Splitting a bio into an empty flush bio and a non-flush data bio is
only necessary if there are multiple underlying devices. Do not split
REQ_PREFLUSH bios if there is only one underlying device. This patch
preserves the order of REQ_PREFLUSH writes if there is only one
underlying device and if multiple writes are queued. This patch fixes
a write error observed with zoned storage devices and with write
pipelining enabled.
Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: Damien Le Moal <dlemoal@xxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
drivers/md/dm.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 66dd5f6ce778..d0791eef21f7 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -490,9 +490,13 @@ u64 dm_start_time_ns_from_clone(struct bio *bio)
}
EXPORT_SYMBOL_GPL(dm_start_time_ns_from_clone);
-static inline bool bio_is_flush_with_data(struct bio *bio)
+static inline bool bio_is_flush_with_data(struct mapped_device *md,
+ struct bio *bio)
{
- return ((bio->bi_opf & REQ_PREFLUSH) && bio->bi_iter.bi_size);
+ guard(rcu)();
+
+ return bio->bi_opf & REQ_PREFLUSH && bio->bi_iter.bi_size &&
+ ((struct dm_table *)rcu_dereference(md->map))->num_targets > 1;
}
static inline unsigned int dm_io_sectors(struct dm_io *io, struct bio *bio)
@@ -501,7 +505,7 @@ static inline unsigned int dm_io_sectors(struct dm_io *io, struct bio *bio)
* If REQ_PREFLUSH set, don't account payload, it will be
* submitted (and accounted) after this flush completes.
*/
- if (bio_is_flush_with_data(bio))
+ if (bio_is_flush_with_data(io->md, bio))
return 0;
if (unlikely(dm_io_flagged(io, DM_IO_WAS_SPLIT)))
return io->sectors;
@@ -976,7 +980,7 @@ static void __dm_io_complete(struct dm_io *io, bool first_stage)
if (requeued)
return;
- if (bio_is_flush_with_data(bio)) {
+ if (bio_is_flush_with_data(md, bio)) {
/*
* Preflush done for flush with data, reissue
* without REQ_PREFLUSH.
@@ -1715,7 +1719,7 @@ static void dm_queue_poll_io(struct bio *bio, struct dm_io *io)
}
/*
- * Select the correct strategy for processing a non-flush bio.
+ * Select the correct strategy for processing a bio.
*/
static blk_status_t __split_and_process_bio(struct clone_info *ci)
{
@@ -1996,7 +2000,7 @@ static void dm_split_and_process_bio(struct mapped_device *md,
}
init_clone_info(&ci, io, map, bio, is_abnormal);
- if (bio->bi_opf & REQ_PREFLUSH) {
+ if (bio->bi_opf & REQ_PREFLUSH && ci.map->num_targets > 1) {
__send_empty_flush(&ci);
/* dm_io_complete submits any data associated with flush */
goto out;
