From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj@kernel.org>
Subject: Re: [RFC PATCH 3/3] cgroup: Do not take css_set_lock in
 cgroup_show_path
Date: Fri, 5 May 2023 08:17:10 -1000
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Sender: Tejun Heo <htejun@gmail.com>
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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>

Hello,

On Fri, May 05, 2023 at 07:32:40PM +0200, Michal Koutn=FD 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:
> > >=20
> > >         R ... cgroup hierarchy root
> > >         M ... mount root
> > >         C ... reader's cgroup NS root
> > >=20
> > > mountinfo is supposed to show path from C to M.
> >=20
> > At least for cgroup2, the path from C to M isn't gonna change once NS is
> > established, right?
>=20
> 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.

--=20
tejun