linux-kernel - Re: [RFC PATCH 02/15] mm: memcontrol: bail out early when !mm in get_mem_cgroup_from

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Message-ID: <YGczdhFJNVphX8uj@cmpxchg.org>
Date:   Fri, 2 Apr 2021 11:08:38 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     guro@...com, mhocko@...nel.org, akpm@...ux-foundation.org,
        shakeelb@...gle.com, vdavydov.dev@...il.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        duanxiongchun@...edance.com
Subject: Re: [RFC PATCH 02/15] mm: memcontrol: bail out early when !mm in
 get_mem_cgroup_from_mm

On Tue, Mar 30, 2021 at 06:15:18PM +0800, Muchun Song wrote:
> When mm is NULL, we do not need to hold rcu lock and call css_tryget for
> the root memcg. And we also do not need to check !mm in every loop of
> while. So bail out early when !mm.
> 
> Signed-off-by: Muchun Song <songmuchun@...edance.com>

Good observation.

Acked-by: Johannes Weiner <hannes@...xchg.org>