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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 /fs/bio.c
parentf31dc1cd490539e2b62a126bc4dc2495b165d772 (diff)
downloadlwn-4363ac7c13a9a4b763c6e8d9fdbfc2468f3b8ca4.tar.gz
lwn-4363ac7c13a9a4b763c6e8d9fdbfc2468f3b8ca4.zip
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 'fs/bio.c')
-rw-r--r--fs/bio.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/fs/bio.c b/fs/bio.c
index 13e956779e10..f855e0e1869c 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1487,9 +1487,12 @@ struct bio_pair *bio_split(struct bio *bi, int first_sectors)
bp->bv1 = bi->bi_io_vec[0];
bp->bv2 = bi->bi_io_vec[0];
- bp->bv2.bv_offset += first_sectors << 9;
- bp->bv2.bv_len -= first_sectors << 9;
- bp->bv1.bv_len = first_sectors << 9;
+
+ if (bio_is_rw(bi)) {
+ bp->bv2.bv_offset += first_sectors << 9;
+ bp->bv2.bv_len -= first_sectors << 9;
+ bp->bv1.bv_len = first_sectors << 9;
+ }
bp->bio1.bi_io_vec = &bp->bv1;
bp->bio2.bi_io_vec = &bp->bv2;