linux-kernel - Re: [PATCH v9 1/7] cgroup/cpuset: Don't let child cpusets restrict parent in default hierarchy

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Message-ID: <Ybev80+h4JArgMDz@slm.duckdns.org>
Date:   Mon, 13 Dec 2021 10:41:23 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <shuah@...nel.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Phil Auld <pauld@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Michal Koutný <mkoutny@...e.com>
Subject: Re: [PATCH v9 1/7] cgroup/cpuset: Don't let child cpusets restrict
 parent in default hierarchy

On Sun, Dec 05, 2021 at 01:32:14PM -0500, Waiman Long wrote:
> In validate_change(), there is a check since v2.6.12 to make sure that
> each of the child cpusets must be a subset of a parent cpuset.  IOW, it
> allows child cpusets to restrict what changes can be made to a parent's
> "cpuset.cpus". This actually violates one of the core principles of the
> default hierarchy where a cgroup higher up in the hierarchy should be
> able to change configuration however it sees fit as deligation breaks
> down otherwise.
> 
> To address this issue, the check is now removed for the default hierarchy
> to free parent cpusets from being restricted by child cpusets. The
> check will still apply for legacy hierarchy.
> 
> Suggested-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Waiman Long <longman@...hat.com>

Applied to cgroup/for-5.17.

Thanks.

-- 
tejun