SBC4 specifies that WRITE SAME requests with the UNMAP bit set to zero
"shall perform the specified write operation to each LBA specified by the
command".  Commit 2237498f ("target/iblock: Convert WRITE_SAME to
blkdev_issue_zeroout") modified the iblock backend to call
blkdev_issue_zeroout() when handling WRITE SAME requests with UNMAP=0 and a
zero data segment.

The iblock blkdev_issue_zeroout() call incorrectly provides a flags
parameter of 0 (bool false), instead of BLKDEV_ZERO_NOUNMAP.  The bool
false parameter reflects the blkdev_issue_zeroout() API prior to commit
ee472d83 ("block: add a flags argument to (__)blkdev_issue_zeroout")
which was merged shortly before 2237498f.

Link: https://lore.kernel.org/r/20200419163109.11689-1-ddiss@suse.de
Fixes: 2237498f ("target/iblock: Convert WRITE_SAME to blkdev_issue_zeroout")
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>