memcg: zap memcg_name argument of memcg_create_kmem_cache

Instead of passing the name of the memory cgroup which the cache is
created for in the memcg_name_argument, let's obtain it immediately in
memcg_create_kmem_cache.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/slab.h

@@ -117,8 +117,7 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
 			void (*)(void *));
 #ifdef CONFIG_MEMCG_KMEM
 struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *,
-					   struct kmem_cache *,
-					   const char *);
+					   struct kmem_cache *);
 #endif
 void kmem_cache_destroy(struct kmem_cache *);
 int kmem_cache_shrink(struct kmem_cache *);

mm/memcontrol.c

@@ -2607,8 +2607,6 @@ void memcg_update_array_size(int num)
 static void memcg_register_cache(struct mem_cgroup *memcg,
 				 struct kmem_cache *root_cache)
 {
-	static char memcg_name_buf[NAME_MAX + 1]; /* protected by
-						     memcg_slab_mutex */
 	struct kmem_cache *cachep;
 	int id;
 
@@ -2624,8 +2622,7 @@ static void memcg_register_cache(struct mem_cgroup *memcg,
 	if (cache_from_memcg_idx(root_cache, id))
 		return;
 
-	cgroup_name(memcg->css.cgroup, memcg_name_buf, NAME_MAX + 1);
-	cachep = memcg_create_kmem_cache(memcg, root_cache, memcg_name_buf);
+	cachep = memcg_create_kmem_cache(memcg, root_cache);
 	/*
 	 * If we could not create a memcg cache, do not complain, because
 	 * that's not critical at all as we can always proceed with the root

mm/slab_common.c

@@ -430,16 +430,15 @@ EXPORT_SYMBOL(kmem_cache_create);
  * memcg_create_kmem_cache - Create a cache for a memory cgroup.
  * @memcg: The memory cgroup the new cache is for.
  * @root_cache: The parent of the new cache.
- * @memcg_name: The name of the memory cgroup (used for naming the new cache).
  *
  * This function attempts to create a kmem cache that will serve allocation
  * requests going from @memcg to @root_cache. The new cache inherits properties
  * from its parent.
  */
 struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
-					   struct kmem_cache *root_cache,
-					   const char *memcg_name)
+					   struct kmem_cache *root_cache)
 {
+	static char memcg_name_buf[NAME_MAX + 1]; /* protected by slab_mutex */
 	struct kmem_cache *s = NULL;
 	char *cache_name;
 
@@ -448,8 +447,10 @@ struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
 
 	mutex_lock(&slab_mutex);
 
+	cgroup_name(mem_cgroup_css(memcg)->cgroup,
+		    memcg_name_buf, sizeof(memcg_name_buf));
 	cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
-			       memcg_cache_id(memcg), memcg_name);
+			       memcg_cache_id(memcg), memcg_name_buf);
 	if (!cache_name)
 		goto out_unlock;