone_idx(zone);
>         struct mem_cgroup_per_zone *mz = mem_cgroup_zoneinfo(memcg, nid, zid);
>
>         return &mz->reclaim_stat;
> }
>
> struct zone_reclaim_stat *
> mem_cgroup_get_reclaim_stat_from_page(struct page *page)
> {
>         struct page_cgroup *pc;
>         struct mem_cgroup_per_zone *mz;
>
>         if (mem_cgroup_disabled())
>                 return NULL;
>
>         pc = lookup_page_cgroup(page);
>         if (!PageCgroupUsed(pc))
>                 return NULL;
>         /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
>         smp_rmb();
>         mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
>         return &mz->reclaim_stat;
> }
>
> unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
>                                         struct list_head *dst,
>                                         unsigned long *scanned, int order,
>                                         int mode, struct zone *z,
>                                         struct mem_cgroup *mem_cont,
>                                         int active, int file)
> {
>         unsigned long nr_taken = 0;
>         struct page *page;
>         unsigned long scan;
>         LIST_HEAD(pc_list);
>         struct list_head *src;
>         struct page_cgroup *pc, *tmp;
>         int nid = zone_to_nid(z);
>         int zid = zone_idx(z);
>         struct mem_cgroup_per_zone *mz;
>         int lru = LRU_FILE * file + active;
>         int ret;
>
>         BUG_ON(!mem_cont);
>         mz = mem_cgroup_zoneinfo(mem_cont, nid, zid);
>         src = &mz->lists[lru];
>
>         scan = 0;
>         list_for_each_entry_safe_reverse(pc, tmp, src, lru) {
>                 if (scan >= nr_to_scan)
>                         break;
>
>                 if (unlikely(!PageCgroupUsed(pc)))
>                         continue;
>
>                 page = lookup_cgroup_page(pc);
>
>                 if (unlikely(!PageLRU(page)))
>                         continue;
>
>                 scan++;
>                 ret = __isolate_lru_page(page, mode, file);
>                 switch (ret) {
>                 case 0:
>                         list_move(&page->lru, dst);
>                         mem_cgroup_del_lru(page);
>                         nr_taken += hpage_nr_pages(page);
>                         break;
>                 case -EBUSY:
>                         /* we don't affect global LRU but rotate in our LRU */
>                         mem_cgroup_rotate_lru_list(page, page_lru(page));
>                         break;
>                 default:
>                         break;
>                 }
>         }
>
>         *scanned = scan;
>
>         trace_mm_vmscan_memcg_isolate(0, nr_to_scan, scan, nr_taken,
>                                       0, 0, 0, mode);
>
>         return nr_taken;
> }
>
> #define mem_cgroup_from_res_counter(counter, member)    \
>         container_of(counter, struct mem_cgroup, member)
>
> /**
>  * mem_cgroup_margin - calculate chargeable space of a memory cgroup
>  * @mem: the memory cgroup
>  *
>  * Returns the maximum amount of memory @mem can be charged with, in
>  * pages.
>  */
> static unsigned long mem_cgroup_margin(struct mem_cgroup *mem)
> {
>         unsigned long long margin;
>
>         margin = res_counter_margin(&mem->res);
>         if (do_swap_account)
>                 margin = min(margin, res_counter_margin(&mem->memsw));
>         return margin >> PAGE_SHIFT;
> }
>
> static unsigned int get_swappiness(struct mem_cgroup *memcg)
> {
>         struct cgroup *cgrp = memcg->css.cgroup;
>
>         /* root ? */
>         if (cgrp->parent == NULL)
>                 return vm_swappiness;
>
>         return memcg->swappiness;
> }
>
> static void mem_cgroup_start_move(struct mem_cgroup *mem)
> {
>         int cpu;
>
>         get_online_cpus();
>         spin_lock(&mem->pcp_counter_lock);
>         for_each_online_cpu(cpu)
>                 per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) += 1;
>         mem->nocpu_base.count[MEM_CGROUP_ON_MOVE] += 1;
>         spin_unlock(&mem->pcp_counter_lock);
>         put_online_cpus();
>
>         synchronize_rcu();
> }
>
> static void mem_cgroup_end_move(struct mem_cgroup *mem)
> {
>         int cpu;
>
>         if (!mem)
>                 return;
>         get_online_cpus();
>         spin_lock(&mem->pcp_counter_lock);
>         for_each_online_cpu(cpu)
>                 per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) -= 1;
>         mem->nocpu_base.count[MEM_CGROUP_ON_MOVE] -= 1;
>         spin_unlock(&mem->pcp_counter_lock);
>         put_online_cpus();
> }
> /*
>  * 2 routines for checking "mem" is under move_account() or not.
>  *
>  * mem_cgroup_stealed() - checking a cgroup is mc.from or not. This is used
>  *                        for avoiding race in accounting. If true,
>  *                        pc->mem_cgroup may be overwritten.
>  *
>  * mem_cgroup_under_move() - checking a cgroup is mc.from or mc.to or
>  *                        under hierarchy of moving cgroups. This is for
>  *                        waiting at hith-memory prressure caused by "move".
>  */
>
> static bool mem_cgroup_stealed(struct mem_cgroup *mem)
> {
>         VM_BUG_ON(!rcu_read_lock_held());
>         return this_cpu_read(mem->stat->count[MEM_CGROUP_ON_MOVE]) > 0;
> }
>
> static bool mem_cgroup_under_move(struct mem_cgroup *mem)
> {
>         struct mem_cgroup *from;
>         struct mem_cgroup *to;
>         bool ret = false;
>         /*
>          * Unlike task_move routines, we access mc.to, mc.from not under
>          * mutual exclusion by cgroup_mutex. Here, we take spinlock instead.
>          */
>         spin_lock(&mc.lock);
>         from = mc.from;
>         to = mc.to;
>         if (!from)
>                 goto unlock;
>         if (from == mem || to == mem
>             || (mem->use_hierarchy && css_is_ancestor(&from->css, &mem->css))
>             || (mem->use_hierarchy && css_is_ancestor(&to->css, &mem->css)))
>                 ret = true;
> unlock:
>         spin_unlock(&mc.lock);
>         return ret;
> }
>
> static bool mem_cgroup_wait_acct_move(struct mem_cgroup *mem)
> {
>         if (mc.moving_task && current != mc.moving_task) {
>                 if (mem_cgroup_under_move(mem)) {
>                         DEFINE_WAIT(wait);
>                         prepare_to_wait(&mc.waitq, &wait, TASK_INTERRUPTIBLE);
>                         /* moving charge context might have finished. */
>                         if (mc.moving_task)
>                                 schedule();
>                         finish_wait(&mc.waitq, &wait);
>                         return true;
>                 }
>         }
>         return false;
> }
>
> /**
>  * mem_cgroup_print_oom_info: Called from OOM with tasklist_lock held in read mode.
>  * @memcg: The memory cgroup that went over limit
>  * @p: Task that is going to be killed
>  *
>  * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
>  * enabled
>  */
> void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
> {
>         struct cgroup *task_cgrp;
>         struct cgroup *mem_cgrp;
>         /*
>          * Need a buffer in BSS, can't rely on allocations. The code relies
>          * on the assumption that OOM is serialized for memory controller.
>          * If this assumption is broken, revisit this code.
>          */
>         static char memcg_name[PATH_MAX];
>         int ret;
>
>         if (!memcg || !p)
>                 return;
>
>
>         rcu_read_lock();
>
>         mem_cgrp = memcg->css.cgroup;
>         task_cgrp = task_cgroup(p, mem_cgroup_subsys_id);
>
>         ret = cgroup_path(task_cgrp, memcg_name, PATH_MAX);
>         if (ret < 0) {
>                 /*
>                  * Unfortunately, we are unable to convert to a useful name
>                  * But we'll still print out the usage information
>                  */
>                 rcu_read_unlock();
>                 goto done;
>         }
>         rcu_read_unlock();
>
>         printk(KERN_INFO "Task in %s killed", memcg_name);
>
>         rcu_read_lock();
>         ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
>         if (ret < 0) {
>                 rcu_read_unlock();
>                 goto done;
>         }
>         rcu_read_unlock();
>
>         /*
>          * Continues from above, so we don't need an KERN_ level
>          */
>         printk(KERN_CONT " as a result of limit of %s\n", memcg_name);
> done:
>
>         printk(KERN_INFO "memory: usage %llukB, limit %llukB, failcnt %llu\n",
>                 res_counter_read_u64(&memcg->res, RES_USAGE) >> 10,
>                 res_counter_read_u64(&memcg->res, RES_LIMIT) >> 10,
>                 res_counter_read_u64(&memcg->res, RES_FAILCNT));
>         printk(KERN_INFO "memory+swap: usage %llukB, limit %llukB, "
>                 "failcnt %llu\n",
>                 res_counter_read_u64(&memcg->memsw, RES_USAGE) >> 10,
>                 res_counter_read_u64(&memcg->memsw, RES_LIMIT) >> 10,
>                 res_counter_read_u64(&memcg->memsw, RES_FAILCNT));
> }
>
> /*
>  * This function returns the number of memcg under hierarchy tree. Returns
>  * 1(self count) if no children.
>  */
> static int mem_cgroup_count_children(struct mem_cgroup *mem)
> {
>         int num = 0;
>         struct mem_cgroup *iter;
>
>         for_each_mem_cgroup_tree(iter, mem)
>                 num++;
>         return num;
> }
>
> /*
>  * Return the memory (and swap, if configured) limit for a memcg.
>  */
> u64 mem_cgroup_get_limit(struct mem_cgroup *memcg)
> {
>         u64 limit;
>         u64 memsw;
>
>         limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
>         limit += total_swap_pages << PAGE_SHIFT;
>
>         memsw = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
>         /*
>          * If memsw is finite and limits the amount of swap space available
>          * to this memcg, return that limit.
>          */
>         return min(limit, memsw);
> }
>
> /*
>  * Visit the first child (need not be the first child as per the ordering
>  * of the cgroup list, since we track last_scanned_child) of @mem and use
>  * that to reclaim free pages from.
>  */
> static struct mem_cgroup *
> mem_cgroup_select_victim(struct mem_cgroup *root_mem)
> {
>         struct mem_cgroup *ret = NULL;
>         struct cgroup_subsys_state *css;
>         int nextid, found;
>
>         if (!root_mem->use_hierarchy) {
>                 css_get(&root_mem->css);
>                 ret = root_mem;
>         }
>
>         while (!ret) {
>                 rcu_read_lock();
>                 nextid = root_mem->last_scanned_child + 1;
>                 css = css_get_next(&mem_cgroup_subsys, nextid, &root_mem->css,
>                                    &found);
>                 if (css && css_tryget(css))
>                         ret = container_of(css, struct mem_cgroup, css);
>
>                 rcu_read_unlock();
>                 /* Updates scanning parameter */
>                 if (!css) {
>                         /* this means start scan from ID:1 */
>                         root_mem->last_scanned_child = 0;
>                 } else
>                         root_mem->last_scanned_child = found;
>         }
>
>         return ret;
> }
>
> /**
>  * test_mem_cgroup_node_reclaimable
>  * @mem: the target memcg
>  * @nid: the node ID to be checked.
>  * @noswap : specify true here if the user wants flle only information.
>  *
>  * This function returns whether the specified memcg contains any
>  * reclaimable pages on a node. Returns true if there are any reclaimable
>  * pages in the node.
>  */
> static bool test_mem_cgroup_node_reclaimable(struct mem_cgroup *mem,
>                 int nid, bool noswap)
> {
>         if (mem_cgroup_node_nr_file_lru_pages(mem, nid))
>                 return true;
>         if (noswap || !total_swap_pages)
>                 return false;
>         if (mem_cgroup_node_nr_anon_lru_pages(mem, nid))
>                 return true;
>         return false;
>
> }
> #if MAX_NUMNODES > 1
>
> /*
>  * Always updating the nodemask is not very good - even if we have an empty
>  * list or the wrong list here, we can start from some node and traverse all
>  * nodes based on the zonelist. So update the list loosely once per 10 secs.
>  *
>  */
> static void mem_cgroup_may_update_nodemask(struct mem_cgroup *mem)
> {
>         int nid;
>         /*
>          * numainfo_events > 0 means there was at least NUMAINFO_EVENTS_TARGET
>          * pagein/pageout changes since the last update.
>          */
>         if (!atomic_read(&mem->numainfo_events))
>                 return;
>         if (atomic_inc_return(&mem->numainfo_updating) > 1)
>                 return;
>
>         /* make a nodemask where this memcg uses memory from */
>         mem->scan_nodes = node_states[N_HIGH_MEMORY];
>
>         for_each_node_mask(nid, node_states[N_HIGH_MEMORY]) {
>
>                 if (!test_mem_cgroup_node_reclaimable(mem, nid, false))
>                         node_clear(nid, mem->scan_nodes);
>         }
>
>         atomic_set(&mem->numainfo_events, 0);
>         atomic_set(&mem->numainfo_updating, 0);
> }
>
> /*
>  * Selecting a node where we start reclaim from. Because what we need is just
>  * reducing usage counter, start from anywhere is O,K. Considering
>  * memory reclaim from current node, there are pros. and cons.
>  *
>  * Freeing memory from current node means freeing memory from a node which
>  * we'll use or we've used. So, it may make LRU bad. And if several threads
>  * hit limits, it will see a contention on a node. But freeing from remote
>  * node means more costs for memory reclaim because of memory latency.
>  *
>  * Now, we use round-robin. Better algorithm is welcomed.
>  */
> int mem_cgroup_select_victim_node(struct mem_cgroup *mem)
> {
>         int node;
>
>         mem_cgroup_may_update_nodemask(mem);
>         node = mem->last_scanned_node;
>
>         node = next_node(node, mem->scan_nodes);
>         if (node == MAX_NUMNODES)
>                 node = first_node(mem->scan_nodes);
>         /*
>          * We call this when we hit limit, not when pages are added to LRU.
>          * No LRU may hold pages because all pages are UNEVICTABLE or
>          * memcg is too small and all pages are not on LRU. In that case,
>          * we use curret node.
>          */
>         if (unlikely(node == MAX_NUMNODES))
>                 node = numa_node_id();
>
>         mem->last_scanned_node = node;
>         return node;
> }
>
> /*
>  * Check all nodes whether it contains reclaimable pages or not.
>  * For quick scan, we make use of scan_nodes. This will allow us to skip
>  * unused nodes. But scan_nodes is lazily updated and may not cotain
>  * enough new information. We need to do double check.
>  */
> bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
> {
>         int nid;
>
>         /*
>          * quick check...making use of scan_node.
>          * We can skip unused nodes.
>          */
>         if (!nodes_empty(mem->scan_nodes)) {
>                 for (nid = first_node(mem->scan_nodes);
>                      nid < MAX_NUMNODES;
>                      nid = next_node(nid, mem->scan_nodes)) {
>
>                         if (test_mem_cgroup_node_reclaimable(mem, nid, noswap))
>                                 return true;
>                 }
>         }
>         /*
>          * Check rest of nodes.
>          */
>         for_each_node_state(nid, N_HIGH_MEMORY) {
>                 if (node_isset(nid, mem->scan_nodes))
>                         continue;
>                 if (test_mem_cgroup_node_reclaimable(mem, nid, noswap))
>                         return true;
>         }
>         return false;
> }
>
> #else
> int mem_cgroup_select_victim_node(struct mem_cgroup *mem)
> {
>         return 0;
> }
>
> bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
> {
>         return test_mem_cgroup_node_reclaimable(mem, 0, noswap);
> }
> #endif
>
> /*
>  * Scan the hierarchy if needed to reclaim memory. We remember the last child
>  * we reclaimed from, so that we don't end up penalizing one child extensively
>  * based on its position in the children list.
>  *
>  * root_mem is the original ancestor that we've been reclaim from.
>  *
>  * We give up and return to the caller when we visit root_mem twice.
>  * (other groups can be removed while we're walking....)
>  *
>  * If shrink==true, for avoiding to free too much, this returns immedieately.
>  */
> static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
>                                                 struct zone *zone,
>                                                 gfp_t gfp_mask,
>                                                 unsigned long reclaim_options,
>                                                 unsigned long *total_scanned)
> {
>         struct mem_cgroup *victim;
>         int ret, total = 0;
>         int loop = 0;
>         bool noswap = reclaim_options & MEM_CGROUP_RECLAIM_NOSWAP;
>         bool shrink = reclaim_options & MEM_CGROUP_RECLAIM_SHRINK;
>         bool check_soft = reclaim_options & MEM_CGROUP_RECLAIM_SOFT;
>         unsigned long excess;
>         unsigned long nr_scanned;
>
>         excess = res_counter_soft_limit_excess(&root_mem->res) >> PAGE_SHIFT;
>
>         /* If memsw_is_minimum==1, swap-out is of-no-use. */
>         if (!check_soft && root_mem->memsw_is_minimum)
>                 noswap = true;
>
>         while (1) {
>                 victim = mem_cgroup_select_victim(root_mem);
>                 if (victim == root_mem) {
>                         loop++;
>                         /*
>                          * We are not draining per cpu cached charges during
>                          * soft limit reclaim  because global reclaim doesn't
>                          * care about charges. It tries to free some memory and
>                          * charges will not give any.
>                          */
>                         if (!check_soft && loop >= 1)
>                                 drain_all_stock_async(root_mem);
>                         if (loop >= 2) {
>                                 /*
>                                  * If we have not been able to reclaim
>                                  * anything, it might because there are
>                                  * no reclaimable pages under this hierarchy
>                                  */
>                                 if (!check_soft || !total) {
>                                         css_put(&victim->css);
>                                         break;
>                                 }
>                                 /*
>                                  * We want to do more targeted reclaim.
>                                  * excess >> 2 is not to excessive so as to
>                                  * reclaim too much, nor too less that we keep
>                                  * coming back to reclaim from this cgroup
>                                  */
>                                 if (total >= (excess >> 2) ||
>                                         (loop > MEM_CGROUP_MAX_RECLAIM_LOOPS)) {
>                                         css_put(&victim->css);
>                                         break;
>                                 }
>                         }
>                 }
>                 if (!mem_cgroup_reclaimable(victim, noswap)) {
>                         /* this cgroup's local usage == 0 */
>                         css_put(&victim->css);
>                         continue;
>                 }
>                 /* we use swappiness of local cgroup */
>                 if (check_soft) {
>                         ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,
>                                 noswap, get_swappiness(victim), zone,
>                                 &nr_scanned);
>                         *total_scanned += nr_scanned;
>                 } else
>                         ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
>                                                 noswap, get_swappiness(victim));
>                 css_put(&victim->css);
>                 /*
>                  * At shrinking usage, we can't check we should stop here or
>                  * reclaim more. It's depends on callers. last_scanned_child
>                  * will work enough for keeping fairness under tree.
>                  */
>                 if (shrink)
>                         return ret;
>                 total += ret;
>                 if (check_soft) {
>                         if (!res_counter_soft_limit_excess(&root_mem->res))
>                                 return total;
>                 } else if (mem_cgroup_margin(root_mem))
>                         return total;
>         }
>         return total;
> }
>
> /*
>  * Check OOM-Killer is already running under our hierarchy.
>  * If someone is running, return false.
>  */
> static bool mem_cgroup_oom_lock(struct mem_cgroup *mem)
> {
>         int x, lock_count = 0;
>         struct mem_cgroup *iter;
>
>         for_each_mem_cgroup_tree(iter, mem) {
>                 x = atomic_inc_return(&iter->oom_lock);
>                 lock_count = max(x, lock_count);
>         }
>
>         if (lock_count == 1)
>                 return true;
>         return false;
> }
>
> static int mem_cgroup_oom_unlock(struct mem_cgroup *mem)
> {
>         struct mem_cgroup *iter;
>
>         /*
>          * When a new child is created while the hierarchy is under oom,
>          * mem_cgroup_oom_lock() may not be called. We have to use
>          * atomic_add_unless() here.
>          */
>         for_each_mem_cgroup_tree(iter, mem)
>                 atomic_add_unless(&iter->oom_lock, -1, 0);
>         return 0;
> }
>
>
> static DEFINE_MUTEX(memcg_oom_mutex);
> static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);
>
> struct oom_wait_info {
>         struct mem_cgroup *mem;
>         wait_queue_t    wait;
> };
>
> static int memcg_oom_wake_function(wait_queue_t *wait,
>         unsigned mode, int sync, void *arg)
> {
>         struct mem_cgroup *wake_mem = (struct mem_cgroup *)arg;
>         struct oom_wait_info *oom_wait_info;
>
>         oom_wait_info = container_of(wait, struct oom_wait_info, wait);
>
>         if (oom_wait_info->mem == wake_mem)
>                 goto wakeup;
>         /* if no hierarchy, no match */
>         if (!oom_wait_info->mem->use_hierarchy || !wake_mem->use_hierarchy)
>                 return 0;
>         /*
>          * Both of oom_wait_info->mem and wake_mem are stable under us.
>          * Then we can use css_is_ancestor without taking care of RCU.
>          */
>         if (!css_is_ancestor(&oom_wait_info->mem->css, &wake_mem->css) &&
>             !css_is_ancestor(&wake_mem->css, &oom_wait_info->mem->css))
>                 return 0;
>
> wakeup:
>         return autoremove_wake_function(wait, mode, sync, arg);
> }
>
> static void memcg_wakeup_oom(struct mem_cgroup *mem)
> {
>         /* for filtering, pass "mem" as argument. */
>         __wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, mem);
> }
>
> static void memcg_oom_recover(struct mem_cgroup *mem)
> {
>         if (mem && atomic_read(&mem->oom_lock))
>                 memcg_wakeup_oom(mem);
> }
>
> /*
>  * try to call OOM killer. returns false if we should exit memory-reclaim loop.
>  */
> bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
> {
>         struct oom_wait_info owait;
>         bool locked, need_to_kill;
>
>         owait.mem = mem;
>         owait.wait.flags = 0;
>         owait.wait.func = memcg_oom_wake_function;
>         owait.wait.private = current;
>         INIT_LIST_HEAD(&owait.wait.task_list);
>         need_to_kill = true;
>         /* At first, try to OOM lock hierarchy under mem.*/
>         mutex_lock(&memcg_oom_mutex);
>         locked = mem_cgroup_oom_lock(mem);
>         /*
>          * Even if signal_pending(), we can't quit charge() loop without
>          * accounting. So, UNINTERRUPTIBLE is appropriate. But SIGKILL
>          * under OOM is always welcomed, use TASK_KILLABLE here.
>          */
>         prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
>         if (!locked || mem->oom_kill_disable)
>                 need_to_kill = false;
>         if (locked)
>                 mem_cgroup_oom_notify(mem);
>         mutex_unlock(&memcg_oom_mutex);
>
>         if (need_to_kill) {
>                 finish_wait(&memcg_oom_waitq, &owait.wait);
>                 mem_cgroup_out_of_memory(mem, mask);
>         } else {
>                 schedule();
>                 finish_wait(&memcg_oom_waitq, &owait.wait);
>         }
>         mutex_lock(&memcg_oom_mutex);
>         mem_cgroup_oom_unlock(mem);
>         memcg_wakeup_oom(mem);
>         mutex_unlock(&memcg_oom_mutex);
>
>         if (test_thread_flag(TIF_MEMDIE) || fatal_signal_pending(current))
>                 return false;
>         /* Give chance to dying process */
>         schedule_timeout(1);
>         return true;
> }
>
> /*
>  * Currently used to update mapped file statistics, but the routine can be
>  * generalized to update other statistics as well.
>  *
>  * Notes: Race condition
>  *
>  * We usually use page_cgroup_lock() for accessing page_cgroup member but
>  * it tends to be costly. But considering some conditions, we doesn't need
>  * to do so _always_.
>  *
>  * Considering "charge", lock_page_cgroup() is not required because all
>  * file-stat operations happen after a page is attached to radix-tree. There
>  * are no race with "charge".
>  *
>  * Considering "uncharge", we know that memcg doesn't clear pc->mem_cgroup
>  * at "uncharge" intentionally. So, we always see valid pc->mem_cgroup even
>  * if there are race with "uncharge". Statistics itself is properly handled
>  * by flags.
>  *
>  * Considering "move", this is an only case we see a race. To make the race
>  * small, we check MEM_CGROUP_ON_MOVE percpu value and detect there are
>  * possibility of race condition. If there is, we take a lock.
>  */
>
> void mem_cgroup_update_page_stat(struct page *page,
>                                  enum mem_cgroup_page_stat_item idx, int val)
> {
>         struct mem_cgroup *mem;
>         struct page_cgroup *pc = lookup_page_cgroup(page);
>         bool need_unlock = false;
>         unsigned long uninitialized_var(flags);
>
>         if (unlikely(!pc))
>                 return;
>
>         rcu_read_lock();
>         mem = pc->mem_cgroup;
>         if (unlikely(!mem || !PageCgroupUsed(pc)))
>                 goto out;
>         /* pc->mem_cgroup is unstable ? */
>         if (unlikely(mem_cgroup_stealed(mem)) || PageTransHuge(page)) {
>                 /* take a lock against to access pc->mem_cgroup */
>                 move_lock_page_cgroup(pc, &flags);
>                 need_unlock = true;
>                 mem = pc->mem_cgroup;
>                 if (!mem || !PageCgroupUsed(pc))
>                         goto out;
>         }
>
>         switch (idx) {
>         case MEMCG_NR_FILE_MAPPED:
>                 if (val > 0)
>                         SetPageCgroupFileMapped(pc);
>                 else if (!page_mapped(page))
>                         ClearPageCgroupFileMapped(pc);
>                 idx = MEM_CGROUP_STAT_FILE_MAPPED;
>                 break;
>         default:
>                 BUG();
>         }
>
>         this_cpu_add(mem->stat->count[idx], val);
>
> out:
>         if (unlikely(need_unlock))
>                 move_unlock_page_cgroup(pc, &flags);
>         rcu_read_unlock();
>         return;
> }
> EXPORT_SYMBOL(mem_cgroup_update_page_stat);
>
> /*
>  * size of first charge trial. "32" comes from vmscan.c's magic value.
>  * TODO: maybe necessary to use big numbers in big irons.
>  */
> #define CHARGE_BATCH    32U
> struct memcg_stock_pcp {
>         struct mem_cgroup *cached; /* this never be root cgroup */
>         unsigned int nr_pages;
>         struct work_struct work;
>         unsigned long flags;
> #define FLUSHING_CACHED_CHARGE  (0)
> };
> static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
> static DEFINE_MUTEX(percpu_charge_mutex);
>
> /*
>  * Try to consume stocked charge on this cpu. If success, one page is consumed
>  * from local stock and true is returned. If the stock is 0 or charges from a
>  * cgroup which is not current target, returns false. This stock will be
>  * refilled.
>  */
> static bool consume_stock(struct mem_cgroup *mem)
> {
>         struct memcg_stock_pcp *stock;
>         bool ret = true;
>
>         stock = &get_cpu_var(memcg_stock);
>         if (mem == stock->cached && stock->nr_pages)
>                 stock->nr_pages--;
>         else /* need to call res_counter_charge */
>                 ret = false;
>         put_cpu_var(memcg_stock);
>         return ret;
> }
>
> /*
>  * Returns stocks cached in percpu to res_counter and reset cached information.
>  */
> static void drain_stock(struct memcg_stock_pcp *stock)
> {
>         struct mem_cgroup *old = stock->cached;
>
>         if (stock->nr_pages) {
>                 unsigned long bytes = stock->nr_pages * PAGE_SIZE;
>
>                 res_counter_uncharge(&old->res, bytes);
>                 if (do_swap_account)
>                         res_counter_uncharge(&old->memsw, bytes);
>                 stock->nr_pages = 0;
>         }
>         stock->cached = NULL;
> }
>
> /*
>  * This must be called under preempt disabled or must be called by
>  * a thread which is pinned to local cpu.
>  */
> static void drain_local_stock(struct work_struct *dummy)
> {
>         struct memcg_stock_pcp *stock = &__get_cpu_var(memcg_stock);
>         drain_stock(stock);
>         clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
> }
>
> /*
>  * Cache charges(val) which is from res_counter, to local per_cpu area.
>  * This will be consumed by consume_stock() function, later.
>  */
> static void refill_stock(struct mem_cgroup *mem, unsigned int nr_pages)
> {
>         struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock);
>
>         if (stock->cached != mem) { /* reset if necessary */
>                 drain_stock(stock);
>                 stock->cached = mem;
>         }
>         stock->nr_pages += nr_pages;
>         put_cpu_var(memcg_stock);
> }
>
> /*
>  * Tries to drain stocked charges in other cpus. This function is asynchronous
>  * and just put a work per cpu for draining localy on each cpu. Caller can
>  * expects some charges will be back to res_counter later but cannot wait for
>  * it.
>  */
> static void drain_all_stock_async(struct mem_cgroup *root_mem)
> {
>         int cpu, curcpu;
>         /*
>          * If someone calls draining, avoid adding more kworker runs.
>          */
>         if (!mutex_trylock(&percpu_charge_mutex))
>                 return;
>         /* Notify other cpus that system-wide "drain" is running */
>         get_online_cpus();
>         /*
>          * Get a hint for avoiding draining charges on the current cpu,
>          * which must be exhausted by our charging.  It is not required that
>          * this be a precise check, so we use raw_smp_processor_id() instead of
>          * getcpu()/putcpu().
>          */
>         curcpu = raw_smp_processor_id();
>         for_each_online_cpu(cpu) {
>                 struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
>                 struct mem_cgroup *mem;
>
>                 if (cpu == curcpu)
>                         continue;
>
>                 mem = stock->cached;
>                 if (!mem)
>                         continue;
>                 if (mem != root_mem) {
>                         if (!root_mem->use_hierarchy)
>                                 continue;
>                         /* check whether "mem" is under tree of "root_mem" */
>                         if (!css_is_ancestor(&mem->css, &root_mem->css))
>                                 continue;
>                 }
>                 if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags))
>                         schedule_work_on(cpu, &stock->work);
>         }
>         put_online_cpus();
>         mutex_unlock(&percpu_charge_mutex);
>         /* We don't wait for flush_work */
> }
>
> /* This is a synchronous drain interface. */
> static void drain_all_stock_sync(void)
> {
>         /* called when force_empty is called */
>         mutex_lock(&percpu_charge_mutex);
>         schedule_on_each_cpu(drain_local_stock);
>         mutex_unlock(&percpu_charge_mutex);
> }
>
> /*
>  * This function drains percpu counter value from DEAD cpu and
>  * move it to local cpu. Note that this function can be preempted.
>  */
> static void mem_cgroup_drain_pcp_counter(struct mem_cgroup *mem, int cpu)
> {
>         int i;
>
>         spin_lock(&mem->pcp_counter_lock);
>         for (i = 0; i < MEM_CGROUP_STAT_DATA; i++) {
>                 long x = per_cpu(mem->stat->count[i], cpu);
>
>                 per_cpu(mem->stat->count[i], cpu) = 0;
>                 mem->nocpu_base.count[i] += x;
>         }
>         for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++) {
>                 unsigned long x = per_cpu(mem->stat->events[i], cpu);
>
>                 per_cpu(mem->stat->events[i], cpu) = 0;
>                 mem->nocpu_base.events[i] += x;
>         }
>         /* need to clear ON_MOVE value, works as a kind of lock. */
>         per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) = 0;
>         spin_unlock(&mem->pcp_counter_lock);
> }
>
> static void synchronize_mem_cgroup_on_move(struct mem_cgroup *mem, int cpu)
> {
>         int idx = MEM_CGROUP_ON_MOVE;
>
>         spin_lock(&mem->pcp_counter_lock);
>         per_cpu(mem->stat->count[idx], cpu) = mem->nocpu_base.count[idx];
>         spin_unlock(&mem->pcp_counter_lock);
> }
>
> static int __cpuinit memcg_cpu_hotplug_callback(struct notifier_block *nb,
>                                         unsigned long action,
>                                         void *hcpu)
> {
>         int cpu = (unsigned long)hcpu;
>         struct memcg_stock_pcp *stock;
>         struct mem_cgroup *iter;
>
>         if ((action == CPU_ONLINE)) {
>                 for_each_mem_cgroup_all(iter)
>                         synchronize_mem_cgroup_on_move(iter, cpu);
>                 return NOTIFY_OK;
>         }
>
>         if ((action != CPU_DEAD) || action != CPU_DEAD_FROZEN)
>                 return NOTIFY_OK;
>
>         for_each_mem_cgroup_all(iter)
>                 mem_cgroup_drain_pcp_counter(iter, cpu);
>
>         stock = &per_cpu(memcg_stock, cpu);
>         drain_stock(stock);
>         return NOTIFY_OK;
> }
>
>
> /* See __mem_cgroup_try_charge() for details */
> enum {
>         CHARGE_OK,              /* success */
>         CHARGE_RETRY,           /* need to retry but retry is not bad */
>         CHARGE_NOMEM,           /* we can't do more. return -ENOMEM */
>         CHARGE_WOULDBLOCK,      /* GFP_WAIT wasn't set and no enough res. */
>         CHARGE_OOM_DIE,         /* the current is killed because of OOM */
> };
>
> static int mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,
>                                 unsigned int nr_pages, bool oom_check)
> {
>         unsigned long csize = nr_pages * PAGE_SIZE;
>         struct mem_cgroup *mem_over_limit;
>         struct res_counter *fail_res;
>         unsigned long flags = 0;
>         int ret;
>
>         ret = res_counter_charge(&mem->res, csize, &fail_res);
>
>         if (likely(!ret)) {
>                 if (!do_swap_account)
>                         return CHARGE_OK;
>                 ret = res_counter_charge(&mem->memsw, csize, &fail_res);
>                 if (likely(!ret))
>                         return CHARGE_OK;
>
>                 res_counter_uncharge(&mem->res, csize);
>                 mem_over_limit = mem_cgroup_from_res_counter(fail_res, memsw);
>                 flags |= MEM_CGROUP_RECLAIM_NOSWAP;
>         } else
>                 mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
>         /*
>          * nr_pages can be either a huge page (HPAGE_PMD_NR), a batch
>          * of regular pages (CHARGE_BATCH), or a single regular page (1).
>          *
>          * Never reclaim on behalf of optional batching, retry with a
>          * single page instead.
>          */
>         if (nr_pages == CHARGE_BATCH)
>                 return CHARGE_RETRY;
>
>         if (!(gfp_mask & __GFP_WAIT))
>                 return CHARGE_WOULDBLOCK;
>
>         ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, NULL,
>                                               gfp_mask, flags, NULL);
>         if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
>                 return CHARGE_RETRY;
>         /*
>          * Even though the limit is exceeded at this point, reclaim
>          * may have been able to free some pages.  Retry the charge
>          * before killing the task.
>          *
>          * Only for regular pages, though: huge pages are rather
>          * unlikely to succeed so close to the limit, and we fall back
>          * to regular pages anyway in case of failure.
>          */
>         if (nr_pages == 1 && ret)
>                 return CHARGE_RETRY;
>
>         /*
>          * At task move, charge accounts can be doubly counted. So, it's
>          * better to wait until the end of task_move if something is going on.
>          */
>         if (mem_cgroup_wait_acct_move(mem_over_limit))
>                 return CHARGE_RETRY;
>
>         /* If we don't need to call oom-killer at el, return immediately */
>         if (!oom_check)
>                 return CHARGE_NOMEM;
>         /* check OOM */
>         if (!mem_cgroup_handle_oom(mem_over_limit, gfp_mask))
>                 return CHARGE_OOM_DIE;
>
>         return CHARGE_RETRY;
> }
>
> /*
>  * Unlike exported interface, "oom" parameter is added. if oom==true,
>  * oom-killer can be invoked.
>  */
> static int __mem_cgroup_try_charge(struct mm_struct *mm,
>                                    gfp_t gfp_mask,
>                                    unsigned int nr_pages,
>                                    struct mem_cgroup **memcg,
>                                    bool oom)
> {
>         unsigned int batch = max(CHARGE_BATCH, nr_pages);
>         int nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
>         struct mem_cgroup *mem = NULL;
>         int ret;
>
>         /*
>          * Unlike gloval-vm's OOM-kill, we're not in memory shortage
>          * in system level. So, allow to go ahead dying process in addition to
>          * MEMDIE process.
>          */
>         if (unlikely(test_thread_flag(TIF_MEMDIE)
>                      || fatal_signal_pending(current)))
>                 goto bypass;
>
>         /*
>          * We always charge the cgroup the mm_struct belongs to.
>          * The mm_struct's mem_cgroup changes on task migration if the
>          * thread group leader migrates. It's possible that mm is not
>          * set, if so charge the init_mm (happens for pagecache usage).
>          */
>         if (!*memcg && !mm)
>                 goto bypass;
> again:
>         if (*memcg) { /* css should be a valid one */
>                 mem = *memcg;
>                 VM_BUG_ON(css_is_removed(&mem->css));
>                 if (mem_cgroup_is_root(mem))
>                         goto done;
>                 if (nr_pages == 1 && consume_stock(mem))
>                         goto done;
>                 css_get(&mem->css);
>         } else {
>                 struct task_struct *p;
>
>                 rcu_read_lock();
>                 p = rcu_dereference(mm->owner);
>                 /*
>                  * Because we don't have task_lock(), "p" can exit.
>                  * In that case, "mem" can point to root or p can be NULL with
>                  * race with swapoff. Then, we have small risk of mis-accouning.
>                  * But such kind of mis-account by race always happens because
>                  * we don't have cgroup_mutex(). It's overkill and we allo that
>                  * small race, here.
>                  * (*) swapoff at el will charge against mm-struct not against
>                  * task-struct. So, mm->owner can be NULL.
>                  */
>                 mem = mem_cgroup_from_task(p);
>                 if (!mem || mem_cgroup_is_root(mem)) {
>                         rcu_read_unlock();
>                         goto done;
>                 }
>                 if (nr_pages == 1 && consume_stock(mem)) {
>                         /*
>                          * It seems dagerous to access memcg without css_get().
>                          * But considering how consume_stok works, it's not
>                          * necessary. If consume_stock success, some charges
>                          * from this memcg are cached on this cpu. So, we
>                          * don't need to call css_get()/css_tryget() before
>                          * calling consume_stock().
>                          */
>                         rcu_read_unlock();
>                         goto done;
>                 }
>                 /* after here, we may be blocked. we need to get refcnt */
>                 if (!css_tryget(&mem->css)) {
>                         rcu_read_unlock();
>                         goto again;
>                 }
>                 rcu_read_unlock();
>         }
>
>         do {
>                 bool oom_check;
>
>                 /* If killed, bypass charge */
>                 if (fatal_signal_pending(current)) {
>                         css_put(&mem->css);
>                         goto bypass;
>                 }
>
>                 oom_check = false;
>                 if (oom && !nr_oom_retries) {
>                         oom_check = true;
>                         nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
>                 }
>
>                 ret = mem_cgroup_do_charge(mem, gfp_mask, batch, oom_check);
>                 switch (ret) {
>                 case CHARGE_OK:
>                         break;
>                 case CHARGE_RETRY: /* not in OOM situation but retry */
>                         batch = nr_pages;
>                         css_put(&mem->css);
>                         mem = NULL;
>                         goto again;
>                 case CHARGE_WOULDBLOCK: /* !__GFP_WAIT */
>                         css_put(&mem->css);
>                         goto nomem;
>                 case CHARGE_NOMEM: /* OOM routine works */
>                         if (!oom) {
>                                 css_put(&mem->css);
>                                 goto nomem;
>                         }
>                         /* If oom, we never return -ENOMEM */
>                         nr_oom_retries--;
>                         break;
>                 case CHARGE_OOM_DIE: /* Killed by OOM Killer */
>                         css_put(&mem->css);
>                         goto bypass;
>                 }
>         } while (ret != CHARGE_OK);
>
>         if (batch > nr_pages)
>                 refill_stock(mem, batch - nr_pages);
>         css_put(&mem->css);
> done:
>         *memcg = mem;
>         return 0;
> nomem:
>         *memcg = NULL;
>         return -ENOMEM;
> bypass:
>         *memcg = NULL;
>         return 0;
> }
>
> /*
>  * Somemtimes we have to undo a charge we got by try_charge().
>  * This function is for that and do uncharge, put css's refcnt.
>  * gotten by try_charge().
>  */
> static void __mem_cgroup_cancel_charge(struct mem_cgroup *mem,
>                                        unsigned int nr_pages)
> {
>         if (!mem_cgroup_is_root(mem)) {
>                 unsigned long bytes = nr_pages * PAGE_SIZE;
>
>                 res_counter_uncharge(&mem->res, bytes);
>                 if (do_swap_account)
>                         res_counter_uncharge(&mem->memsw, bytes);
>         }
> }
>
> /*
>  * A helper function to get mem_cgroup from ID. must be called under
>  * rcu_read_lock(). The caller must check css_is_removed() or some if
>  * it's concern. (dropping refcnt from swap can be called against removed
>  * memcg.)
>  */
> static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
> {
>         struct cgroup_subsys_state *css;
>
>         /* ID 0 is unused ID */
>         if (!id)
>                 return NULL;
>         css = css_lookup(&mem_cgroup_subsys, id);
>         if (!css)
>                 return NULL;
>         return container_of(css, struct mem_cgroup, css);
> }
>
> struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
> {
>         struct mem_cgroup *mem = NULL;
>         struct page_cgroup *pc;
>         unsigned short id;
>         swp_entry_t ent;
>
>         VM_BUG_ON(!PageLocked(page));
>
>         pc = lookup_page_cgroup(page);
>         lock_page_cgroup(pc);
>         if (PageCgroupUsed(pc)) {
>                 mem = pc->mem_cgroup;
>                 if (mem && !css_tryget(&mem->css))
>                         mem = NULL;
>         } else if (PageSwapCache(page)) {
>                 ent.val = page_private(page);
>                 id = lookup_swap_cgroup(ent);
>                 rcu_read_lock();
>                 mem = mem_cgroup_lookup(id);
>                 if (mem && !css_tryget(&mem->css))
>                         mem = NULL;
>                 rcu_read_unlock();
>         }
>         unlock_page_cgroup(pc);
>         return mem;
> }
>
> static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
>                                        struct page *page,
>                                        unsigned int nr_pages,
>                                        struct page_cgroup *pc,
>                                        enum charge_type ctype)
> {
>         lock_page_cgroup(pc);
>         if (unlikely(PageCgroupUsed(pc))) {
>                 unlock_page_cgroup(pc);
>                 __mem_cgroup_cancel_charge(mem, nr_pages);
>                 return;
>         }
>         /*
>          * we don't need page_cgroup_lock about tail pages, becase they are not
>          * accessed by any other context at this point.
>          */
>         pc->mem_cgroup = mem;
>         /*
>          * We access a page_cgroup asynchronously without lock_page_cgroup().
>          * Especially when a page_cgroup is taken from a page, pc->mem_cgroup
>          * is accessed after testing USED bit. To make pc->mem_cgroup visible
>          * before USED bit, we need memory barrier here.
>          * See mem_cgroup_add_lru_list(), etc.
>          */
>         smp_wmb();
>         switch (ctype) {
>         case MEM_CGROUP_CHARGE_TYPE_CACHE:
>         case MEM_CGROUP_CHARGE_TYPE_SHMEM:
>                 SetPageCgroupCache(pc);
>                 SetPageCgroupUsed(pc);
>                 break;
>         case MEM_CGROUP_CHARGE_TYPE_MAPPED:
>                 ClearPageCgroupCache(pc);
>                 SetPageCgroupUsed(pc);
>                 break;
>         default:
>                 break;
>         }
>
>         mem_cgroup_charge_statistics(mem, PageCgroupCache(pc), nr_pages);
>         unlock_page_cgroup(pc);
>         /*
>          * "charge_statistics" updated event counter. Then, check it.
>          * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
>          * if they exceeds softlimit.
>          */
>         memcg_check_events(mem, page);
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>
> #define PCGF_NOCOPY_AT_SPLIT ((1 << PCG_LOCK) | (1 << PCG_MOVE_LOCK) |\
>                         (1 << PCG_ACCT_LRU) | (1 << PCG_MIGRATION))
> /*
>  * Because tail pages are not marked as "used", set it. We're under
>  * zone->lru_lock, 'splitting on pmd' and compund_lock.
>  */
> void mem_cgroup_split_huge_fixup(struct page *head, struct page *tail)
> {
>         struct page_cgroup *head_pc = lookup_page_cgroup(head);
>         struct page_cgroup *tail_pc = lookup_page_cgroup(tail);
>         unsigned long flags;
>
>         if (mem_cgroup_disabled())
>                 return;
>         /*
>          * We have no races with charge/uncharge but will have races with
>          * page state accounting.
>          */
>         move_lock_page_cgroup(head_pc, &flags);
>
>         tail_pc->mem_cgroup = head_pc->mem_cgroup;
>         smp_wmb(); /* see __commit_charge() */
>         if (PageCgroupAcctLRU(head_pc)) {
>                 enum lru_list lru;
>                 struct mem_cgroup_per_zone *mz;
>
>                 /*
>                  * LRU flags cannot be copied because we need to add tail
>                  *.page to LRU by generic call and our hook will be called.
>                  * We hold lru_lock, then, reduce counter directly.
>                  */
>                 lru = page_lru(head);
>                 mz = page_cgroup_zoneinfo(head_pc->mem_cgroup, head);
>                 MEM_CGROUP_ZSTAT(mz, lru) -= 1;
>         }
>         tail_pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
>         move_unlock_page_cgroup(head_pc, &flags);
> }
> #endif
>
> /**
>  * mem_cgroup_move_account - move account of the page
>  * @page: the page
>  * @nr_pages: number of regular pages (>1 for huge pages)
>  * @pc: page_cgroup of the page.
>  * @from: mem_cgroup which the page is moved from.
>  * @to: mem_cgroup which the page is moved to. @from != @to.
>  * @uncharge: whether we should call uncharge and css_put against @from.
>  *
>  * The caller must confirm following.
>  * - page is not on LRU (isolate_page() is useful.)
>  * - compound_lock is held when nr_pages > 1
>  *
>  * This function doesn't do "charge" nor css_get to new cgroup. It should be
>  * done by a caller(__mem_cgroup_try_charge would be useful). If @uncharge is
>  * true, this function does "uncharge" from old cgroup, but it doesn't if
>  * @uncharge is false, so a caller should do "uncharge".
>  */
> static int mem_cgroup_move_account(struct page *page,
>                                    unsigned int nr_pages,
>                                    struct page_cgroup *pc,
>                                    struct mem_cgroup *from,
>                                    struct mem_cgroup *to,
>                                    bool uncharge)
> {
>         unsigned long flags;
>         int ret;
>
>         VM_BUG_ON(from == to);
>         VM_BUG_ON(PageLRU(page));
>         /*
>          * The page is isolated from LRU. So, collapse function
>          * will not handle this page. But page splitting can happen.
>          * Do this check under compound_page_lock(). The caller should
>          * hold it.
>          */
>         ret = -EBUSY;
>         if (nr_pages > 1 && !PageTransHuge(page))
>                 goto out;
>
>         lock_page_cgroup(pc);
>
>         ret = -EINVAL;
>         if (!PageCgroupUsed(pc) || pc->mem_cgroup != from)
>                 goto unlock;
>
>         move_lock_page_cgroup(pc, &flags);
>
>         if (PageCgroupFileMapped(pc)) {
>                 /* Update mapped_file data for mem_cgroup */
>                 preempt_disable();
>                 __this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
>                 __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
>                 preempt_enable();
>         }
>         mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -nr_pages);
>         if (uncharge)
>                 /* This is not "cancel", but cancel_charge does all we need. */
>                 __mem_cgroup_cancel_charge(from, nr_pages);
>
>         /* caller should have done css_get */
>         pc->mem_cgroup = to;
>         mem_cgroup_charge_statistics(to, PageCgroupCache(pc), nr_pages);
>         /*
>          * We charges against "to" which may not have any tasks. Then, "to"
>          * can be under rmdir(). But in current implementation, caller of
>          * this function is just force_empty() and move charge, so it's
>          * guaranteed that "to" is never removed. So, we don't check rmdir
>          * status here.
>          */
>         move_unlock_page_cgroup(pc, &flags);
>         ret = 0;
> unlock:
>         unlock_page_cgroup(pc);
>         /*
>          * check events
>          */
>         memcg_check_events(to, page);
>         memcg_check_events(from, page);
> out:
>         return ret;
> }
>
> /*
>  * move charges to its parent.
>  */
>
> static int mem_cgroup_move_parent(struct page *page,
>                                   struct page_cgroup *pc,
>                                   struct mem_cgroup *child,
>                                   gfp_t gfp_mask)
> {
>         struct cgroup *cg = child->css.cgroup;
>         struct cgroup *pcg = cg->parent;
>         struct mem_cgroup *parent;
>         unsigned int nr_pages;
>         unsigned long uninitialized_var(flags);
>         int ret;
>
>         /* Is ROOT ? */
>         if (!pcg)
>                 return -EINVAL;
>
>         ret = -EBUSY;
>         if (!get_page_unless_zero(page))
>                 goto out;
>         if (isolate_lru_page(page))
>                 goto put;
>
>         nr_pages = hpage_nr_pages(page);
>
>         parent = mem_cgroup_from_cont(pcg);
>         ret = __mem_cgroup_try_charge(NULL, gfp_mask, nr_pages, &parent, false);
>         if (ret || !parent)
>                 goto put_back;
>
>         if (nr_pages > 1)
>                 flags = compound_lock_irqsave(page);
>
>         ret = mem_cgroup_move_account(page, nr_pages, pc, child, parent, true);
>         if (ret)
>                 __mem_cgroup_cancel_charge(parent, nr_pages);
>
>         if (nr_pages > 1)
>                 compound_unlock_irqrestore(page, flags);
> put_back:
>         putback_lru_page(page);
> put:
>         put_page(page);
> out:
>         return ret;
> }
>
> /*
>  * Charge the memory controller for page usage.
>  * Return
>  * 0 if the charge was successful
>  * < 0 if the cgroup is over its limit
>  */
> static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
>                                 gfp_t gfp_mask, enum charge_type ctype)
> {
>         struct mem_cgroup *mem = NULL;
>         unsigned int nr_pages = 1;
>         struct page_cgroup *pc;
>         bool oom = true;
>         int ret;
>
>         if (PageTransHuge(page)) {
>                 nr_pages <<= compound_order(page);
>                 VM_BUG_ON(!PageTransHuge(page));
>                 /*
>                  * Never OOM-kill a process for a huge page.  The
>                  * fault handler will fall back to regular pages.
>                  */
>                 oom = false;
>         }
>
>         pc = lookup_page_cgroup(page);
>         BUG_ON(!pc); /* XXX: remove this and move pc lookup into commit */
>
>         ret = __mem_cgroup_try_charge(mm, gfp_mask, nr_pages, &mem, oom);
>         if (ret || !mem)
>                 return ret;
>
>         __mem_cgroup_commit_charge(mem, page, nr_pages, pc, ctype);
>         return 0;
> }
>
> int mem_cgroup_newpage_charge(struct page *page,
>                               struct mm_struct *mm, gfp_t gfp_mask)
> {
>         if (mem_cgroup_disabled())
>                 return 0;
>         /*
>          * If already mapped, we don't have to account.
>          * If page cache, page->mapping has address_space.
>          * But page->mapping may have out-of-use anon_vma pointer,
>          * detecit it by PageAnon() check. newly-mapped-anon's page->mapping
>          * is NULL.
>          */
>         if (page_mapped(page) || (page->mapping && !PageAnon(page)))
>                 return 0;
>         if (unlikely(!mm))
>                 mm = &init_mm;
>         return mem_cgroup_charge_common(page, mm, gfp_mask,
>                                 MEM_CGROUP_CHARGE_TYPE_MAPPED);
> }
>
> static void
> __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
>                                         enum charge_type ctype);
>
> static void
> __mem_cgroup_commit_charge_lrucare(struct page *page, struct mem_cgroup *mem,
>                                         enum charge_type ctype)
> {
>         struct page_cgroup *pc = lookup_page_cgroup(page);
>         /*
>          * In some case, SwapCache, FUSE(splice_buf->radixtree), the page
>          * is already on LRU. It means the page may on some other page_cgroup's
>          * LRU. Take care of it.
>          */
>         mem_cgroup_lru_del_before_commit(page);
>         __mem_cgroup_commit_charge(mem, page, 1, pc, ctype);
>         mem_cgroup_lru_add_after_commit(page);
>         return;
> }
>
> int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
>                                 gfp_t gfp_mask)
> {
>         struct mem_cgroup *mem = NULL;
>         int ret;
>
>         if (mem_cgroup_disabled())
>                 return 0;
>         if (PageCompound(page))
>                 return 0;
>         /*
>          * Corner case handling. This is called from add_to_page_cache()
>          * in usual. But some FS (shmem) precharges this page before calling it
>          * and call add_to_page_cache() with GFP_NOWAIT.
>          *
>          * For GFP_NOWAIT case, the page may be pre-charged before calling
>          * add_to_page_cache(). (See shmem.c) check it here and avoid to call
>          * charge twice. (It works but has to pay a bit larger cost.)
>          * And when the page is SwapCache, it should take swap information
>          * into account. This is under lock_page() now.
>          */
>         if (!(gfp_mask & __GFP_WAIT)) {
>                 struct page_cgroup *pc;
>
>                 pc = lookup_page_cgroup(page);
>                 if (!pc)
>                         return 0;
>                 lock_page_cgroup(pc);
>                 if (PageCgroupUsed(pc)) {
>                         unlock_page_cgroup(pc);
>                         return 0;
>                 }
>                 unlock_page_cgroup(pc);
>         }
>
>         if (unlikely(!mm))
>                 mm = &init_mm;
>
>         if (page_is_file_cache(page)) {
>                 ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, &mem, true);
>                 if (ret || !mem)
>                         return ret;
>
>                 /*
>                  * FUSE reuses pages without going through the final
>                  * put that would remove them from the LRU list, make
>                  * sure that they get relinked properly.
>                  */
>                 __mem_cgroup_commit_charge_lrucare(page, mem,
>                                         MEM_CGROUP_CHARGE_TYPE_CACHE);
>                 return ret;
>         }
>         /* shmem */
>         if (PageSwapCache(page)) {
>                 ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem);
>                 if (!ret)
>                         __mem_cgroup_commit_charge_swapin(page, mem,
>                                         MEM_CGROUP_CHARGE_TYPE_SHMEM);
>         } else
>                 ret = mem_cgroup_charge_common(page, mm, gfp_mask,
>                                         MEM_CGROUP_CHARGE_TYPE_SHMEM);
>
>         return ret;
> }
>
> /*
>  * While swap-in, try_charge -> commit or cancel, the page is locked.
>  * And when try_charge() successfully returns, one refcnt to memcg without
>  * struct page_cgroup is acquired. This refcnt will be consumed by
>  * "commit()" or removed by "cancel()"
>  */
> int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
>                                  struct page *page,
>                                  gfp_t mask, struct mem_cgroup **ptr)
> {
>         struct mem_cgroup *mem;
>         int ret;
>
>         *ptr = NULL;
>
>         if (mem_cgroup_disabled())
>                 return 0;
>
>         if (!do_swap_account)
>                 goto charge_cur_mm;
>         /*
>          * A racing thread's fault, or swapoff, may have already updated
>          * the pte, and even removed page from swap cache: in those cases
>          * do_swap_page()'s pte_same() test will fail; but there's also a
>          * KSM case which does need to charge the page.
>          */
>         if (!PageSwapCache(page))
>                 goto charge_cur_mm;
>         mem = try_get_mem_cgroup_from_page(page);
>         if (!mem)
>                 goto charge_cur_mm;
>         *ptr = mem;
>         ret = __mem_cgroup_try_charge(NULL, mask, 1, ptr, true);
>         css_put(&mem->css);
>         return ret;
> charge_cur_mm:
>         if (unlikely(!mm))
>                 mm = &init_mm;
>         return __mem_cgroup_try_charge(mm, mask, 1, ptr, true);
> }
>
> static void
> __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
>                                         enum charge_type ctype)
> {
>         if (mem_cgroup_disabled())
>                 return;
>         if (!ptr)
>                 return;
>         cgroup_exclude_rmdir(&ptr->css);
>
>         __mem_cgroup_commit_charge_lrucare(page, ptr, ctype);
>         /*
>          * Now swap is on-memory. This means this page may be
>          * counted both as mem and swap....double count.
>          * Fix it by uncharging from memsw. Basically, this SwapCache is stable
>          * under lock_page(). But in do_swap_page()::memory.c, reuse_swap_page()
>          * may call delete_from_swap_cache() before reach here.
>          */
>         if (do_swap_account && PageSwapCache(page)) {
>                 swp_entry_t ent = {.val = page_private(page)};
>                 unsigned short id;
>                 struct mem_cgroup *memcg;
>
>                 id = swap_cgroup_record(ent, 0);
>                 rcu_read_lock();
>                 memcg = mem_cgroup_lookup(id);
>                 if (memcg) {
>                         /*
>                          * This recorded memcg can be obsolete one. So, avoid
>                          * calling css_tryget
>                          */
>                         if (!mem_cgroup_is_root(memcg))
>                                 res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
>                         mem_cgroup_swap_statistics(memcg, false);
>                         mem_cgroup_put(memcg);
>                 }
>                 rcu_read_unlock();
>         }
>         /*
>          * At swapin, we may charge account against cgroup which has no tasks.
>          * So, rmdir()->pre_destroy() can be called while we do this charge.
>          * In that case, we need to call pre_destroy() again. check it here.
>          */
>         cgroup_release_and_wakeup_rmdir(&ptr->css);
> }
>
> void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr)
> {
>         __mem_cgroup_commit_charge_swapin(page, ptr,
>                                         MEM_CGROUP_CHARGE_TYPE_MAPPED);
> }
>
> void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *mem)
> {
>         if (mem_cgroup_disabled())
>                 return;
>         if (!mem)
>                 return;
>         __mem_cgroup_cancel_charge(mem, 1);
> }
>
> static void mem_cgroup_do_uncharge(struct mem_cgroup *mem,
>                                    unsigned int nr_pages,
>                                    const enum charge_type ctype)
> {
>         struct memcg_batch_info *batch = NULL;
>         bool uncharge_memsw = true;
>
>         /* If swapout, usage of swap doesn't decrease */
>         if (!do_swap_account || ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
>                 uncharge_memsw = false;
>
>         batch = &current->memcg_batch;
>         /*
>          * In usual, we do css_get() when we remember memcg pointer.
>          * But in this case, we keep res->usage until end of a series of
>          * uncharges. Then, it's ok to ignore memcg's refcnt.
>          */
>         if (!batch->memcg)
>                 batch->memcg = mem;
>         /*
>          * do_batch > 0 when unmapping pages or inode invalidate/truncate.
>          * In those cases, all pages freed continuously can be expected to be in
>          * the same cgroup and we have chance to coalesce uncharges.
>          * But we do uncharge one by one if this is killed by OOM(TIF_MEMDIE)
>          * because we want to do uncharge as soon as possible.
>          */
>
>         if (!batch->do_batch || test_thread_flag(TIF_MEMDIE))
>                 goto direct_uncharge;
>
>         if (nr_pages > 1)
>                 goto direct_uncharge;
>
>         /*
>          * In typical case, batch->memcg == mem. This means we can
>          * merge a series of uncharges to an uncharge of res_counter.
>          * If not, we uncharge res_counter ony by one.
>          */
>         if (batch->memcg != mem)
>                 goto direct_uncharge;
>         /* remember freed charge and uncharge it later */
>         batch->nr_pages++;
>         if (uncharge_memsw)
>                 batch->memsw_nr_pages++;
>         return;
> direct_uncharge:
>         res_counter_uncharge(&mem->res, nr_pages * PAGE_SIZE);
>         if (uncharge_memsw)
>                 res_counter_uncharge(&mem->memsw, nr_pages * PAGE_SIZE);
>         if (unlikely(batch->memcg != mem))
>                 memcg_oom_recover(mem);
>         return;
> }
>
> /*
>  * uncharge if !page_mapped(page)
>  */
> static struct mem_cgroup *
> __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
> {
>         struct mem_cgroup *mem = NULL;
>         unsigned int nr_pages = 1;
>         struct page_cgroup *pc;
>
>         if (mem_cgroup_disabled())
>                 return NULL;
>
>         if (PageSwapCache(page))
>                 return NULL;
>
>         if (PageTransHuge(page)) {
>                 nr_pages <<= compound_order(page);
>                 VM_BUG_ON(!PageTransHuge(page));
>         }
>         /*
>          * Check if our page_cgroup is valid
>          */
>         pc = lookup_page_cgroup(page);
>         if (unlikely(!pc || !PageCgroupUsed(pc)))
>                 return NULL;
>
>         lock_page_cgroup(pc);
>
>         mem = pc->mem_cgroup;
>
>         if (!PageCgroupUsed(pc))
>                 goto unlock_out;
>
>         switch (ctype) {
>         case MEM_CGROUP_CHARGE_TYPE_MAPPED:
>         case MEM_CGROUP_CHARGE_TYPE_DROP:
>                 /* See mem_cgroup_prepare_migration() */
>                 if (page_mapped(page) || PageCgroupMigration(pc))
>                         goto unlock_out;
>                 break;
>         case MEM_CGROUP_CHARGE_TYPE_SWAPOUT:
>                 if (!PageAnon(page)) {  /* Shared memory */
>                         if (page->mapping && !page_is_file_cache(page))
>                                 goto unlock_out;
>                 } else if (page_mapped(page)) /* Anon */
>                                 goto unlock_out;
>                 break;
>         default:
>                 break;
>         }
>
>         mem_cgroup_charge_statistics(mem, PageCgroupCache(pc), -nr_pages);
>
>         ClearPageCgroupUsed(pc);
>         /*
>          * pc->mem_cgroup is not cleared here. It will be accessed when it's
>          * freed from LRU. This is safe because uncharged page is expected not
>          * to be reused (freed soon). Exception is SwapCache, it's handled by
>          * special functions.
>          */
>
>         unlock_page_cgroup(pc);
>         /*
>          * even after unlock, we have mem->res.usage here and this memcg
>          * will never be freed.
>          */
>         memcg_check_events(mem, page);
>         if (do_swap_account && ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT) {
>                 mem_cgroup_swap_statistics(mem, true);
>                 mem_cgroup_get(mem);
>         }
>         if (!mem_cgroup_is_root(mem))
>                 mem_cgroup_do_uncharge(mem, nr_pages, ctype);
>
>         return mem;
>
> unlock_out:
>         unlock_page_cgroup(pc);
>         return NULL;
> }
>
> void mem_cgroup_uncharge_page(struct page *page)
> {
>         /* early check. */
>         if (page_mapped(page))
>                 return;
>         if (page->mapping && !PageAnon(page))
>                 return;
>         __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_MAPPED);
> }
>
> void mem_cgroup_uncharge_cache_page(struct page *page)
> {
>         VM_BUG_ON(page_mapped(page));
>         VM_BUG_ON(page->mapping);
>         __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE);
> }
>
> /*
>  * Batch_start/batch_end is called in unmap_page_range/invlidate/trucate.
>  * In that cases, pages are freed continuously and we can expect pages
>  * are in the same memcg. All these calls itself limits the number of
>  * pages freed at once, then uncharge_start/end() is called properly.
>  * This may be called prural(2) times in a context,
>  */
>
> void mem_cgroup_uncharge_start(void)
> {
>         current->memcg_batch.do_batch++;
>         /* We can do nest. */
>         if (current->memcg_batch.do_batch == 1) {
>                 current->memcg_batch.memcg = NULL;
>                 current->memcg_batch.nr_pages = 0;
>                 current->memcg_batch.memsw_nr_pages = 0;
>         }
> }
>
> void mem_cgroup_uncharge_end(void)
> {
>         struct memcg_batch_info *batch = &current->memcg_batch;
>
>         if (!batch->do_batch)
>                 return;
>
>         batch->do_batch--;
>         if (batch->do_batch) /* If stacked, do nothing. */
>                 return;
>
>         if (!batch->memcg)
>                 return;
>         /*
>          * This "batch->memcg" is valid without any css_get/put etc...
>          * bacause we hide charges behind us.
>          */
>         if (batch->nr_pages)
>                 res_counter_uncharge(&batch->memcg->res,
>                                      batch->nr_pages * PAGE_SIZE);
>         if (batch->memsw_nr_pages)
>                 res_counter_uncharge(&batch->memcg->memsw,
>                                      batch->memsw_nr_pages * PAGE_SIZE);
>         memcg_oom_recover(batch->memcg);
>         /* forget this pointer (for sanity check) */
>         batch->memcg = NULL;
> }
>
> #ifdef CONFIG_SWAP
> /*
>  * called after __delete_from_swap_cache() and drop "page" account.
>  * memcg information is recorded to swap_cgroup of "ent"
>  */
> void
> mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
> {
>         struct mem_cgroup *memcg;
>         int ctype = MEM_CGROUP_CHARGE_TYPE_SWAPOUT;
>
>         if (!swapout) /* this was a swap cache but the swap is unused ! */
>                 ctype = MEM_CGROUP_CHARGE_TYPE_DROP;
>
>         memcg = __mem_cgroup_uncharge_common(page, ctype);
>
>         /*
>          * record memcg information,  if swapout && memcg != NULL,
>          * mem_cgroup_get() was called in uncharge().
>          */
>         if (do_swap_account && swapout && memcg)
>                 swap_cgroup_record(ent, css_id(&memcg->css));
> }
> #endif
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> /*
>  * called from swap_entry_free(). remove record in swap_cgroup and
>  * uncharge "memsw" account.
>  */
> void mem_cgroup_uncharge_swap(swp_entry_t ent)
> {
>         struct mem_cgroup *memcg;
>         unsigned short id;
>
>         if (!do_swap_account)
>                 return;
>
>         id = swap_cgroup_record(ent, 0);
>         rcu_read_lock();
>         memcg = mem_cgroup_lookup(id);
>         if (memcg) {
>                 /*
>                  * We uncharge this because swap is freed.
>                  * This memcg can be obsolete one. We avoid calling css_tryget
>                  */
>                 if (!mem_cgroup_is_root(memcg))
>                         res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
>                 mem_cgroup_swap_statistics(memcg, false);
>                 mem_cgroup_put(memcg);
>         }
>         rcu_read_unlock();
> }
>
> /**
>  * mem_cgroup_move_swap_account - move swap charge and swap_cgroup's record.
>  * @entry: swap entry to be moved
>  * @from:  mem_cgroup which the entry is moved from
>  * @to:  mem_cgroup which the entry is moved to
>  * @need_fixup: whether we should fixup res_counters and refcounts.
>  *
>  * It succeeds only when the swap_cgroup's record for this entry is the same
>  * as the mem_cgroup's id of @from.
>  *
>  * Returns 0 on success, -EINVAL on failure.
>  *
>  * The caller must have charged to @to, IOW, called res_counter_charge() about
>  * both res and memsw, and called css_get().
>  */
> static int mem_cgroup_move_swap_account(swp_entry_t entry,
>                 struct mem_cgroup *from, struct mem_cgroup *to, bool need_fixup)
> {
>         unsigned short old_id, new_id;
>
>         old_id = css_id(&from->css);
>         new_id = css_id(&to->css);
>
>         if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
>                 mem_cgroup_swap_statistics(from, false);
>                 mem_cgroup_swap_statistics(to, true);
>                 /*
>                  * This function is only called from task migration context now.
>                  * It postpones res_counter and refcount handling till the end
>                  * of task migration(mem_cgroup_clear_mc()) for performance
>                  * improvement. But we cannot postpone mem_cgroup_get(to)
>                  * because if the process that has been moved to @to does
>                  * swap-in, the refcount of @to might be decreased to 0.
>                  */
>                 mem_cgroup_get(to);
>                 if (need_fixup) {
>                         if (!mem_cgroup_is_root(from))
>                                 res_counter_uncharge(&from->memsw, PAGE_SIZE);
>                         mem_cgroup_put(from);
>                         /*
>                          * we charged both to->res and to->memsw, so we should
>                          * uncharge to->res.
>                          */
>                         if (!mem_cgroup_is_root(to))
>                                 res_counter_uncharge(&to->res, PAGE_SIZE);
>                 }
>                 return 0;
>         }
>         return -EINVAL;
> }
> #else
> static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
>                 struct mem_cgroup *from, struct mem_cgroup *to, bool need_fixup)
> {
>         return -EINVAL;
> }
> #endif
>
> /*
>  * Before starting migration, account PAGE_SIZE to mem_cgroup that the old
>  * page belongs to.
>  */
> int mem_cgroup_prepare_migration(struct page *page,
>         struct page *newpage, struct mem_cgroup **ptr, gfp_t gfp_mask)
> {
>         struct mem_cgroup *mem = NULL;
>         struct page_cgroup *pc;
>         enum charge_type ctype;
>         int ret = 0;
>
>         *ptr = NULL;
>
>         VM_BUG_ON(PageTransHuge(page));
>         if (mem_cgroup_disabled())
>                 return 0;
>
>         pc = lookup_page_cgroup(page);
>         lock_page_cgroup(pc);
>         if (PageCgroupUsed(pc)) {
>                 mem = pc->mem_cgroup;
>                 css_get(&mem->css);
>                 /*
>                  * At migrating an anonymous page, its mapcount goes down
>                  * to 0 and uncharge() will be called. But, even if it's fully
>                  * unmapped, migration may fail and this page has to be
>                  * charged again. We set MIGRATION flag here and delay uncharge
>                  * until end_migration() is called
>                  *
>                  * Corner Case Thinking
>                  * A)
>                  * When the old page was mapped as Anon and it's unmap-and-freed
>                  * while migration was ongoing.
>                  * If unmap finds the old page, uncharge() of it will be delayed
>                  * until end_migration(). If unmap finds a new page, it's
>                  * uncharged when it make mapcount to be 1->0. If unmap code
>                  * finds swap_migration_entry, the new page will not be mapped
>                  * and end_migration() will find it(mapcount==0).
>                  *
>                  * B)
>                  * When the old page was mapped but migraion fails, the kernel
>                  * remaps it. A charge for it is kept by MIGRATION flag even
>                  * if mapcount goes down to 0. We can do remap successfully
>                  * without charging it again.
>                  *
>                  * C)
>                  * The "old" page is under lock_page() until the end of
>                  * migration, so, the old page itself will not be swapped-out.
>                  * If the new page is swapped out before end_migraton, our
>                  * hook to usual swap-out path will catch the event.
>                  */
>                 if (PageAnon(page))
>                         SetPageCgroupMigration(pc);
>         }
>         unlock_page_cgroup(pc);
>         /*
>          * If the page is not charged at this point,
>          * we return here.
>          */
>         if (!mem)
>                 return 0;
>
>         *ptr = mem;
>         ret = __mem_cgroup_try_charge(NULL, gfp_mask, 1, ptr, false);
>         css_put(&mem->css);/* drop extra refcnt */
>         if (ret || *ptr == NULL) {
>                 if (PageAnon(page)) {
>                         lock_page_cgroup(pc);
>                         ClearPageCgroupMigration(pc);
>                         unlock_page_cgroup(pc);
>                         /*
>                          * The old page may be fully unmapped while we kept it.
>                          */
>                         mem_cgroup_uncharge_page(page);
>                 }
>                 return -ENOMEM;
>         }
>         /*
>          * We charge new page before it's used/mapped. So, even if unlock_page()
>          * is called before end_migration, we can catch all events on this new
>          * page. In the case new page is migrated but not remapped, new page's
>          * mapcount will be finally 0 and we call uncharge in end_migration().
>          */
>         pc = lookup_page_cgroup(newpage);
>         if (PageAnon(page))
>                 ctype = MEM_CGROUP_CHARGE_TYPE_MAPPED;
>         else if (page_is_file_cache(page))
>                 ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
>         else
>                 ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;
>         __mem_cgroup_commit_charge(mem, page, 1, pc, ctype);
>         return ret;
> }
>
> /* remove redundant charge if migration failed*/
> void mem_cgroup_end_migration(struct mem_cgroup *mem,
>         struct page *oldpage, struct page *newpage, bool migration_ok)
> {
>         struct page *used, *unused;
>         struct page_cgroup *pc;
>
>         if (!mem)
>                 return;
>         /* blocks rmdir() */
>         cgroup_exclude_rmdir(&mem->css);
>         if (!migration_ok) {
>                 used = oldpage;
>                 unused = newpage;
>         } else {
>                 used = newpage;
>                 unused = oldpage;
>         }
>         /*
>          * We disallowed uncharge of pages under migration because mapcount
>          * of the page goes down to zero, temporarly.
>          * Clear the flag and check the page should be charged.
>          */
>         pc = lookup_page_cgroup(oldpage);
>         lock_page_cgroup(pc);
>         ClearPageCgroupMigration(pc);
>         unlock_page_cgroup(pc);
>
>         __mem_cgroup_uncharge_common(unused, MEM_CGROUP_CHARGE_TYPE_FORCE);
>
>         /*
>          * If a page is a file cache, radix-tree replacement is very atomic
>          * and we can skip this check. When it was an Anon page, its mapcount
>          * goes down to 0. But because we added MIGRATION flage, it's not
>          * uncharged yet. There are several case but page->mapcount check
>          * and USED bit check in mem_cgroup_uncharge_page() will do enough
>          * check. (see prepare_charge() also)
>          */
>         if (PageAnon(used))
>                 mem_cgroup_uncharge_page(used);
>         /*
>          * At migration, we may charge account against cgroup which has no
>          * tasks.
>          * So, rmdir()->pre_destroy() can be called while we do this charge.
>          * In that case, we need to call pre_destroy() again. check it here.
>          */
>         cgroup_release_and_wakeup_rmdir(&mem->css);
> }
>
> /*
>  * A call to try to shrink memory usage on charge failure at shmem's swapin.
>  * Calling hierarchical_reclaim is not enough because we should update
>  * last_oom_jiffies to prevent pagefault_out_of_memory from invoking global OOM.
>  * Moreover considering hierarchy, we should reclaim from the mem_over_limit,
>  * not from the memcg which this page would be charged to.
>  * try_charge_swapin does all of these works properly.
>  */
> int mem_cgroup_shmem_charge_fallback(struct page *page,
>                             struct mm_struct *mm,
>                             gfp_t gfp_mask)
> {
>         struct mem_cgroup *mem;
>         int ret;
>
>         if (mem_cgroup_disabled())
>                 return 0;
>
>         ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem);
>         if (!ret)
>                 mem_cgroup_cancel_charge_swapin(mem); /* it does !mem check */
>
>         return ret;
> }
>
> #ifdef CONFIG_DEBUG_VM
> static struct page_cgroup *lookup_page_cgroup_used(struct page *page)
> {
>         struct page_cgroup *pc;
>
>         pc = lookup_page_cgroup(page);
>         if (likely(pc) && PageCgroupUsed(pc))
>                 return pc;
>         return NULL;
> }
>
> bool mem_cgroup_bad_page_check(struct page *page)
> {
>         if (mem_cgroup_disabled())
>                 return false;
>
>         return lookup_page_cgroup_used(page) != NULL;
> }
>
> void mem_cgroup_print_bad_page(struct page *page)
> {
>         struct page_cgroup *pc;
>
>         pc = lookup_page_cgroup_used(page);
>         if (pc) {
>                 int ret = -1;
>                 char *path;
>
>                 printk(KERN_ALERT "pc:%p pc->flags:%lx pc->mem_cgroup:%p",
>                        pc, pc->flags, pc->mem_cgroup);
>
>                 path = kmalloc(PATH_MAX, GFP_KERNEL);
>                 if (path) {
>                         rcu_read_lock();
>                         ret = cgroup_path(pc->mem_cgroup->css.cgroup,
>                                                         path, PATH_MAX);
>                         rcu_read_unlock();
>                 }
>
>                 printk(KERN_CONT "(%s)\n",
>                                 (ret < 0) ? "cannot get the path" : path);
>                 kfree(path);
>         }
> }
> #endif
>
> static DEFINE_MUTEX(set_limit_mutex);
>
> static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
>                                 unsigned long long val)
> {
>         int retry_count;
>         u64 memswlimit, memlimit;
>         int ret = 0;
>         int children = mem_cgroup_count_children(memcg);
>         u64 curusage, oldusage;
>         int enlarge;
>
>         /*
>          * For keeping hierarchical_reclaim simple, how long we should retry
>          * is depends on callers. We set our retry-count to be function
>          * of # of children which we should visit in this loop.
>          */
>         retry_count = MEM_CGROUP_RECLAIM_RETRIES * children;
>
>         oldusage = res_counter_read_u64(&memcg->res, RES_USAGE);
>
>         enlarge = 0;
>         while (retry_count) {
>                 if (signal_pending(current)) {
>                         ret = -EINTR;
>                         break;
>                 }
>                 /*
>                  * Rather than hide all in some function, I do this in
>                  * open coded manner. You see what this really does.
>                  * We have to guarantee mem->res.limit < mem->memsw.limit.
>                  */
>                 mutex_lock(&set_limit_mutex);
>                 memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
>                 if (memswlimit < val) {
>                         ret = -EINVAL;
>                         mutex_unlock(&set_limit_mutex);
>                         break;
>                 }
>
>                 memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
>                 if (memlimit < val)
>                         enlarge = 1;
>
>                 ret = res_counter_set_limit(&memcg->res, val);
>                 if (!ret) {
>                         if (memswlimit == val)
>                                 memcg->memsw_is_minimum = true;
>                         else
>                                 memcg->memsw_is_minimum = false;
>                 }
>                 mutex_unlock(&set_limit_mutex);
>
>                 if (!ret)
>                         break;
>
>                 mem_cgroup_hierarchical_reclaim(memcg, NULL, GFP_KERNEL,
>                                                 MEM_CGROUP_RECLAIM_SHRINK,
>                                                 NULL);
>                 curusage = res_counter_read_u64(&memcg->res, RES_USAGE);
>                 /* Usage is reduced ? */
>                 if (curusage >= oldusage)
>                         retry_count--;
>                 else
>                         oldusage = curusage;
>         }
>         if (!ret && enlarge)
>                 memcg_oom_recover(memcg);
>
>         return ret;
> }
>
> static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
>                                         unsigned long long val)
> {
>         int retry_count;
>         u64 memlimit, memswlimit, oldusage, curusage;
>         int children = mem_cgroup_count_children(memcg);
>         int ret = -EBUSY;
>         int enlarge = 0;
>
>         /* see mem_cgroup_resize_res_limit */
>         retry_count = children * MEM_CGROUP_RECLAIM_RETRIES;
>         oldusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
>         while (retry_count) {
>                 if (signal_pending(current)) {
>                         ret = -EINTR;
>                         break;
>                 }
>                 /*
>                  * Rather than hide all in some function, I do this in
>                  * open coded manner. You see what this really does.
>                  * We have to guarantee mem->res.limit < mem->memsw.limit.
>                  */
>                 mutex_lock(&set_limit_mutex);
>                 memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
>                 if (memlimit > val) {
>                         ret = -EINVAL;
>                         mutex_unlock(&set_limit_mutex);
>                         break;
>                 }
>                 memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
>                 if (memswlimit < val)
>                         enlarge = 1;
>                 ret = res_counter_set_limit(&memcg->memsw, val);
>                 if (!ret) {
>                         if (memlimit == val)
>                                 memcg->memsw_is_minimum = true;
>                         else
>                                 memcg->memsw_is_minimum = false;
>                 }
>                 mutex_unlock(&set_limit_mutex);
>
>                 if (!ret)
>                         break;
>
>                 mem_cgroup_hierarchical_reclaim(memcg, NULL, GFP_KERNEL,
>                                                 MEM_CGROUP_RECLAIM_NOSWAP |
>                                                 MEM_CGROUP_RECLAIM_SHRINK,
>                                                 NULL);
>                 curusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
>                 /* Usage is reduced ? */
>                 if (curusage >= oldusage)
>                         retry_count--;
>                 else
>                         oldusage = curusage;
>         }
>         if (!ret && enlarge)
>                 memcg_oom_recover(memcg);
>         return ret;
> }
>
> unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
>                                             gfp_t gfp_mask,
>                                             unsigned long *total_scanned)
> {
>         unsigned long nr_reclaimed = 0;
>         struct mem_cgroup_per_zone *mz, *next_mz = NULL;
>         unsigned long reclaimed;
>         int loop = 0;
>         struct mem_cgroup_tree_per_zone *mctz;
>         unsigned long long excess;
>         unsigned long nr_scanned;
>
>         if (order > 0)
>                 return 0;
>
>         mctz = soft_limit_tree_node_zone(zone_to_nid(zone), zone_idx(zone));
>         /*
>          * This loop can run a while, specially if mem_cgroup's continuously
>          * keep exceeding their soft limit and putting the system under
>          * pressure
>          */
>         do {
>                 if (next_mz)
>                         mz = next_mz;
>                 else
>                         mz = mem_cgroup_largest_soft_limit_node(mctz);
>                 if (!mz)
>                         break;
>
>                 nr_scanned = 0;
>                 reclaimed = mem_cgroup_hierarchical_reclaim(mz->mem, zone,
>                                                 gfp_mask,
>                                                 MEM_CGROUP_RECLAIM_SOFT,
>                                                 &nr_scanned);
>                 nr_reclaimed += reclaimed;
>                 *total_scanned += nr_scanned;
>                 spin_lock(&mctz->lock);
>
>                 /*
>                  * If we failed to reclaim anything from this memory cgroup
>                  * it is time to move on to the next cgroup
>                  */
>                 next_mz = NULL;
>                 if (!reclaimed) {
>                         do {
>                                 /*
>                                  * Loop until we find yet another one.
>                                  *
>                                  * By the time we get the soft_limit lock
>                                  * again, someone might have aded the
>                                  * group back on the RB tree. Iterate to
>                                  * make sure we get a different mem.
>                                  * mem_cgroup_largest_soft_limit_node returns
>                                  * NULL if no other cgroup is present on
>                                  * the tree
>                                  */
>                                 next_mz =
>                                 __mem_cgroup_largest_soft_limit_node(mctz);
>                                 if (next_mz == mz)
>                                         css_put(&next_mz->mem->css);
>                                 else /* next_mz == NULL or other memcg */
>                                         break;
>                         } while (1);
>                 }
>                 __mem_cgroup_remove_exceeded(mz->mem, mz, mctz);
>                 excess = res_counter_soft_limit_excess(&mz->mem->res);
>                 /*
>                  * One school of thought says that we should not add
>                  * back the node to the tree if reclaim returns 0.
>                  * But our reclaim could return 0, simply because due
>                  * to priority we are exposing a smaller subset of
>                  * memory to reclaim from. Consider this as a longer
>                  * term TODO.
>                  */
>                 /* If excess == 0, no tree ops */
>                 __mem_cgroup_insert_exceeded(mz->mem, mz, mctz, excess);
>                 spin_unlock(&mctz->lock);
>                 css_put(&mz->mem->css);
>                 loop++;
>                 /*
>                  * Could not reclaim anything and there are no more
>                  * mem cgroups to try or we seem to be looping without
>                  * reclaiming anything.
>                  */
>                 if (!nr_reclaimed &&
>                         (next_mz == NULL ||
>                         loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS))
>                         break;
>         } while (!nr_reclaimed);
>         if (next_mz)
>                 css_put(&next_mz->mem->css);
>         return nr_reclaimed;
> }
>
> /*
>  * This routine traverse page_cgroup in given list and drop them all.
>  * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
>  */
> static int mem_cgroup_force_empty_list(struct mem_cgroup *mem,
>                                 int node, int zid, enum lru_list lru)
> {
>         struct zone *zone;
>         struct mem_cgroup_per_zone *mz;
>         struct page_cgroup *pc, *busy;
>         unsigned long flags, loop;
>         struct list_head *list;
>         int ret = 0;
>
>         zone = &NODE_DATA(node)->node_zones[zid];
>         mz = mem_cgroup_zoneinfo(mem, node, zid);
>         list = &mz->lists[lru];
>
>         loop = MEM_CGROUP_ZSTAT(mz, lru);
>         /* give some margin against EBUSY etc...*/
>         loop += 256;
>         busy = NULL;
>         while (loop--) {
>                 struct page *page;
>
>                 ret = 0;
>                 spin_lock_irqsave(&zone->lru_lock, flags);
>                 if (list_empty(list)) {
>                         spin_unlock_irqrestore(&zone->lru_lock, flags);
>                         break;
>                 }
>                 pc = list_entry(list->prev, struct page_cgroup, lru);
>                 if (busy == pc) {
>                         list_move(&pc->lru, list);
>                         busy = NULL;
>                         spin_unlock_irqrestore(&zone->lru_lock, flags);
>                         continue;
>                 }
>                 spin_unlock_irqrestore(&zone->lru_lock, flags);
>
>                 page = lookup_cgroup_page(pc);
>
>                 ret = mem_cgroup_move_parent(page, pc, mem, GFP_KERNEL);
>                 if (ret == -ENOMEM)
>                         break;
>
>                 if (ret == -EBUSY || ret == -EINVAL) {
>                         /* found lock contention or "pc" is obsolete. */
>                         busy = pc;
>                         cond_resched();
>                 } else
>                         busy = NULL;
>         }
>
>         if (!ret && !list_empty(list))
>                 return -EBUSY;
>         return ret;
> }
>
> /*
>  * make mem_cgroup's charge to be 0 if there is no task.
>  * This enables deleting this mem_cgroup.
>  */
> static int mem_cgroup_force_empty(struct mem_cgroup *mem, bool free_all)
> {
>         int ret;
>         int node, zid, shrink;
>         int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
>         struct cgroup *cgrp = mem->css.cgroup;
>
>         css_get(&mem->css);
>
>         shrink = 0;
>         /* should free all ? */
>         if (free_all)
>                 goto try_to_free;
> move_account:
>         do {
>                 ret = -EBUSY;
>                 if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
>                         goto out;
>                 ret = -EINTR;
>                 if (signal_pending(current))
>                         goto out;
>                 /* This is for making all *used* pages to be on LRU. */
>                 lru_add_drain_all();
>                 drain_all_stock_sync();
>                 ret = 0;
>                 mem_cgroup_start_move(mem);
>                 for_each_node_state(node, N_HIGH_MEMORY) {
>                         for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
>                                 enum lru_list l;
>                                 for_each_lru(l) {
>                                         ret = mem_cgroup_force_empty_list(mem,
>                                                         node, zid, l);
>                                         if (ret)
>                                                 break;
>                                 }
>                         }
>                         if (ret)
>                                 break;
>                 }
>                 mem_cgroup_end_move(mem);
>                 memcg_oom_recover(mem);
>                 /* it seems parent cgroup doesn't have enough mem */
>                 if (ret == -ENOMEM)
>                         goto try_to_free;
>                 cond_resched();
>         /* "ret" should also be checked to ensure all lists are empty. */
>         } while (mem->res.usage > 0 || ret);
> out:
>         css_put(&mem->css);
>         return ret;
>
> try_to_free:
>         /* returns EBUSY if there is a task or if we come here twice. */
>         if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children) || shrink) {
>                 ret = -EBUSY;
>                 goto out;
>         }
>         /* we call try-to-free pages for make this cgroup empty */
>         lru_add_drain_all();
>         /* try to free all pages in this cgroup */
>         shrink = 1;
>         while (nr_retries && mem->res.usage > 0) {
>                 int progress;
>
>                 if (signal_pending(current)) {
>                         ret = -EINTR;
>                         goto out;
>                 }
>                 progress = try_to_free_mem_cgroup_pages(mem, GFP_KERNEL,
>                                                 false, get_swappiness(mem));
>                 if (!progress) {
>                         nr_retries--;
>                         /* maybe some writeback is necessary */
>                         congestion_wait(BLK_RW_ASYNC, HZ/10);
>                 }
>
>         }
>         lru_add_drain();
>         /* try move_account...there may be some *locked* pages. */
>         goto move_account;
> }
>
> int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event)
> {
>         return mem_cgroup_force_empty(mem_cgroup_from_cont(cont), true);
> }
>
>
> static u64 mem_cgroup_hierarchy_read(struct cgroup *cont, struct cftype *cft)
> {
>         return mem_cgroup_from_cont(cont)->use_hierarchy;
> }
>
> static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
>                                         u64 val)
> {
>         int retval = 0;
>         struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
>         struct cgroup *parent = cont->parent;
>         struct mem_cgroup *parent_mem = NULL;
>
>         if (parent)
>                 parent_mem = mem_cgroup_from_cont(parent);
>
>         cgroup_lock();
>         /*
>          * If parent's use_hierarchy is set, we can't make any modifications
>          * in the child subtrees. If it is unset, then the change can
>          * occur, provided the current cgroup has no children.
>          *
>          * For the root cgroup, parent_mem is NULL, we allow value to be
>          * set if there are no children.
>          */
>         if ((!parent_mem || !parent_mem->use_hierarchy) &&
>                                 (val == 1 || val == 0)) {
>                 if (list_empty(&cont->children))
>                         mem->use_hierarchy = val;
>                 else
>                         retval = -EBUSY;
>         } else
>                 retval = -EINVAL;
>         cgroup_unlock();
>
>         return retval;
> }
>
>
> static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *mem,
>                                                enum mem_cgroup_stat_index idx)
> {
>         struct mem_cgroup *iter;
>         long val = 0;
>
>         /* Per-cpu values can be negative, use a signed accumulator */
>         for_each_mem_cgroup_tree(iter, mem)
>                 val += mem_cgroup_read_stat(iter, idx);
>
>         if (val < 0) /* race ? */
>                 val = 0;
>         return val;
> }
>
> static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
> {
>         u64 val;
>
>         if (!mem_cgroup_is_root(mem)) {
>                 if (!swap)
>                         return res_counter_read_u64(&mem->res, RES_USAGE);
>                 else
>                         return res_counter_read_u64(&mem->memsw, RES_USAGE);
>         }
>
>         val = mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_CACHE);
>         val += mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_RSS);
>
>         if (swap)
>                 val += mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_SWAPOUT);
>
>         return val << PAGE_SHIFT;
> }
>
> static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
> {
>         struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
>         u64 val;
>         int type, name;
>
>         type = MEMFILE_TYPE(cft->private);
>         name = MEMFILE_ATTR(cft->private);
>         switch (type) {
>         case _MEM:
>                 if (name == RES_USAGE)
>                         val = mem_cgroup_usage(mem, false);
>                 else
>                         val = res_counter_read_u64(&mem->res, name);
>                 break;
>         case _MEMSWAP:
>                 if (name == RES_USAGE)
>                         val = mem_cgroup_usage(mem, true);
>                 else
>                         val = res_counter_read_u64(&mem->memsw, name);
>                 break;
>         default:
>                 BUG();
>                 break;
>         }
>         return val;
> }
> /*
>  * The user of this function is...
>  * RES_LIMIT.
>  */
> static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
>                             const char *buffer)
> {
>         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
>         int type, name;
>         unsigned long long val;
>         int ret;
>
>         type = MEMFILE_TYPE(cft->private);
>         name = MEMFILE_ATTR(cft->private);
>         switch (name) {
>         case RES_LIMIT:
>                 if (mem_cgroup_is_root(memcg)) { /* Can't set limit on root */
>                         ret = -EINVAL;
>                         break;
>                 }
>                 /* This function does all necessary parse...reuse it */
>                 ret = res_counter_memparse_write_strategy(buffer, &val);
>                 if (ret)
>                         break;
>                 if (type == _MEM)
>                         ret = mem_cgroup_resize_limit(memcg, val);
>                 else
>                         ret = mem_cgroup_resize_memsw_limit(memcg, val);
>                 break;
>         case RES_SOFT_LIMIT:
>                 ret = res_counter_memparse_write_strategy(buffer, &val);
>                 if (ret)
>                         break;
>                 /*
>                  * For memsw, soft limits are hard to implement in terms
>                  * of semantics, for now, we support soft limits for
>                  * control without swap
>                  */
>                 if (type == _MEM)
>                         ret = res_counter_set_soft_limit(&memcg->res, val);
>                 else
>                         ret = -EINVAL;
>                 break;
>         default:
>                 ret = -EINVAL; /* should be BUG() ? */
>                 break;
>         }
>         return ret;
> }
>
> static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
>                 unsigned long long *mem_limit, unsigned long long *memsw_limit)
> {
>         struct cgroup *cgroup;
>         unsigned long long min_limit, min_memsw_limit, tmp;
>
>         min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
>         min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
>         cgroup = memcg->css.cgroup;
>         if (!memcg->use_hierarchy)
>                 goto out;
>
>         while (cgroup->parent) {
>                 cgroup = cgroup->parent;
>                 memcg = mem_cgroup_from_cont(cgroup);
>                 if (!memcg->use_hierarchy)
>                         break;
>                 tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
>                 min_limit = min(min_limit, tmp);
>                 tmp = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
>                 min_memsw_limit = min(min_memsw_limit, tmp);
>         }
> out:
>         *mem_limit = min_limit;
>         *memsw_limit = min_memsw_limit;
>         return;
> }
>
> static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
> {
>         struct mem_cgroup *mem;
>         int type, name;
>
>         mem = mem_cgroup_from_cont(cont);
>         type = MEMFILE_TYPE(event);
>         name = MEMFILE_ATTR(event);
>         switch (name) {
>         case RES_MAX_USAGE:
>                 if (type == _MEM)
>                         res_counter_reset_max(&mem->res);
>                 else
>                         res_counter_reset_max(&mem->memsw);
>                 break;
>         case RES_FAILCNT:
>                 if (type == _MEM)
>                         res_counter_reset_failcnt(&mem->res);
>                 else
>                         res_counter_reset_failcnt(&mem->memsw);
>                 break;
>         }
>
>         return 0;
> }
>
> static u64 mem_cgroup_move_charge_read(struct cgroup *cgrp,
>                                         struct cftype *cft)
> {
>         return mem_cgroup_from_cont(cgrp)->move_charge_at_immigrate;
> }
>
> #ifdef CONFIG_MMU
> static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
>                                         struct cftype *cft, u64 val)
> {
>         struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
>
>         if (val >= (1 << NR_MOVE_TYPE))
>                 return -EINVAL;
>         /*
>          * We check this value several times in both in can_attach() and
>          * attach(), so we need cgroup lock to prevent this value from being
>          * inconsistent.
>          */
>         cgroup_lock();
>         mem->move_charge_at_immigrate = val;
>         cgroup_unlock();
>
>         return 0;
> }
> #else
> static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
>                                         struct cftype *cft, u64 val)
> {
>         return -ENOSYS;
> }
> #endif
>
>
> /* For read statistics */
> enum {
>         MCS_CACHE,
>         MCS_RSS,
>         MCS_FILE_MAPPED,
>         MCS_PGPGIN,
>         MCS_PGPGOUT,
>         MCS_SWAP,
>         MCS_PGFAULT,
>         MCS_PGMAJFAULT,
>         MCS_INACTIVE_ANON,
>         MCS_ACTIVE_ANON,
>         MCS_INACTIVE_FILE,
>         MCS_ACTIVE_FILE,
>         MCS_UNEVICTABLE,
>         NR_MCS_STAT,
> };
>
> struct mcs_total_stat {
>         s64 stat[NR_MCS_STAT];
> };
>
> struct {
>         char *local_name;
>         char *total_name;
> } memcg_stat_strings[NR_MCS_STAT] = {
>         {"cache", "total_cache"},
>         {"rss", "total_rss"},
>         {"mapped_file", "total_mapped_file"},
>         {"pgpgin", "total_pgpgin"},
>         {"pgpgout", "total_pgpgout"},
>         {"swap", "total_swap"},
>         {"pgfault", "total_pgfault"},
>         {"pgmajfault", "total_pgmajfault"},
>         {"inactive_anon", "total_inactive_anon"},
>         {"active_anon", "total_active_anon"},
>         {"inactive_file", "total_inactive_file"},
>         {"active_file", "total_active_file"},
>         {"unevictable", "total_unevictable"}
> };
>
>
> static void
> mem_cgroup_get_local_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
> {
>         s64 val;
>
>         /* per cpu stat */
>         val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
>         s->stat[MCS_CACHE] += val * PAGE_SIZE;
>         val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
>         s->stat[MCS_RSS] += val * PAGE_SIZE;
>         val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_MAPPED);
>         s->stat[MCS_FILE_MAPPED] += val * PAGE_SIZE;
>         val = mem_cgroup_read_events(mem, MEM_CGROUP_EVENTS_PGPGIN);
>         s->stat[MCS_PGPGIN] += val;
>         val = mem_cgroup_read_events(mem, MEM_CGROUP_EVENTS_PGPGOUT);
>         s->stat[MCS_PGPGOUT] += val;
>         if (do_swap_account) {
>                 val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_SWAPOUT);
>                 s->stat[MCS_SWAP] += val * PAGE_SIZE;
>         }
>         val = mem_cgroup_read_events(mem, MEM_CGROUP_EVENTS_PGFAULT);
>         s->stat[MCS_PGFAULT] += val;
>         val = mem_cgroup_read_events(mem, MEM_CGROUP_EVENTS_PGMAJFAULT);
>         s->stat[MCS_PGMAJFAULT] += val;
>
>         /* per zone stat */
>         val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON);
>         s->stat[MCS_INACTIVE_ANON] += val * PAGE_SIZE;
>         val = mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_ANON);
>         s->stat[MCS_ACTIVE_ANON] += val * PAGE_SIZE;
>         val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_FILE);
>         s->stat[MCS_INACTIVE_FILE] += val * PAGE_SIZE;
>         val = mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_FILE);
>         s->stat[MCS_ACTIVE_FILE] += val * PAGE_SIZE;
>         val = mem_cgroup_get_local_zonestat(mem, LRU_UNEVICTABLE);
>         s->stat[MCS_UNEVICTABLE] += val * PAGE_SIZE;
> }
>
> static void
> mem_cgroup_get_total_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
> {
>         struct mem_cgroup *iter;
>
>         for_each_mem_cgroup_tree(iter, mem)
>                 mem_cgroup_get_local_stat(iter, s);
> }
>
> #ifdef CONFIG_NUMA
> static int mem_control_numa_stat_show(struct seq_file *m, void *arg)
> {
>         int nid;
>         unsigned long total_nr, file_nr, anon_nr, unevictable_nr;
>         unsigned long node_nr;
>         struct cgroup *cont = m->private;
>         struct mem_cgroup *mem_cont = mem_cgroup_from_cont(cont);
>
>         total_nr = mem_cgroup_nr_lru_pages(mem_cont);
>         seq_printf(m, "total=%lu", total_nr);
>         for_each_node_state(nid, N_HIGH_MEMORY) {
>                 node_nr = mem_cgroup_node_nr_lru_pages(mem_cont, nid);
>                 seq_printf(m, " N%d=%lu", nid, node_nr);
>         }
>         seq_putc(m, '\n');
>
>         file_nr = mem_cgroup_nr_file_lru_pages(mem_cont);
>         seq_printf(m, "file=%lu", file_nr);
>         for_each_node_state(nid, N_HIGH_MEMORY) {
>                 node_nr = mem_cgroup_node_nr_file_lru_pages(mem_cont, nid);
>                 seq_printf(m, " N%d=%lu", nid, node_nr);
>         }
>         seq_putc(m, '\n');
>
>         anon_nr = mem_cgroup_nr_anon_lru_pages(mem_cont);
>         seq_printf(m, "anon=%lu", anon_nr);
>         for_each_node_state(nid, N_HIGH_MEMORY) {
>                 node_nr = mem_cgroup_node_nr_anon_lru_pages(mem_cont, nid);
>                 seq_printf(m, " N%d=%lu", nid, node_nr);
>         }
>         seq_putc(m, '\n');
>
>         unevictable_nr = mem_cgroup_nr_unevictable_lru_pages(mem_cont);
>         seq_printf(m, "unevictable=%lu", unevictable_nr);
>         for_each_node_state(nid, N_HIGH_MEMORY) {
>                 node_nr = mem_cgroup_node_nr_unevictable_lru_pages(mem_cont,
>                                                                         nid);
>                 seq_printf(m, " N%d=%lu", nid, node_nr);
>         }
>         seq_putc(m, '\n');
>         return 0;
> }
> #endif /* CONFIG_NUMA */
>
> static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
>                                  struct cgroup_map_cb *cb)
> {
>         struct mem_cgroup *mem_cont = mem_cgroup_from_cont(cont);
>         struct mcs_total_stat mystat;
>         int i;
>
>         memset(&mystat, 0, sizeof(mystat));
>         mem_cgroup_get_local_stat(mem_cont, &mystat);
>
>
>         for (i = 0; i < NR_MCS_STAT; i++) {
>                 if (i == MCS_SWAP && !do_swap_account)
>                         continue;
>                 cb->fill(cb, memcg_stat_strings[i].local_name, mystat.stat[i]);
>         }
>
>         /* Hierarchical information */
>         {
>                 unsigned long long limit, memsw_limit;
>                 memcg_get_hierarchical_limit(mem_cont, &limit, &memsw_limit);
>                 cb->fill(cb, "hierarchical_memory_limit", limit);
>                 if (do_swap_account)
>                         cb->fill(cb, "hierarchical_memsw_limit", memsw_limit);
>         }
>
>         memset(&mystat, 0, sizeof(mystat));
>         mem_cgroup_get_total_stat(mem_cont, &mystat);
>         for (i = 0; i < NR_MCS_STAT; i++) {
>                 if (i == MCS_SWAP && !do_swap_account)
>                         continue;
>                 cb->fill(cb, memcg_stat_strings[i].total_name, mystat.stat[i]);
>         }
>
> #ifdef CONFIG_DEBUG_VM
>         cb->fill(cb, "inactive_ratio", calc_inactive_ratio(mem_cont, NULL));
>
>         {
>                 int nid, zid;
>                 struct mem_cgroup_per_zone *mz;
>                 unsigned long recent_rotated[2] = {0, 0};
>                 unsigned long recent_scanned[2] = {0, 0};
>
>                 for_each_online_node(nid)
>                         for (zid = 0; zid < MAX_NR_ZONES; zid++) {
>                                 mz = mem_cgroup_zoneinfo(mem_cont, nid, zid);
>
>                                 recent_rotated[0] +=
>                                         mz->reclaim_stat.recent_rotated[0];
>                                 recent_rotated[1] +=
>                                         mz->reclaim_stat.recent_rotated[1];
>                                 recent_scanned[0] +=
>                                         mz->reclaim_stat.recent_scanned[0];
>                                 recent_scanned[1] +=
>                                         mz->reclaim_stat.recent_scanned[1];
>                         }
>                 cb->fill(cb, "recent_rotated_anon", recent_rotated[0]);
>                 cb->fill(cb, "recent_rotated_file", recent_rotated[1]);
>                 cb->fill(cb, "recent_scanned_anon", recent_scanned[0]);
>                 cb->fill(cb, "recent_scanned_file", recent_scanned[1]);
>         }
> #endif
>
>         return 0;
> }
>
> static u64 mem_cgroup_swappiness_read(struct cgroup *cgrp, struct cftype *cft)
> {
>         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
>
>         return get_swappiness(memcg);
> }
>
> static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
>                                        u64 val)
> {
>         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
>         struct mem_cgroup *parent;
>
>         if (val > 100)
>                 return -EINVAL;
>
>         if (cgrp->parent == NULL)
>                 return -EINVAL;
>
>         parent = mem_cgroup_from_cont(cgrp->parent);
>
>         cgroup_lock();
>
>         /* If under hierarchy, only empty-root can set this value */
>         if ((parent->use_hierarchy) ||
>             (memcg->use_hierarchy && !list_empty(&cgrp->children))) {
>                 cgroup_unlock();
>                 return -EINVAL;
>         }
>
>         memcg->swappiness = val;
>
>         cgroup_unlock();
>
>         return 0;
> }
>
> static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
> {
>         struct mem_cgroup_threshold_ary *t;
>         u64 usage;
>         int i;
>
>         rcu_read_lock();
>         if (!swap)
>                 t = rcu_dereference(memcg->thresholds.primary);
>         else
>                 t = rcu_dereference(memcg->memsw_thresholds.primary);
>
>         if (!t)
>                 goto unlock;
>
>         usage = mem_cgroup_usage(memcg, swap);
>
>         /*
>          * current_threshold points to threshold just below usage.
>          * If it's not true, a threshold was crossed after last
>          * call of __mem_cgroup_threshold().
>          */
>         i = t->current_threshold;
>
>         /*
>          * Iterate backward over array of thresholds starting from
>          * current_threshold and check if a threshold is crossed.
>          * If none of thresholds below usage is crossed, we read
>          * only one element of the array here.
>          */
>         for (; i >= 0 && unlikely(t->entries[i].threshold > usage); i--)
>                 eventfd_signal(t->entries[i].eventfd, 1);
>
>         /* i = current_threshold + 1 */
>         i++;
>
>         /*
>          * Iterate forward over array of thresholds starting from
>          * current_threshold+1 and check if a threshold is crossed.
>          * If none of thresholds above usage is crossed, we read
>          * only one element of the array here.
>          */
>         for (; i < t->size && unlikely(t->entries[i].threshold <= usage); i++)
>                 eventfd_signal(t->entries[i].eventfd, 1);
>
>         /* Update current_threshold */
>         t->current_threshold = i - 1;
> unlock:
>         rcu_read_unlock();
> }
>
> static void mem_cgroup_threshold(struct mem_cgroup *memcg)
> {
>         while (memcg) {
>                 __mem_cgroup_threshold(memcg, false);
>                 if (do_swap_account)
>                         __mem_cgroup_threshold(memcg, true);
>
>                 memcg = parent_mem_cgroup(memcg);
>         }
> }
>
> static int compare_thresholds(const void *a, const void *b)
> {
>         const struct mem_cgroup_threshold *_a = a;
>         const struct mem_cgroup_threshold *_b = b;
>
>         return _a->threshold - _b->threshold;
> }
>
> static int mem_cgroup_oom_notify_cb(struct mem_cgroup *mem)
> {
>         struct mem_cgroup_eventfd_list *ev;
>
>         list_for_each_entry(ev, &mem->oom_notify, list)
>                 eventfd_signal(ev->eventfd, 1);
>         return 0;
> }
>
> static void mem_cgroup_oom_notify(struct mem_cgroup *mem)
> {
>         struct mem_cgroup *iter;
>
>         for_each_mem_cgroup_tree(iter, mem)
>                 mem_cgroup_oom_notify_cb(iter);
> }
>
> static int mem_cgroup_usage_register_event(struct cgroup *cgrp,
>         struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
> {
>         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
>         struct mem_cgroup_thresholds *thresholds;
>         struct mem_cgroup_threshold_ary *new;
>         int type = MEMFILE_TYPE(cft->private);
>         u64 threshold, usage;
>         int i, size, ret;
>
>         ret = res_counter_memparse_write_strategy(args, &threshold);
>         if (ret)
>                 return ret;
>
>         mutex_lock(&memcg->thresholds_lock);
>
>         if (type == _MEM)
>                 thresholds = &memcg->thresholds;
>         else if (type == _MEMSWAP)
>                 thresholds = &memcg->memsw_thresholds;
>         else
>                 BUG();
>
>         usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
>
>         /* Check if a threshold crossed before adding a new one */
>         if (thresholds->primary)
>                 __mem_cgroup_threshold(memcg, type == _MEMSWAP);
>
>         size = thresholds->primary ? thresholds->primary->size + 1 : 1;
>
>         /* Allocate memory for new array of thresholds */
>         new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold),
>                         GFP_KERNEL);
>         if (!new) {
>                 ret = -ENOMEM;
>                 goto unlock;
>         }
>         new->size = size;
>
>         /* Copy thresholds (if any) to new array */
>         if (thresholds->primary) {
>                 memcpy(new->entries, thresholds->primary->entries, (size - 1) *
>                                 sizeof(struct mem_cgroup_threshold));
>         }
>
>         /* Add new threshold */
>         new->entries[size - 1].eventfd = eventfd;
>         new->entries[size - 1].threshold = threshold;
>
>         /* Sort thresholds. Registering of new threshold isn't time-critical */
>         sort(new->entries, size, sizeof(struct mem_cgroup_threshold),
>                         compare_thresholds, NULL);
>
>         /* Find current threshold */
>         new->current_threshold = -1;
>         for (i = 0; i < size; i++) {
>                 if (new->entries[i].threshold < usage) {
>                         /*
>                          * new->current_threshold will not be used until
>                          * rcu_assign_pointer(), so it's safe to increment
>                          * it here.
>                          */
>                         ++new->current_threshold;
>                 }
>         }
>
>         /* Free old spare buffer and save old primary buffer as spare */
>         kfree(thresholds->spare);
>         thresholds->spare = thresholds->primary;
>
>         rcu_assign_pointer(thresholds->primary, new);
>
>         /* To be sure that nobody uses thresholds */
>         synchronize_rcu();
>
> unlock:
>         mutex_unlock(&memcg->thresholds_lock);
>
>         return ret;
> }
>
> static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp,
>         struct cftype *cft, struct eventfd_ctx *eventfd)
> {
>         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
>         struct mem_cgroup_thresholds *thresholds;
>         struct mem_cgroup_threshold_ary *new;
>         int type = MEMFILE_TYPE(cft->private);
>         u64 usage;
>         int i, j, size;
>
>         mutex_lock(&memcg->thresholds_lock);
>         if (type == _MEM)
>                 thresholds = &memcg->thresholds;
>         else if (type == _MEMSWAP)
>                 thresholds = &memcg->memsw_thresholds;
>         else
>                 BUG();
>
>         /*
>          * Something went wrong if we trying to unregister a threshold
>          * if we don't have thresholds
>          */
>         BUG_ON(!thresholds);
>
>         usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
>
>         /* Check if a threshold crossed before removing */
>         __mem_cgroup_threshold(memcg, type == _MEMSWAP);
>
>         /* Calculate new number of threshold */
>         size = 0;
>         for (i = 0; i < thresholds->primary->size; i++) {
>                 if (thresholds->primary->entries[i].eventfd != eventfd)
>                         size++;
>         }
>
>         new = thresholds->spare;
>
>         /* Set thresholds array to NULL if we don't have thresholds */
>         if (!size) {
>                 kfree(new);
>                 new = NULL;
>                 goto swap_buffers;
>         }
>
>         new->size = size;
>
>         /* Copy thresholds and find current threshold */
>         new->current_threshold = -1;
>         for (i = 0, j = 0; i < thresholds->primary->size; i++) {
>                 if (thresholds->primary->entries[i].eventfd == eventfd)
>                         continue;
>
>                 new->entries[j] = thresholds->primary->entries[i];
>                 if (new->entries[j].threshold < usage) {
>                         /*
>                          * new->current_threshold will not be used
>                          * until rcu_assign_pointer(), so it's safe to increment
>                          * it here.
>                          */
>                         ++new->current_threshold;
>                 }
>                 j++;
>         }
>
> swap_buffers:
>         /* Swap primary and spare array */
>         thresholds->spare = thresholds->primary;
>         rcu_assign_pointer(thresholds->primary, new);
>
>         /* To be sure that nobody uses thresholds */
>         synchronize_rcu();
>
>         mutex_unlock(&memcg->thresholds_lock);
> }
>
> static int mem_cgroup_oom_register_event(struct cgroup *cgrp,
>         struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
> {
>         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
>         struct mem_cgroup_eventfd_list *event;
>         int type = MEMFILE_TYPE(cft->private);
>
>         BUG_ON(type != _OOM_TYPE);
>         event = kmalloc(sizeof(*event), GFP_KERNEL);
>         if (!event)
>                 return -ENOMEM;
>
>         mutex_lock(&memcg_oom_mutex);
>
>         event->eventfd = eventfd;
>         list_add(&event->list, &memcg->oom_notify);
>
>         /* already in OOM ? */
>         if (atomic_read(&memcg->oom_lock))
>                 eventfd_signal(eventfd, 1);
>         mutex_unlock(&memcg_oom_mutex);
>
>         return 0;
> }
>
> static void mem_cgroup_oom_unregister_event(struct cgroup *cgrp,
>         struct cftype *cft, struct eventfd_ctx *eventfd)
> {
>         struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
>         struct mem_cgroup_eventfd_list *ev, *tmp;
>         int type = MEMFILE_TYPE(cft->private);
>
>         BUG_ON(type != _OOM_TYPE);
>
>         mutex_lock(&memcg_oom_mutex);
>
>         list_for_each_entry_safe(ev, tmp, &mem->oom_notify, list) {
>                 if (ev->eventfd == eventfd) {
>                         list_del(&ev->list);
>                         kfree(ev);
>                 }
>         }
>
>         mutex_unlock(&memcg_oom_mutex);
> }
>
> static int mem_cgroup_oom_control_read(struct cgroup *cgrp,
>         struct cftype *cft,  struct cgroup_map_cb *cb)
> {
>         struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
>
>         cb->fill(cb, "oom_kill_disable", mem->oom_kill_disable);
>
>         if (atomic_read(&mem->oom_lock))
>                 cb->fill(cb, "under_oom", 1);
>         else
>                 cb->fill(cb, "under_oom", 0);
>         return 0;
> }
>
> static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
>         struct cftype *cft, u64 val)
> {
>         struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
>         struct mem_cgroup *parent;
>
>         /* cannot set to root cgroup and only 0 and 1 are allowed */
>         if (!cgrp->parent || !((val == 0) || (val == 1)))
>                 return -EINVAL;
>
>         parent = mem_cgroup_from_cont(cgrp->parent);
>
>         cgroup_lock();
>         /* oom-kill-disable is a flag for subhierarchy. */
>         if ((parent->use_hierarchy) ||
>             (mem->use_hierarchy && !list_empty(&cgrp->children))) {
>                 cgroup_unlock();
>                 return -EINVAL;
>         }
>         mem->oom_kill_disable = val;
>         if (!val)
>                 memcg_oom_recover(mem);
>         cgroup_unlock();
>         return 0;
> }
>
> #ifdef CONFIG_NUMA
> static const struct file_operations mem_control_numa_stat_file_operations = {
>         .read = seq_read,
>         .llseek = seq_lseek,
>         .release = single_release,
> };
>
> static int mem_control_numa_stat_open(struct inode *unused, struct file *file)
> {
>         struct cgroup *cont = file->f_dentry->d_parent->d_fsdata;
>
>         file->f_op = &mem_control_numa_stat_file_operations;
>         return single_open(file, mem_control_numa_stat_show, cont);
> }
> #endif /* CONFIG_NUMA */
>
> static struct cftype mem_cgroup_files[] = {
>         {
>                 .name = "usage_in_bytes",
>                 .private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
>                 .read_u64 = mem_cgroup_read,
>                 .register_event = mem_cgroup_usage_register_event,
>                 .unregister_event = mem_cgroup_usage_unregister_event,
>         },
>         {
>                 .name = "max_usage_in_bytes",
>                 .private = MEMFILE_PRIVATE(_MEM, RES_MAX_USAGE),
>                 .trigger = mem_cgroup_reset,
>                 .read_u64 = mem_cgroup_read,
>         },
>         {
>                 .name = "limit_in_bytes",
>                 .private = MEMFILE_PRIVATE(_MEM, RES_LIMIT),
>                 .write_string = mem_cgroup_write,
>                 .read_u64 = mem_cgroup_read,
>         },
>         {
>                 .name = "soft_limit_in_bytes",
>                 .private = MEMFILE_PRIVATE(_MEM, RES_SOFT_LIMIT),
>                 .write_string = mem_cgroup_write,
>                 .read_u64 = mem_cgroup_read,
>         },
>         {
>                 .name = "failcnt",
>                 .private = MEMFILE_PRIVATE(_MEM, RES_FAILCNT),
>                 .trigger = mem_cgroup_reset,
>                 .read_u64 = mem_cgroup_read,
>         },
>         {
>                 .name = "stat",
>                 .read_map = mem_control_stat_show,
>         },
>         {
>                 .name = "force_empty",
>                 .trigger = mem_cgroup_force_empty_write,
>         },
>         {
>                 .name = "use_hierarchy",
>                 .write_u64 = mem_cgroup_hierarchy_write,
>                 .read_u64 = mem_cgroup_hierarchy_read,
>         },
>         {
>                 .name = "swappiness",
>                 .read_u64 = mem_cgroup_swappiness_read,
>                 .write_u64 = mem_cgroup_swappiness_write,
>         },
>         {
>                 .name = "move_charge_at_immigrate",
>                 .read_u64 = mem_cgroup_move_charge_read,
>                 .write_u64 = mem_cgroup_move_charge_write,
>         },
>         {
>                 .name = "oom_control",
>                 .read_map = mem_cgroup_oom_control_read,
>                 .write_u64 = mem_cgroup_oom_control_write,
>                 .register_event = mem_cgroup_oom_register_event,
>                 .unregister_event = mem_cgroup_oom_unregister_event,
>                 .private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
>         },
> #ifdef CONFIG_NUMA
>         {
>                 .name = "numa_stat",
>                 .open = mem_control_numa_stat_open,
>                 .mode = S_IRUGO,
>         },
> #endif
> };
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> static struct cftype memsw_cgroup_files[] = {
>         {
>                 .name = "memsw.usage_in_bytes",
>                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
>                 .read_u64 = mem_cgroup_read,
>                 .register_event = mem_cgroup_usage_register_event,
>                 .unregister_event = mem_cgroup_usage_unregister_event,
>         },
>         {
>                 .name = "memsw.max_usage_in_bytes",
>                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_MAX_USAGE),
>                 .trigger = mem_cgroup_reset,
>                 .read_u64 = mem_cgroup_read,
>         },
>         {
>                 .name = "memsw.limit_in_bytes",
>                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_LIMIT),
>                 .write_string = mem_cgroup_write,
>                 .read_u64 = mem_cgroup_read,
>         },
>         {
>                 .name = "memsw.failcnt",
>                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_FAILCNT),
>                 .trigger = mem_cgroup_reset,
>                 .read_u64 = mem_cgroup_read,
>         },
> };
>
> static int register_memsw_files(struct cgroup *cont, struct cgroup_subsys *ss)
> {
>         if (!do_swap_account)
>                 return 0;
>         return cgroup_add_files(cont, ss, memsw_cgroup_files,
>                                 ARRAY_SIZE(memsw_cgroup_files));
> };
> #else
> static int register_memsw_files(struct cgroup *cont, struct cgroup_subsys *ss)
> {
>         return 0;
> }
> #endif
>
> static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
> {
>         struct mem_cgroup_per_node *pn;
>         struct mem_cgroup_per_zone *mz;
>         enum lru_list l;
>         int zone, tmp = node;
>         /*
>          * This routine is called against possible nodes.
>          * But it's BUG to call kmalloc() against offline node.
>          *
>          * TODO: this routine can waste much memory for nodes which will
>          *       never be onlined. It's better to use memory hotplug callback
>          *       function.
>          */
>         if (!node_state(node, N_NORMAL_MEMORY))
>                 tmp = -1;
>         pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, tmp);
>         if (!pn)
>                 return 1;
>
>         mem->info.nodeinfo[node] = pn;
>         for (zone = 0; zone < MAX_NR_ZONES; zone++) {
>                 mz = &pn->zoneinfo[zone];
>                 for_each_lru(l)
>                         INIT_LIST_HEAD(&mz->lists[l]);
>                 mz->usage_in_excess = 0;
>                 mz->on_tree = false;
>                 mz->mem = mem;
>         }
>         return 0;
> }
>
> static void free_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
> {
>         kfree(mem->info.nodeinfo[node]);
> }
>
> static struct mem_cgroup *mem_cgroup_alloc(void)
> {
>         struct mem_cgroup *mem;
>         int size = sizeof(struct mem_cgroup);
>
>         /* Can be very big if MAX_NUMNODES is very big */
>         if (size < PAGE_SIZE)
>                 mem = kzalloc(size, GFP_KERNEL);
>         else
>                 mem = vzalloc(size);
>
>         if (!mem)
>                 return NULL;
>
>         mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
>         if (!mem->stat)
>                 goto out_free;
>         spin_lock_init(&mem->pcp_counter_lock);
>         return mem;
>
> out_free:
>         if (size < PAGE_SIZE)
>                 kfree(mem);
>         else
>                 vfree(mem);
>         return NULL;
> }
>
> /*
>  * At destroying mem_cgroup, references from swap_cgroup can remain.
>  * (scanning all at force_empty is too costly...)
>  *
>  * Instead of clearing all references at force_empty, we remember
>  * the number of reference from swap_cgroup and free mem_cgroup when
>  * it goes down to 0.
>  *
>  * Removal of cgroup itself succeeds regardless of refs from swap.
>  */
>
> static void __mem_cgroup_free(struct mem_cgroup *mem)
> {
>         int node;
>
>         mem_cgroup_remove_from_trees(mem);
>         free_css_id(&mem_cgroup_subsys, &mem->css);
>
>         for_each_node_state(node, N_POSSIBLE)
>                 free_mem_cgroup_per_zone_info(mem, node);
>
>         free_percpu(mem->stat);
>         if (sizeof(struct mem_cgroup) < PAGE_SIZE)
>                 kfree(mem);
>         else
>                 vfree(mem);
> }
>
> static void mem_cgroup_get(struct mem_cgroup *mem)
> {
>         atomic_inc(&mem->refcnt);
> }
>
> static void __mem_cgroup_put(struct mem_cgroup *mem, int count)
> {
>         if (atomic_sub_and_test(count, &mem->refcnt)) {
>                 struct mem_cgroup *parent = parent_mem_cgroup(mem);
>                 __mem_cgroup_free(mem);
>                 if (parent)
>                         mem_cgroup_put(parent);
>         }
> }
>
> static void mem_cgroup_put(struct mem_cgroup *mem)
> {
>         __mem_cgroup_put(mem, 1);
> }
>
> /*
>  * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled.
>  */
> static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem)
> {
>         if (!mem->res.parent)
>                 return NULL;
>         return mem_cgroup_from_res_counter(mem->res.parent, res);
> }
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> static void __init enable_swap_cgroup(void)
> {
>         if (!mem_cgroup_disabled() && really_do_swap_account)
>                 do_swap_account = 1;
> }
> #else
> static void __init enable_swap_cgroup(void)
> {
> }
> #endif
>
> static int mem_cgroup_soft_limit_tree_init(void)
> {
>         struct mem_cgroup_tree_per_node *rtpn;
>         struct mem_cgroup_tree_per_zone *rtpz;
>         int tmp, node, zone;
>
>         for_each_node_state(node, N_POSSIBLE) {
>                 tmp = node;
>                 if (!node_state(node, N_NORMAL_MEMORY))
>                         tmp = -1;
>                 rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, tmp);
>                 if (!rtpn)
>                         return 1;
>
>                 soft_limit_tree.rb_tree_per_node[node] = rtpn;
>
>                 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
>                         rtpz = &rtpn->rb_tree_per_zone[zone];
>                         rtpz->rb_root = RB_ROOT;
>                         spin_lock_init(&rtpz->lock);
>                 }
>         }
>         return 0;
> }
>
> static struct cgroup_subsys_state * __ref
> mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
> {
>         struct mem_cgroup *mem, *parent;
>         long error = -ENOMEM;
>         int node;
>
>         mem = mem_cgroup_alloc();
>         if (!mem)
>                 return ERR_PTR(error);
>
>         for_each_node_state(node, N_POSSIBLE)
>                 if (alloc_mem_cgroup_per_zone_info(mem, node))
>                         goto free_out;
>
>         /* root ? */
>         if (cont->parent == NULL) {
>                 int cpu;
>                 enable_swap_cgroup();
>                 parent = NULL;
>                 root_mem_cgroup = mem;
>                 if (mem_cgroup_soft_limit_tree_init())
>                         goto free_out;
>                 for_each_possible_cpu(cpu) {
>                         struct memcg_stock_pcp *stock =
>                                                 &per_cpu(memcg_stock, cpu);
>                         INIT_WORK(&stock->work, drain_local_stock);
>                 }
>                 hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
>         } else {
>                 parent = mem_cgroup_from_cont(cont->parent);
>                 mem->use_hierarchy = parent->use_hierarchy;
>                 mem->oom_kill_disable = parent->oom_kill_disable;
>         }
>
>         if (parent && parent->use_hierarchy) {
>                 res_counter_init(&mem->res, &parent->res);
>                 res_counter_init(&mem->memsw, &parent->memsw);
>                 /*
>                  * We increment refcnt of the parent to ensure that we can
>                  * safely access it on res_counter_charge/uncharge.
>                  * This refcnt will be decremented when freeing this
>                  * mem_cgroup(see mem_cgroup_put).
>                  */
>                 mem_cgroup_get(parent);
>         } else {
>                 res_counter_init(&mem->res, NULL);
>                 res_counter_init(&mem->memsw, NULL);
>         }
>         mem->last_scanned_child = 0;
>         mem->last_scanned_node = MAX_NUMNODES;
>         INIT_LIST_HEAD(&mem->oom_notify);
>
>         if (parent)
>                 mem->swappiness = get_swappiness(parent);
>         atomic_set(&mem->refcnt, 1);
>         mem->move_charge_at_immigrate = 0;
>         mutex_init(&mem->thresholds_lock);
>         return &mem->css;
> free_out:
>         __mem_cgroup_free(mem);
>         root_mem_cgroup = NULL;
>         return ERR_PTR(error);
> }
>
> static int mem_cgroup_pre_destroy(struct cgroup_subsys *ss,
>                                         struct cgroup *cont)
> {
>         struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
>
>         return mem_cgroup_force_empty(mem, false);
> }
>
> static void mem_cgroup_destroy(struct cgroup_subsys *ss,
>                                 struct cgroup *cont)
> {
>         struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
>
>         mem_cgroup_put(mem);
> }
>
> static int mem_cgroup_populate(struct cgroup_subsys *ss,
>                                 struct cgroup *cont)
> {
>         int ret;
>
>         ret = cgroup_add_files(cont, ss, mem_cgroup_files,
>                                 ARRAY_SIZE(mem_cgroup_files));
>
>         if (!ret)
>                 ret = register_memsw_files(cont, ss);
>         return ret;
> }
>
> #ifdef CONFIG_MMU
> /* Handlers for move charge at task migration. */
> #define PRECHARGE_COUNT_AT_ONCE 256
> static int mem_cgroup_do_precharge(unsigned long count)
> {
>         int ret = 0;
>         int batch_count = PRECHARGE_COUNT_AT_ONCE;
>         struct mem_cgroup *mem = mc.to;
>
>         if (mem_cgroup_is_root(mem)) {
>                 mc.precharge += count;
>                 /* we don't need css_get for root */
>                 return ret;
>         }
>         /* try to charge at once */
>         if (count > 1) {
>                 struct res_counter *dummy;
>                 /*
>                  * "mem" cannot be under rmdir() because we've already checked
>                  * by cgroup_lock_live_cgroup() that it is not removed and we
>                  * are still under the same cgroup_mutex. So we can postpone
>                  * css_get().
>                  */
>                 if (res_counter_charge(&mem->res, PAGE_SIZE * count, &dummy))
>                         goto one_by_one;
>                 if (do_swap_account && res_counter_charge(&mem->memsw,
>                                                 PAGE_SIZE * count, &dummy)) {
>                         res_counter_uncharge(&mem->res, PAGE_SIZE * count);
>                         goto one_by_one;
>                 }
>                 mc.precharge += count;
>                 return ret;
>         }
> one_by_one:
>         /* fall back to one by one charge */
>         while (count--) {
>                 if (signal_pending(current)) {
>                         ret = -EINTR;
>                         break;
>                 }
>                 if (!batch_count--) {
>                         batch_count = PRECHARGE_COUNT_AT_ONCE;
>                         cond_resched();
>                 }
>                 ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, 1, &mem, false);
>                 if (ret || !mem)
>                         /* mem_cgroup_clear_mc() will do uncharge later */
>                         return -ENOMEM;
>                 mc.precharge++;
>         }
>         return ret;
> }
>
> /**
>  * is_target_pte_for_mc - check a pte whether it is valid for move charge
>  * @vma: the vma the pte to be checked belongs
>  * @addr: the address corresponding to the pte to be checked
>  * @ptent: the pte to be checked
>  * @target: the pointer the target page or swap ent will be stored(can be NULL)
>  *
>  * Returns
>  *   0(MC_TARGET_NONE): if the pte is not a target for move charge.
>  *   1(MC_TARGET_PAGE): if the page corresponding to this pte is a target for
>  *     move charge. if @target is not NULL, the page is stored in target->page
>  *     with extra refcnt got(Callers should handle it).
>  *   2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
>  *     target for charge migration. if @target is not NULL, the entry is stored
>  *     in target->ent.
>  *
>  * Called with pte lock held.
>  */
> union mc_target {
>         struct page     *page;
>         swp_entry_t     ent;
> };
>
> enum mc_target_type {
>         MC_TARGET_NONE, /* not used */
>         MC_TARGET_PAGE,
>         MC_TARGET_SWAP,
> };
>
> static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
>                                                 unsigned long addr, pte_t ptent)
> {
>         struct page *page = vm_normal_page(vma, addr, ptent);
>
>         if (!page || !page_mapped(page))
>                 return NULL;
>         if (PageAnon(page)) {
>                 /* we don't move shared anon */
>                 if (!move_anon() || page_mapcount(page) > 2)
>                         return NULL;
>         } else if (!move_file())
>                 /* we ignore mapcount for file pages */
>                 return NULL;
>         if (!get_page_unless_zero(page))
>                 return NULL;
>
>         return page;
> }
>
> static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
>                         unsigned long addr, pte_t ptent, swp_entry_t *entry)
> {
>         int usage_count;
>         struct page *page = NULL;
>         swp_entry_t ent = pte_to_swp_entry(ptent);
>
>         if (!move_anon() || non_swap_entry(ent))
>                 return NULL;
>         usage_count = mem_cgroup_count_swap_user(ent, &page);
>         if (usage_count > 1) { /* we don't move shared anon */
>                 if (page)
>                         put_page(page);
>                 return NULL;
>         }
>         if (do_swap_account)
>                 entry->val = ent.val;
>
>         return page;
> }
>
> static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
>                         unsigned long addr, pte_t ptent, swp_entry_t *entry)
> {
>         struct page *page = NULL;
>         struct inode *inode;
>         struct address_space *mapping;
>         pgoff_t pgoff;
>
>         if (!vma->vm_file) /* anonymous vma */
>                 return NULL;
>         if (!move_file())
>                 return NULL;
>
>         inode = vma->vm_file->f_path.dentry->d_inode;
>         mapping = vma->vm_file->f_mapping;
>         if (pte_none(ptent))
>                 pgoff = linear_page_index(vma, addr);
>         else /* pte_file(ptent) is true */
>                 pgoff = pte_to_pgoff(ptent);
>
>         /* page is moved even if it's not RSS of this task(page-faulted). */
>         if (!mapping_cap_swap_backed(mapping)) { /* normal file */
>                 page = find_get_page(mapping, pgoff);
>         } else { /* shmem/tmpfs file. we should take account of swap too. */
>                 swp_entry_t ent;
>                 mem_cgroup_get_shmem_target(inode, pgoff, &page, &ent);
>                 if (do_swap_account)
>                         entry->val = ent.val;
>         }
>
>         return page;
> }
>
> static int is_target_pte_for_mc(struct vm_area_struct *vma,
>                 unsigned long addr, pte_t ptent, union mc_target *target)
> {
>         struct page *page = NULL;
>         struct page_cgroup *pc;
>         int ret = 0;
>         swp_entry_t ent = { .val = 0 };
>
>         if (pte_present(ptent))
>                 page = mc_handle_present_pte(vma, addr, ptent);
>         else if (is_swap_pte(ptent))
>                 page = mc_handle_swap_pte(vma, addr, ptent, &ent);
>         else if (pte_none(ptent) || pte_file(ptent))
>                 page = mc_handle_file_pte(vma, addr, ptent, &ent);
>
>         if (!page && !ent.val)
>                 return 0;
>         if (page) {
>                 pc = lookup_page_cgroup(page);
>                 /*
>                  * Do only loose check w/o page_cgroup lock.
>                  * mem_cgroup_move_account() checks the pc is valid or not under
>                  * the lock.
>                  */
>                 if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
>                         ret = MC_TARGET_PAGE;
>                         if (target)
>                                 target->page = page;
>                 }
>                 if (!ret || !target)
>                         put_page(page);
>         }
>         /* There is a swap entry and a page doesn't exist or isn't charged */
>         if (ent.val && !ret &&
>                         css_id(&mc.from->css) == lookup_swap_cgroup(ent)) {
>                 ret = MC_TARGET_SWAP;
>                 if (target)
>                         target->ent = ent;
>         }
>         return ret;
> }
>
> static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
>                                         unsigned long addr, unsigned long end,
>                                         struct mm_walk *walk)
> {
>         struct vm_area_struct *vma = walk->private;
>         pte_t *pte;
>         spinlock_t *ptl;
>
>         split_huge_page_pmd(walk->mm, pmd);
>
>         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
>         for (; addr != end; pte++, addr += PAGE_SIZE)
>                 if (is_target_pte_for_mc(vma, addr, *pte, NULL))
>                         mc.precharge++; /* increment precharge temporarily */
>         pte_unmap_unlock(pte - 1, ptl);
>         cond_resched();
>
>         return 0;
> }
>
> static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
> {
>         unsigned long precharge;
>         struct vm_area_struct *vma;
>
>         down_read(&mm->mmap_sem);
>         for (vma = mm->mmap; vma; vma = vma->vm_next) {
>                 struct mm_walk mem_cgroup_count_precharge_walk = {
>                         .pmd_entry = mem_cgroup_count_precharge_pte_range,
>                         .mm = mm,
>                         .private = vma,
>                 };
>                 if (is_vm_hugetlb_page(vma))
>                         continue;
>                 walk_page_range(vma->vm_start, vma->vm_end,
>                                         &mem_cgroup_count_precharge_walk);
>         }
>         up_read(&mm->mmap_sem);
>
>         precharge = mc.precharge;
>         mc.precharge = 0;
>
>         return precharge;
> }
>
> static int mem_cgroup_precharge_mc(struct mm_struct *mm)
> {
>         unsigned long precharge = mem_cgroup_count_precharge(mm);
>
>         VM_BUG_ON(mc.moving_task);
>         mc.moving_task = current;
>         return mem_cgroup_do_precharge(precharge);
> }
>
> /* cancels all extra charges on mc.from and mc.to, and wakes up all waiters. */
> static void __mem_cgroup_clear_mc(void)
> {
>         struct mem_cgroup *from = mc.from;
>         struct mem_cgroup *to = mc.to;
>
>         /* we must uncharge all the leftover precharges from mc.to */
>         if (mc.precharge) {
>                 __mem_cgroup_cancel_charge(mc.to, mc.precharge);
>                 mc.precharge = 0;
>         }
>         /*
>          * we didn't uncharge from mc.from at mem_cgroup_move_account(), so
>          * we must uncharge here.
>          */
>         if (mc.moved_charge) {
>                 __mem_cgroup_cancel_charge(mc.from, mc.moved_charge);
>                 mc.moved_charge = 0;
>         }
>         /* we must fixup refcnts and charges */
>         if (mc.moved_swap) {
>                 /* uncharge swap account from the old cgroup */
>                 if (!mem_cgroup_is_root(mc.from))
>                         res_counter_uncharge(&mc.from->memsw,
>                                                 PAGE_SIZE * mc.moved_swap);
>                 __mem_cgroup_put(mc.from, mc.moved_swap);
>
>                 if (!mem_cgroup_is_root(mc.to)) {
>                         /*
>                          * we charged both to->res and to->memsw, so we should
>                          * uncharge to->res.
>                          */
>                         res_counter_uncharge(&mc.to->res,
>                                                 PAGE_SIZE * mc.moved_swap);
>                 }
>                 /* we've already done mem_cgroup_get(mc.to) */
>                 mc.moved_swap = 0;
>         }
>         memcg_oom_recover(from);
>         memcg_oom_recover(to);
>         wake_up_all(&mc.waitq);
> }
>
> static void mem_cgroup_clear_mc(void)
> {
>         struct mem_cgroup *from = mc.from;
>
>         /*
>          * we must clear moving_task before waking up waiters at the end of
>          * task migration.
>          */
>         mc.moving_task = NULL;
>         __mem_cgroup_clear_mc();
>         spin_lock(&mc.lock);
>         mc.from = NULL;
>         mc.to = NULL;
>         spin_unlock(&mc.lock);
>         mem_cgroup_end_move(from);
> }
>
> static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
>                                 struct cgroup *cgroup,
>                                 struct task_struct *p)
> {
>         int ret = 0;
>         struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);
>
>         if (mem->move_charge_at_immigrate) {
>                 struct mm_struct *mm;
>                 struct mem_cgroup *from = mem_cgroup_from_task(p);
>
>                 VM_BUG_ON(from == mem);
>
>                 mm = get_task_mm(p);
>                 if (!mm)
>                         return 0;
>                 /* We move charges only when we move a owner of the mm */
>                 if (mm->owner == p) {
>                         VM_BUG_ON(mc.from);
>                         VM_BUG_ON(mc.to);
>                         VM_BUG_ON(mc.precharge);
>                         VM_BUG_ON(mc.moved_charge);
>                         VM_BUG_ON(mc.moved_swap);
>                         mem_cgroup_start_move(from);
>                         spin_lock(&mc.lock);
>                         mc.from = from;
>                         mc.to = mem;
>                         spin_unlock(&mc.lock);
>                         /* We set mc.moving_task later */
>
>                         ret = mem_cgroup_precharge_mc(mm);
>                         if (ret)
>                                 mem_cgroup_clear_mc();
>                 }
>                 mmput(mm);
>         }
>         return ret;
> }
>
> static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
>                                 struct cgroup *cgroup,
>                                 struct task_struct *p)
> {
>         mem_cgroup_clear_mc();
> }
>
> static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
>                                 unsigned long addr, unsigned long end,
>                                 struct mm_walk *walk)
> {
>         int ret = 0;
>         struct vm_area_struct *vma = walk->private;
>         pte_t *pte;
>         spinlock_t *ptl;
>
>         split_huge_page_pmd(walk->mm, pmd);
> retry:
>         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
>         for (; addr != end; addr += PAGE_SIZE) {
>                 pte_t ptent = *(pte++);
>                 union mc_target target;
>                 int type;
>                 struct page *page;
>                 struct page_cgroup *pc;
>                 swp_entry_t ent;
>
>                 if (!mc.precharge)
>                         break;
>
>                 type = is_target_pte_for_mc(vma, addr, ptent, &target);
>                 switch (type) {
>                 case MC_TARGET_PAGE:
>                         page = target.page;
>                         if (isolate_lru_page(page))
>                                 goto put;
>                         pc = lookup_page_cgroup(page);
>                         if (!mem_cgroup_move_account(page, 1, pc,
>                                                      mc.from, mc.to, false)) {
>                                 mc.precharge--;
>                                 /* we uncharge from mc.from later. */
>                                 mc.moved_charge++;
>                         }
>                         putback_lru_page(page);
> put:                    /* is_target_pte_for_mc() gets the page */
>                         put_page(page);
>                         break;
>                 case MC_TARGET_SWAP:
>                         ent = target.ent;
>                         if (!mem_cgroup_move_swap_account(ent,
>                                                 mc.from, mc.to, false)) {
>                                 mc.precharge--;
>                                 /* we fixup refcnts and charges later. */
>                                 mc.moved_swap++;
>                         }
>                         break;
>                 default:
>                         break;
>                 }
>         }
>         pte_unmap_unlock(pte - 1, ptl);
>         cond_resched();
>
>         if (addr != end) {
>                 /*
>                  * We have consumed all precharges we got in can_attach().
>                  * We try charge one by one, but don't do any additional
>                  * charges to mc.to if we have failed in charge once in attach()
>                  * phase.
>                  */
>                 ret = mem_cgroup_do_precharge(1);
>                 if (!ret)
>                         goto retry;
>         }
>
>         return ret;
> }
>
> static void mem_cgroup_move_charge(struct mm_struct *mm)
> {
>         struct vm_area_struct *vma;
>
>         lru_add_drain_all();
> retry:
>         if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
>                 /*
>                  * Someone who are holding the mmap_sem might be waiting in
>                  * waitq. So we cancel all extra charges, wake up all waiters,
>                  * and retry. Because we cancel precharges, we might not be able
>                  * to move enough charges, but moving charge is a best-effort
>                  * feature anyway, so it wouldn't be a big problem.
>                  */
>                 __mem_cgroup_clear_mc();
>                 cond_resched();
>                 goto retry;
>         }
>         for (vma = mm->mmap; vma; vma = vma->vm_next) {
>                 int ret;
>                 struct mm_walk mem_cgroup_move_charge_walk = {
>                         .pmd_entry = mem_cgroup_move_charge_pte_range,
>                         .mm = mm,
>                         .private = vma,
>                 };
>                 if (is_vm_hugetlb_page(vma))
>                         continue;
>                 ret = walk_page_range(vma->vm_start, vma->vm_end,
>                                                 &mem_cgroup_move_charge_walk);
>                 if (ret)
>                         /*
>                          * means we have consumed all precharges and failed in
>                          * doing additional charge. Just abandon here.
>                          */
>                         break;
>         }
>         up_read(&mm->mmap_sem);
> }
>
> static void mem_cgroup_move_task(struct cgroup_subsys *ss,
>                                 struct cgroup *cont,
>                                 struct cgroup *old_cont,
>                                 struct task_struct *p)
> {
>         struct mm_struct *mm = get_task_mm(p);
>
>         if (mm) {
>                 if (mc.to)
>                         mem_cgroup_move_charge(mm);
>                 put_swap_token(mm);
>                 mmput(mm);
>         }
>         if (mc.to)
>                 mem_cgroup_clear_mc();
> }
> #else   /* !CONFIG_MMU */
> static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
>                                 struct cgroup *cgroup,
>                                 struct task_struct *p)
> {
>         return 0;
> }
> static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
>                                 struct cgroup *cgroup,
>                                 struct task_struct *p)
> {
> }
> static void mem_cgroup_move_task(struct cgroup_subsys *ss,
>                                 struct cgroup *cont,
>                                 struct cgroup *old_cont,
>                                 struct task_struct *p)
> {
> }
> #endif
>
> struct cgroup_subsys mem_cgroup_subsys = {
>         .name = "memory",
>         .subsys_id = mem_cgroup_subsys_id,
>         .create = mem_cgroup_create,
>         .pre_destroy = mem_cgroup_pre_destroy,
>         .destroy = mem_cgroup_destroy,
>         .populate = mem_cgroup_populate,
>         .can_attach = mem_cgroup_can_attach,
>         .cancel_attach = mem_cgroup_cancel_attach,
>         .attach = mem_cgroup_move_task,
>         .early_init = 0,
>         .use_id = 1,
> };
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> static int __init enable_swap_account(char *s)
> {
>         /* consider enabled if no parameter or 1 is given */
>         if (!strcmp(s, "1"))
>                 really_do_swap_account = 1;
>         else if (!strcmp(s, "0"))
>                 really_do_swap_account = 0;
>         return 1;
> }
> __setup("swapaccount=", enable_swap_account);
>
> #endif




--
Thanks
Yafang

Re: [PATCH 0/3] mm: improve proportional memcg protection

[Michal Hocko]

On Tue 28-04-20 09:45:27, Yafang Shao wrote:
[...]
> Seems we can't get an agreement on how to improve current code.
> So I will submit a patch to revert the commit 9783aa9917f8 ("mm,
> memcg: proportional memory.{low,min} reclaim") first.

My current understanding is that the issue we are discussing here is
mostly theoretical. Your changelog doesn't really talk about any real
life workloads that would be suffering. While it is possible to construct
one that misbehaves it is really important to know whether this actually
happens in real life. My guess would be that it is not because nax/high
limits do not tend to be close to protection usually.

With that in mind I do not really believe that reverting 9783aa9917f8
is a reasonable approach. Try to weigh pros and cons of the
functionality. Useful functionality for reasonable setups vs. potential
corner cases which are not really likely.

Please also note that we might disagree on implementation details
because people usually have very different taste for code. But it seems
that we are in agreement with Johannes that your patch does not really
improve the overall situation all that much while it adds stuff that we
actively disagree with.

So it would be really more helpful to not insist on unrelated
implementation details and focus on two things 1) split up the effective
values calculation from the predicate (cleanup without any functional
changes) 2) make the calculation more robust against racing reclaimers.

I plan to get to this unless you beat me to it.
-- 
Michal Hocko
SUSE Labs

Re: [PATCH 0/3] mm: improve proportional memcg protection

[Yafang Shao]

On Tue, Apr 28, 2020 at 4:05 PM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Tue 28-04-20 09:45:27, Yafang Shao wrote:
> [...]
> > Seems we can't get an agreement on how to improve current code.
> > So I will submit a patch to revert the commit 9783aa9917f8 ("mm,
> > memcg: proportional memory.{low,min} reclaim") first.
>
> My current understanding is that the issue we are discussing here is
> mostly theoretical. Your changelog doesn't really talk about any real
> life workloads that would be suffering.

Is real life workload really important ?
If so, why an issue[1] occured in the real workload report by me in
2019 that memcg proection can't protect inactive pages (inodes) is
ignored again and again ?
So I'm questioning that what is the real life workload ? The great
FACEBOOK workload ? These issues can all be igored if they don't
impact the great FACEBOOK workload ?

BTW, you don't need to answer me as this is another issue.

[1]. https://lore.kernel.org/linux-mm/1584355198-10137-1-git-send-email-laoar.shao@gmail.com/

>  While it is possible to construct
> one that misbehaves it is really important to know whether this actually
> happens in real life. My guess would be that it is not because nax/high
> limits do not tend to be close to protection usually.
>
> With that in mind I do not really believe that reverting 9783aa9917f8
> is a reasonable approach. Try to weigh pros and cons of the
> functionality. Useful functionality for reasonable setups vs. potential
> corner cases which are not really likely.
>
> Please also note that we might disagree on implementation details
> because people usually have very different taste for code. But it seems
> that we are in agreement with Johannes that your patch does not really
> improve the overall situation all that much while it adds stuff that we
> actively disagree with.
>
> So it would be really more helpful to not insist on unrelated
> implementation details and focus on two things 1) split up the effective
> values calculation from the predicate (cleanup without any functional
> changes) 2) make the calculation more robust against racing reclaimers.
>

Another thing should be considered as well, 0) don't access
memroy.emin and elow in get_scan_count().

> I plan to get to this unless you beat me to it.
> --


-- 
Thanks
Yafang

Re: [PATCH 0/3] mm: improve proportional memcg protection

[Michal Hocko]

On Tue 28-04-20 16:22:46, Yafang Shao wrote:
> On Tue, Apr 28, 2020 at 4:05 PM Michal Hocko <mhocko@kernel.org> wrote:
> >
> > On Tue 28-04-20 09:45:27, Yafang Shao wrote:
> > [...]
> > > Seems we can't get an agreement on how to improve current code.
> > > So I will submit a patch to revert the commit 9783aa9917f8 ("mm,
> > > memcg: proportional memory.{low,min} reclaim") first.
> >
> > My current understanding is that the issue we are discussing here is
> > mostly theoretical. Your changelog doesn't really talk about any real
> > life workloads that would be suffering.
> 
> Is real life workload really important ?

It is really important to make cost vs. benefit decisions. Like whether
to rever the said commit or not.

> If so, why an issue[1] occured in the real workload report by me in
> 2019 that memcg proection can't protect inactive pages (inodes) is
> ignored again and again ?

I do not think it is ignored. IIRC there was not an agreement on the way
to fix this. I could get involved very much because there were other
higher priority things to take care. People are simply busy.

> So I'm questioning that what is the real life workload ?

It is a workload which does something useful for their users.
[...]
> > So it would be really more helpful to not insist on unrelated
> > implementation details and focus on two things 1) split up the effective
> > values calculation from the predicate (cleanup without any functional
> > changes) 2) make the calculation more robust against racing reclaimers.
> >
> 
> Another thing should be considered as well, 0) don't access
> memroy.emin and elow in get_scan_count().

If you can achieve the gradual transition over protections by other
means then I am really interested in more details.
-- 
Michal Hocko
SUSE Labs

Re: [PATCH 0/3] mm: improve proportional memcg protection

[Yafang Shao]

On Tue, Apr 28, 2020 at 6:43 PM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Tue 28-04-20 16:22:46, Yafang Shao wrote:
> > On Tue, Apr 28, 2020 at 4:05 PM Michal Hocko <mhocko@kernel.org> wrote:
> > >
> > > On Tue 28-04-20 09:45:27, Yafang Shao wrote:
> > > [...]
> > > > Seems we can't get an agreement on how to improve current code.
> > > > So I will submit a patch to revert the commit 9783aa9917f8 ("mm,
> > > > memcg: proportional memory.{low,min} reclaim") first.
> > >
> > > My current understanding is that the issue we are discussing here is
> > > mostly theoretical. Your changelog doesn't really talk about any real
> > > life workloads that would be suffering.
> >
> > Is real life workload really important ?
>
> It is really important to make cost vs. benefit decisions. Like whether
> to rever the said commit or not.
>
> > If so, why an issue[1] occured in the real workload report by me in
> > 2019 that memcg proection can't protect inactive pages (inodes) is
> > ignored again and again ?
>
> I do not think it is ignored. IIRC there was not an agreement on the way
> to fix this. I could get involved very much because there were other
> higher priority things to take care. People are simply busy.
>

In your theory - issues with real life workload has a higher priority,
you should pay more attention to that one, rather than wasting your
time on a comment war in this one.
Alright,  the comment war really wastes time, that is not expected by me.
So let's turn back to the techichal discussion.

> > So I'm questioning that what is the real life workload ?
>
> It is a workload which does something useful for their users.
> [...]
> > > So it would be really more helpful to not insist on unrelated
> > > implementation details and focus on two things 1) split up the effective
> > > values calculation from the predicate (cleanup without any functional
> > > changes) 2) make the calculation more robust against racing reclaimers.
> > >
> >
> > Another thing should be considered as well, 0) don't access
> > memroy.emin and elow in get_scan_count().
>
> If you can achieve the gradual transition over protections by other
> means then I am really interested in more details.

sc->protection

I make my statement again - accessing the realy fragile emin & elow
in very deep reclaiming code is a totally horrible HACK, that is the
root of all evil.

-- 
Thanks
Yafang

Re: [PATCH 0/3] mm: improve proportional memcg protection

[Michal Hocko]

On Tue 28-04-20 20:25:49, Yafang Shao wrote:
> On Tue, Apr 28, 2020 at 6:43 PM Michal Hocko <mhocko@kernel.org> wrote:
[...]
> > [...]
> > > > So it would be really more helpful to not insist on unrelated
> > > > implementation details and focus on two things 1) split up the effective
> > > > values calculation from the predicate (cleanup without any functional
> > > > changes) 2) make the calculation more robust against racing reclaimers.
> > > >
> > >
> > > Another thing should be considered as well, 0) don't access
> > > memroy.emin and elow in get_scan_count().
> >
> > If you can achieve the gradual transition over protections by other
> > means then I am really interested in more details.
> 
> sc->protection

I believe I have covered this one already.

> I make my statement again - accessing the realy fragile emin & elow
> in very deep reclaiming code is a totally horrible HACK, that is the
> root of all evil.

Both me and Johannes tried to explain that we simply have to calculate
effective values for the whole reclaim tree. That has to be done
somehow. Caching effective values is a tricky solution but I am not
really aware of another without requiring to allocate storage for
intermediate results. Maybe there is a way to make that storage really
small to live on the stack or some other tricks. If you do not have any
clever ideas how to achieve that then we have to live with the caching
at the memcg level. And then we have to deal with 2) mentioned above.
-- 
Michal Hocko
SUSE Labs