linux-kernel - Re: [PATCH 5/8] blk-mq: make blk_abort

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Date:   Mon, 8 Jan 2018 22:10:01 +0000
From:   Bart Van Assche <Bart.VanAssche@....com>
To:     "jbacik@...com" <jbacik@...com>, "tj@...nel.org" <tj@...nel.org>,
        "jack@...e.cz" <jack@...e.cz>, "clm@...com" <clm@...com>,
        "axboe@...nel.dk" <axboe@...nel.dk>
CC:     "hoeppner@...ux.vnet.ibm.com" <hoeppner@...ux.vnet.ibm.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "sth@...ux.vnet.ibm.com" <sth@...ux.vnet.ibm.com>,
        "kernel-team@...com" <kernel-team@...com>,
        "asamymuthupa@...ron.com" <asamymuthupa@...ron.com>,
        "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
        "jianchao.w.wang@...cle.com" <jianchao.w.wang@...cle.com>
Subject: Re: [PATCH 5/8] blk-mq: make blk_abort_request() trigger timeout path

On Mon, 2018-01-08 at 11:15 -0800, Tejun Heo wrote:
> @@ -156,12 +156,12 @@ void blk_timeout_work(struct work_struct *work)
>   */
>  void blk_abort_request(struct request *req)
>  {
> -	if (blk_mark_rq_complete(req))
> -		return;
> -
>  	if (req->q->mq_ops) {
> -		blk_mq_rq_timed_out(req, false);
> +		req->deadline = jiffies;
> +		mod_timer(&req->q->timeout, 0);
>  	} else {
> +		if (blk_mark_rq_complete(req))
> +			return;
>  		blk_delete_timer(req);
>  		blk_rq_timed_out(req);
>  	}

Other req->deadline writes are protected by preempt_disable(),
write_seqcount_begin(&rq->gstate_seq), write_seqcount_end(&rq->gstate_seq)
and preempt_enable(). I think it's fine that the above req->deadline store
does not have that protection but I also think that that deserves a comment.

Thanks,

Bart.