slub: adjust memcg caches when creating cache alias

Otherwise, kzalloc() called from a memcg won't clear the whole object.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Glauber Costa <glommer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Vladimir Davydov

mm/slub.c

@@ -3748,14 +3748,27 @@ __kmem_cache_alias(const char *name, size_t size, size_t align,
 
 	s = find_mergeable(size, align, flags, name, ctor);
 	if (s) {
+		int i;
+		struct kmem_cache *c;
+
 		s->refcount++;
+
 		/*
 		 * Adjust the object sizes so that we clear
 		 * the complete object on kzalloc.
 		 */
 		s->object_size = max(s->object_size, (int)size);
 		s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *)));
 
+		for_each_memcg_cache_index(i) {
+			c = cache_from_memcg_idx(s, i);
+			if (!c)
+				continue;
+			c->object_size = s->object_size;
+			c->inuse = max_t(int, c->inuse,
+					 ALIGN(size, sizeof(void *)));
+		}
+
 		if (sysfs_slab_alias(s, name)) {
 			s->refcount--;
 			s = NULL;