linux-kernel - Re: [PATCH] mm/memcg: return value of the function mem_cgroup_from

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Message-ID: <20190822201200.GP12785@dhcp22.suse.cz>
Date:   Thu, 22 Aug 2019 22:12:00 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Yizhuo Zhai <yzhai003@....edu>
Cc:     Chengyu Song <csong@...ucr.edu>, Zhiyun Qian <zhiyunq@...ucr.edu>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/memcg: return value of the function
 mem_cgroup_from_css() is not checked

On Thu 22-08-19 13:07:17, Yizhuo Zhai wrote:
> This will happen if variable "wb->memcg_css" is NULL. This case is reported
> by our analysis tool.

Does your tool report the particular call path and conditions when that
happen? Or is it just a "it mignt happen" kinda thing?

> Since the function mem_cgroup_wb_domain() is visible to the global, we
> cannot control caller's behavior.

I am sorry but I do not understand what is this supposed to mean.
-- 
Michal Hocko
SUSE Labs