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 <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index db026b6..e5cf12f 100644 (file)
--- 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
 };