dm-devel.redhat.com archive mirror
 help / color / mirror / Atom feed
From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Mike Snitzer <snitzer@redhat.com>,
	linux-block@vger.kernel.org, dm-devel@redhat.com,
	Jeffle Xu <jefflexu@linux.alibaba.com>
Subject: Re: [dm-devel] [RFC PATCH V2 2/3] block: add ->poll_bio to block_device_operations
Date: Mon, 21 Jun 2021 16:41:33 +0800	[thread overview]
Message-ID: <YNBQvSR3glgt59J9@T590> (raw)
In-Reply-To: <20210621072502.GC6651@lst.de>

On Mon, Jun 21, 2021 at 09:25:02AM +0200, Christoph Hellwig wrote:
> > +	struct gendisk *disk = bio->bi_bdev->bd_disk;
> > +	struct request_queue *q = disk->queue;
> >  	blk_qc_t cookie = READ_ONCE(bio->bi_cookie);
> >  	int ret;
> >  
> > -	if (cookie == BLK_QC_T_NONE || !blk_queue_poll(q))
> > +	if ((queue_is_mq(q) && cookie == BLK_QC_T_NONE) ||
> > +			!blk_queue_poll(q))
> >  		return 0;
> 
> How does polling for a bio without a cookie make sense even when
> polling bio based?

It isn't necessary to use bio->bi_cookie, that is why I doesn't use it,
which actually provides one free 32bit in bio for bio based driver.

> 
> But if we come up for a good rationale for this I'd really
> split the conditions to make them more readable:
> 
> 	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
> 		return 0;
> 	if (queue_is_mq(q) && cookie == BLK_QC_T_NONE)
> 		return 0;

OK.

> 
> > +	if (!queue_is_mq(q)) {
> > +		if (disk->fops->poll_bio) {
> > +			ret = disk->fops->poll_bio(bio, flags);
> > +		} else {
> > +			WARN_ON_ONCE(1);
> > +			ret = 0;
> > +		}
> > +	} else {
> >  		ret = blk_mq_poll(q, cookie, flags);
> 
> I'd go for someting like:
> 
> 	if (queue_is_mq(q))
> 		ret = blk_mq_poll(q, cookie, flags);
> 	else if (disk->fops->poll_bio)
> 		ret = disk->fops->poll_bio(bio, flags);
> 	else
> 		WARN_ON_ONCE(1);
> 
> with ret initialized to 0 at declaration time.

Fine.

> 
> >  struct block_device_operations {
> >  	void (*submit_bio)(struct bio *bio);
> > +	/* ->poll_bio is for bio driver only */
> 
> I'd drop the comment, this is already nicely documented in add_disk
> together with the actual check.  We also don't note this for submit_bio
> here.

OK.



thanks,
Ming

--
dm-devel mailing list
dm-devel@redhat.com
https://listman.redhat.com/mailman/listinfo/dm-devel


  reply	other threads:[~2021-06-21  8:42 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-17 10:35 [dm-devel] [RFC PATCH V2 0/3] block/dm: support bio polling Ming Lei
2021-06-17 10:35 ` [dm-devel] [RFC PATCH V2 1/3] block: add helper of blk_queue_poll Ming Lei
2021-06-21  7:20   ` Christoph Hellwig
2021-06-21  8:38     ` Ming Lei
2021-06-17 10:35 ` [dm-devel] [RFC PATCH V2 2/3] block: add ->poll_bio to block_device_operations Ming Lei
2021-06-21  7:25   ` Christoph Hellwig
2021-06-21  8:41     ` Ming Lei [this message]
2021-06-17 10:35 ` [dm-devel] [RFC PATCH V2 3/3] dm: support bio polling Ming Lei
2021-06-17 23:08   ` Ming Lei
2021-06-18  8:19   ` JeffleXu
2021-06-18 13:29     ` Ming Lei
2021-06-18 14:39     ` Ming Lei
2021-06-18 20:56       ` Mike Snitzer
2021-06-19  0:27         ` Ming Lei
2021-06-21  1:32         ` JeffleXu
2021-06-21 11:33       ` JeffleXu
2021-06-21 14:04         ` Ming Lei
2021-06-22  2:26           ` JeffleXu
2021-06-22  2:45             ` Ming Lei
2021-06-22  7:45               ` JeffleXu
2021-06-30  8:30         ` Ming Lei
2021-06-21  7:36   ` Christoph Hellwig
2021-06-21  9:09     ` Ming Lei

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YNBQvSR3glgt59J9@T590 \
    --to=ming.lei@redhat.com \
    --cc=axboe@kernel.dk \
    --cc=dm-devel@redhat.com \
    --cc=hch@lst.de \
    --cc=jefflexu@linux.alibaba.com \
    --cc=linux-block@vger.kernel.org \
    --cc=snitzer@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).