linux-kernel - [PATCH v2 7/8] mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set

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Date:   Fri, 16 Apr 2021 13:14:06 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     guro@...com, hannes@...xchg.org, mhocko@...nel.org,
        akpm@...ux-foundation.org, shakeelb@...gle.com,
        vdavydov.dev@...il.com
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        duanxiongchun@...edance.com, Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v2 7/8] mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set_lock

The css_set_lock is used to guard the list of inherited objcgs. So there
is no need to uncharge kernel memory under css_set_lock. Just move it
out of the lock.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
Reviewed-by: Shakeel Butt <shakeelb@...gle.com>
Acked-by: Roman Gushchin <guro@...com>
Acked-by: Johannes Weiner <hannes@...xchg.org>
---
 mm/memcontrol.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c4eebe2a2914..e0c398fe7443 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -289,9 +289,10 @@ static void obj_cgroup_release(struct percpu_ref *ref)
 	WARN_ON_ONCE(nr_bytes & (PAGE_SIZE - 1));
 	nr_pages = nr_bytes >> PAGE_SHIFT;
 
-	spin_lock_irqsave(&css_set_lock, flags);
 	if (nr_pages)
 		obj_cgroup_uncharge_pages(objcg, nr_pages);
+
+	spin_lock_irqsave(&css_set_lock, flags);
 	list_del(&objcg->list);
 	spin_unlock_irqrestore(&css_set_lock, flags);
 
-- 
2.11.0