7676e2c597
Now that active layer block-commit is supported, the 'top' argument no longer needs to be mandatory. Change it to optional, with the default being the active layer in the device chain. [kwolf: Rebased and resolved conflict in tests/qemu-iotests/040] Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Benoit Canet <benoit@irqsave.net> Signed-off-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>