As described in the launchpad bug [1], backup operations must take care
to ensure encryption key ID resources aren't lost, and that restored
volumes always have a unique encryption key ID.
[1] https://bugs.launchpad.net/cinder/+bug/1745180
This patch adds an 'encryption_key_id' column to the backups table. Now,
when a backup is created and the source volume's encryption key is
cloned, the cloned key ID is stored in the table. This makes it possible
to delete the cloned key ID when the backup is deleted. The code that
clones the volume's encryption key has been relocated from the common
backup driver layer to the backup manager. The backup manager now has
full responsibility for managing encryption key IDs.
When restoring a backup of an encrypted volume, the backup manager now
does this:
1) If the restored volume's encryption key ID has changed, delete the
key ID it had prior to the restore operation. This ensures no key IDs
are leaked.
2) If the 'encryption_key_id' field in the backup table is empty, glean
the backup's cloned key ID from the backup's "volume base metadata."
This helps populate the 'encryption_key_id' column for backup table
entries created prior to when the column existed.
3) Re-clone the backup's key ID to ensure the restored volume's key ID
is always unique.
Closes-Bug: #1745180
Change-Id: I6cadcbf839d146b2fd57d7019f73dce303f9e10b
bec756e040