dm: Forbid requeue of writes to zones

A target map method requesting the requeue of a bio with
DM_MAPIO_REQUEUE or completing it with DM_ENDIO_REQUEUE can cause
unaligned write errors if the bio is a write operation targeting a
sequential zone. If a zoned target request such a requeue, warn about
it and kill the IO.

The function dm_is_zone_write() is introduced to detect write operations
to zoned targets.

This change does not affect the target drivers supporting zoned devices
and exposing a zoned device, namely dm-crypt, dm-linear and dm-flakey as
none of these targets ever request a requeue.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 19 insertions, 6 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c49976cc4e44..6134a97f9016 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -841,22 +841,27 @@ static void dec_pending(struct dm_io *io, blk_status_t error)
 	}
 
 	if (atomic_dec_and_test(&io->io_count)) {
+		bio = io->orig_bio;
 		if (io->status == BLK_STS_DM_REQUEUE) {
 			/*
 			 * Target requested pushing back the I/O.
 			 */
 			spin_lock_irqsave(&md->deferred_lock, flags);
-			if (__noflush_suspending(md))
+			if (__noflush_suspending(md) &&
+			    !WARN_ON_ONCE(dm_is_zone_write(md, bio))) {
 				/* NOTE early return due to BLK_STS_DM_REQUEUE below */
-				bio_list_add_head(&md->deferred, io->orig_bio);
-			else
-				/* noflush suspend was interrupted. */
+				bio_list_add_head(&md->deferred, bio);
+			} else {
+				/*
+				 * noflush suspend was interrupted or this is
+				 * a write to a zoned target.
+				 */
 				io->status = BLK_STS_IOERR;
+			}
 			spin_unlock_irqrestore(&md->deferred_lock, flags);
 		}
 
 		io_error = io->status;
-		bio = io->orig_bio;
 		end_io_acct(io);
 		free_io(md, io);
 
@@ -947,7 +952,15 @@ static void clone_endio(struct bio *bio)
 		int r = endio(tio->ti, bio, &error);
 		switch (r) {
 		case DM_ENDIO_REQUEUE:
-			error = BLK_STS_DM_REQUEUE;
+			/*
+			 * Requeuing writes to a sequential zone of a zoned
+			 * target will break the sequential write pattern:
+			 * fail such IO.
+			 */
+			if (WARN_ON_ONCE(dm_is_zone_write(md, bio)))
+				error = BLK_STS_IOERR;
+			else
+				error = BLK_STS_DM_REQUEUE;
 			fallthrough;
 		case DM_ENDIO_DONE:
 			break;