libvirt: Skip fetching the virtual size of block devices17.0.5

In this latest episode of `Which CI job has lyarwood broken today?!` we
find that I464bc2b88123a012cd12213beac4b572c3c20a56 introduced a
regression in the nova-lvm experimental job as n-cpu attempted to run
qemu-img info against block devices as an unprivileged user.

For the time being we should skip any attempt to use this command
against block devices until the disk_api layer can make privileged
calls using privsep.

Closes-bug: #1771700
Change-Id: I9653f81ec716f80eb638810f65e2d3cdfeedaa22
(cherry picked from commit fda48219a378d09a9a363078ba161d7f54e32c0a)

2 files changed, 48 insertions, 3 deletions

diff --git a/nova/tests/unit/virt/libvirt/test_driver.py b/nova/tests/unit/virt/libvirt/test_driver.py
index b8b4600d86..9bf18ace9c 100644
--- a/nova/tests/unit/virt/libvirt/test_driver.py
+++ b/nova/tests/unit/virt/libvirt/test_driver.py
@@ -14241,6 +14241,43 @@ class LibvirtConnTestCase(test.NoDBTestCase,
         self.assertRaises(exception.DiskNotFound,
                           drvr._get_disk_over_committed_size_total)
 
+    @mock.patch('nova.virt.libvirt.storage.lvm.get_volume_size')
+    @mock.patch('nova.virt.disk.api.get_disk_size',
+                new_callable=mock.NonCallableMock)
+    def test_get_instance_disk_info_from_config_block_devices(self,
+            mock_disk_api, mock_get_volume_size):
+        """Test that for block devices the actual and virtual sizes are
+        reported as the same and that the disk_api is not used.
+        """
+        c = context.get_admin_context()
+        instance = objects.Instance(root_device_name='/dev/vda',
+                                    **self.test_instance)
+        bdms = objects.BlockDeviceMappingList(objects=[
+            fake_block_device.fake_bdm_object(c, {
+                'device_name': '/dev/mapper/vg-lv',
+                'source_type': 'image',
+                'destination_type': 'local'
+            }),
+
+        ])
+        block_device_info = driver.get_block_device_info(instance, bdms)
+
+        config = vconfig.LibvirtConfigGuest()
+        disk_config = vconfig.LibvirtConfigGuestDisk()
+        disk_config.source_type = "block"
+        disk_config.source_path = mock.sentinel.volume_path
+        config.devices.append(disk_config)
+
+        mock_get_volume_size.return_value = mock.sentinel.volume_size
+
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
+        disk_info = drvr._get_instance_disk_info_from_config(config,
+                                                             block_device_info)
+
+        mock_get_volume_size.assert_called_once_with(mock.sentinel.volume_path)
+        self.assertEqual(disk_info[0]['disk_size'],
+                         disk_info[0]['virt_disk_size'])
+
     def test_cpu_info(self):
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
 
diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
index bedad38956..ca4414fb70 100644
--- a/nova/virt/libvirt/driver.py
+++ b/nova/virt/libvirt/driver.py
@@ -7916,17 +7916,25 @@ class LibvirtDriver(driver.ComputeDriver):
                             dk_size += os.path.getsize(fp)
                 else:
                     dk_size = disk_api.get_allocated_disk_size(path)
+
+                # NOTE(lyarwood): Fetch the virtual size for all file disks.
+                virt_size = disk_api.get_disk_size(path)
+
             elif disk_type == 'block' and block_device_info:
+                # FIXME(lyarwood): There's no reason to use a separate call
+                # here, once disk_api uses privsep this should be removed along
+                # with the surrounding conditionals to simplify this mess.
                 dk_size = lvm.get_volume_size(path)
+                # NOTE(lyarwood): As above, we should be using disk_api to
+                # fetch the virt-size but can't as it currently runs qemu-img
+                # as an unprivileged user, causing a failure for block devices.
+                virt_size = dk_size
             else:
                 LOG.debug('skipping disk %(path)s (%(target)s) - unable to '
                           'determine if volume',
                           {'path': path, 'target': target})
                 continue
 
-            # NOTE(lyarwood): Always fetch the virtual size for all disk types.
-            virt_size = disk_api.get_disk_size(path)
-
             if driver_type in ("qcow2", "ploop"):
                 backing_file = libvirt_utils.get_disk_backing_file(path)
                 over_commit_size = int(virt_size) - dk_size