Merge "Use absolute path during qemu img rebase" into stable/victoria

Author: Zuul

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

@@ -26638,8 +26638,23 @@ def test_volume_snapshot_delete_when_dom_not_running(self, mock_execute,
         not running should trigger a blockRebase using qemu-img not libvirt.
         In this test, we rebase the image with another image as backing file.
         """
+        dom_xml = """
+              <domain type='kvm'>
+                <devices>
+                  <disk type='file'>
+                     <source file='/var/lib/nova/instances/%s/disk1_file'/>
+                     <target dev='vda' bus='virtio'/>
+                     <serial>0e38683e-f0af-418f-a3f1-6b67ea0f919d</serial>
+                  </disk>
+                  <disk type='block'>
+                    <source dev='/path/to/dev/1'/>
+                    <target dev='vdb' bus='virtio' serial='1234'/>
+                  </disk>
+                </devices>
+              </domain>""" % self.inst['uuid']
+
         mock_domain, guest = self._setup_block_rebase_domain_and_guest_mocks(
-                                self.dom_xml)
+                                dom_xml)
 
         instance = objects.Instance(**self.inst)
         snapshot_id = 'snapshot-1234'
@@ -26650,10 +26665,13 @@ def test_volume_snapshot_delete_when_dom_not_running(self, mock_execute,
                                               self.delete_info_1)
 
         mock_disk_op_sema.__enter__.assert_called_once()
-        mock_qemu_img_info.assert_called_once_with("snap.img")
-        mock_execute.assert_called_once_with('qemu-img', 'rebase',
-                                             '-b', 'snap.img', '-F',
-                                             'fake_fmt', 'disk1_file')
+        mock_qemu_img_info.assert_called_once_with(
+            "/var/lib/nova/instances/%s/snap.img" % instance.uuid)
+        mock_execute.assert_called_once_with(
+            'qemu-img', 'rebase',
+            '-b', '/var/lib/nova/instances/%s/snap.img' % instance.uuid,
+            '-F', 'fake_fmt',
+            '/var/lib/nova/instances/%s/disk1_file' % instance.uuid)
 
     @mock.patch.object(compute_utils, 'disk_ops_semaphore')
     @mock.patch.object(host.Host, "has_min_version",

nova/virt/libvirt/driver.py

@@ -3012,7 +3012,16 @@ def _rebase_with_qemu_img(source_path, rebase_base):
             # If the rebased image is going to have a backing file then
             # explicitly set the backing file format to avoid any security
             # concerns related to file format auto detection.
-            backing_file = rebase_base
+            if os.path.isabs(rebase_base):
+                backing_file = rebase_base
+            else:
+                # this is a probably a volume snapshot case where the
+                # rebase_base is relative. See bug
+                # https://bugs.launchpad.net/nova/+bug/1885528
+                backing_file_name = os.path.basename(rebase_base)
+                volume_path = os.path.dirname(source_path)
+                backing_file = os.path.join(volume_path, backing_file_name)
+
             b_file_fmt = images.qemu_img_info(backing_file).file_format
             qemu_img_extra_arg = ['-F', b_file_fmt]