Comment 15 for bug 1419577

I'm trying to sort this out a bit.

Looking at the nova.virt.libvirt.driver.pre_live_migration() method, I see it's connecting to a volume and the connection_info dictionary is updated in the nova.virt.libvirt.volume code, but I don't see where that connection_info dict comes back to the virt driver's pre_live_migration method and persists the change to the database.

This is where pre_live_migration() connects the volume:

http://git.openstack.org/cgit/openstack/nova/tree/nova/virt/libvirt/driver.py?id=2015.1.0#n5813

Let's assume we're using the LibvirtISCSIVolumeDriver volume driver, the connect_volume method in there will update the connection_info dict here:

http://git.openstack.org/cgit/openstack/nova/tree/nova/virt/libvirt/volume.py?id=2015.1.0#n483

That change never gets persisted back to the block_device_mapping table for the bdm instance, but we've connected the volume potentially on another host so if live migration fails and we never rollback the volume connection_info to the source host (before pre_live_migration), and reboot the instance, then the bdm will be recreated from what's in the database which will be wrong.