volume: allow extend cow preallocated

Relax assumption that cow volumes do now need
to be extended to only those that are sparse.
Preallocated volumes should be extended to avoid
pausing VMs when it reaches its truesize, while
having bigger capacity.

Bug-Url: https://bugzilla.redhat.com/2170689
Signed-off-by: Albert Esteve <aesteve@redhat.com>

lib/vdsm/storage/volume.py

@@ -1381,11 +1381,11 @@ def extendSize(self, new_capacity):
             raise se.VolumeNonWritable(self.volUUID)
 
         volFormat = self.getFormat()
-        if volFormat == sc.COW_FORMAT:
+        if volFormat == sc.COW_FORMAT and self.getType() == sc.SPARSE_VOL:
             self.log.debug("skipping cow size extension for volume %s to "
                            "capacity %s", self.volUUID, new_capacity)
             return
-        elif volFormat != sc.RAW_FORMAT:
+        if volFormat not in [sc.RAW_FORMAT, sc.COW_FORMAT]:
             raise se.IncorrectFormat(self.volUUID)
 
         # Note: This function previously prohibited extending non-leaf volumes.

tests/storage/blocksd_test.py

@@ -1859,7 +1859,6 @@ def test_reduce_volume_skipped(domain_factory, fake_task, fake_sanlock):
 
 @requires_root
 @pytest.mark.root
-@pytest.mark.xfail(reason='Cow volumes are not extended.')
 def test_extend_volume(domain_factory, fake_task, fake_sanlock):
     """
     Test added to verify fix for https://bugzilla.redhat.com/2170689.