live migration failed when using shared instance path with QCOW2

[Guangya Liu (Jay Lau)]

Currently, live migration will be failed when using shared instance path with QCOW2 because of 'instance_dir' was not defined.

File "/usr/lib/python2.6/site-packages/oslo/messaging/rpc/dispatcher.py", line 123, in _do_dispatch
    result = getattr(endpoint, method)(ctxt, **new_args)

  File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 410, in decorated_function
    return function(self, context, *args, **kwargs)

  File "/usr/lib/python2.6/site-packages/nova/exception.py", line 88, in wrapped
    payload)

  File "/usr/lib/python2.6/site-packages/nova/openstack/common/excutils.py", line 82, in __exit__
    six.reraise(self.type_, self.value, self.tb)

  File "/usr/lib/python2.6/site-packages/nova/exception.py", line 71, in wrapped
    return f(self, context, *args, **kw)

  File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 323, in decorated_function
    kwargs['instance'], e, sys.exc_info())

  File "/usr/lib/python2.6/site-packages/nova/openstack/common/excutils.py", line 82, in __exit__
    six.reraise(self.type_, self.value, self.tb)

  File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 311, in decorated_function
    return function(self, context, *args, **kwargs)

  File "/usr/lib/python2.6/site-packages/nova/compute/manager.py", line 4661, in pre_live_migration
    migrate_data)

  File "/usr/lib/python2.6/site-packages/nova/virt/libvirt/driver.py", line 4739, in pre_live_migration
    instance_dir, disk_info)

UnboundLocalError: local variable 'instance_dir' referenced before assignment
 to caller

[Guangya Liu (Jay Lau) (jay-lau-513)]

def pre_live_migration(self, context, instance, block_device_info,
                           network_info, disk_info, migrate_data=None):
        """Preparation live migration."""
        # Steps for volume backed instance live migration w/o shared storage.
        is_shared_block_storage = True
        is_shared_instance_path = True
        is_block_migration = True
        instance_relative_path = None
        if migrate_data:
            is_shared_block_storage = migrate_data.get(
                    'is_shared_block_storage', True)
            is_shared_instance_path = migrate_data.get(
                    'is_shared_instance_path', True)
            is_block_migration = migrate_data.get('block_migration', True)
            instance_relative_path = migrate_data.get('instance_relative_path')

        if not (is_shared_instance_path and is_shared_block_storage):
            # NOTE(mikal): live migration of instances using config drive is
            # not supported because of a bug in libvirt (read only devices
            # are not copied by libvirt). See bug/1246201
            if configdrive.required_by(instance):
                raise exception.NoLiveMigrationForConfigDriveInLibVirt()

        if not is_shared_instance_path:
            # NOTE(mikal): this doesn't use libvirt_utils.get_instance_path
            # because we are ensuring that the same instance directory name
            # is used as was at the source
            if instance_relative_path:
                instance_dir = os.path.join(CONF.instances_path,
                                            instance_relative_path) <<<<<<<<<<<<<<< instance_dir define here
            else:
                instance_dir = libvirt_utils.get_instance_path(instance) <<<<<<<<<<<<<<< instance_dir define here

            if os.path.exists(instance_dir):
                raise exception.DestinationDiskExists(path=instance_dir)
            os.mkdir(instance_dir)

        if not is_shared_block_storage:
            # Ensure images and backing files are present.
            self._create_images_and_backing(context, instance,
                                            instance_dir, disk_info) <<<<<<<<<<<<<<< using instance_dir here, but if I was using shared instance path, then instance_dir will be a undefined variable

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/108618

[OpenStack Infra (hudson-openstack)]

Change abandoned by Jay Lau (<email address hidden>) on branch: master
Review: https://review.openstack.org/108618