linux-kernel - [PATCH 5.10.y 07/11] mm: memcontrol: change ug->dummy

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Date:   Mon, 16 Aug 2021 07:21:43 +0000
From:   Chen Huang <chenhuang5@...wei.com>
To:     Roman Gushchin <guro@...com>,
        Muchun Song <songmuchun@...edance.com>,
        "Wang Hai" <wanghai38@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <stable@...r.kernel.org>, Chen Huang <chenhuang5@...wei.com>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        "Xiongchun Duan" <duanxiongchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.10.y 07/11] mm: memcontrol: change ug->dummy_page only if memcg changed

From: Muchun Song <songmuchun@...edance.com>

Just like assignment to ug->memcg, we only need to update ug->dummy_page
if memcg changed.  So move it to there.  This is a very small
optimization.

Link: https://lkml.kernel.org/r/20210319163821.20704-5-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@...edance.com>
Acked-by: Johannes Weiner <hannes@...xchg.org>
Reviewed-by: Shakeel Butt <shakeelb@...gle.com>
Cc: Michal Hocko <mhocko@...nel.org>
Cc: Roman Gushchin <guro@...com>
Cc: Vladimir Davydov <vdavydov.dev@...il.com>
Cc: Xiongchun Duan <duanxiongchun@...edance.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Chen Huang <chenhuang5@...wei.com>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d45c2c97d9b8..73418413958c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6907,6 +6907,7 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
 			uncharge_gather_clear(ug);
 		}
 		ug->memcg = page_memcg(page);
+		ug->dummy_page = page;
 
 		/* pairs with css_put in uncharge_batch */
 		css_get(&ug->memcg->css);
@@ -6920,7 +6921,6 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
 	else
 		ug->pgpgout++;
 
-	ug->dummy_page = page;
 	page->memcg_data = 0;
 	css_put(&ug->memcg->css);
 }
-- 
2.18.0.huawei.25