From: Max Reitz <mreitz@redhat.com>

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20180421132929.21610-5-mreitz@redhat.com
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/io.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/block/io.c b/block/io.c
index 9e8449e795..ca96b487eb 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1118,13 +1118,15 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
                 /* FIXME: Should we (perhaps conditionally) be setting
                  * BDRV_REQ_MAY_UNMAP, if it will allow for a sparser copy
                  * that still correctly reads as zero? */
-                ret = bdrv_co_do_pwrite_zeroes(bs, cluster_offset, pnum, 0);
+                ret = bdrv_co_do_pwrite_zeroes(bs, cluster_offset, pnum,
+                                               BDRV_REQ_WRITE_UNCHANGED);
             } else {
                 /* This does not change the data on the disk, it is not
                  * necessary to flush even in cache=writethrough mode.
                  */
                 ret = bdrv_driver_pwritev(bs, cluster_offset, pnum,
-                                          &local_qiov, 0);
+                                          &local_qiov,
+                                          BDRV_REQ_WRITE_UNCHANGED);
             }
 
             if (ret < 0) {
-- 
2.13.6