CA-400106: disable leaf coalesce with VDI snapshot secondary

When the secondary/mirror option is provided to the vdi_snasphot
operation we do not want any leaf coalesce garbage collection taking
place. Unfortunately xapi will delete the snapshot once it's finished
copying the new parent to the destination SR in SXM and whilst the
mirroring operation is still live. This will kick the GC process and
if the GC gets to the point of performing the leaf coalesce before the
migrate completes will result in a failure of the mirror operation. So
block the leaf-coalesce operation in this case. The block will be
removed if another snapshot were to be taken but in the case of SXM
the next expected operation is a vdi_delete of the leaf which will
clear the entire chain.

Signed-off-by: Mark Syms <[email protected]>

drivers/FileSR.py

@@ -707,7 +707,7 @@ def reset_leaf(self, sr_uuid, vdi_uuid):
         vhdutil.killData(self.path)
 
     def _do_snapshot(self, sr_uuid, vdi_uuid, snap_type,
-                     secondary=None, cbtlog=None):
+                     _=False, secondary=None, cbtlog=None):
         # If cbt enabled, save file consistency state
         if cbtlog is not None:
             if blktap2.VDI.tap_status(self.session, vdi_uuid):
@@ -727,6 +727,7 @@ def _do_snapshot(self, sr_uuid, vdi_uuid, snap_type,
         try:
             return self._snapshot(snap_type, cbtlog, consistency_state)
         finally:
+            self.disable_leaf_on_secondary(vdi_uuid, secondary=secondary)
             blktap2.VDI.tap_unpause(self.session, sr_uuid, vdi_uuid, secondary)
 
     def _rename(self, src, dst):

drivers/LVHDSR.py

@@ -1656,6 +1656,7 @@ def _do_snapshot(self, sr_uuid, vdi_uuid, snapType,
                 util.SMlog('WARNING: failed to clean up failed snapshot: '
                         '%s (error ignored)' % e2)
             raise
+        self.disable_leaf_on_secondary(vdi_uuid, secondary=secondary)
         blktap2.VDI.tap_unpause(self.session, sr_uuid, vdi_uuid, secondary)
         unpause_time = time.time()
         if (unpause_time - pause_time) > LONG_SNAPTIME:

drivers/VDI.py

@@ -16,6 +16,7 @@
 # VDI: Base class for virtual disk instances
 #
 
+import cleanup
 import SR
 import xmlrpc.client
 import xs_errors
@@ -28,6 +29,7 @@
 from bitarray import bitarray
 import uuid
 
+
 SM_CONFIG_PASS_THROUGH_FIELDS = ["base_mirror", "key_hash"]
 
 SNAPSHOT_SINGLE = 1  # true snapshot: 1 leaf, 1 read-only parent
@@ -902,3 +904,14 @@ def _disable_cbt_on_error(self, alert_name, alert_str):
                                               alert_prio_warning,
                                               alert_obj, alert_uuid,
                                               alert_str)
+
+    def disable_leaf_on_secondary(self, vdi_uuid, secondary=None):
+        vdi_ref = self.session.xenapi.VDI.get_by_uuid(vdi_uuid)
+        self.session.xenapi.VDI.remove_from_other_config(
+            vdi_ref, cleanup.VDI.DB_LEAFCLSC)
+        if secondary is not None:
+            util.SMlog(f"We have secondary for {vdi_uuid}, "
+                       "blocking leaf coalesce")
+            self.session.xenapi.VDI.add_to_other_config(
+                vdi_ref, cleanup.VDI.DB_LEAFCLSC,
+                cleanup.VDI.LEAFCLSC_DISABLED)

tests/test_LVHDSR.py

@@ -4,6 +4,7 @@
 
 import uuid
 
+import cleanup
 import LVHDSR
 import lvhdutil
 import lvutil
@@ -423,3 +424,46 @@ def test_snapshot_attached_cbt_success(self, mock_xenapi, mock_lock):
         # Assert
         self.assertIsNotNone(snap)
         self.assertEqual(self.mock_cbtutil.set_cbt_child.call_count, 3)
+
+    @mock.patch('LVHDSR.Lock', autospec=True)
+    @mock.patch('SR.XenAPI')
+    def test_snapshot_secondary_success(self, mock_xenapi, mock_lock):
+        """
+        LVHDSR.snapshot, attached on host with secondary mirror
+        """
+        # Arrange
+        xapi_session = mock_xenapi.xapi_local.return_value
+        xapi_session.xenapi.VDI.get_sm_config.return_value = {}
+
+        vdi_ref = mock.MagicMock()
+        xapi_session.xenapi.VDI.get_by_uuid.return_value = vdi_ref
+        vdi_uuid = 'some VDI UUID'
+        self.get_dummy_vdi(vdi_uuid)
+        self.get_dummy_vhd(vdi_uuid, False)
+
+        sr = self.create_LVHDSR()
+        sr.isMaster = True
+        sr.legacyMode = False
+        sr.srcmd.params = {
+            'vdi_ref': 'test ref',
+            'driver_params': {
+                'type': 'double',
+                'mirror': 'nbd:mirror_vbd/5/xvda'}
+            }
+        sr.cmd = "vdi_snapshot"
+
+        vdi = sr.vdi('some VDI UUID')
+        vdi.vdi_type = vhdutil.VDI_TYPE_VHD
+        self.mock_sr_util.pathexists.return_value = True
+        self.mock_sr_util.get_hosts_attached_on.return_value = ["hostref2"]
+        self.mock_sr_util.get_this_host_ref.return_value = ["hostref1"]
+        self.mock_vhdutil.getDepth.return_value = 1
+
+        # Act
+        with mock.patch('lock.Lock'):
+            snap = vdi.snapshot(sr.uuid, "Dummy UUID")
+
+        # Assert
+        self.assertIsNotNone(snap)
+        xapi_session.xenapi.VDI.add_to_other_config.assert_called_once_with(
+            vdi_ref, cleanup.VDI.DB_LEAFCLSC, cleanup.VDI.LEAFCLSC_DISABLED)