tree 6ab32a9b9699656c8d9147b38a776f615c1c737a
parent 4f0b70b0479101522b8645ddc1f5ee7137821db3
author Mike Snitzer <snitzer@redhat.com> 1356121417 +0000
committer Alasdair G Kergon <agk@redhat.com> 1356121417 +0000

dm kcopyd: add WRITE SAME support to dm_kcopyd_zero

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>