mm, slub: fix incorrect memcg slab count for bulk free

kmem_cache_free_bulk() will call memcg_slab_free_hook() for all objects
when doing bulk free.  So we shouldn't call memcg_slab_free_hook() again
for bulk free to avoid incorrect memcg slab count.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: d1b2cf6 ("mm: memcg/slab: uncharge during kmem_cache_free_bulk()")
Signed-off-by: Miaohe Lin <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Bharata B Rao <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Faiyaz Mohammed <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/slub.c

@@ -3420,7 +3420,9 @@ static __always_inline void do_slab_free(struct kmem_cache *s,
 	struct kmem_cache_cpu *c;
 	unsigned long tid;
 
-	memcg_slab_free_hook(s, &head, 1);
+	/* memcg_slab_free_hook() is already called for bulk free. */
+	if (!tail)
+		memcg_slab_free_hook(s, &head, 1);
 redo:
 	/*
 	 * Determine the currently cpus per cpu slab.