From: Waiman Long <longman@redhat.com>
To: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Shakeel Butt <shakeelb@google.com>,
Muchun Song <muchun.song@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
linux-mm@kvack.org, Waiman Long <longman@redhat.com>
Subject: [PATCH] mm: memcontrol: Don't css_get() on root_mem_cgroup in get_mem_cgroup_from_mm()
Date: Thu, 12 Oct 2023 12:15:04 -0400 [thread overview]
Message-ID: <20231012161504.3445042-1-longman@redhat.com> (raw)
As reference counting in the root memcg is disabled, there is no need
to get a reference if root memcg is to be returned.
Signed-off-by: Waiman Long <longman@redhat.com>
---
mm/memcontrol.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5b009b233ab8..2b3864194042 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1060,8 +1060,10 @@ struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
rcu_read_lock();
do {
memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
- if (unlikely(!memcg))
+ if (unlikely(!memcg)) {
memcg = root_mem_cgroup;
+ break;
+ }
} while (!css_tryget(&memcg->css));
rcu_read_unlock();
return memcg;
--
2.39.3
next reply other threads:[~2023-10-12 16:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-12 16:15 Waiman Long [this message]
2023-10-13 14:17 ` Michal Hocko
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