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-core.c b/block/blk-core.c
index 33eded0..3b08054 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1704,6 +1704,11 @@
goto end_io;
}
+ if (bio->bi_rw & REQ_WRITE_SAME && !bdev_write_same(bio->bi_bdev)) {
+ err = -EOPNOTSUPP;
+ goto end_io;
+ }
+
/*
* Various block parts want %current->io_context and lazy ioc
* allocation ends up trading a lot of pain for a small amount of
@@ -1809,8 +1814,6 @@
*/
void submit_bio(int rw, struct bio *bio)
{
- int count = bio_sectors(bio);
-
bio->bi_rw |= rw;
/*
@@ -1818,6 +1821,13 @@
* go through the normal accounting stuff before submission.
*/
if (bio_has_data(bio)) {
+ unsigned int count;
+
+ if (unlikely(rw & REQ_WRITE_SAME))
+ count = bdev_logical_block_size(bio->bi_bdev) >> 9;
+ else
+ count = bio_sectors(bio);
+
if (rw & WRITE) {
count_vm_events(PGPGOUT, count);
} else {