When invoking drive-mirror in absolute-paths mode, the target's backing BDS is assigned to it in mirror_complete(). The current logic only does so if the target does not have that backing BDS already; but it actually cannot have a backing BDS at all (the BDS is opened with O_NO_BACKING in qmp_drive_mirror()), so just assert that and assign the new backing BDS unconditionally.
Signed-off-by: Max Reitz <mre...@redhat.com> Reviewed-by: Alberto Garcia <be...@igalia.com> --- block/mirror.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index 301ba9219a..4ece624549 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -888,9 +888,9 @@ static void mirror_complete(BlockJob *job, Error **errp) if (s->backing_mode == MIRROR_SOURCE_BACKING_CHAIN) { BlockDriverState *backing = s->is_none_mode ? src : s->base; - if (backing_bs(target) != backing) { - bdrv_set_backing_hd(target, backing); - } + + assert(!target->backing); + bdrv_set_backing_hd(target, backing); } s->should_complete = true; -- 2.11.0