Description of problem:
Live-migration with shared nfs storage fails with error "UnboundLocalError: local variable 'instance_dir' referenced before assignment".

Version-Release number of selected component (if applicable):
openstack-nova-2014.1.1-1.el6ost.noarch
(RH6-RHOS5 repo, 2014-07-14.2 puddle)

How reproducible:
100%

Steps to Reproduce:
1. Deploy openstack with packstack in 3 node setup (controller + 2 compute nodes). Use another RHEL 6.5 system as an external storage

2. Create nova user and nova group on the external storage and set UID and GID to be the same as the one on the compute nodes. 

3. Export shared directory and restart NFS service on external storage

4. Mount the NFS shared directory on both compute nodes.

  mount $EXTERNAL_STORAGE:/export/instances /export/instances;

5. Set required options in nova.conf on both compute nodes:

   instances_path = /export/instances
   novncproxy_base_url = "http://$CONTROLLER_IP:6080/vnc_auto.html"
   vncserver_listen = '0.0.0.0'
   live_migration_flag = VIR_MIGRATE_UNDEFINE_SOURCE, VIR_MIGRATE_PEER2PEER, VIR_MIGRATE_LIVE'

6. Set required options in libvirtd.conf on both compute nodes

  listen_tls = 0
  listen_tcp = 1
  auth_tcp = "none"

7. Set required options in qemu.conf on both compute nodes

  user = "root"
  group = "root"
  vnc_listen = "0.0.0.0"

8. Set required options in nova.conf on controller:

   vncserver_listen '0.0.0.0'

9. Turn off firewall and SELinux on all nodes as far as this bug manifests itself regardless of firewall and SELinux settings.

10. Restart all relevant services on all nodes

11. Spawn an instance

12. Check actual compute node where the instance is running. Use the other one in the next step.

13. Run command:

  nova live-migration $INSTANCE $COMPUTE_NODE


Actual results:

Instance is not migrated to $COMPUTE_NODE. No error is being shown in CLI. 

/var/log/nova/compute.log shows an error: 

UnboundLocalError: local variable 'instance_dir' referenced before assignment


Expected results:

Instance is migrated, No error in /var/log/nova/compute


Additional info:

The bug was already reported in the upstream:
https://bugs.launchpad.net/nova/+bug/1281295