Always store old instance_type during a migration

Previously, we were trying to optimize for the migration (as opposed
to resize) case by not storing the old_ instance_type. However,
this is confusing to the vast amount of shared code that works on
migrations and resizes because the "is old == new" logic must be
replicated everywhere. To cut our losses and hopefully avoid other
hidden dragons, this patch removes the optimization and makes both
paths the same.

Fixes bug #1160489

Change-Id: I2ad7b02239baada5fd2174f5b61cdc90ec91e6f5

2 files changed, 13 insertions, 19 deletions

diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 8798e4aee..6cb0bbb94 100755
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -1989,11 +1989,8 @@ class ComputeManager(manager.SchedulerDependentManager):
         Returns the updated system_metadata as a dict, as well as the
         post-cleanup current instance type.
         """
-        same_type = (migration['old_instance_type_id'] ==
-                     migration['new_instance_type_id'])
-
         sys_meta = utils.metadata_to_dict(instance['system_metadata'])
-        if restore_old and not same_type:
+        if restore_old:
             instance_type = instance_types.extract_instance_type(instance,
                                                                  'old_')
             sys_meta = instance_types.save_instance_type_info(sys_meta,
@@ -2001,10 +1998,7 @@ class ComputeManager(manager.SchedulerDependentManager):
         else:
             instance_type = instance_types.extract_instance_type(instance)
 
-        if not same_type:
-            instance_types.delete_instance_type_info(sys_meta, 'old_')
-
-        # NOTE(danms): new instance type is always stored in prep_resize
+        instance_types.delete_instance_type_info(sys_meta, 'old_')
         instance_types.delete_instance_type_info(sys_meta, 'new_')
 
         return sys_meta, instance_type
@@ -2380,14 +2374,14 @@ class ComputeManager(manager.SchedulerDependentManager):
         resize_instance = False
         old_instance_type_id = migration['old_instance_type_id']
         new_instance_type_id = migration['new_instance_type_id']
+        old_instance_type = instance_types.extract_instance_type(instance)
+        sys_meta = utils.metadata_to_dict(instance['system_metadata'])
+        instance_types.save_instance_type_info(sys_meta,
+                                               old_instance_type,
+                                               prefix='old_')
         if old_instance_type_id != new_instance_type_id:
             instance_type = instance_types.extract_instance_type(instance,
                                                                  prefix='new_')
-            old_instance_type = instance_types.extract_instance_type(instance)
-            sys_meta = utils.metadata_to_dict(instance['system_metadata'])
-            instance_types.save_instance_type_info(sys_meta,
-                                                    old_instance_type,
-                                                    prefix='old_')
             instance_types.save_instance_type_info(sys_meta, instance_type)
 
             instance = self._instance_update(
@@ -2398,7 +2392,7 @@ class ComputeManager(manager.SchedulerDependentManager):
                     vcpus=instance_type['vcpus'],
                     root_gb=instance_type['root_gb'],
                     ephemeral_gb=instance_type['ephemeral_gb'],
-                    system_metadata=sys_meta)
+                    system_metadata=dict(sys_meta))
 
             resize_instance = True
 
@@ -2414,7 +2408,8 @@ class ComputeManager(manager.SchedulerDependentManager):
 
         instance = self._instance_update(context, instance['uuid'],
                               task_state=task_states.RESIZE_FINISH,
-                              expected_task_state=task_states.RESIZE_MIGRATED)
+                              expected_task_state=task_states.RESIZE_MIGRATED,
+                              system_metadata=sys_meta)
 
         self._notify_about_instance_usage(
             context, instance, "finish_resize.start",
diff --git a/nova/tests/compute/test_compute.py b/nova/tests/compute/test_compute.py
index c36496f79..3a1526522 100644
--- a/nova/tests/compute/test_compute.py
+++ b/nova/tests/compute/test_compute.py
@@ -2806,7 +2806,7 @@ class ComputeTestCase(BaseTestCase):
         self.mox.StubOutWithMock(instance_types, 'extract_instance_type')
         self.mox.StubOutWithMock(instance_types, 'delete_instance_type_info')
         self.mox.StubOutWithMock(instance_types, 'save_instance_type_info')
-        if revert and old != new:
+        if revert:
             instance_types.extract_instance_type(instance, 'old_').AndReturn(
                 {'instance_type_id': old})
             instance_types.save_instance_type_info(
@@ -2814,9 +2814,8 @@ class ComputeTestCase(BaseTestCase):
         else:
             instance_types.extract_instance_type(instance).AndReturn(
                 {'instance_type_id': new})
-        if old != new:
-            instance_types.delete_instance_type_info(
-                sys_meta, 'old_').AndReturn(sys_meta)
+        instance_types.delete_instance_type_info(
+            sys_meta, 'old_').AndReturn(sys_meta)
         instance_types.delete_instance_type_info(
             sys_meta, 'new_').AndReturn(sys_meta)