improve test for qemu-img convert with backing file

Additionally to testing the qemu-img convert -B option, also test
-o backing_file.

Also, the old test acidentlly used a pattern of zeros for most of the writes,
so that the allocation test didn't really work out. This is fixed by using an
explicit pattern.

Signed-off-by: Kevin Wolf <>
Signed-off-by: Christoph Hellwig <>
1 file changed