NFS driver: Fix fail to resize NFS volume with snapshots

The NFS driver may fail to update the virtual size of the
Image-volume to the new size when it has snapshots created, due
to image_utils incorrectly rejecting qcow2 backing files as they
were not allowed.

This patch explicitly tells `image_utils.qemu_img_info` to allow
the use of qcow2 backing files when performing a extend operation.

Closes-Bug: #2103742
Change-Id: I0582daac259dbda78481b56378562350def59598

cinder/tests/unit/volume/drivers/test_nfs.py

@@ -1151,26 +1151,30 @@ class NfsDriverTestCase(test.TestCase):
         self._set_driver()
         drv = self._driver
         path = 'fake/path'
+        volume_name = 'volume1'
         size = 2
         data = mock.MagicMock()
         data.virtual_size = size * units.Gi
 
-        with mock.patch.object(image_utils, 'qemu_img_info',
-                               return_value=data):
-            self.assertTrue(drv._is_file_size_equal(path, size))
+        with mock.patch.object(drv, '_qemu_img_info',
+                               return_value=data) as mock_qemu_img_info:
+            self.assertTrue(drv._is_file_size_equal(path, volume_name, size))
+            mock_qemu_img_info.assert_called_once_with(path, volume_name)
 
     def test_is_file_size_equal_false(self):
         """File sizes are not equal."""
         self._set_driver()
         drv = self._driver
         path = 'fake/path'
+        volume_name = 'volume1'
         size = 2
         data = mock.MagicMock()
         data.virtual_size = (size + 1) * units.Gi
 
-        with mock.patch.object(image_utils, 'qemu_img_info',
-                               return_value=data):
-            self.assertFalse(drv._is_file_size_equal(path, size))
+        with mock.patch.object(drv, '_qemu_img_info',
+                               return_value=data) as mock_qemu_img_info:
+            self.assertFalse(drv._is_file_size_equal(path, volume_name, size))
+            mock_qemu_img_info.assert_called_once_with(path, volume_name)
 
     @mock.patch.object(nfs, 'LOG')
     def test_set_nas_security_options_when_true(self, LOG):

cinder/volume/drivers/nfs.py

@@ -408,14 +408,13 @@ class NfsDriver(remotefs.RemoteFSSnapDriverDistributed):
                                  run_as_root=self._execute_as_root,
                                  file_format=file_format)
         if file_format == 'qcow2' and not self._is_file_size_equal(
-                active_file_path, new_size):
+                active_file_path, volume.name, new_size):
             raise exception.ExtendVolumeError(
                 reason='Resizing image file failed.')
 
-    def _is_file_size_equal(self, path, size):
+    def _is_file_size_equal(self, path, volume_name, size):
         """Checks if file size at path is equal to size."""
-        data = image_utils.qemu_img_info(path,
-                                         run_as_root=self._execute_as_root)
+        data = self._qemu_img_info(path, volume_name)
         virt_size = int(data.virtual_size / units.Gi)
         return virt_size == size
 

releasenotes/notes/bug-2103742-fix-fail-resize-nfs-volumes-with-snapshots-e861d69b1ae6f97d.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    NFS driver `bug #2103742
+    <https://bugs.launchpad.net/cinder/+bug/2103742>`_: Fixed issue 
+    preventing the volume resize operation from properly updating the NFS 
+    image virtual size with the new size when volume has snapshots.