mm: memcg/slab: use a single set of kmem_caches for all accounted allocations

This is fairly big but mostly red patch, which makes all accounted slab
allocations use a single set of kmem_caches instead of creating a separate
set for each memory cgroup.

Because the number of non-root kmem_caches is now capped by the number of
root kmem_caches, there is no need to shrink or destroy them prematurely.
They can be perfectly destroyed together with their root counterparts.
This allows to dramatically simplify the management of non-root
kmem_caches and delete a ton of code.

This patch performs the following changes:
1) introduces memcg_params.memcg_cache pointer to represent the
   kmem_cache which will be used for all non-root allocations
2) reuses the existing memcg kmem_cache creation mechanism
   to create memcg kmem_cache on the first allocation attempt
3) memcg kmem_caches are named <kmemcache_name>-memcg,
   e.g. dentry-memcg
4) simplifies memcg_kmem_get_cache() to just return memcg kmem_cache
   or schedule it's creation and return the root cache
5) removes almost all non-root kmem_cache management code
   (separate refcounter, reparenting, shrinking, etc)
6) makes slab debugfs to display root_mem_cgroup css id and never
   show :dead and :deact flags in the memcg_slabinfo attribute.

Following patches in the series will simplify the kmem_cache creation.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/20200623174037.3951353-13-guro@fb.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -317,7 +317,6 @@ struct mem_cgroup {
         /* Index in the kmem_cache->memcg_params.memcg_caches array */
 	int kmemcg_id;
 	enum memcg_kmem_state kmem_state;
-	struct list_head kmem_caches;
 	struct obj_cgroup __rcu *objcg;
 	struct list_head objcg_list; /* list of inherited objcgs */
 #endif
@@ -1404,9 +1403,7 @@ static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
 }
 #endif
 
-struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep,
-					struct obj_cgroup **objcgp);
-void memcg_kmem_put_cache(struct kmem_cache *cachep);
+struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep);
 
 #ifdef CONFIG_MEMCG_KMEM
 int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp,

include/linux/slab.h

@@ -155,8 +155,7 @@ struct kmem_cache *kmem_cache_create_usercopy(const char *name,
 void kmem_cache_destroy(struct kmem_cache *);
 int kmem_cache_shrink(struct kmem_cache *);
 
-void memcg_create_kmem_cache(struct mem_cgroup *, struct kmem_cache *);
-void memcg_deactivate_kmem_caches(struct mem_cgroup *, struct mem_cgroup *);
+void memcg_create_kmem_cache(struct kmem_cache *cachep);
 
 /*
  * Please use this macro to create slab caches. Simply specify the
@@ -580,8 +579,6 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
 	return __kmalloc_node(size, flags, node);
 }
 
-int memcg_update_all_caches(int num_memcgs);
-
 /**
  * kmalloc_array - allocate memory for an array.
  * @n: number of elements.

mm/memcontrol.c

@@ -350,7 +350,7 @@ static void memcg_reparent_objcgs(struct mem_cgroup *memcg,
 }
 
 /*
- * This will be the memcg's index in each cache's ->memcg_params.memcg_caches.
+ * This will be used as a shrinker list's index.
  * The main reason for not using cgroup id for this:
  *  this works better in sparse environments, where we have a lot of memcgs,
  *  but only a few kmem-limited. Or also, if we have, for instance, 200
@@ -569,9 +569,6 @@ ino_t page_cgroup_ino(struct page *page)
 	unsigned long ino = 0;
 
 	rcu_read_lock();
-	if (PageSlab(page) && !PageTail(page)) {
-		memcg = memcg_from_slab_page(page);
-	} else {
 	memcg = page->mem_cgroup;
 
 	/*
@@ -582,7 +579,6 @@ ino_t page_cgroup_ino(struct page *page)
 	 */
 	if ((unsigned long) memcg & 0x1UL)
 		memcg = NULL;
-	}
 
 	while (memcg && !(memcg->css.flags & CSS_ONLINE))
 		memcg = parent_mem_cgroup(memcg);
@@ -2822,12 +2818,18 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p)
 	page = virt_to_head_page(p);
 
 	/*
-	 * Slab pages don't have page->mem_cgroup set because corresponding
-	 * kmem caches can be reparented during the lifetime. That's why
-	 * memcg_from_slab_page() should be used instead.
+	 * Slab objects are accounted individually, not per-page.
+	 * Memcg membership data for each individual object is saved in
+	 * the page->obj_cgroups.
 	 */
-	if (PageSlab(page))
-		return memcg_from_slab_page(page);
+	if (page_has_obj_cgroups(page)) {
+		struct obj_cgroup *objcg;
+		unsigned int off;
+
+		off = obj_to_index(page->slab_cache, page, p);
+		objcg = page_obj_cgroups(page)[off];
+		return obj_cgroup_memcg(objcg);
+	}
 
 	/* All other pages use page->mem_cgroup */
 	return page->mem_cgroup;
@@ -2882,8 +2884,6 @@ static int memcg_alloc_cache_id(void)
 	else if (size > MEMCG_CACHES_MAX_SIZE)
 		size = MEMCG_CACHES_MAX_SIZE;
 
-	err = memcg_update_all_caches(size);
-	if (!err)
 	err = memcg_update_all_list_lrus(size);
 	if (!err)
 		memcg_nr_cache_ids = size;
@@ -2903,7 +2903,6 @@ static void memcg_free_cache_id(int id)
 }
 
 struct memcg_kmem_cache_create_work {
-	struct mem_cgroup *memcg;
 	struct kmem_cache *cachep;
 	struct work_struct work;
 };
@@ -2912,33 +2911,24 @@ static void memcg_kmem_cache_create_func(struct work_struct *w)
 {
 	struct memcg_kmem_cache_create_work *cw =
 		container_of(w, struct memcg_kmem_cache_create_work, work);
-	struct mem_cgroup *memcg = cw->memcg;
 	struct kmem_cache *cachep = cw->cachep;
 
-	memcg_create_kmem_cache(memcg, cachep);
+	memcg_create_kmem_cache(cachep);
 
-	css_put(&memcg->css);
 	kfree(cw);
 }
 
 /*
  * Enqueue the creation of a per-memcg kmem_cache.
  */
-static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
-					       struct kmem_cache *cachep)
+static void memcg_schedule_kmem_cache_create(struct kmem_cache *cachep)
 {
 	struct memcg_kmem_cache_create_work *cw;
 
-	if (!css_tryget_online(&memcg->css))
-		return;
-
 	cw = kmalloc(sizeof(*cw), GFP_NOWAIT | __GFP_NOWARN);
-	if (!cw) {
-		css_put(&memcg->css);
+	if (!cw)
 		return;
-	}
 
-	cw->memcg = memcg;
 	cw->cachep = cachep;
 	INIT_WORK(&cw->work, memcg_kmem_cache_create_func);
 
@@ -2946,102 +2936,26 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
 }
 
 /**
- * memcg_kmem_get_cache: select the correct per-memcg cache for allocation
+ * memcg_kmem_get_cache: select memcg or root cache for allocation
  * @cachep: the original global kmem cache
  *
  * Return the kmem_cache we're supposed to use for a slab allocation.
- * We try to use the current memcg's version of the cache.
  *
  * If the cache does not exist yet, if we are the first user of it, we
  * create it asynchronously in a workqueue and let the current allocation
  * go through with the original cache.
- *
- * This function takes a reference to the cache it returns to assure it
- * won't get destroyed while we are working with it. Once the caller is
- * done with it, memcg_kmem_put_cache() must be called to release the
- * reference.
  */
-struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep,
-					struct obj_cgroup **objcgp)
+struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep)
 {
-	struct mem_cgroup *memcg;
 	struct kmem_cache *memcg_cachep;
-	struct memcg_cache_array *arr;
-	int kmemcg_id;
-
-	VM_BUG_ON(!is_root_cache(cachep));
 
-	if (memcg_kmem_bypass())
+	memcg_cachep = READ_ONCE(cachep->memcg_params.memcg_cache);
+	if (unlikely(!memcg_cachep)) {
+		memcg_schedule_kmem_cache_create(cachep);
 		return cachep;
-
-	rcu_read_lock();
-
-	if (unlikely(current->active_memcg))
-		memcg = current->active_memcg;
-	else
-		memcg = mem_cgroup_from_task(current);
-
-	if (!memcg || memcg == root_mem_cgroup)
-		goto out_unlock;
-
-	kmemcg_id = READ_ONCE(memcg->kmemcg_id);
-	if (kmemcg_id < 0)
-		goto out_unlock;
-
-	arr = rcu_dereference(cachep->memcg_params.memcg_caches);
-
-	/*
-	 * Make sure we will access the up-to-date value. The code updating
-	 * memcg_caches issues a write barrier to match the data dependency
-	 * barrier inside READ_ONCE() (see memcg_create_kmem_cache()).
-	 */
-	memcg_cachep = READ_ONCE(arr->entries[kmemcg_id]);
-
-	/*
-	 * If we are in a safe context (can wait, and not in interrupt
-	 * context), we could be be predictable and return right away.
-	 * This would guarantee that the allocation being performed
-	 * already belongs in the new cache.
-	 *
-	 * However, there are some clashes that can arrive from locking.
-	 * For instance, because we acquire the slab_mutex while doing
-	 * memcg_create_kmem_cache, this means no further allocation
-	 * could happen with the slab_mutex held. So it's better to
-	 * defer everything.
-	 *
-	 * If the memcg is dying or memcg_cache is about to be released,
-	 * don't bother creating new kmem_caches. Because memcg_cachep
-	 * is ZEROed as the fist step of kmem offlining, we don't need
-	 * percpu_ref_tryget_live() here. css_tryget_online() check in
-	 * memcg_schedule_kmem_cache_create() will prevent us from
-	 * creation of a new kmem_cache.
-	 */
-	if (unlikely(!memcg_cachep))
-		memcg_schedule_kmem_cache_create(memcg, cachep);
-	else if (percpu_ref_tryget(&memcg_cachep->memcg_params.refcnt)) {
-		struct obj_cgroup *objcg = rcu_dereference(memcg->objcg);
-
-		if (!objcg || !obj_cgroup_tryget(objcg)) {
-			percpu_ref_put(&memcg_cachep->memcg_params.refcnt);
-			goto out_unlock;
 	}
 
-		*objcgp = objcg;
-		cachep = memcg_cachep;
-	}
-out_unlock:
-	rcu_read_unlock();
-	return cachep;
-}
-
-/**
- * memcg_kmem_put_cache: drop reference taken by memcg_kmem_get_cache
- * @cachep: the cache returned by memcg_kmem_get_cache
- */
-void memcg_kmem_put_cache(struct kmem_cache *cachep)
-{
-	if (!is_root_cache(cachep))
-		percpu_ref_put(&cachep->memcg_params.refcnt);
+	return memcg_cachep;
 }
 
 /**
@@ -3731,7 +3645,6 @@ static int memcg_online_kmem(struct mem_cgroup *memcg)
 	 */
 	memcg->kmemcg_id = memcg_id;
 	memcg->kmem_state = KMEM_ONLINE;
-	INIT_LIST_HEAD(&memcg->kmem_caches);
 
 	return 0;
 }
@@ -3744,22 +3657,13 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
 
 	if (memcg->kmem_state != KMEM_ONLINE)
 		return;
-	/*
-	 * Clear the online state before clearing memcg_caches array
-	 * entries. The slab_mutex in memcg_deactivate_kmem_caches()
-	 * guarantees that no cache will be created for this cgroup
-	 * after we are done (see memcg_create_kmem_cache()).
-	 */
+
 	memcg->kmem_state = KMEM_ALLOCATED;
 
 	parent = parent_mem_cgroup(memcg);
 	if (!parent)
 		parent = root_mem_cgroup;
 
-	/*
-	 * Deactivate and reparent kmem_caches and objcgs.
-	 */
-	memcg_deactivate_kmem_caches(memcg, parent);
 	memcg_reparent_objcgs(memcg, parent);
 
 	kmemcg_id = memcg->kmemcg_id;
@@ -5384,9 +5288,6 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
 
 	/* The following stuff does not apply to the root */
 	if (!parent) {
-#ifdef CONFIG_MEMCG_KMEM
-		INIT_LIST_HEAD(&memcg->kmem_caches);
-#endif
 		root_mem_cgroup = memcg;
 		return &memcg->css;
 	}

mm/slab.c

@@ -1249,7 +1249,7 @@ void __init kmem_cache_init(void)
 				  nr_node_ids * sizeof(struct kmem_cache_node *),
 				  SLAB_HWCACHE_ALIGN, 0, 0);
 	list_add(&kmem_cache->list, &slab_caches);
-	memcg_link_cache(kmem_cache, NULL);
+	memcg_link_cache(kmem_cache);
 	slab_state = PARTIAL;
 
 	/*
@@ -2253,17 +2253,6 @@ int __kmem_cache_shrink(struct kmem_cache *cachep)
 	return (ret ? 1 : 0);
 }
 
-#ifdef CONFIG_MEMCG
-void __kmemcg_cache_deactivate(struct kmem_cache *cachep)
-{
-	__kmem_cache_shrink(cachep);
-}
-
-void __kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s)
-{
-}
-#endif
-
 int __kmem_cache_shutdown(struct kmem_cache *cachep)
 {
 	return __kmem_cache_shrink(cachep);
@@ -3872,7 +3861,8 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
 		return ret;
 
 	lockdep_assert_held(&slab_mutex);
-	for_each_memcg_cache(c, cachep) {
+	c = memcg_cache(cachep);
+	if (c) {
 		/* return value determined by the root cache only */
 		__do_tune_cpucache(c, limit, batchcount, shared, gfp);
 	}

mm/slab.h

@@ -32,66 +32,25 @@ struct kmem_cache {
 
 #else /* !CONFIG_SLOB */
 
-struct memcg_cache_array {
-	struct rcu_head rcu;
-	struct kmem_cache *entries[0];
-};
-
 /*
  * This is the main placeholder for memcg-related information in kmem caches.
- * Both the root cache and the child caches will have it. For the root cache,
- * this will hold a dynamically allocated array large enough to hold
- * information about the currently limited memcgs in the system. To allow the
- * array to be accessed without taking any locks, on relocation we free the old
- * version only after a grace period.
- *
- * Root and child caches hold different metadata.
+ * Both the root cache and the child cache will have it. Some fields are used
+ * in both cases, other are specific to root caches.
  *
  * @root_cache:	Common to root and child caches.  NULL for root, pointer to
  *		the root cache for children.
  *
  * The following fields are specific to root caches.
  *
- * @memcg_caches: kmemcg ID indexed table of child caches.  This table is
- *		used to index child cachces during allocation and cleared
- *		early during shutdown.
- *
- * @root_caches_node: List node for slab_root_caches list.
- *
- * @children:	List of all child caches.  While the child caches are also
- *		reachable through @memcg_caches, a child cache remains on
- *		this list until it is actually destroyed.
- *
- * The following fields are specific to child caches.
- *
- * @memcg:	Pointer to the memcg this cache belongs to.
- *
- * @children_node: List node for @root_cache->children list.
- *
- * @kmem_caches_node: List node for @memcg->kmem_caches list.
+ * @memcg_cache: pointer to memcg kmem cache, used by all non-root memory
+ *		cgroups.
+ * @root_caches_node: list node for slab_root_caches list.
  */
 struct memcg_cache_params {
 	struct kmem_cache *root_cache;
-	union {
-		struct {
-			struct memcg_cache_array __rcu *memcg_caches;
+
+	struct kmem_cache *memcg_cache;
 	struct list_head __root_caches_node;
-			struct list_head children;
-			bool dying;
-		};
-		struct {
-			struct mem_cgroup *memcg;
-			struct list_head children_node;
-			struct list_head kmem_caches_node;
-			struct percpu_ref refcnt;
-
-			void (*work_fn)(struct kmem_cache *);
-			union {
-				struct rcu_head rcu_head;
-				struct work_struct work;
-			};
-		};
-	};
 };
 #endif /* CONFIG_SLOB */
 
@@ -236,8 +195,6 @@ bool __kmem_cache_empty(struct kmem_cache *);
 int __kmem_cache_shutdown(struct kmem_cache *);
 void __kmem_cache_release(struct kmem_cache *);
 int __kmem_cache_shrink(struct kmem_cache *);
-void __kmemcg_cache_deactivate(struct kmem_cache *s);
-void __kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s);
 void slab_kmem_cache_release(struct kmem_cache *);
 void kmem_cache_shrink_all(struct kmem_cache *s);
 
@@ -311,14 +268,6 @@ static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t fla
 extern struct list_head		slab_root_caches;
 #define root_caches_node	memcg_params.__root_caches_node
 
-/*
- * Iterate over all memcg caches of the given root cache. The caller must hold
- * slab_mutex.
- */
-#define for_each_memcg_cache(iter, root) \
-	list_for_each_entry(iter, &(root)->memcg_params.children, \
-			    memcg_params.children_node)
-
 static inline bool is_root_cache(struct kmem_cache *s)
 {
 	return !s->memcg_params.root_cache;
@@ -349,6 +298,13 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
 	return s->memcg_params.root_cache;
 }
 
+static inline struct kmem_cache *memcg_cache(struct kmem_cache *s)
+{
+	if (is_root_cache(s))
+		return s->memcg_params.memcg_cache;
+	return NULL;
+}
+
 static inline struct obj_cgroup **page_obj_cgroups(struct page *page)
 {
 	/*
@@ -361,25 +317,9 @@ static inline struct obj_cgroup **page_obj_cgroups(struct page *page)
 		((unsigned long)page->obj_cgroups & ~0x1UL);
 }
 
-/*
- * Expects a pointer to a slab page. Please note, that PageSlab() check
- * isn't sufficient, as it returns true also for tail compound slab pages,
- * which do not have slab_cache pointer set.
- * So this function assumes that the page can pass PageSlab() && !PageTail()
- * check.
- *
- * The kmem_cache can be reparented asynchronously. The caller must ensure
- * the memcg lifetime, e.g. by taking rcu_read_lock() or cgroup_mutex.
- */
-static inline struct mem_cgroup *memcg_from_slab_page(struct page *page)
+static inline bool page_has_obj_cgroups(struct page *page)
 {
-	struct kmem_cache *s;
-
-	s = READ_ONCE(page->slab_cache);
-	if (s && !is_root_cache(s))
-		return READ_ONCE(s->memcg_params.memcg);
-
-	return NULL;
+	return ((unsigned long)page->obj_cgroups & 0x1UL);
 }
 
 static inline int memcg_alloc_page_obj_cgroups(struct page *page,
@@ -418,17 +358,25 @@ static inline struct kmem_cache *memcg_slab_pre_alloc_hook(struct kmem_cache *s,
 						size_t objects, gfp_t flags)
 {
 	struct kmem_cache *cachep;
+	struct obj_cgroup *objcg;
+
+	if (memcg_kmem_bypass())
+		return s;
 
-	cachep = memcg_kmem_get_cache(s, objcgp);
+	cachep = memcg_kmem_get_cache(s);
 	if (is_root_cache(cachep))
 		return s;
 
-	if (obj_cgroup_charge(*objcgp, flags, objects * obj_full_size(s))) {
-		obj_cgroup_put(*objcgp);
-		memcg_kmem_put_cache(cachep);
+	objcg = get_obj_cgroup_from_current();
+	if (!objcg)
+		return s;
+
+	if (obj_cgroup_charge(objcg, flags, objects * obj_full_size(s))) {
+		obj_cgroup_put(objcg);
 		cachep = NULL;
 	}
 
+	*objcgp = objcg;
 	return cachep;
 }
 
@@ -467,7 +415,6 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
 		}
 	}
 	obj_cgroup_put(objcg);
-	memcg_kmem_put_cache(s);
 }
 
 static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
@@ -491,7 +438,7 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
 }
 
 extern void slab_init_memcg_params(struct kmem_cache *);
-extern void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg);
+extern void memcg_link_cache(struct kmem_cache *s);
 
 #else /* CONFIG_MEMCG_KMEM */
 
@@ -499,9 +446,6 @@ extern void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg);
 #define slab_root_caches	slab_caches
 #define root_caches_node	list
 
-#define for_each_memcg_cache(iter, root) \
-	for ((void)(iter), (void)(root); 0; )
-
 static inline bool is_root_cache(struct kmem_cache *s)
 {
 	return true;
@@ -523,7 +467,17 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
 	return s;
 }
 
-static inline struct mem_cgroup *memcg_from_slab_page(struct page *page)
+static inline struct kmem_cache *memcg_cache(struct kmem_cache *s)
+{
+	return NULL;
+}
+
+static inline bool page_has_obj_cgroups(struct page *page)
+{
+	return false;
+}
+
+static inline struct mem_cgroup *memcg_from_slab_obj(void *ptr)
 {
 	return NULL;
 }
@@ -560,8 +514,7 @@ static inline void slab_init_memcg_params(struct kmem_cache *s)
 {
 }
 
-static inline void memcg_link_cache(struct kmem_cache *s,
-				    struct mem_cgroup *memcg)
+static inline void memcg_link_cache(struct kmem_cache *s)
 {
 }
 
@@ -582,17 +535,14 @@ static __always_inline int charge_slab_page(struct page *page,
 					    gfp_t gfp, int order,
 					    struct kmem_cache *s)
 {
-#ifdef CONFIG_MEMCG_KMEM
 	if (memcg_kmem_enabled() && !is_root_cache(s)) {
 		int ret;
 
 		ret = memcg_alloc_page_obj_cgroups(page, s, gfp);
 		if (ret)
 			return ret;
-
-		percpu_ref_get_many(&s->memcg_params.refcnt, 1 << order);
 	}
-#endif
+
 	mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
 			    PAGE_SIZE << order);
 	return 0;
@@ -601,12 +551,9 @@ static __always_inline int charge_slab_page(struct page *page,
 static __always_inline void uncharge_slab_page(struct page *page, int order,
 					       struct kmem_cache *s)
 {
-#ifdef CONFIG_MEMCG_KMEM
-	if (memcg_kmem_enabled() && !is_root_cache(s)) {
+	if (memcg_kmem_enabled() && !is_root_cache(s))
 		memcg_free_page_obj_cgroups(page);
-		percpu_ref_put_many(&s->memcg_params.refcnt, 1 << order);
-	}
-#endif
+
 	mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
 			    -(PAGE_SIZE << order));
 }
@@ -749,9 +696,6 @@ static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
 void *slab_start(struct seq_file *m, loff_t *pos);
 void *slab_next(struct seq_file *m, void *p, loff_t *pos);
 void slab_stop(struct seq_file *m, void *p);
-void *memcg_slab_start(struct seq_file *m, loff_t *pos);
-void *memcg_slab_next(struct seq_file *m, void *p, loff_t *pos);
-void memcg_slab_stop(struct seq_file *m, void *p);
 int memcg_slab_show(struct seq_file *m, void *p);
 
 #if defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG)

mm/slub.c

@@ -4204,36 +4204,6 @@ int __kmem_cache_shrink(struct kmem_cache *s)
 	return ret;
 }
 
-#ifdef CONFIG_MEMCG
-void __kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s)
-{
-	/*
-	 * Called with all the locks held after a sched RCU grace period.
-	 * Even if @s becomes empty after shrinking, we can't know that @s
-	 * doesn't have allocations already in-flight and thus can't
-	 * destroy @s until the associated memcg is released.
-	 *
-	 * However, let's remove the sysfs files for empty caches here.
-	 * Each cache has a lot of interface files which aren't
-	 * particularly useful for empty draining caches; otherwise, we can
-	 * easily end up with millions of unnecessary sysfs files on
-	 * systems which have a lot of memory and transient cgroups.
-	 */
-	if (!__kmem_cache_shrink(s))
-		sysfs_slab_remove(s);
-}
-
-void __kmemcg_cache_deactivate(struct kmem_cache *s)
-{
-	/*
-	 * Disable empty slabs caching. Used to avoid pinning offline
-	 * memory cgroups by kmem pages that can be freed.
-	 */
-	slub_set_cpu_partial(s, 0);
-	s->min_partial = 0;
-}
-#endif	/* CONFIG_MEMCG */
-
 static int slab_mem_going_offline_callback(void *arg)
 {
 	struct kmem_cache *s;
@@ -4390,7 +4360,7 @@ static struct kmem_cache * __init bootstrap(struct kmem_cache *static_cache)
 	}
 	slab_init_memcg_params(s);
 	list_add(&s->list, &slab_caches);
-	memcg_link_cache(s, NULL);
+	memcg_link_cache(s);
 	return s;
 }
 
@@ -4458,7 +4428,8 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
 		s->object_size = max(s->object_size, size);
 		s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));
 
-		for_each_memcg_cache(c, s) {
+		c = memcg_cache(s);
+		if (c) {
 			c->object_size = s->object_size;
 			c->inuse = max(c->inuse, ALIGN(size, sizeof(void *)));
 		}
@@ -5591,7 +5562,8 @@ static ssize_t slab_attr_store(struct kobject *kobj,
 		 * directly either failed or succeeded, in which case we loop
 		 * through the descendants with best-effort propagation.
 		 */
-		for_each_memcg_cache(c, s)
+		c = memcg_cache(s);
+		if (c)
 			attribute->store(c, buf, len);
 		mutex_unlock(&slab_mutex);
 	}