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

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Date:   Tue, 30 Nov 2021 06:26:18 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Yu Kuai <yukuai3@...wei.com>
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()

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.

Thanks.

-- 
tejun