mm/slub: make add_full() condition more explicit

The commit below is incomplete, as it didn't handle the add_full() part.
commit a4d3f89 ("slub: remove useless kmem_cache_debug() before
remove_full()")

This patch checks for SLAB_STORE_USER instead of kmem_cache_debug(), since
that should be the only context in which we need the list_lock for
add_full().

Signed-off-by: Abel Wu <wuyun.wu@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Liu Xiang <liu.xiang6@zte.com.cn>
Link: https://lkml.kernel.org/r/20200811020240.1231-1-wuyun.wu@huawei.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slub.c

@@ -2245,7 +2245,8 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
 		}
 	} else {
 		m = M_FULL;
-		if (kmem_cache_debug(s) && !lock) {
+#ifdef CONFIG_SLUB_DEBUG
+		if ((s->flags & SLAB_STORE_USER) && !lock) {
 			lock = 1;
 			/*
 			 * This also ensures that the scanning of full
@@ -2254,6 +2255,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
 			 */
 			spin_lock(&n->list_lock);
 		}
+#endif
 	}
 
 	if (l != m) {