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From: Tejun Heo <tj@kernel.org>
To: Waiman Long <longman@redhat.com>
Cc: Zefan Li <lizefan.x@bytedance.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Jonathan Corbet <corbet@lwn.net>, Shuah Khan <shuah@kernel.org>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Roman Gushchin <guro@fb.com>, Phil Auld <pauld@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>
Subject: Re: [PATCH 1/5] cgroup/cpuset: Don't call validate_change() for some flag changes
Date: Wed, 16 Jun 2021 16:39:32 -0400	[thread overview]
Message-ID: <YMphhLAzmRRyD+cm@slm.duckdns.org> (raw)
In-Reply-To: <20210603212416.25934-2-longman@redhat.com>

Hello,

On Thu, Jun 03, 2021 at 05:24:12PM -0400, Waiman Long wrote:
> The update_flag() is called with one flag bit change and without change
> in the various cpumasks in the cpuset. Moreover, not all changes in the
> flag bits are validated in validate_change().  In particular, the load
> balance flag and the two spread flags are not checked there. So there
> is no point in calling validate_change() if those flag bits change.

The fact that it's escaping validation conditionally from caller side is
bothersome given that the idea is to have self-contained verifier to ensure
correctness. I'd prefer to make the validation more complete and optimized
(ie. detect or keep track of what changed) if really necessary rather than
escaping partially because certain conditions aren't checked.

Thanks.

-- 
tejun

  reply	other threads:[~2021-06-16 20:39 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-03 21:24 [PATCH 0/5] cgroup/cpuset: Enable cpuset partition with no load balancing Waiman Long
2021-06-03 21:24 ` [PATCH 1/5] cgroup/cpuset: Don't call validate_change() for some flag changes Waiman Long
2021-06-16 20:39   ` Tejun Heo [this message]
2021-06-17  2:53     ` Waiman Long
2021-06-03 21:24 ` [PATCH 2/5] cgroup/cpuset: Add new cpus.partition type with no load balancing Waiman Long
2021-06-10 18:50   ` Peter Zijlstra
2021-06-10 18:50     ` Peter Zijlstra
2021-06-10 19:16     ` Waiman Long
2021-06-10 19:39       ` Peter Zijlstra
2021-06-10 19:00   ` Peter Zijlstra
2021-06-10 19:00     ` Peter Zijlstra
2021-06-10 19:21     ` Waiman Long
2021-06-16 20:47   ` Tejun Heo
2021-06-17  2:57     ` Waiman Long
2021-06-17  2:57       ` Waiman Long
2021-06-03 21:24 ` [PATCH 3/5] cgroup/cpuset: Allow non-top parent partition root to distribute out all CPUs Waiman Long
2021-06-03 21:24   ` Waiman Long
2021-06-16 20:57   ` Tejun Heo
2021-06-16 20:57     ` Tejun Heo
2021-06-17 20:45     ` Waiman Long
2021-06-17 20:45       ` Waiman Long
2021-06-03 21:24 ` [PATCH 4/5] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Waiman Long
2021-06-03 21:24 ` [PATCH 5/5] kselftest/cgroup: Add cpuset v2 partition root state test Waiman Long
2021-06-10 14:19 ` [PATCH 0/5] cgroup/cpuset: Enable cpuset partition with no load balancing Phil Auld
2021-06-10 14:19   ` Phil Auld

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