linux-kernel - Re: [PATCH 6/6] blk-mq: remove REQ_ATOM

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Date:   Tue, 12 Dec 2017 09:26:29 -0800
From:   Tejun Heo <tj@...nel.org>
To:     "jianchao.wang" <jianchao.w.wang@...cle.com>
Cc:     axboe@...nel.dk, linux-kernel@...r.kernel.org, oleg@...hat.com,
        peterz@...radead.org, kernel-team@...com, osandov@...com
Subject: Re: [PATCH 6/6] blk-mq: remove REQ_ATOM_STARTED

Hello, again.

Sorry, I missed part of your comment in the previous reply.

On Tue, Dec 12, 2017 at 06:09:32PM +0800, jianchao.wang wrote:
> >  static void __blk_mq_requeue_request(struct request *rq)
> >  {
> > @@ -679,7 +672,7 @@ static void __blk_mq_requeue_request(struct request *rq)
> >  	wbt_requeue(q->rq_wb, &rq->issue_stat);
> >  	blk_mq_sched_requeue_request(rq);
> >  
> > -	if (test_and_clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags)) {
> > +	if (blk_mq_rq_state(rq) != MQ_RQ_IDLE) {
> >  		blk_mq_rq_update_state(rq, MQ_RQ_IDLE);
>
> The MQ_RQ_IDLE looks confused here. It is not freed , but idled.
> And when the requeued request is started again, the generation
> number will be increased.  But it is not a recycle instance of the
> request. Maybe another state needed here ?

I don't quite follow it.  At this point, the request can't be
in-flight on the device side and is scheduled for re-submission.  I'm
not sure the distinction from IDLE is necessary.  Am I missing
something?

Thanks.

-- 
tejun