Comment 4 for bug 1745072

Reviewed: https://review.openstack.org/604203
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=dba00dbe11361a12d2602dd9601ee365a0755051
Submitter: Zuul
Branch: stable/rocky

commit dba00dbe11361a12d2602dd9601ee365a0755051
Author: Brooks Kaminski <email address hidden>
Date: Fri Jan 12 06:05:36 2018 -0600

    XenAPI/Stops the migration of volume backed VHDS

    This commit aims to correct problems with the resize_up codebase that allows
    the snapshot and migration of volume backed VDI/VHDs. Since these are empty
    stub disks, and the XenAPI does not allow these VDIs to be snapped, this results
    in an SR_OPERATION_NOT_ALLOWED or similar error on attempt.

    This change adds a check into the _process_ephemeral_chain_recursive method to
    run the current userdevice through volume_utils.is_booted_from_volume. To
    achieve this, the method has been opened in scope to accept custom user_device
    objects. In a future commit we will need to rename this method for clarity
    and correct its dependancies that call it. I have added a TODO for this to be
    done by myself. The check will ensure that the userdevice is not volume backed
    and then continue to snapshot and migrate the disk as needed, else increment
    and move on.

    Closes-Bug: #1745072
    Change-Id: I7cd2977c8268c1f73062b5d0b2b68ea686db99fe
    (cherry picked from commit eefb20e4658e17f91fa76b74fef6ff899babe51b)