slub: fix kmem_cache_shrink return value

It is supposed to return 0 if the cache has no remaining objects and 1
otherwise, while currently it always returns 0.  Fix it.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slub.c

@@ -3379,6 +3379,7 @@ int __kmem_cache_shrink(struct kmem_cache *s)
 	struct list_head discard;
 	struct list_head promote[SHRINK_PROMOTE_MAX];
 	unsigned long flags;
+	int ret = 0;
 
 	flush_all(s);
 	for_each_kmem_cache_node(s, node, n) {
@@ -3425,9 +3426,12 @@ int __kmem_cache_shrink(struct kmem_cache *s)
 		/* Release empty slabs */
 		list_for_each_entry_safe(page, t, &discard, lru)
 			discard_slab(s, page);
+
+		if (slabs_node(s, node))
+			ret = 1;
 	}
 
-	return 0;
+	return ret;
 }
 
 static int slab_mem_going_offline_callback(void *arg)