[PATCH v3 1/5] mm: list_lru: allow external numa node and cgroup tracking

[Nhat Pham <nphamcs@gmail.com>]

The interface of list_lru is based on the assumption that objects are
allocated on the correct node/memcg, with this change it is introduced the
possibility to explicitly specify numa node and memcgroup when adding and
removing objects. This is so that users of list_lru can track node/memcg
of the items outside of the list_lru, like in zswap, where the allocations
can be made by kswapd for data that's charged to a different cgroup.

Signed-off-by: Nhat Pham <nphamcs@gmail.com>
---
 include/linux/list_lru.h | 38 +++++++++++++++++++++++++++++++++++
 mm/list_lru.c            | 43 +++++++++++++++++++++++++++++++++++-----
 2 files changed, 76 insertions(+), 5 deletions(-)

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index b35968ee9fb5..0f5f39cacbbb 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -89,6 +89,24 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren
  */
 bool list_lru_add(struct list_lru *lru, struct list_head *item);
 
+/**
+ * __list_lru_add: add an element to a specific sublist.
+ * @list_lru: the lru pointer
+ * @item: the item to be added.
+ * @memcg: the cgroup of the sublist to add the item to.
+ * @nid: the node id of the sublist to add the item to.
+ *
+ * This function is similar to list_lru_add(), but it allows the caller to
+ * specify the sublist to which the item should be added. This can be useful
+ * when the list_head node is not necessarily in the same cgroup and NUMA node
+ * as the data it represents, such as zswap, where the list_head node could be
+ * from kswapd and the data from a different cgroup altogether.
+ *
+ * Return value: true if the list was updated, false otherwise
+ */
+bool __list_lru_add(struct list_lru *lru, struct list_head *item, int nid,
+		    struct mem_cgroup *memcg);
+
 /**
  * list_lru_del: delete an element to the lru list
  * @list_lru: the lru pointer
@@ -102,6 +120,18 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item);
  */
 bool list_lru_del(struct list_lru *lru, struct list_head *item);
 
+/**
+ * __list_lru_del: delete an element from a specific sublist.
+ * @list_lru: the lru pointer
+ * @item: the item to be deleted.
+ * @memcg: the cgroup of the sublist to delete the item from.
+ * @nid: the node id of the sublist to delete the item from.
+ *
+ * Return value: true if the list was updated, false otherwise.
+ */
+bool __list_lru_del(struct list_lru *lru, struct list_head *item, int nid,
+		    struct mem_cgroup *memcg);
+
 /**
  * list_lru_count_one: return the number of objects currently held by @lru
  * @lru: the lru pointer.
@@ -136,6 +166,14 @@ static inline unsigned long list_lru_count(struct list_lru *lru)
 void list_lru_isolate(struct list_lru_one *list, struct list_head *item);
 void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
 			   struct list_head *head);
+/*
+ * list_lru_putback: undo list_lru_isolate.
+ *
+ * Since we might have dropped the LRU lock in between, recompute list_lru_one
+ * from the node's id and memcg.
+ */
+void list_lru_putback(struct list_lru *lru, struct list_head *item, int nid,
+		      struct mem_cgroup *memcg);
 
 typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
 		struct list_lru_one *list, spinlock_t *lock, void *cb_arg);
diff --git a/mm/list_lru.c b/mm/list_lru.c
index a05e5bef3b40..63b75163c6ad 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -119,13 +119,22 @@ list_lru_from_kmem(struct list_lru *lru, int nid, void *ptr,
 bool list_lru_add(struct list_lru *lru, struct list_head *item)
 {
 	int nid = page_to_nid(virt_to_page(item));
+	struct mem_cgroup *memcg = list_lru_memcg_aware(lru) ?
+		mem_cgroup_from_slab_obj(item) : NULL;
+
+	return __list_lru_add(lru, item, nid, memcg);
+}
+EXPORT_SYMBOL_GPL(list_lru_add);
+
+bool __list_lru_add(struct list_lru *lru, struct list_head *item, int nid,
+		    struct mem_cgroup *memcg)
+{
 	struct list_lru_node *nlru = &lru->node[nid];
-	struct mem_cgroup *memcg;
 	struct list_lru_one *l;
 
 	spin_lock(&nlru->lock);
 	if (list_empty(item)) {
-		l = list_lru_from_kmem(lru, nid, item, &memcg);
+		l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
 		list_add_tail(item, &l->list);
 		/* Set shrinker bit if the first element was added */
 		if (!l->nr_items++)
@@ -138,17 +147,27 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item)
 	spin_unlock(&nlru->lock);
 	return false;
 }
-EXPORT_SYMBOL_GPL(list_lru_add);
+EXPORT_SYMBOL_GPL(__list_lru_add);
 
 bool list_lru_del(struct list_lru *lru, struct list_head *item)
 {
 	int nid = page_to_nid(virt_to_page(item));
+	struct mem_cgroup *memcg = list_lru_memcg_aware(lru) ?
+		mem_cgroup_from_slab_obj(item) : NULL;
+
+	return __list_lru_del(lru, item, nid, memcg);
+}
+EXPORT_SYMBOL_GPL(list_lru_del);
+
+bool __list_lru_del(struct list_lru *lru, struct list_head *item, int nid,
+		    struct mem_cgroup *memcg)
+{
 	struct list_lru_node *nlru = &lru->node[nid];
 	struct list_lru_one *l;
 
 	spin_lock(&nlru->lock);
 	if (!list_empty(item)) {
-		l = list_lru_from_kmem(lru, nid, item, NULL);
+		l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
 		list_del_init(item);
 		l->nr_items--;
 		nlru->nr_items--;
@@ -158,7 +177,7 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item)
 	spin_unlock(&nlru->lock);
 	return false;
 }
-EXPORT_SYMBOL_GPL(list_lru_del);
+EXPORT_SYMBOL_GPL(__list_lru_del);
 
 void list_lru_isolate(struct list_lru_one *list, struct list_head *item)
 {
@@ -175,6 +194,20 @@ void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
 }
 EXPORT_SYMBOL_GPL(list_lru_isolate_move);
 
+void list_lru_putback(struct list_lru *lru, struct list_head *item, int nid,
+		      struct mem_cgroup *memcg)
+{
+	struct list_lru_one *list =
+		list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
+
+	if (list_empty(item)) {
+		list_add_tail(item, &list->list);
+		if (!list->nr_items++)
+			set_shrinker_bit(memcg, nid, lru_shrinker_id(lru));
+	}
+}
+EXPORT_SYMBOL_GPL(list_lru_putback);
+
 unsigned long list_lru_count_one(struct list_lru *lru,
 				 int nid, struct mem_cgroup *memcg)
 {
-- 
2.34.1