CA-255945: fix race on mkdir

Signed-off-by: Stefano Panella <stefano.panella@citrix.com>
Reviewed-by: Germano Percossi <germano.percossi@citrix.com>

drivers/mpath_dmp.py

@@ -25,6 +25,7 @@
 import scsiutil
 import mpp_luncheck
 import wwid_conf
+import errno
 
 iscsi_mpath_file = "/etc/iscsi/iscsid-mpath.conf"
 iscsi_default_file = "/etc/iscsi/iscsid-default.conf"
@@ -55,8 +56,13 @@ def _is_mpp_daemon_running():
         return False
 
 def activate_MPdev(sid, dst):
-    if not os.path.exists(MP_INUSEDIR):
+    try:
         os.mkdir(MP_INUSEDIR)
+    except OSError as exc:
+        if exc.errno == errno.EEXIST:
+            pass
+        else:
+            raise
     if (mpp_luncheck.is_RdacLun(sid)):
         suffix = get_TargetID_LunNUM(sid)
         sid_with_suffix = sid + "-" + suffix

tests/test_mpath_dmp.py

@@ -1,11 +1,22 @@
-import mock
+"""
+Unit tests for mpath dmp
+"""
+import errno
+import os
 import unittest
+import mock
 import testlib
 import mpath_dmp
 import SR
 
 
-class Test_mpath_dmp(unittest.TestCase):
+# pylint: disable=W0613; mocks don't need to be accessed
+# pylint: disable=R0201; methods must be instance for nose to work
+# pylint: disable=W0212; unit tests are permitted to snoop
+class TestMpathDmp(unittest.TestCase):
+    """
+    Unit tests for mpath dmp
+    """
 
     @testlib.with_context
     @mock.patch('mpath_dmp.util', autospec=True)
@@ -38,3 +49,37 @@ def test_is_valid_multipath_device(self, context, util_mod):
         # Test when everything is fine
         util_mod.doexec.side_effect = [(0, "out", "err"), (0, "out", "err")]
         self.assertTrue(mpath_dmp._is_valid_multipath_device("fake_dev"))
+
+    @mock.patch('mpath_dmp.mpp_luncheck.is_RdacLun', autospec=True)
+    @mock.patch('util.pread2', autospec=True)
+    @mock.patch('mpath_dmp.os.mkdir', autospec=True)
+    def test_activate_no_exception(self, mock_mkdir, pread2, is_rdaclun):
+        """
+        Test that activeate MPDev works if directory does not exist
+        """
+        is_rdaclun.return_value = False
+        mpath_dmp.activate_MPdev("sid", "dst")
+        pread2.assert_called_with(['ln', '-sf', "dst", os.path.join(mpath_dmp.MP_INUSEDIR, "sid")])
+
+    @mock.patch('mpath_dmp.mpp_luncheck.is_RdacLun', autospec=True)
+    @mock.patch('util.pread2', autospec=True)
+    @mock.patch('mpath_dmp.os.mkdir', autospec=True)
+    def test_activate_exists_success(self, mock_mkdir, pread2, is_rdaclun):
+        """
+        Test that activeate MPDev works if directory exists
+        """
+        mock_mkdir.side_effect = [OSError(errno.EEXIST, "Directory exists")]
+        is_rdaclun.return_value = False
+        mpath_dmp.activate_MPdev("sid", "dst")
+        pread2.assert_called_with(['ln', '-sf', "dst", os.path.join(mpath_dmp.MP_INUSEDIR, "sid")])
+
+    @mock.patch('mpath_dmp.os.mkdir', autospec=True)
+    def test_activate_permission_denied(self, mock_mkdir):
+        """
+        Test that activeate MPDev works if mkdir returns permission denied
+        """
+        mock_mkdir.side_effect = [OSError(errno.EPERM, "Permission denied")]
+        with self.assertRaises(OSError) as context:
+            mpath_dmp.activate_MPdev("sid", "dst")
+
+        self.assertEqual(errno.EPERM, context.exception.errno)