[PATCH 6/7] mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set_lock

From: Muchun Song <songmuchun@bytedance.com>
To: guro@fb.com, hannes@cmpxchg.org, mhocko@kernel.org,
	akpm@linux-foundation.org, shakeelb@google.com,
	vdavydov.dev@gmail.com
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	duanxiongchun@bytedance.com, fam.zheng@bytedance.com,
	Muchun Song <songmuchun@bytedance.com>
Subject: [PATCH 6/7] mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set_lock
Date: Tue, 13 Apr 2021 14:51:52 +0800	[thread overview]
Message-ID: <20210413065153.63431-7-songmuchun@bytedance.com> (raw)
In-Reply-To: <20210413065153.63431-1-songmuchun@bytedance.com>

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@bytedance.com>
---
 mm/memcontrol.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 42d8c0f4ab1d..d9c7e44abcd0 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

