diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 629be1be2c01..8ae0ed8d2530 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -1562,20 +1562,22 @@ class ComputeManager(manager.Manager):
                 'swap': swap,
                 'block_device_mapping': mapping})
 
-    def _check_dev_name(self, bdms, instance):
-        bdms_no_device_name = [x for x in bdms if x.device_name is None]
-        for bdm in bdms_no_device_name:
+    def _add_missing_dev_names(self, bdms, instance):
+        for bdm in bdms:
+            if bdm.device_name is not None:
+                continue
+
             device_name = self._get_device_name_for_instance(instance,
-                                                             bdms,
-                                                             bdm)
+                                                             bdms, bdm)
             values = {'device_name': device_name}
             bdm.update(values)
+            bdm.save()
 
     def _prep_block_device(self, context, instance, bdms,
                            do_check_attach=True):
         """Set up the block device for an instance with error logging."""
         try:
-            self._check_dev_name(bdms, instance)
+            self._add_missing_dev_names(bdms, instance)
             block_device_info = driver.get_block_device_info(instance, bdms)
             mapping = driver.block_device_info_get_mapping(block_device_info)
             driver_block_device.attach_block_devices(
diff --git a/nova/tests/unit/compute/test_compute.py b/nova/tests/unit/compute/test_compute.py
index dfa08b50d316..39dd19e2c979 100644
--- a/nova/tests/unit/compute/test_compute.py
+++ b/nova/tests/unit/compute/test_compute.py
@@ -1261,8 +1261,14 @@ class ComputeVolumeTestCase(BaseTestCase):
 
         manager = compute_manager.ComputeManager()
         manager.use_legacy_block_device_info = False
-        block_device_info = manager._prep_block_device(self.context, instance,
-                                                       bdms)
+        mock_bdm_saves = [mock.patch.object(bdm, 'save') for bdm in bdms]
+        with test.nested(*mock_bdm_saves):
+            block_device_info = manager._prep_block_device(self.context,
+                                                           instance, bdms)
+
+            for bdm in bdms:
+                bdm.save.assert_called_once_with()
+                self.assertIsNotNone(bdm.device_name)
 
         convert_swap.assert_called_once_with(bdms)
         convert_ephemerals.assert_called_once_with(bdms)
@@ -8970,7 +8976,7 @@ class ComputeAPITestCase(BaseTestCase):
                 None,
                 '/invalid')
 
-    def test_check_dev_name_assign_dev_name(self):
+    def test_add_missing_dev_names_assign_dev_name(self):
         instance = self._create_fake_instance_obj()
         bdms = [objects.BlockDeviceMapping(
                 **fake_block_device.FakeDbBlockDeviceDict(
@@ -8984,12 +8990,16 @@ class ComputeAPITestCase(BaseTestCase):
                  'disk_bus': None,
                  'device_type': None
                  }))]
-        self.compute._check_dev_name(bdms, instance)
+        with mock.patch.object(objects.BlockDeviceMapping,
+                               'save') as mock_save:
+            self.compute._add_missing_dev_names(bdms, instance)
+            mock_save.assert_called_once_with()
         self.assertIsNotNone(bdms[0].device_name)
 
     @mock.patch.object(compute_manager.ComputeManager,
                        '_get_device_name_for_instance')
-    def test_check_dev_name_skip_bdms_with_dev_name(self, mock_get_dev_name):
+    def test_add_missing_dev_names_skip_bdms_with_dev_name(self,
+                                                       mock_get_dev_name):
         instance = self._create_fake_instance_obj()
         bdms = [objects.BlockDeviceMapping(
                 **fake_block_device.FakeDbBlockDeviceDict(
@@ -9003,7 +9013,7 @@ class ComputeAPITestCase(BaseTestCase):
                  'disk_bus': None,
                  'device_type': None
                  }))]
-        self.compute._check_dev_name(bdms, instance)
+        self.compute._add_missing_dev_names(bdms, instance)
         self.assertFalse(mock_get_dev_name.called)
 
     def test_no_attach_volume_in_rescue_state(self):