linux-kernel - [RFC PATCH 0/3] Rework locking when rendering mountinfo cgroup paths

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Message-Id: <20230502133847.14570-1-mkoutny@suse.com>
Date:   Tue,  2 May 2023 15:38:44 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Dave Chinner <dchinner@...hat.com>,
        Rik van Riel <riel@...riel.com>,
        Jiri Wiesner <jwiesner@...e.de>
Subject: [RFC PATCH 0/3] Rework locking when rendering mountinfo cgroup paths

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
individual commits.

Michal Koutný (3):
  cgroup: Drop unused function for cgroup_path
  cgroup: Rely on namespace_sem in current_cgns_cgroup_from_root
    explicitly
  cgroup: Do not take css_set_lock in cgroup_show_path

 fs/namespace.c         |  5 +++-
 include/linux/mount.h  |  4 +++
 kernel/cgroup/cgroup.c | 58 ++++++++----------------------------------
 3 files changed, 18 insertions(+), 49 deletions(-)

-- 
2.40.1