[Qemu-devel] [PATCH V4 4/4] Change default to qcow2 for sync mode none.

[Ian Main <imain@redhat.com>]

qcow2 supports backing files so it makes sense to default to qcow2
for MIRROR_SYNC_MODE_NONE so that we can use the source as a backing
drive and export it via nbd.  Defaulting FULL and TOP to SYNC_MODE_NONE
breaks tests but that could be fixed if we wanted it.

Signed-off-by: Ian Main <imain@redhat.com>
---
 blockdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index 000dea6..805b0e5 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1462,7 +1462,7 @@ void qmp_drive_backup(const char *device, const char *target,
     }
 
     if (!has_format) {
-        format = mode == NEW_IMAGE_MODE_EXISTING ? NULL : bs->drv->format_name;
+        format = mode == NEW_IMAGE_MODE_EXISTING ? NULL : "qcow2";
     }
     if (format) {
         drv = bdrv_find_format(format);
-- 
1.8.1.4