When invoking drive-mirror in absolute-paths mode, the target's backing BDS is assigned to it in mirror_exit(). 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> --- block/mirror.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index 4618853..db57bee 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -529,12 +529,12 @@ static void mirror_exit(BlockJob *job, void *opaque) &error_abort); if (s->backing_mode == MIRROR_SOURCE_BACKING_CHAIN) { BlockDriverState *backing = s->is_none_mode ? src : s->base; - if (backing_bs(target_bs) != backing) { - bdrv_set_backing_hd(target_bs, backing, &local_err); - if (local_err) { - error_report_err(local_err); - data->ret = -EPERM; - } + + assert(!target_bs->backing); + bdrv_set_backing_hd(target_bs, backing, &local_err); + if (local_err) { + error_report_err(local_err); + data->ret = -EPERM; } } -- 2.9.4