linux-kernel - Re: [PATCH v2 2/2] block: cancel all throttled bios in del

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Date:   Wed, 1 Dec 2021 17:26:17 +0800
From:   "yukuai (C)" <yukuai3@...wei.com>
To:     Tejun Heo <tj@...nel.org>
CC:     <hch@...radead.org>, <axboe@...nel.dk>, <cgroups@...r.kernel.org>,
        <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <yi.zhang@...wei.com>
Subject: Re: [PATCH v2 2/2] block: cancel all throttled bios in del_gendisk()

在 2021/12/01 0:26, Tejun Heo 写道:
> Hello,
> 
> On Tue, Nov 30, 2021 at 09:17:30AM +0800, Yu Kuai wrote:
>> +void blk_throtl_cancel_bios(struct request_queue *q)
>> +{
>> +	struct throtl_data *td = q->td;
>> +	struct blkcg_gq *blkg;
>> +	struct cgroup_subsys_state *pos_css;
>> +	struct bio *bio;
>> +	int rw;
>> +
>> +	rcu_read_lock();
> 
> So, all of the draining is being performed without holding the q lock, which
> *might* be okay given that we're in the del_gendisk path but is likely risky
> - ie. there can still be timers or whatever racing against it.

I'll hold queue_lock to draining bios in next iteration,

Thanks,
Kuai
> 
> Thanks.
>