Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Sender: Tejun Heo <htejun@gmail.com>
Date:   Fri, 5 May 2023 08:17:10 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        cgroups@vger.kernel.org, Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Dave Chinner <dchinner@redhat.com>,
        Rik van Riel <riel@surriel.com>,
        Jiri Wiesner <jwiesner@suse.de>
Subject: Re: [RFC PATCH 3/3] cgroup: Do not take css_set_lock in
 cgroup_show_path
Message-ID: <ZFVIJlAMyzTh3QTP@slm.duckdns.org>
References: <20230502133847.14570-1-mkoutny@suse.com>
 <20230502133847.14570-4-mkoutny@suse.com>
 <ZFUktg4Yxa30jRBX@slm.duckdns.org>
 <ta7bilcvc7lzt5tvs44y5wxqt6i3gdmvzwcr5h2vxhjhshmivk@3mecui76fxvy>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <ta7bilcvc7lzt5tvs44y5wxqt6i3gdmvzwcr5h2vxhjhshmivk@3mecui76fxvy>
Precedence: bulk

Hello,

On Fri, May 05, 2023 at 07:32:40PM +0200, Michal Koutn? wrote:
> On Fri, May 05, 2023 at 05:45:58AM -1000, Tejun Heo <tj@kernel.org> wrote:
> > > There are three relevant nodes for each cgroupfs entry:
> > > 
> > >         R ... cgroup hierarchy root
> > >         M ... mount root
> > >         C ... reader's cgroup NS root
> > > 
> > > mountinfo is supposed to show path from C to M.
> > 
> > At least for cgroup2, the path from C to M isn't gonna change once NS is
> > established, right?
> 
> Right. Although, the argument about M (when C above M or when C and M in
> different subtrees) implicitly relies on the namespace_sem.

I don't follow. Can you please elaborate a bit more?

Thanks.

-- 
tejun