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authorMartin K. Petersen <martin.petersen@oracle.com>2012-09-18 12:19:27 -0400
committerJens Axboe <axboe@kernel.dk>2012-09-20 14:31:45 +0200
commit4363ac7c13a9a4b763c6e8d9fdbfc2468f3b8ca4 (patch)
tree010b05699eb9544b9cdfe5e1b3affdaea80132e7 /block/blk-merge.c
parentf31dc1cd490539e2b62a126bc4dc2495b165d772 (diff)
downloadlinux-linaro-stable-4363ac7c13a9a4b763c6e8d9fdbfc2468f3b8ca4.tar.gz
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>
Diffstat (limited to 'block/blk-merge.c')
-rw-r--r--block/blk-merge.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 642b862608a1..936a110de0b9 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -419,6 +419,10 @@ static int attempt_merge(struct request_queue *q, struct request *req,
|| 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 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
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;
}