[PATCH -mm 1/2] mm: vmscan: account slab pages on memcg reclaim

[Vladimir Davydov <vdavydov@parallels.com>]

Since try_to_free_mem_cgroup_pages() can now call slab shrinkers, we
should initialize reclaim_state and account reclaimed slab pages in
scan_control->nr_reclaimed.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
---
 mm/vmscan.c |   33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 16f3e45742d6..b2c041139a51 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -367,13 +367,16 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
  * the ->seeks setting of the shrink function, which indicates the
  * cost to recreate an object relative to that of an LRU page.
  *
- * Returns the number of reclaimed slab objects.
+ * Returns the number of reclaimed slab objects. The number of reclaimed
+ * pages is added to *@ret_nr_reclaimed.
  */
 static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
 				 struct mem_cgroup *memcg,
 				 unsigned long nr_scanned,
-				 unsigned long nr_eligible)
+				 unsigned long nr_eligible,
+				 unsigned long *ret_nr_reclaimed)
 {
+	struct reclaim_state *reclaim_state = current->reclaim_state;
 	struct shrinker *shrinker;
 	unsigned long freed = 0;
 
@@ -412,6 +415,10 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
 
 	up_read(&shrinker_rwsem);
 out:
+	if (reclaim_state) {
+		*ret_nr_reclaimed += reclaim_state->reclaimed_slab;
+		reclaim_state->reclaimed_slab = 0;
+	}
 	cond_resched();
 	return freed;
 }
@@ -419,6 +426,7 @@ out:
 void drop_slab_node(int nid)
 {
 	unsigned long freed;
+	unsigned long nr_reclaimed = 0;
 
 	do {
 		struct mem_cgroup *memcg = NULL;
@@ -426,7 +434,7 @@ void drop_slab_node(int nid)
 		freed = 0;
 		do {
 			freed += shrink_slab(GFP_KERNEL, nid, memcg,
-					     1000, 1000);
+					     1000, 1000, &nr_reclaimed);
 		} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
 	} while (freed > 10);
 }
@@ -2339,7 +2347,6 @@ static inline bool should_continue_reclaim(struct zone *zone,
 static bool shrink_zone(struct zone *zone, struct scan_control *sc,
 			bool is_classzone)
 {
-	struct reclaim_state *reclaim_state = current->reclaim_state;
 	unsigned long nr_reclaimed, nr_scanned;
 	bool reclaimable = false;
 
@@ -2371,7 +2378,7 @@ static bool shrink_zone(struct zone *zone, struct scan_control *sc,
 			if (memcg && is_classzone)
 				shrink_slab(sc->gfp_mask, zone_to_nid(zone),
 					    memcg, sc->nr_scanned - scanned,
-					    lru_pages);
+					    lru_pages, &sc->nr_reclaimed);
 
 			/*
 			 * Direct reclaim and kswapd have to scan all memory
@@ -2398,12 +2405,7 @@ static bool shrink_zone(struct zone *zone, struct scan_control *sc,
 		if (global_reclaim(sc) && is_classzone)
 			shrink_slab(sc->gfp_mask, zone_to_nid(zone), NULL,
 				    sc->nr_scanned - nr_scanned,
-				    zone_lru_pages);
-
-		if (reclaim_state) {
-			sc->nr_reclaimed += reclaim_state->reclaimed_slab;
-			reclaim_state->reclaimed_slab = 0;
-		}
+				    zone_lru_pages, &sc->nr_reclaimed);
 
 		vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
 			   sc->nr_scanned - nr_scanned,
@@ -2865,6 +2867,9 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 		.may_unmap = 1,
 		.may_swap = may_swap,
 	};
+	struct reclaim_state reclaim_state = {
+		.reclaimed_slab = 0,
+	};
 
 	/*
 	 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
@@ -2875,6 +2880,9 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 
 	zonelist = NODE_DATA(nid)->node_zonelists;
 
+	lockdep_set_current_reclaim_state(gfp_mask);
+	current->reclaim_state = &reclaim_state;
+
 	trace_mm_vmscan_memcg_reclaim_begin(0,
 					    sc.may_writepage,
 					    sc.gfp_mask);
@@ -2883,6 +2891,9 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 
 	trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
 
+	current->reclaim_state = NULL;
+	lockdep_clear_current_reclaim_state();
+
 	return nr_reclaimed;
 }
 #endif
-- 
1.7.10.4

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