With the new approach we are actually able to correctly detect node
names for the two instances of the same backing file.
Test images were created as:
qemu-img create -f qcow2 /var/lib/libvirt/images/base.qcow2 10M
qemu-img create -f qcow2 \
-o "backing_fmt=qcow2,backing_file=/var/lib/libvirt/images/base.qcow2 \
/var/lib/libvirt/images/a.qcow2
qemu-img create -f qcow2 \
-o "backing_fmt=qcow2,backing_file=/var/lib/libvirt/images/base.qcow2 \
/var/lib/libvirt/images/b.qcow2
and then used for two separate disks.
Reviewed-by: Eric Blake <eblake@redhat.com>