invocations. You can only fully override the backing file options
if you either specify a node reference (as done here) or the new
options contain file.filename (which in this case they do not).
In other cases, file.filename will be set to whatever the image
header of the overlay contains (which we do not want). I consider
this a FIXME because with -blockdev, you cannot specify "partial"
options, so setting file.filename but leaving the rest as specified
by the user does not make sense.
invocations. You can only fully override the backing file options if you either specify a node reference (as done here) or the new options contain file.filename (which in this case they do not). In other cases, file.filename will be set to whatever the image header of the overlay contains (which we do not want). I consider this a FIXME because with -blockdev, you cannot specify "partial" options, so setting file.filename but leaving the rest as specified by the user does not make sense.
Line: 111 https://github.com/hack-different/qemu-xnu/blob/125df44362c69051a518c1dee949e09ecea85998//tests/qemu-iotests/225#L108-L118