block: introduce BIO_ZONE_WRITE_LOCKED bio flag

Introduce the BIO flag BIO_ZONE_WRITE_LOCKED to indicate that a BIO owns
the write lock of the zone it is targeting. This is the counterpart of
the struct request flag RQF_ZONE_WRITE_LOCKED.

This new BIO flag is reserved for now for zone write locking control
for device mapper targets exposing a zoned block device. Since in this
case, the lock flag must not be propagated to the struct request that
will be used to process the BIO, a BIO private flag is used rather than
changing the RQF_ZONE_WRITE_LOCKED request flag into a common REQ_XXX
flag that could be used for both BIO and request. This avoids conflicts
down the stack with the block IO scheduler zone write locking
(in mq-deadline).

Signed-off-by: Damien Le Moal <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Chaitanya Kulkarni <[email protected]>
Reviewed-by: Himanshu Madhani <[email protected]>
Acked-by: Jens Axboe <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index db026b6ec15a..e5cf12f102a2 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -304,6 +304,7 @@ enum {
 	BIO_CGROUP_ACCT,	/* has been accounted to a cgroup */
 	BIO_TRACKED,		/* set if bio goes through the rq_qos path */
 	BIO_REMAPPED,
+	BIO_ZONE_WRITE_LOCKED,	/* Owns a zoned device zone write lock */
 	BIO_FLAG_LAST
 };