Fix tests using O_TMPFILE

Unit tests using O_TMPFILE only rely on the kernel version to check
for the feature. This is wrong, as some filesystem, like tmpfs, doesn't
support O_TMPFILE.

So, instead of checking kernel version, this patch actually attempts to
open a file using O_TMPFILE and see if that's supported. If not, then
the test is skipped.

Change-Id: I5d652f1634b1ef940838573cfdd799ea17b8b572

swift/common/utils.py

@@ -45,7 +45,7 @@ import ctypes
 import ctypes.util
 from optparse import OptionParser
 
-from tempfile import mkstemp, NamedTemporaryFile
+from tempfile import gettempdir, mkstemp, NamedTemporaryFile
 import glob
 import itertools
 import stat
@@ -4358,6 +4358,43 @@ def modify_priority(conf, logger):
     _ioprio_set(io_class, io_priority)
 
 
+def o_tmpfile_in_path_supported(dirpath):
+    if not hasattr(os, 'O_TMPFILE'):
+        return False
+
+    testfile = os.path.join(dirpath, ".o_tmpfile.test")
+
+    hasO_TMPFILE = True
+    fd = None
+    try:
+        fd = os.open(testfile, os.O_CREAT | os.O_WRONLY | os.O_TMPFILE)
+    except OSError as e:
+        if e.errno == errno.EINVAL:
+            hasO_TMPFILE = False
+        else:
+            raise Exception("Error on '%(path)s' while checking "
+                            "O_TMPFILE: '%(ex)s'",
+                            {'path': dirpath, 'ex': e})
+
+    except Exception as e:
+        raise Exception("Error on '%(path)s' while checking O_TMPFILE: "
+                        "'%(ex)s'", {'path': dirpath, 'ex': e})
+
+    finally:
+        if fd is not None:
+            os.close(fd)
+
+        # ensure closing the fd will actually remove the file
+        if os.path.isfile(testfile):
+            return False
+
+    return hasO_TMPFILE
+
+
+def o_tmpfile_in_tmpdir_supported():
+    return o_tmpfile_in_path_supported(gettempdir())
+
+
 def o_tmpfile_supported():
     """
     Returns True if O_TMPFILE flag is supported.

test/unit/__init__.py

@@ -1080,6 +1080,15 @@ class Timeout(object):
         raise TimeoutException
 
 
+def requires_o_tmpfile_support_in_tmp(func):
+    @functools.wraps(func)
+    def wrapper(*args, **kwargs):
+        if not utils.o_tmpfile_in_tmpdir_supported():
+            raise SkipTest('Requires O_TMPFILE support in TMPDIR')
+        return func(*args, **kwargs)
+    return wrapper
+
+
 def requires_o_tmpfile_support(func):
     @functools.wraps(func)
     def wrapper(*args, **kwargs):

test/unit/common/test_linkat.py

@@ -25,7 +25,7 @@ from tempfile import gettempdir
 from swift.common.linkat import linkat
 from swift.common.utils import O_TMPFILE
 
-from test.unit import requires_o_tmpfile_support
+from test.unit import requires_o_tmpfile_support_in_tmp
 
 
 class TestLinkat(unittest.TestCase):
@@ -38,7 +38,7 @@ class TestLinkat(unittest.TestCase):
     def test_available(self):
         self.assertFalse(linkat.available)
 
-    @requires_o_tmpfile_support
+    @requires_o_tmpfile_support_in_tmp
     def test_errno(self):
         with open('/dev/null', 'r') as fd:
             self.assertRaises(IOError, linkat,
@@ -77,7 +77,7 @@ class TestLinkat(unittest.TestCase):
         mock_cdll.assert_called_once_with(libc_name, use_errno=True)
         self.assertTrue(libc.linkat_retrieved)
 
-    @requires_o_tmpfile_support
+    @requires_o_tmpfile_support_in_tmp
     def test_linkat_success(self):
 
         fd = None

test/unit/common/test_utils.py

@@ -72,7 +72,7 @@ from swift.common.header_key_dict import HeaderKeyDict
 from swift.common.storage_policy import POLICIES, reload_storage_policies
 from swift.common.swob import Request, Response
 from test.unit import FakeLogger, requires_o_tmpfile_support, \
-    quiet_eventlet_exceptions
+    requires_o_tmpfile_support_in_tmp, quiet_eventlet_exceptions
 
 threading = eventlet.patcher.original('threading')
 
@@ -3838,7 +3838,7 @@ cluster_dfw1 = http://dfw1.host/v1/
                 patch('platform.architecture', return_value=('64bit', '')):
             self.assertRaises(OSError, utils.NR_ioprio_set)
 
-    @requires_o_tmpfile_support
+    @requires_o_tmpfile_support_in_tmp
     def test_link_fd_to_path_linkat_success(self):
         tempdir = mkdtemp()
         fd = os.open(tempdir, utils.O_TMPFILE | os.O_WRONLY)
@@ -3858,7 +3858,7 @@ cluster_dfw1 = http://dfw1.host/v1/
             os.close(fd)
             shutil.rmtree(tempdir)
 
-    @requires_o_tmpfile_support
+    @requires_o_tmpfile_support_in_tmp
     def test_link_fd_to_path_target_exists(self):
         tempdir = mkdtemp()
         # Create and write to a file
@@ -3893,7 +3893,7 @@ cluster_dfw1 = http://dfw1.host/v1/
                 self.fail("Expecting IOError exception")
         self.assertTrue(_m_linkat.called)
 
-    @requires_o_tmpfile_support
+    @requires_o_tmpfile_support_in_tmp
     def test_linkat_race_dir_not_exists(self):
         tempdir = mkdtemp()
         target_dir = os.path.join(tempdir, uuid4().hex)