From: Keith Busch <keith.busch@intel.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Ming Lei <ming.lei@redhat.com>,
linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
Martin Petersen <martin.petersen@oracle.com>,
Bart Van Assche <bvanassche@acm.org>
Subject: Re: [PATCHv4 0/3] scsi timeout handling updates
Date: Thu, 29 Nov 2018 10:20:34 -0700 [thread overview]
Message-ID: <20181129172034.GD8332@localhost.localdomain> (raw)
In-Reply-To: <20181129171159.GA28238@lst.de>
On Thu, Nov 29, 2018 at 06:11:59PM +0100, Christoph Hellwig wrote:
> > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > index a82830f39933..d0ef540711c7 100644
> > --- a/block/blk-mq.c
> > +++ b/block/blk-mq.c
> > @@ -647,7 +647,7 @@ EXPORT_SYMBOL(blk_mq_complete_request);
> >
> > int blk_mq_request_started(struct request *rq)
> > {
> > - return blk_mq_rq_state(rq) != MQ_RQ_IDLE;
> > + return blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT;
> > }
> > EXPORT_SYMBOL_GPL(blk_mq_request_started);
>
> Independ of this series this change looks like the right thing to do.
> But this whole area is a mine field, so separate testing would be
> very helpful.
>
> I also wonder why we even bother with the above helper, a direct
> state comparism seems a lot more obvious to the reader.
I think it's just because blk_mq_rq_state() is a private interface. The
enum mq_rq_state is defined under include/linux/, so it looks okay to
make getting the state public too.
> Last but not least the blk_mq_request_started check in nbd
> should probably be lifted into blk_mq_tag_to_rq while we're at it..
>
> As for the nvme issue - it seems to me like we need to decouple the
> nvme loop frontend request from the target backend request. In case
> of a timeout/reset we'll complete struct request like all other nvme
> transport drivers, but we leave the backend target state around, which
> will be freed when it completes (or leaks when the completion is lost).
I don't think nvme's loop target should do anything to help a command
complete. It shouldn't even implement a timeout for the same reason
no stacking block driver implements these. If a request is stuck, the
lowest level is the only driver that should have the responsibility to
make it unstuck.
next prev parent reply other threads:[~2018-11-29 17:23 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-26 16:54 [PATCHv4 0/3] scsi timeout handling updates Keith Busch
2018-11-26 16:54 ` [PATCHv4 1/3] blk-mq: Return true if request was completed Keith Busch
2018-11-26 17:00 ` Christoph Hellwig
2018-11-26 16:54 ` [PATCHv4 2/3] scsi: Do not rely on blk-mq for double completions Keith Busch
2018-11-26 17:01 ` Christoph Hellwig
2018-11-26 16:54 ` [PATCHv4 3/3] blk-mq: Simplify request completion state Keith Busch
2018-11-26 17:01 ` Christoph Hellwig
2018-11-26 17:33 ` [PATCHv4 0/3] scsi timeout handling updates Jens Axboe
2018-11-28 2:20 ` Ming Lei
2018-11-28 7:00 ` Christoph Hellwig
2018-11-28 10:07 ` Ming Lei
2018-11-28 10:08 ` Christoph Hellwig
2018-11-28 15:49 ` Keith Busch
2018-11-28 15:58 ` Jens Axboe
2018-11-28 16:26 ` Keith Busch
2018-11-28 16:31 ` Jens Axboe
2018-11-28 17:56 ` Keith Busch
2018-11-29 1:18 ` Ming Lei
2018-11-28 22:31 ` Keith Busch
2018-11-28 23:36 ` Keith Busch
2018-11-29 17:11 ` Christoph Hellwig
2018-11-29 17:20 ` Keith Busch [this message]
2018-12-28 12:47 ` Hannes Reinecke
2018-11-29 2:15 ` Ming Lei
2018-11-29 2:39 ` Martin K. Petersen
2018-11-29 8:12 ` Ming Lei
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