dm: split write BIOs on zone boundaries when zone append is not emulated

Commit 2df7168 ("dm: Always split write BIOs to zoned device
limits") updates the device-mapper driver to perform splits for the
write BIOs. However, it did not address the cases where DM targets do
not emulate zone append, such as in the cases of dm-linear or dm-flakey.
For these targets, when the write BIOs span across zone boundaries, they
trigger WARN_ON_ONCE(bio_straddles_zones(bio)) in
blk_zone_wplug_handle_write(). This results in I/O errors. The errors
are reproduced by running blktests test case zbd/004 using zoned
dm-linear or dm-flakey devices.

To avoid the I/O errors, handle the write BIOs regardless whether DM
targets emulate zone append or not, so that all write BIOs are split at
zone boundaries. For that purpose, drop the check for zone append
emulation in dm_zone_bio_needs_split(). Its argument 'md' is no longer
used then drop it also.

Fixes: 2df7168 ("dm: Always split write BIOs to zoned device limits")
Signed-off-by: Shin'ichiro Kawasaki <[email protected]>
Reviewed-by: Damien Le Moal <[email protected]>
Reviewed-by: Mikulas Patocka <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: kawasaki

drivers/md/dm.c

@@ -1785,8 +1785,7 @@ static void init_clone_info(struct clone_info *ci, struct dm_io *io,
 }
 
 #ifdef CONFIG_BLK_DEV_ZONED
-static inline bool dm_zone_bio_needs_split(struct mapped_device *md,
-					   struct bio *bio)
+static inline bool dm_zone_bio_needs_split(struct bio *bio)
 {
 	/*
 	 * Special case the zone operations that cannot or should not be split.
@@ -1802,13 +1801,11 @@ static inline bool dm_zone_bio_needs_split(struct mapped_device *md,
 	}
 
 	/*
-	 * Mapped devices that require zone append emulation will use the block
-	 * layer zone write plugging. In such case, we must split any large BIO
-	 * to the mapped device limits to avoid potential deadlocks with queue
-	 * freeze operations.
+	 * When mapped devices use the block layer zone write plugging, we must
+	 * split any large BIO to the mapped device limits to not submit BIOs
+	 * that span zone boundaries and to avoid potential deadlocks with
+	 * queue freeze operations.
 	 */
-	if (!dm_emulate_zone_append(md))
-		return false;
 	return bio_needs_zone_write_plugging(bio) || bio_straddles_zones(bio);
 }
 
@@ -1932,8 +1929,7 @@ static blk_status_t __send_zone_reset_all(struct clone_info *ci)
 }
 
 #else
-static inline bool dm_zone_bio_needs_split(struct mapped_device *md,
-					   struct bio *bio)
+static inline bool dm_zone_bio_needs_split(struct bio *bio)
 {
 	return false;
 }
@@ -1960,7 +1956,7 @@ static void dm_split_and_process_bio(struct mapped_device *md,
 
 	is_abnormal = is_abnormal_io(bio);
 	if (static_branch_unlikely(&zoned_enabled)) {
-		need_split = is_abnormal || dm_zone_bio_needs_split(md, bio);
+		need_split = is_abnormal || dm_zone_bio_needs_split(bio);
 	} else {
 		need_split = is_abnormal;
 	}