Libvirt support for tagged volume attachment

This patch adds support for tagged volume attachment to the libvirt
driver.

Change-Id: I8b475992b881db08cf1354299cc86042413074cc
Implements: blueprint bp/virt-device-tagged-attach-detach

nova/tests/unit/virt/libvirt/test_driver.py

@@ -6329,11 +6329,16 @@ class LibvirtConnTestCase(test.NoDBTestCase):
             mock.patch.object(drvr, '_get_volume_config',
                               return_value=mock_conf),
             mock.patch.object(drvr, '_set_cache_mode'),
-            mock.patch.object(drvr, '_check_discard_for_attach_volume')
+            mock.patch.object(drvr, '_check_discard_for_attach_volume'),
+            mock.patch.object(drvr, '_build_device_metadata'),
+            mock.patch.object(objects.Instance, 'save')
         ) as (mock_connect_volume, mock_get_volume_config,
-              mock_set_cache_mode, mock_check_discard):
+              mock_set_cache_mode, mock_check_discard,
+              mock_build_metadata, mock_save):
             for state in (power_state.RUNNING, power_state.PAUSED):
                 mock_dom.info.return_value = [state, 512, 512, 2, 1234, 5678]
+                mock_build_metadata.return_value = \
+                    objects.InstanceDeviceMetadata()
 
                 drvr.attach_volume(self.context, connection_info, instance,
                                    "/dev/vdb", disk_bus=bdm['disk_bus'],
@@ -6353,6 +6358,8 @@ class LibvirtConnTestCase(test.NoDBTestCase):
                 mock_dom.attachDeviceFlags.assert_called_with(
                     mock_conf.to_xml(), flags=flags)
                 mock_check_discard.assert_called_with(mock_conf, instance)
+                mock_build_metadata.assert_called_with(self.context, instance)
+                mock_save.assert_called_with()
 
     @mock.patch('nova.virt.libvirt.host.Host.get_domain')
     def test_detach_volume_with_vir_domain_affect_live_flag(self,

nova/tests/unit/virt/test_virt_drivers.py

@@ -469,7 +469,9 @@ class _VirtDriverTestCase(_FakeDriverBackendTestCase):
         self.assertEqual(storage_ip, result['ip'])
 
     @catch_notimplementederror
-    def test_attach_detach_volume(self):
+    @mock.patch.object(libvirt.driver.LibvirtDriver, '_build_device_metadata',
+                       return_value=objects.InstanceDeviceMetadata())
+    def test_attach_detach_volume(self, _):
         instance_ref, network_info = self._get_running_instance()
         connection_info = {
             "driver_volume_type": "fake",
@@ -484,7 +486,9 @@ class _VirtDriverTestCase(_FakeDriverBackendTestCase):
                                           '/dev/sda'))
 
     @catch_notimplementederror
-    def test_swap_volume(self):
+    @mock.patch.object(libvirt.driver.LibvirtDriver, '_build_device_metadata',
+                       return_value=objects.InstanceDeviceMetadata())
+    def test_swap_volume(self, _):
         instance_ref, network_info = self._get_running_instance()
         self.assertIsNone(
             self.connection.attach_volume(None, {'driver_volume_type': 'fake',
@@ -500,7 +504,9 @@ class _VirtDriverTestCase(_FakeDriverBackendTestCase):
                                         '/dev/sda', 2))
 
     @catch_notimplementederror
-    def test_attach_detach_different_power_states(self):
+    @mock.patch.object(libvirt.driver.LibvirtDriver, '_build_device_metadata',
+                       return_value=objects.InstanceDeviceMetadata())
+    def test_attach_detach_different_power_states(self, _):
         instance_ref, network_info = self._get_running_instance()
         connection_info = {
             "driver_volume_type": "fake",

nova/virt/driver.py

@@ -129,6 +129,7 @@ class ComputeDriver(object):
         "supports_attach_interface": False,
         "supports_device_tagging": False,
         "supports_tagged_attach_interface": False,
+        "supports_tagged_attach_volume": False,
     }
 
     def __init__(self, virtapi):

nova/virt/libvirt/driver.py

@@ -302,6 +302,7 @@ class LibvirtDriver(driver.ComputeDriver):
         "supports_attach_interface": True,
         "supports_device_tagging": True,
         "supports_tagged_attach_interface": True,
+        "supports_tagged_attach_volume": True,
     }
 
     def __init__(self, virtapi, read_only=False):
@@ -1234,6 +1235,17 @@ class LibvirtDriver(driver.ComputeDriver):
                 encryptor.attach_volume(context, **encryption)
 
             guest.attach_device(conf, persistent=True, live=live)
+            # NOTE(artom) If we're attaching with a device role tag, we need to
+            # rebuild device_metadata. If we're attaching without a role
+            # tag, we're rebuilding it here needlessly anyways. This isn't a
+            # massive deal, and it helps reduce code complexity by not having
+            # to indicate to the virt driver that the attach is tagged. The
+            # really important optimization of not calling the database unless
+            # device_metadata has actually changed is done for us by
+            # instance.save().
+            instance.device_metadata = self._build_device_metadata(
+                context, instance)
+            instance.save()
         except Exception as ex:
             LOG.exception(_LE('Failed to attach volume at mountpoint: %s'),
                           mountpoint, instance=instance)