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From: Tejun Heo <tj@kernel.org>
To: Yu Kuai <yukuai1@huaweicloud.com>
Cc: hch@infradead.org, josef@toxicpanda.com, axboe@kernel.dk,
	cgroups@vger.kernel.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, yukuai3@huawei.com,
	yi.zhang@huawei.com
Subject: Re: [PATCH -next 2/4] blk-iocost: don't throttle bio if iocg is offlined
Date: Mon, 19 Dec 2022 11:28:48 -1000	[thread overview]
Message-ID: <Y6DXkLeOmu7VWovz@slm.duckdns.org> (raw)
In-Reply-To: <20221217030527.1250083-3-yukuai1@huaweicloud.com>

On Sat, Dec 17, 2022 at 11:05:25AM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> bio will grab blkg reference, however, blkcg->online_pin is not grabbed,
> hence cgroup can be removed after thread exit while bio is still in
> progress. Bypass io in this case since it doesn't make sense to
> throttle bio while cgroup is removed.

I don't get it. Why wouldn't that make sense? ISTR some occasions where we
clear the config to mitigate exits stalling for too long but in general a
policy being active on a draining cgroup shouldn't be a problem.

Thanks.

-- 
tejun

  reply	other threads:[~2022-12-19 21:29 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-17  3:05 [PATCH -next 0/4] blk-iocost: make sure parent iocg is exited before child Yu Kuai
2022-12-17  3:05 ` Yu Kuai
2022-12-17  3:05 ` [PATCH -next 1/4] blk-iocost: track whether iocg is still online Yu Kuai
2022-12-17  3:05   ` Yu Kuai
2022-12-21 10:33   ` Christoph Hellwig
2022-12-26  1:10     ` Yu Kuai
2022-12-26  1:10       ` Yu Kuai
2022-12-17  3:05 ` [PATCH -next 2/4] blk-iocost: don't throttle bio if iocg is offlined Yu Kuai
2022-12-19 21:28   ` Tejun Heo [this message]
2022-12-20  9:38     ` Yu Kuai
2022-12-20  9:38       ` Yu Kuai
2022-12-17  3:05 ` [PATCH -next 3/4] blk-iocost: dispatch all throttled bio in ioc_pd_offline Yu Kuai
2022-12-19 21:31   ` Tejun Heo
2022-12-19 21:31     ` Tejun Heo
2022-12-17  3:05 ` [PATCH -next 4/4] blk-iocost: guarantee the exit order of iocg Yu Kuai

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