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>
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 642b862..936a110 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -419,6 +419,10 @@
|| next->special)
return 0;
+ if (req->cmd_flags & REQ_WRITE_SAME &&
+ !blk_write_same_mergeable(req->bio, next->bio))
+ return 0;
+
/*
* If we are allowed to merge, then append bio list
* from next to rq and release next. merge_requests_fn
@@ -518,6 +522,11 @@
if (bio_integrity(bio) != blk_integrity_rq(rq))
return false;
+ /* must be using the same buffer */
+ if (rq->cmd_flags & REQ_WRITE_SAME &&
+ !blk_write_same_mergeable(rq->bio, bio))
+ return false;
+
return true;
}