From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christian Brauner <brauner@kernel.org>
Subject: Re: [RFC PATCH 0/3] Rework locking when rendering mountinfo cgroup
 paths
Date: Tue, 23 May 2023 14:09:12 +0200
Message-ID: <20230523-salamander-gemeldet-b549ea345cf8@brauner>
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To: Michal =?utf-8?Q?Koutn=C3=BD?= <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>, Tejun Heo <tj@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>

On Tue, May 02, 2023 at 03:38:44PM +0200, Michal Koutn=C3=BD wrote:
> Idea for these modification came up when css_set_lock seemed unneeded in
> cgroup_show_path.
> It's a delicate change, so the deciding factor was when cgroup_show_path =
popped
> up also in some profiles of frequent mountinfo readers.
> The idea is to trade the exclusive css_set_lock for the shared
> namespace_sem when rendering cgroup paths. Details are described more in

I have no issue with the cgroup specific part of relying on
namespace_sem but kernel/cgroup/ has no business of being aware of
namespace semaphore in any way. Leave a comment to clarify what you're
doing but we're not going to sprinkle namespace_sem references - even if
only for the sake of lockdep - into other subsystems.