block: Block layer data integrity support

Some block devices support verifying the integrity of requests by way
of checksums or other protection information that is submitted along
with the I/O.

This patch implements support for generating and verifying integrity
metadata, as well as correctly merging, splitting and cloning bios and
requests that have this extra information attached.

See Documentation/block/data-integrity.txt for more information.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 902dd1344d56..1f5bfe696026 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -86,6 +86,12 @@ int elv_rq_merge_ok(struct request *rq, struct bio *bio)
         if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
                 return 0;
 
+        /*
+         * only merge integrity protected bio into ditto rq
+         */
+        if (bio_integrity(bio) != blk_integrity_rq(rq))
+                return 0;
+
         if (!elv_iosched_allow_merge(rq, bio))
                 return 0;