storage: add logic for discard_no_unref

discard-no-unref support was added in ovirt-engine: oVirt/ovirt-engine@142d791.
Update vdsm to recognize and remember this parameter.

Signed-off-by: Jasper Berton <jasper.berton@team.blue>

Author: JasperB-TeamBlue

lib/vdsm/virt/vmdevices/storage.py

@@ -113,7 +113,7 @@ class Drive(core.Base):
                  'vm_custom', '_block_info', '_threshold_state', '_lock',
                  '_monitor_lock', '_monitorable', 'guestName', '_iotune',
                  'RBD', 'managed', 'scratch_disk', 'exceeded_time',
-                 'extend_time', 'managed_reservation')
+                 'extend_time', 'managed_reservation', 'discard_no_unref')
     # pylint: disable=used-before-assignment
     VOLWM_CHUNK_SIZE = (
         config.getint('irs', 'volume_utilization_chunk_mb') * MiB)
@@ -1125,6 +1125,8 @@ def _getDriverXML(drive):
 
     if 'discard' in drive and drive['discard']:
         driverAttrs['discard'] = 'unmap'
+        if 'discard_no_unref' in drive and drive['discard_no_unref']:
+            driverAttrs['discard_no_unref'] = 'on'
 
     try:
         driverAttrs['iothread'] = str(drive['specParams']['pinToIoThread'])

lib/vdsm/virt/vmdevices/storagexml.py

@@ -218,6 +218,7 @@ def _update_serial_params(params, dev):
 def _get_driver_params(driver):
     params = {
         'discard': driver.attrib.get('discard') == 'unmap',
+        'discard_no_unref': driver.attrib.get("discard_no_unref") == "on",
         'format': 'cow' if driver.attrib.get('type') == 'qcow2' else 'raw',
     }
 

tests/virt/device_compat_test.py

@@ -99,6 +99,7 @@ def test_drive(self):
             'cache': 'none',
             'device': 'disk',
             'discard': 'False',
+            'discard_no_unref': 'False',
             'diskType': 'block',
             'format': 'cow',
             'iface': 'scsi',