diff --git a/nova/privsep/utils.py b/nova/privsep/utils.py
index 2b9d9703acdd..b51bcf5926ed 100644
--- a/nova/privsep/utils.py
+++ b/nova/privsep/utils.py
@@ -23,23 +23,32 @@
 import errno
 import mmap
 import os
+import random
+import sys
 
 from oslo_log import log as logging
 from oslo_utils import excutils
 
-from nova import utils as nova_utils
+# NOTE(mriedem): Avoid importing nova.utils since that can cause a circular
+# import with the privsep code. In fact, avoid importing anything outside
+# of nova/privsep/ if possible.
 
 LOG = logging.getLogger(__name__)
 
 
+def generate_random_string():
+    return str(random.randint(0, sys.maxsize))
+
+
 def supports_direct_io(dirpath):
 
     if not hasattr(os, 'O_DIRECT'):
         LOG.debug("This python runtime does not support direct I/O")
         return False
 
-    file_name = "%s.%s" % (".directio.test",
-                           nova_utils.generate_random_string())
+    # Use a random filename to avoid issues with $dirpath being on shared
+    # storage.
+    file_name = "%s.%s" % (".directio.test", generate_random_string())
     testfile = os.path.join(dirpath, file_name)
 
     hasDirectIO = True
diff --git a/nova/tests/unit/privsep/test_utils.py b/nova/tests/unit/privsep/test_utils.py
index cdb64331fa31..84d0767c2963 100644
--- a/nova/tests/unit/privsep/test_utils.py
+++ b/nova/tests/unit/privsep/test_utils.py
@@ -36,15 +36,15 @@ class SupportDirectIOTestCase(test.NoDBTestCase):
         self.einval.errno = errno.EINVAL
         self.enoent = OSError()
         self.enoent.errno = errno.ENOENT
-        self.test_path = os.path.join('.', '.directio.test.abc123')
+        self.test_path = os.path.join('.', '.directio.test.123')
         self.io_flags = os.O_CREAT | os.O_WRONLY | os.O_DIRECT
 
         open_patcher = mock.patch('os.open')
         write_patcher = mock.patch('os.write')
         close_patcher = mock.patch('os.close')
         unlink_patcher = mock.patch('os.unlink')
-        random_string_patcher = mock.patch('nova.utils.generate_random_string',
-                                           return_value='abc123')
+        random_string_patcher = mock.patch(
+            'nova.privsep.utils.generate_random_string', return_value='123')
         self.addCleanup(open_patcher.stop)
         self.addCleanup(write_patcher.stop)
         self.addCleanup(close_patcher.stop)