mm, slub: use kmem_cache_debug_flags() in deactivate_slab()

Commit 9cf7a11 ("mm/slub: make add_full() condition more explicit")
replaced an unnecessarily generic kmem_cache_debug(s) check with an
explicit check of SLAB_STORE_USER and #ifdef CONFIG_SLUB_DEBUG.

We can achieve the same specific check with the recently added
kmem_cache_debug_flags() which removes the #ifdef and restores the
no-branch-overhead benefit of static key check when slub debugging is not
enabled.

Link: https://lkml.kernel.org/r/3ef24214-38c7-1238-8296-88caf7f48ab6@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Abel Wu <wuyun.wu@huawei.com>
Cc: Christopher 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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slub.c

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