Comment 31 for bug 1578036

I am still seeing the error with the above commit (https://review.openstack.org/511232)for "in-use" volume with ceph volume & backup backend. The 2nd issue pointed out by Gaudenz in post#16 doesn't seem be resolved where ceph driver is trying to perform the differential export with a snapshot created against the original ceph volume instead of the snap-clone of the original ceph volume returned by "get_backup_device" in "cinder/backup/manager.py".

When "rbd export-diff --id xxx --conf /tmp/tmpN0XVXO --pool xxx <email address hidden> -" is attemped, it will fail with "Numerical argument out of domain" since the snapshot (backup.737df596-3922-4f60-8028-81e22a22a57f.snap.1507841205.47) generated by "source_rbd_image.create_snap(new_snap)" is against the snap-clone instead.

I am testing this against our Newton tree but I don't see any code in the latest master branch addressing this mix-up issue.