memcg: get rid of memcg_create_cache_name

Instead of calling back to memcontrol.c from kmem_cache_create_memcg in
order to just create the name of a per memcg cache, let's allocate it in
place.  We only need to pass the memcg name to kmem_cache_create_memcg for
that - everything else can be done in slab_common.c.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 7e348cf..3217561 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -264,13 +264,15 @@
  * kmem_cache_create_memcg - 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 *kmem_cache_create_memcg(struct mem_cgroup *memcg,
-					   struct kmem_cache *root_cache)
+					   struct kmem_cache *root_cache,
+					   const char *memcg_name)
 {
 	struct kmem_cache *s = NULL;
 	char *cache_name;
@@ -280,7 +282,8 @@
 
 	mutex_lock(&slab_mutex);
 
-	cache_name = memcg_create_cache_name(memcg, root_cache);
+	cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
+			       memcg_cache_id(memcg), memcg_name);
 	if (!cache_name)
 		goto out_unlock;