Commit 444fe04f authored by Ming Lei's avatar Ming Lei Committed by Mike Snitzer
Browse files

dm: improve BLK_STS_DM_REQUEUE and BLK_STS_AGAIN handling 



If either BLK_STS_DM_REQUEUE or BLK_STS_AGAIN is returned for POLLED
io, we requeue the original bio into deferred list and kick md->wq to
re-submit it to block layer.

Improve the handling in the following way:

1) Factor out dm_handle_requeue() for handling dm_io requeue.

2) Unify handling for BLK_STS_DM_REQUEUE and BLK_STS_AGAIN: clear
   REQ_POLLED for BLK_STS_DM_REQUEUE too, for the sake of simplicity,
   given BLK_STS_DM_REQUEUE is very unusual.

3) Queue md->wq explicitly in dm_handle_requeue(), so requeue handling
   becomes more robust.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent e810cb78

drivers/md/dm.c

+45 −25
Original line number Diff line number Diff line
@@ -880,22 +880,41 @@ static int __noflush_suspending(struct mapped_device *md) 
	return test_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);

}



static void dm_io_complete(struct dm_io *io)

/*

 * Return true if the dm_io's original bio is requeued.

 * io->status is updated with error if requeue disallowed.

 */

static bool dm_handle_requeue(struct dm_io *io)

{

	blk_status_t io_error;

	struct mapped_device *md = io->md;

	struct bio *bio = io->split_bio ? io->split_bio : io->orig_bio;

	bool handle_requeue = (io->status == BLK_STS_DM_REQUEUE);

	bool handle_polled_eagain = ((io->status == BLK_STS_AGAIN) &&

				     (bio->bi_opf & REQ_POLLED));

	struct mapped_device *md = io->md;

	bool requeued = false;



	if (io->status == BLK_STS_DM_REQUEUE) {

	if (handle_requeue || handle_polled_eagain) {

		unsigned long flags;



		if (bio->bi_opf & REQ_POLLED) {

			/*

		 * Target requested pushing back the I/O.

			 * Upper layer won't help us poll split bio

			 * (io->orig_bio may only reflect a subset of the

			 * pre-split original) so clear REQ_POLLED.

			 */

			bio_clear_polled(bio);

		}



		/*

		 * Target requested pushing back the I/O or

		 * polled IO hit BLK_STS_AGAIN.

		 */

		spin_lock_irqsave(&md->deferred_lock, flags);

		if (__noflush_suspending(md) &&

		    !WARN_ON_ONCE(dm_is_zone_write(md, bio))) {

			/* NOTE early return due to BLK_STS_DM_REQUEUE below */

		if ((__noflush_suspending(md) &&

		     !WARN_ON_ONCE(dm_is_zone_write(md, bio))) ||

		    handle_polled_eagain) {

			bio_list_add_head(&md->deferred, bio);

			requeued = true;

		} else {

			/*

			 * noflush suspend was interrupted or this is
@@ -906,6 +925,21 @@ static void dm_io_complete(struct dm_io *io) 
		spin_unlock_irqrestore(&md->deferred_lock, flags);

	}



	if (requeued)

		queue_work(md->wq, &md->work);



	return requeued;

}



static void dm_io_complete(struct dm_io *io)

{

	struct bio *bio = io->split_bio ? io->split_bio : io->orig_bio;

	struct mapped_device *md = io->md;

	blk_status_t io_error;

	bool requeued;



	requeued = dm_handle_requeue(io);



	io_error = io->status;

	if (dm_io_flagged(io, DM_IO_ACCOUNTED))

		dm_end_io_acct(io);
@@ -925,23 +959,9 @@ static void dm_io_complete(struct dm_io *io) 
	if (unlikely(wq_has_sleeper(&md->wait)))

		wake_up(&md->wait);



	if (io_error == BLK_STS_DM_REQUEUE || io_error == BLK_STS_AGAIN) {

		if (bio->bi_opf & REQ_POLLED) {

			/*

			 * Upper layer won't help us poll split bio (io->orig_bio

			 * may only reflect a subset of the pre-split original)

			 * so clear REQ_POLLED in case of requeue.

			 */

			bio_clear_polled(bio);

			if (io_error == BLK_STS_AGAIN) {

				/* io_uring doesn't handle BLK_STS_AGAIN (yet) */

				queue_io(md, bio);

	/* Return early if the original bio was requeued */

	if (requeued)

		return;

			}

		}

		if (io_error == BLK_STS_DM_REQUEUE)

			return;

	}



	if (bio_is_flush_with_data(bio)) {

		/*