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>

diff --git a/drivers/md/dm-zone.c b/drivers/md/dm-zone.c
index b424740..edc3bbb 100644 (file)
--- a/drivers/md/dm-zone.c
+++ b/drivers/md/dm-zone.c
@@ -104,6 +104,23 @@ int dm_report_zones(struct block_device *bdev, sector_t start, sector_t sector,
 }
 EXPORT_SYMBOL_GPL(dm_report_zones);
 
+bool dm_is_zone_write(struct mapped_device *md, struct bio *bio)
+{
+       struct request_queue *q = md->queue;
+
+       if (!blk_queue_is_zoned(q))
+               return false;
+
+       switch (bio_op(bio)) {
+       case REQ_OP_WRITE_ZEROES:
+       case REQ_OP_WRITE_SAME:
+       case REQ_OP_WRITE:
+               return !op_is_flush(bio->bi_opf) && bio_sectors(bio);
+       default:
+               return false;
+       }
+}
+
 void dm_set_zones_restrictions(struct dm_table *t, struct request_queue *q)
 {
        if (!blk_queue_is_zoned(q))

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c49976c..6134a97 100644 (file)
--- 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;

diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index fdf1536..39c2432 100644 (file)
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -107,8 +107,13 @@ void dm_set_zones_restrictions(struct dm_table *t, struct request_queue *q);
 #ifdef CONFIG_BLK_DEV_ZONED
 int dm_blk_report_zones(struct gendisk *disk, sector_t sector,
                        unsigned int nr_zones, report_zones_cb cb, void *data);
+bool dm_is_zone_write(struct mapped_device *md, struct bio *bio);
 #else
 #define dm_blk_report_zones    NULL
+static inline bool dm_is_zone_write(struct mapped_device *md, struct bio *bio)
+{
+       return false;
+}
 #endif
 
 /*-----------------------------------------------------------------