Comment 2 for bug 2002535

I think it's even more broken than I thought.

Actually, when I create a volume from an image with or without image volume cache enabled, the file format ends up as raw.

After the volume below has been created on the nfs backend:
stack@e2e-os-pstorenfs105:~$ qemu-img info volume-ba7960d9-d169-4b27-90a1-9b7aa1dc3452
image: volume-ba7960d9-d169-4b27-90a1-9b7aa1dc3452
file format: raw
virtual size: 1 GiB (1073741824 bytes)
disk size: 16.4 MiB

as we can see in the log from cinder:
DEBUG oslo_concurrency.processutils [None req-a0ba2364-c743-405c-a698-3ca6b6248e54 admin None] CMD "sudo cinder-rootwrap /etc/cinder/rootwrap.conf qemu-img convert -O raw -f qcow2 /opt/stack/data/cinder/conversion/image_fetch_a087ca5c-af22-4e80-a126-649ac96212bd_iqnhlpm6e2e-os-pstorenfs105@powerstorenfs1 /opt/stack/data/cinder/mnt/0f31b785b44925eea1ad3ce3b8eff927/volume-ba7960d9-d169-4b27-90a1-9b7aa1dc3452" returned: 0 in 0.530s {{(pid=1840449) execute /usr/local/lib/python3.8/dist-packages/oslo_concurrency/processutils.py:422}}