Silence warning when running in a container with overlayfs

When running in a container using overlayfs we may see the following
warning:

  WARNING os_brick.initiator.connectors.nvmeof process execution error
  in _get_host_uuid: Unexpected error while running command.
  Command: blkid overlay -s UUID -o value
  Exit code: 2
  Stdout: ''
  Stderr: '': oslo_concurrency.processutils.ProcessExecutionError:
  Unexpected error while running command.

This change fixes the issue by not running the command when the file
system source is overlay.

Closes-Bug: #2045557
Change-Id: I3abc5bee7f474a9a40d396c559a42edff86334e0

os_brick/initiator/connectors/nvmeof.py

@@ -792,8 +792,13 @@ class NVMeOFConnector(base.BaseLinuxConnector):
         try:
             lines, err = self._execute(
                 *cmd, run_as_root=True, root_helper=self._root_helper)
+            source = lines.split('\n')[0]
+            # In a container this could be 'overlay', which causes the blkid
+            # command to fail.
+            if source == "overlay":
+                return None
             blkid_cmd = (
-                'blkid', lines.split('\n')[0], '-s', 'UUID', '-o', 'value')
+                'blkid', source, '-s', 'UUID', '-o', 'value')
             lines, _err = self._execute(
                 *blkid_cmd, run_as_root=True, root_helper=self._root_helper)
             return lines.split('\n')[0]

os_brick/tests/initiator/connectors/test_nvmeof.py

@@ -909,8 +909,10 @@ class NVMeOFConnectorTestCase(test_connector.ConnectorTestCase):
 
     @mock.patch.object(nvmeof.NVMeOFConnector, '_execute', autospec=True)
     def test_get_sysuuid_without_newline(self, mock_execute):
-        mock_execute.return_value = (
-            "9126E942-396D-11E7-B0B7-A81E84C186D1\n", "")
+        mock_execute.side_effect = [
+            ("/dev/sda1", ""),
+            ("9126E942-396D-11E7-B0B7-A81E84C186D1\n", "")
+        ]
         uuid = self.connector._get_host_uuid()
         expected_uuid = "9126E942-396D-11E7-B0B7-A81E84C186D1"
         self.assertEqual(expected_uuid, uuid)
@@ -921,6 +923,12 @@ class NVMeOFConnectorTestCase(test_connector.ConnectorTestCase):
         uuid = self.connector._get_host_uuid()
         self.assertIsNone(uuid)
 
+    @mock.patch.object(nvmeof.NVMeOFConnector, '_execute', autospec=True)
+    def test_get_sysuuid_overlay(self, mock_execute):
+        mock_execute.return_value = ("overlay\n", "")
+        uuid = self.connector._get_host_uuid()
+        self.assertIsNone(uuid)
+
     @mock.patch.object(utils, 'get_nvme_host_id',
                        return_value=SYS_UUID)
     @mock.patch.object(nvmeof.NVMeOFConnector,

releasenotes/notes/fix-host-uuid-warning-3814b7e47bde8010.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Fixes an warning seen when running in a container using ``overlayfs``.