CLOUDSTACK-2276: NPE while attaching the volume to the instance which is created from ROOT Disk Snapshot

The NPE comes as the storage pool id is set to null in the in-memory volume object which is not in sync with the db. entry. Reloading the volume from db. fixes the issue

server/src/com/cloud/storage/VolumeManagerImpl.java

@@ -1725,6 +1725,8 @@ public class VolumeManagerImpl extends ManagerBase implements VolumeManager {
             }
         }
 
+        // reload the volume from db
+        volumeOnPrimaryStorage = volFactory.getVolume(volumeOnPrimaryStorage.getId());
         boolean moveVolumeNeeded = needMoveVolume(rootVolumeOfVm, volumeOnPrimaryStorage);
 
         if (moveVolumeNeeded) {