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dm kcopyd: add WRITE SAME support to dm_kcopyd_zero

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Add WRITE SAME support to dm-io and make it accessible to
dm_kcopyd_zero().  dm_kcopyd_zero() provides an asynchronous interface
whereas the blkdev_issue_write_same() interface is synchronous.

WRITE SAME is a SCSI command that can be leveraged for more efficient
zeroing of a specified logical extent of a device which supports it.
Only a single zeroed logical block is transfered to the target for each
WRITE SAME and the target then writes that same block across the
specified extent.

The dm thin target uses this.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mike Snitzer
2012-12-21 20:23:37 +00:00
committed by Alasdair G Kergon
parent 4f0b70b047
commit 70d6c400ac
3 changed files with 33 additions and 10 deletions
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drivers/md/dm-thin.c
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@@ -2779,7 +2779,7 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)
static struct target_type thin_target = {
.name = "thin",
.version = {1, 5, 0},
.version = {1, 6, 0},
.module = THIS_MODULE,
.ctr = thin_ctr,
.dtr = thin_dtr,