No mechanism for drivers to update info on migrated volumes

[John Griffith]

The migration workflow currently allows two possibilities:
1. The backend handle the migration
2. The Cinder host assists and does a general migration

The problem is that in most cases option 2 is going to be used, BUT there's currently no mechanism to communicate to the driver that it's objects are a part of a migration or that a migration has been completed and volume-id's have been swapped around. The swapping of ID's is something a big ugly IMO but nevertheless it's how the process works, and if we're going to go and change the ID of a volume after a creation we need to give drives some sort of notification that we've done this so that they can update their internal information, whether that be names, provider_locations etc.

[John Griffith (john-griffith)]

Relates to bug: 1381943

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/130307

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/130307
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=f3df1c8d57587bf112c464feedd523080550b7a6
Submitter: Jenkins
Branch: master

commit f3df1c8d57587bf112c464feedd523080550b7a6
Author: John Griffith <email address hidden>
Date: Tue Oct 21 23:19:22 2014 +0000

    Add ability to update migration info on backend

    The current migration process creates a new volume,
    xfr's it's contents, then deletes the original and
    modifies the new volume to have the previous ID.

    All in all this is kinda troublesome, but regardless
    the bigger problem is that the generic impl doesn't
    provide any method to tell the backend devices that
    their device names/id's have changed.

    This patch provides a method to inform backends
    that a migration operation has been completed on
    their target volume.

    It shouldn't be necessary to do anything with the originating
    or source volume because it's deleted as part of the process.

    Change-Id: Ib5e6a47fe9eedab3e60e77a6c2d987355c0bf167
    Closes-Bug: #1383499