From 4363ac7c13a9a4b763c6e8d9fdbfc2468f3b8ca4 Mon Sep 17 00:00:00 2001 From: "Martin K. Petersen" Date: Tue, 18 Sep 2012 12:19:27 -0400 Subject: 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 Acked-by: Mike Snitzer Signed-off-by: Jens Axboe --- fs/bio.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'fs/bio.c') 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; -- cgit v1.2.3-59-g8ed1b