linux-kernel - [PATCH 5/5] mm, slub: fix incorrect memcg slab count for bulk free

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Date:   Thu, 16 Sep 2021 20:39:20 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <cl@...ux.com>, <penberg@...nel.org>,
        <rientjes@...gle.com>, <iamjoonsoo.kim@....com>, <vbabka@...e.cz>
CC:     <gregkh@...uxfoundation.org>, <faiyazm@...eaurora.org>,
        <andreyknvl@...il.com>, <ryabinin.a.a@...il.com>,
        <thgarnie@...gle.com>, <keescook@...omium.org>,
        <bharata@...ux.ibm.com>, <guro@...com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linmiaohe@...wei.com>
Subject: [PATCH 5/5] 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.

Fixes: d1b2cf6cb84a ("mm: memcg/slab: uncharge during kmem_cache_free_bulk()")
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/slub.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index f3df0f04a472..d8f77346376d 100644
--- a/mm/slub.c
+++ b/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.
-- 
2.23.0