list_lru: introduce per-memcg lists

There are several FS shrinkers, including super_block::s_shrink, that
keep reclaimable objects in the list_lru structure.  Hence to turn them
to memcg-aware shrinkers, it is enough to make list_lru per-memcg.

This patch does the trick.  It adds an array of lru lists to the
list_lru_node structure (per-node part of the list_lru), one for each
kmem-active memcg, and dispatches every item addition or removal to the
list corresponding to the memcg which the item is accounted to.  So now
the list_lru structure is not just per node, but per node and per memcg.

Not all list_lrus need this feature, so this patch also adds a new
method, list_lru_init_memcg, which initializes a list_lru as memcg
aware.  Otherwise (i.e.  if initialized with old list_lru_init), the
list_lru won't have per memcg lists.

Just like per memcg caches arrays, the arrays of per-memcg lists are
indexed by memcg_cache_id, so we must grow them whenever
memcg_nr_cache_ids is increased.  So we introduce a callback,
memcg_update_all_list_lrus, invoked by memcg_alloc_cache_id if the id
space is full.

The locking is implemented in a manner similar to lruvecs, i.e.  we have
one lock per node that protects all lists (both global and per cgroup) on
the node.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/list_lru.h

@@ -11,6 +11,8 @@
 #include <linux/nodemask.h>
 #include <linux/shrinker.h>
 
+struct mem_cgroup;
+
 /* list_lru_walk_cb has to always return one of those */
 enum lru_status {
 	LRU_REMOVED,		/* item removed from list */
@@ -22,11 +24,26 @@ enum lru_status {
 				   internally, but has to return locked. */
 };
 
-struct list_lru_node {
-	spinlock_t		lock;
+struct list_lru_one {
 	struct list_head	list;
 	/* kept as signed so we can catch imbalance bugs */
 	long			nr_items;
+};
+
+struct list_lru_memcg {
+	/* array of per cgroup lists, indexed by memcg_cache_id */
+	struct list_lru_one	*lru[0];
+};
+
+struct list_lru_node {
+	/* protects all lists on the node, including per cgroup */
+	spinlock_t		lock;
+	/* global list, used for the root cgroup in cgroup aware lrus */
+	struct list_lru_one	lru;
+#ifdef CONFIG_MEMCG_KMEM
+	/* for cgroup aware lrus points to per cgroup lists, otherwise NULL */
+	struct list_lru_memcg	*memcg_lrus;
+#endif
 } ____cacheline_aligned_in_smp;
 
 struct list_lru {
@@ -37,11 +54,14 @@ struct list_lru {
 };
 
 void list_lru_destroy(struct list_lru *lru);
-int list_lru_init_key(struct list_lru *lru, struct lock_class_key *key);
-static inline int list_lru_init(struct list_lru *lru)
-{
-	return list_lru_init_key(lru, NULL);
-}
+int __list_lru_init(struct list_lru *lru, bool memcg_aware,
+		    struct lock_class_key *key);
+
+#define list_lru_init(lru)		__list_lru_init((lru), false, NULL)
+#define list_lru_init_key(lru, key)	__list_lru_init((lru), false, (key))
+#define list_lru_init_memcg(lru)	__list_lru_init((lru), true, NULL)
+
+int memcg_update_all_list_lrus(int num_memcgs);
 
 /**
  * list_lru_add: add an element to the lru list's tail
@@ -75,20 +95,23 @@ 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_count_node: return the number of objects currently held by @lru
+ * list_lru_count_one: return the number of objects currently held by @lru
  * @lru: the lru pointer.
  * @nid: the node id to count from.
+ * @memcg: the cgroup to count from.
  *
  * Always return a non-negative number, 0 for empty lists. There is no
  * guarantee that the list is not updated while the count is being computed.
  * Callers that want such a guarantee need to provide an outer lock.
  */
+unsigned long list_lru_count_one(struct list_lru *lru,
+				 int nid, struct mem_cgroup *memcg);
 unsigned long list_lru_count_node(struct list_lru *lru, int nid);
 
 static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
 						  struct shrink_control *sc)
 {
-	return list_lru_count_node(lru, sc->nid);
+	return list_lru_count_one(lru, sc->nid, sc->memcg);
 }
 
 static inline unsigned long list_lru_count(struct list_lru *lru)
@@ -105,9 +128,10 @@ static inline unsigned long list_lru_count(struct list_lru *lru)
 typedef enum lru_status
 (*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg);
 /**
- * list_lru_walk_node: walk a list_lru, isolating and disposing freeable items.
+ * list_lru_walk_one: walk a list_lru, isolating and disposing freeable items.
  * @lru: the lru pointer.
  * @nid: the node id to scan from.
+ * @memcg: the cgroup to scan from.
  * @isolate: callback function that is resposible for deciding what to do with
  *  the item currently being scanned
  * @cb_arg: opaque type that will be passed to @isolate
@@ -125,6 +149,10 @@ typedef enum lru_status
  *
  * Return value: the number of objects effectively removed from the LRU.
  */
+unsigned long list_lru_walk_one(struct list_lru *lru,
+				int nid, struct mem_cgroup *memcg,
+				list_lru_walk_cb isolate, void *cb_arg,
+				unsigned long *nr_to_walk);
 unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
 				 list_lru_walk_cb isolate, void *cb_arg,
 				 unsigned long *nr_to_walk);
@@ -133,8 +161,8 @@ static inline unsigned long
 list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
 		     list_lru_walk_cb isolate, void *cb_arg)
 {
-	return list_lru_walk_node(lru, sc->nid, isolate, cb_arg,
-				  &sc->nr_to_scan);
+	return list_lru_walk_one(lru, sc->nid, sc->memcg, isolate, cb_arg,
+				 &sc->nr_to_scan);
 }
 
 static inline unsigned long