linux-kernel - Re: [PATCH v4.15-rc9] sched, cgroup: Don't reject lower cpu.max on ancestors

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Message-ID: <20180129191535.GC1121507@devbig577.frc2.facebook.com>
Date:   Mon, 29 Jan 2018 11:15:35 -0800
From:   Tejun Heo <tj@...nel.org>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v4.15-rc9] sched, cgroup: Don't reject lower cpu.max on
 ancestors

Hello,

On Mon, Jan 22, 2018 at 11:26:18AM -0800, Tejun Heo wrote:
> While adding cgroup2 interface for the cpu controller, 0d5936344f30
> ("sched: Implement interface for cgroup unified hierarchy") forgot to
> update input validation and left it to reject cpu.max config if any
> descendant has set a higher value.
> 
> cgroup2 officially supports delegation and a descendant must not be
> able to restrict what its ancestors can configure.  For absolute
> limits such as cpu.max and memory.max, this means that the config at
> each level should only act as the upper limit at that level and
> shouldn't interfere with what other cgroups can configure.
> 
> This patch updates config validation on cgroup2 so that the cpu
> controller follows the same convention.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Fixes: 0d5936344f30 ("sched: Implement interface for cgroup unified hierarchy")

Peter, can you please take a look?  I can route it through cgroup tree
if that's preferable.

Thanks.

-- 
tejun