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From: Niklas Cassel <Niklas.Cassel@wdc.com>
To: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc: Bart Van Assche <bvanassche@acm.org>,
	Jens Axboe <axboe@kernel.dk>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Jaegeuk Kim <jaegeuk@kernel.org>,
	Avri Altman <Avri.Altman@wdc.com>
Subject: Re: [PATCH 2/8] block: Introduce the blk_rq_is_seq_zone_write() function
Date: Tue, 10 Jan 2023 12:13:09 +0000	[thread overview]
Message-ID: <Y71WVAAVzYEyKedM@x1-carbon> (raw)
In-Reply-To: <278a9c42-bfa3-1602-622d-bdbbf72649a6@opensource.wdc.com>

On Tue, Jan 10, 2023 at 08:54:24PM +0900, Damien Le Moal wrote:
> On 1/10/23 18:52, Niklas Cassel wrote:
> > On Mon, Jan 09, 2023 at 03:52:23PM -0800, Bart Van Assche wrote:
> >> On 1/9/23 15:38, Damien Le Moal wrote:
> >>> On 1/10/23 08:27, Bart Van Assche wrote:
> >>>> +static inline bool blk_rq_is_seq_zone_write(struct request *rq)
> >>>> +{
> >>>> +	switch (req_op(rq)) {
> >>>> +	case REQ_OP_WRITE:
> >>>> +	case REQ_OP_WRITE_ZEROES:
> >>>
> >>> REQ_OP_ZONE_APPEND ?
> >>
> >> I will add REQ_OP_ZONE_APPEND.
> >>
> > 
> > Hello Bart, Damien,
> > 
> > +       if (blk_queue_pipeline_zoned_writes(rq->q) &&
> > +           blk_rq_is_seq_zone_write(rq))
> > +               cmd->allowed += rq->q->nr_requests;
> > 
> > Considering that this function, blk_rq_is_seq_zone_write(), only seems to
> > be used to determine if a request should be allowed to be retried, I think
> > that it is incorrect to add REQ_OP_ZONE_APPEND, since a zone append
> > operation will never result in a ILLEGAL REQUEST/UNALIGNED WRITE COMMAND.
> > 
> > (If this instead was a function that said which operations that needed to
> > be held back, then you would probably need to include REQ_OP_ZONE_APPEND,
> > as otherwise the reordered+retried write would never be able to succeed.)
> 
> Unless UFS defines a zone append operation, REQ_OP_ZONE_APPEND will be
> processed using regular writes in the sd driver.

Sure, but I still think that my point is valid.

A REQ_OP_ZONE_APPEND should never be able to result in a
"UNALIGNED WRITE COMMAND".

If the SCSI REQ_OP_ZONE_APPEND emulation can result in a
"UNALIGNED WRITE COMMAND", I would argue that the SCSI zone append
emulation is faulty.


Kind regards,
Niklas

  reply	other threads:[~2023-01-10 12:15 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-09 23:27 [PATCH 0/8] Enable zoned write pipelining for UFS devices Bart Van Assche
2023-01-09 23:27 ` [PATCH 1/8] block: Document blk_queue_zone_is_seq() and blk_rq_zone_is_seq() Bart Van Assche
2023-01-09 23:36   ` Damien Le Moal
2023-01-09 23:27 ` [PATCH 2/8] block: Introduce the blk_rq_is_seq_zone_write() function Bart Van Assche
2023-01-09 23:38   ` Damien Le Moal
2023-01-09 23:52     ` Bart Van Assche
2023-01-10  9:52       ` Niklas Cassel
2023-01-10 11:54         ` Damien Le Moal
2023-01-10 12:13           ` Niklas Cassel [this message]
2023-01-10 12:41             ` Damien Le Moal
2023-01-09 23:27 ` [PATCH 3/8] block: Introduce a request queue flag for pipelining zoned writes Bart Van Assche
2023-01-09 23:27 ` [PATCH 4/8] block/mq-deadline: Only use zone locking if necessary Bart Van Assche
2023-01-09 23:46   ` Damien Le Moal
2023-01-09 23:51     ` Bart Van Assche
2023-01-09 23:56       ` Damien Le Moal
2023-01-10  0:19         ` Bart Van Assche
2023-01-10  0:32           ` Damien Le Moal
2023-01-10  0:38             ` Jens Axboe
2023-01-10  0:41               ` Jens Axboe
2023-01-10  0:44                 ` Bart Van Assche
2023-01-10  0:48                   ` Jens Axboe
2023-01-10  0:56                     ` Bart Van Assche
2023-01-10  1:03                       ` Jens Axboe
2023-01-10  1:17                         ` Bart Van Assche
2023-01-10  1:48                           ` Jens Axboe
2023-01-10  2:24                     ` Damien Le Moal
2023-01-10  3:00                       ` Jens Axboe
2023-01-09 23:27 ` [PATCH 5/8] block/null_blk: Refactor null_queue_rq() Bart Van Assche
2023-01-09 23:27 ` [PATCH 6/8] block/null_blk: Add support for pipelining zoned writes Bart Van Assche
2023-01-09 23:27 ` [PATCH 7/8] scsi: Retry unaligned " Bart Van Assche
2023-01-09 23:51   ` Damien Le Moal
2023-01-09 23:55     ` Bart Van Assche
2023-01-09 23:27 ` [PATCH 8/8] scsi: ufs: Enable zoned write pipelining Bart Van Assche
2023-01-10  9:16   ` Avri Altman
2023-01-10 17:42     ` Bart Van Assche
2023-01-10 12:23   ` Bean Huo
2023-01-10 17:41     ` Bart Van Assche

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