libvirt: Remove reference to transient domain when detaching devices

When detaching a device from a domain we first attempt to remove the
device from both the persistent and live configs before looping to
ensure the device has really been detached from the running live config.

Previously when this failed we logged an error message that suggested
that this was due to issues detaching the device from a transient
domain, however this is not the case as the domain is persistent.

This change simply updates the error and associated comments to only
reference the live config of the domain.

Additionally a DEBUG line claiming that a device has been successfully
detached is now only logged once the device is removed from the live
config, hopefully avoiding any confusion from this line been logged
each time an attempt is made to detach the device.

Change-Id: If869470216600c303d47cf79f12c4fc88abcf813
(cherry picked from commit 636c7461dee4002571da6e99986eb17e9a28b0f4)

3 files changed, 15 insertions, 12 deletions

diff --git a/nova/tests/unit/virt/libvirt/test_driver.py b/nova/tests/unit/virt/libvirt/test_driver.py
index e5c85a54aa..06ecc41185 100644
--- a/nova/tests/unit/virt/libvirt/test_driver.py
+++ b/nova/tests/unit/virt/libvirt/test_driver.py
@@ -7450,7 +7450,8 @@ class LibvirtConnTestCase(test.NoDBTestCase,
         mock_dom = mock.MagicMock()
 
         # Second time don't return anything about disk vdc so it looks removed
-        return_list = [mock_xml_with_disk, mock_xml_without_disk]
+        return_list = [mock_xml_with_disk, mock_xml_without_disk,
+                       mock_xml_without_disk]
         # Doubling the size of return list because we test with two guest power
         # states
         mock_dom.XMLDesc.side_effect = return_list + return_list
@@ -18950,7 +18951,7 @@ class LibvirtDriverTestCase(test.NoDBTestCase):
             # DeviceNotFound
             get_interface_calls = [expected_cfg, None]
         else:
-            get_interface_calls = [expected_cfg, expected_cfg, None]
+            get_interface_calls = [expected_cfg, expected_cfg, None, None]
 
         with test.nested(
             mock.patch.object(host.Host, 'get_guest', return_value=guest),
@@ -19087,7 +19088,7 @@ class LibvirtDriverTestCase(test.NoDBTestCase):
         domain.detachDeviceFlags(expected.to_xml(), flags=expected_flags)
         self.mox.ReplayAll()
         with mock.patch.object(libvirt_guest.Guest, 'get_interface_by_cfg',
-                               side_effect=[expected, expected, None]):
+                               side_effect=[expected, expected, None, None]):
             self.drvr.detach_interface(self.context, instance, network_info[0])
         self.mox.VerifyAll()
 
diff --git a/nova/tests/unit/virt/libvirt/test_guest.py b/nova/tests/unit/virt/libvirt/test_guest.py
index 7c61334a5a..70299dfe1e 100644
--- a/nova/tests/unit/virt/libvirt/test_guest.py
+++ b/nova/tests/unit/virt/libvirt/test_guest.py
@@ -228,7 +228,7 @@ class GuestTestCase(test.NoDBTestCase):
         conf = mock.Mock(spec=vconfig.LibvirtConfigGuestDevice)
         conf.to_xml.return_value = "</xml>"
         get_config = mock.Mock()
-        get_config.side_effect = [conf, conf, None]
+        get_config.side_effect = [conf, conf, conf, None, None]
         dev_path = "/dev/vdb"
         self.domain.isPersistent.return_value = False
         retry_detach = self.guest.detach_device_with_retry(
@@ -244,7 +244,7 @@ class GuestTestCase(test.NoDBTestCase):
         conf.to_xml.return_value = "</xml>"
         get_config = mock.Mock()
         # Force multiple retries of detach
-        get_config.side_effect = [conf, conf, conf, None]
+        get_config.side_effect = [conf, conf, conf, conf, conf, None, None]
         dev_path = "/dev/vdb"
         self.domain.isPersistent.return_value = True
 
@@ -356,7 +356,7 @@ class GuestTestCase(test.NoDBTestCase):
         get_config = mock.Mock()
         # Simulate the persistent domain attach attempt followed by the live
         # domain attach attempt and success
-        get_config.side_effect = [conf, conf, None]
+        get_config.side_effect = [conf, conf, conf, None, None]
         fake_device = "vdb"
         fake_exc = fakelibvirt.make_libvirtError(
             fakelibvirt.libvirtError, "",
diff --git a/nova/virt/libvirt/guest.py b/nova/virt/libvirt/guest.py
index 86e9aa051b..573d800bf7 100644
--- a/nova/virt/libvirt/guest.py
+++ b/nova/virt/libvirt/guest.py
@@ -398,9 +398,11 @@ class Guest(object):
             # Raise DeviceNotFound if the device isn't found during detach
             try:
                 self.detach_device(conf, persistent=persistent, live=live)
-                LOG.debug('Successfully detached device %s from guest. '
-                          'Persistent? %s. Live? %s',
-                          device, persistent, live)
+                if get_device_conf_func(device) is None:
+                    LOG.debug('Successfully detached device %s from guest. '
+                              'Persistent? %s. Live? %s',
+                              device, persistent, live)
+
             except libvirt.libvirtError as ex:
                 with excutils.save_and_reraise_exception():
                     errcode = ex.get_error_code()
@@ -452,11 +454,11 @@ class Guest(object):
         def _do_wait_and_retry_detach():
             config = get_device_conf_func(device)
             if config is not None:
-                # Device is already detached from persistent domain
-                # and only transient domain needs update
+                # Device is already detached from persistent config
+                # and only the live config needs to be updated.
                 _try_detach_device(config, persistent=False, live=live)
 
-                reason = _("Unable to detach from guest transient domain.")
+                reason = _("Unable to detach the device from the live config.")
                 raise exception.DeviceDetachFailed(
                     device=alternative_device_name, reason=reason)