Add methods that convert any volume BDM to driver format

There are places in the code where we need to get the DriverBlockDevice
instance based on the BDM object for a volume block device, however the
DriverBlockDevice class the object maps to (based on source of
the data) can be any of the following: volume, snapshot or image, all of
which are actually separate classes that extend VolumeDriverBlockDevice.

This patch adds a method to transform a volume BDM object to the correct
class instance, so that we can more easily avoid bugs such as 1411847.

Related-Bug: #1411847

Change-Id: I3496bab7aac448722240483b86c013e5f80d0cb5

nova/compute/manager.py

@@ -4611,7 +4611,7 @@ class ComputeManager(manager.Manager):
         if not bdm:
             bdm = objects.BlockDeviceMapping.get_by_volume_id(
                     context, volume_id)
-        driver_bdm = driver_block_device.DriverVolumeBlockDevice(bdm)
+        driver_bdm = driver_block_device.convert_volume(bdm)
 
         @utils.synchronized(instance.uuid)
         def do_attach_volume(context, instance, driver_bdm):

nova/tests/unit/virt/test_block_device.py

@@ -627,6 +627,22 @@ class TestDriverBlockDevice(test.NoDBTestCase):
             [self.volume_bdm, self.ephemeral_bdm])
         self.assertEqual(converted, [self.volume_driver_bdm])
 
+    def test_convert_all_volumes(self):
+        converted = driver_block_device.convert_all_volumes()
+        self.assertEqual([], converted)
+
+        converted = driver_block_device.convert_all_volumes(
+            self.volume_bdm, self.ephemeral_bdm, self.image_bdm)
+        self.assertEqual(converted, [self.volume_driver_bdm,
+                                     self.image_driver_bdm])
+
+    def test_convert_volume(self):
+        self.assertIsNone(driver_block_device.convert_volume(self.swap_bdm))
+        self.assertEqual(self.volume_driver_bdm,
+                         driver_block_device.convert_volume(self.volume_bdm))
+        self.assertEqual(self.snapshot_driver_bdm,
+                         driver_block_device.convert_volume(self.snapshot_bdm))
+
     def test_legacy_block_devices(self):
         test_snapshot = self.driver_classes['snapshot'](
             self.snapshot_bdm)

nova/virt/block_device.py

@@ -13,6 +13,7 @@
 #    under the License.
 
 import functools
+import itertools
 import operator
 
 from oslo.serialization import jsonutils
@@ -392,6 +393,22 @@ convert_blanks = functools.partial(_convert_block_devices,
                                    DriverBlankBlockDevice)
 
 
+def convert_all_volumes(*volume_bdms):
+    source_volume = convert_volumes(volume_bdms)
+    source_snapshot = convert_snapshots(volume_bdms)
+    source_image = convert_images(volume_bdms)
+
+    return [vol for vol in
+            itertools.chain(source_volume, source_snapshot, source_image)]
+
+
+def convert_volume(volume_bdm):
+    try:
+        return convert_all_volumes(volume_bdm)[0]
+    except IndexError:
+        pass
+
+
 def attach_block_devices(block_device_mapping, *attach_args, **attach_kwargs):
     def _log_and_attach(bdm):
         context = attach_args[0]

nova/virt/libvirt/driver.py

@@ -1648,14 +1648,10 @@ class LibvirtDriver(driver.ComputeDriver):
         bdm = objects.BlockDeviceMapping.get_by_volume_id(context,
                                                           volume_id)
 
-        if bdm['source_type'] == 'image':
-            driver_bdm = driver_block_device.DriverImageBlockDevice(bdm)
-        else:
-            # source_type = 'volume'
-            driver_bdm = driver_block_device.DriverVolumeBlockDevice(bdm)
-
-        driver_bdm.refresh_connection_info(context, instance,
-                                           self._volume_api, self)
+        driver_bdm = driver_block_device.convert_volume(bdm)
+        if driver_bdm:
+            driver_bdm.refresh_connection_info(context, instance,
+                                               self._volume_api, self)
 
     def volume_snapshot_create(self, context, instance, volume_id,
                                create_info):