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Sender: Tejun Heo <htejun@gmail.com>
Date:   Mon, 19 Dec 2022 11:28:48 -1000
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
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References: <20221217030527.1250083-1-yukuai1@huaweicloud.com>
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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