A recent change [1] introduced the allow_qcow2_backing_file flag (besides other things) for image_utils.qemu_img_info(). This can be set in e.g. the remotefs class based drivers that use qcow2 backing files.

However this flag cannot be passed into other image_utils methods that internally use the qemu_img_info() method, e.g. image_utils.convert_image()[2].
That method calls image_utils.qemu_img_info() via image_utils.check_image_format()[3].

If following this trace there's no way to pass the allow_qcow2_backing_file flag into the qemu_img_info() method and the ops do fail.

Note that there might be a workaround by supplying the 'data' parameter [4] but i'm not sure that is intended to be used in such a manner.

Affected are e.g. vzstorage, dell_emc powerstore nfs and quobyte (more are possible).

[1] https://review.opendev.org/c/openstack/cinder/+/923244
[2] https://opendev.org/openstack/cinder/src/commit/d2e1b64681eb8a386c8e62b6f31831a2514657d4/cinder/image/image_utils.py#L813
[3] https://opendev.org/openstack/cinder/src/commit/d2e1b64681eb8a386c8e62b6f31831a2514657d4/cinder/image/image_utils.py#L526
[4] https://opendev.org/openstack/cinder/src/commit/d2e1b64681eb8a386c8e62b6f31831a2514657d4/cinder/image/image_utils.py#L812
[5] https://opendev.org/openstack/cinder/src/commit/d2e1b64681eb8a386c8e62b6f31831a2514657d4/cinder/volume/drivers/vzstorage.py#L528
[6] https://opendev.org/openstack/cinder/src/commit/d2e1b64681eb8a386c8e62b6f31831a2514657d4/cinder/volume/drivers/quobyte.py#L416
[7] https://opendev.org/openstack/cinder/src/commit/d2e1b64681eb8a386c8e62b6f31831a2514657d4/cinder/volume/drivers/dell_emc/powerstore/nfs.py#L198