[PATCH 5.10.y 07/11] mm: memcontrol: change ug->dummy_page only if memcg changed

[Chen Huang <chenhuang5@huawei.com>]

From: Muchun Song <songmuchun@bytedance.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@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Chen Huang <chenhuang5@huawei.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