Follow up for Ib50b6b02208f5bd2972de8a6f8f685c19745514c

* Extract out the provider mapping code from finish_revert_resize

* Fix nits in the code comments

Change-Id: If48134a87aaedcd1c7cfef0229a7e0af05514910
blueprint: support-move-ops-with-qos-ports

Author: Balazs Gibizer

nova/compute/api.py

@@ -3463,9 +3463,9 @@ def revert_resize(self, context, instance):
         # RequestSpec.requested_resources as others like cyborg might added
         # to things there already
         # NOTE(gibi): We need to collect the requested resource again as it is
-        # intentionally not persisted in nova. Note that this is needs to be
-        # done here as the nova REST API code directly calls revert on the
-        # compute_api skipping the conductor.
+        # intentionally not persisted in nova. Note that this needs to be
+        # done here as the nova API code directly calls revert on the
+        # dest compute service skipping the conductor.
         port_res_req = self.network_api.get_requested_resource_for_instance(
             context, instance.uuid)
         reqspec.requested_resources = port_res_req

nova/compute/manager.py

@@ -4295,23 +4295,8 @@ def finish_revert_resize(
                            'migration_uuid': migration.uuid})
                 raise
 
-            if request_spec:
-                # NOTE(gibi): We need to re-calculate the resource provider -
-                # port mapping as we have to have the neutron ports allocate
-                # from the source compute after revert.
-                scheduler_utils.fill_provider_mapping_based_on_allocation(
-                    context, self.reportclient, request_spec,
-                    source_allocations)
-                provider_mappings = self._get_request_group_mapping(
-                    request_spec)
-            else:
-                # NOTE(gibi): The compute RPC is pinned to be older than 5.2
-                # and therefore request_spec is not sent. We cannot calculate
-                # the provider mappings. If the instance has ports with
-                # resource request then the port update will fail in
-                # _update_port_binding_for_instance() called via
-                # _finish_revert_resize_network_migrate_finish() below.
-                provider_mappings = None
+            provider_mappings = self._fill_provider_mapping_based_on_allocs(
+                context, source_allocations, request_spec)
 
             self.network_api.setup_networks_on_host(context, instance,
                                                     migration.source_compute)
@@ -4363,6 +4348,39 @@ def finish_revert_resize(
                 self.host, action=fields.NotificationAction.RESIZE_REVERT,
                     phase=fields.NotificationPhase.END, bdms=bdms)
 
+    def _fill_provider_mapping_based_on_allocs(
+            self, context, allocations, request_spec):
+        """Fills and returns the request group - resource provider mapping
+        based on the allocation passed in.
+
+        :param context: The security context
+        :param allocation: allocation dict keyed by RP UUID.
+        :param request_spec: The RequestSpec object associated with the
+            operation
+        :returns: None if the request_spec is None. Otherwise a mapping
+            between RequestGroup requester_id, currently Neutron port_id,
+            and a list of resource provider UUIDs providing resource for
+            that RequestGroup.
+        """
+        if request_spec:
+            # NOTE(gibi): We need to re-calculate the resource provider -
+            # port mapping as we have to have the neutron ports allocate
+            # from the source compute after revert.
+            scheduler_utils.fill_provider_mapping_based_on_allocation(
+                context, self.reportclient, request_spec, allocations)
+            provider_mappings = self._get_request_group_mapping(
+                request_spec)
+        else:
+            # NOTE(gibi): The compute RPC is pinned to be older than 5.2
+            # and therefore request_spec is not sent. We cannot calculate
+            # the provider mappings. If the instance has ports with
+            # resource request then the port update will fail in
+            # _update_port_binding_for_instance() called via
+            # _finish_revert_resize_network_migrate_finish() in
+            # finish_revert_resize.
+            provider_mappings = None
+        return provider_mappings
+
     def _revert_allocation(self, context, instance, migration):
         """Revert an allocation that is held by migration to our instance."""