block: Implement support for WRITE SAME

The WRITE SAME command supported on some SCSI devices allows the same
block to be efficiently replicated throughout a block range. Only a
single logical block is transferred from the host and the storage device
writes the same data to all blocks described by the I/O.

This patch implements support for WRITE SAME in the block layer. The
blkdev_issue_write_same() function can be used by filesystems and block
drivers to replicate a buffer across a block range. This can be used to
efficiently initialize software RAID devices, etc.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/bio.h b/include/linux/bio.h
index e54305cacc98..820e7aaad4fd 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -399,6 +399,9 @@ static inline bool bio_is_rw(struct bio *bio)
         if (!bio_has_data(bio))
                 return false;
 
+        if (bio->bi_rw & REQ_WRITE_SAME)
+                return false;
+
         return true;
 }