773edb4a5d
Linux 3.11 introduced O_TMPFILE as a flag to open() sys call. This would enable users to get a fd to an unnamed temporary file. As it's unnamed, it does not require the caller to devise unique names. It is also not accessible through any path. Hence, file creation is race-free. This file is initially unreachable. It is then populated with data(write), metadata(fsetxattr) and fsync'd before being atomically linked into the filesystem in a fully formed state using linkat() sys call. Only after a successful linkat() will the object file will be available for reference. Caveats * Unlike os.rename(), linkat() cannot overwrite destination path if it already exists. If path exists, we unlink and try again. * XFS support for O_TMPFILE was only added in Linux 3.15. * If client disconnects during object upload, although there is no incomplete/stale file on disk, the object directory would persist and is not cleaned up immediately. Change-Id: I8402439fab3aba5d7af449b5e465f89332f606ec Signed-off-by: Prashanth Pai <ppai@redhat.com>
104 lines
3.4 KiB
Python
104 lines
3.4 KiB
Python
# Copyright (c) 2016 OpenStack Foundation
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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'''Tests for `swift.common.linkat`'''
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import ctypes
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import unittest
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import os
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import mock
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from uuid import uuid4
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from swift.common.linkat import linkat
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from swift.common.utils import O_TMPFILE
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from test.unit import requires_o_tmpfile_support
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class TestLinkat(unittest.TestCase):
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def test_flags(self):
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self.assertTrue(hasattr(linkat, 'AT_FDCWD'))
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self.assertTrue(hasattr(linkat, 'AT_SYMLINK_FOLLOW'))
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@mock.patch('swift.common.linkat.linkat._c_linkat', None)
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def test_available(self):
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self.assertFalse(linkat.available)
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@requires_o_tmpfile_support
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def test_errno(self):
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with open('/dev/null', 'r') as fd:
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self.assertRaises(IOError, linkat,
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linkat.AT_FDCWD, "/proc/self/fd/%s" % (fd),
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linkat.AT_FDCWD, "/tmp/testlinkat",
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linkat.AT_SYMLINK_FOLLOW)
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self.assertEqual(ctypes.get_errno(), 0)
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@mock.patch('swift.common.linkat.linkat._c_linkat', None)
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def test_unavailable(self):
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self.assertRaises(EnvironmentError, linkat, 0, None, 0, None, 0)
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def test_unavailable_in_libc(self):
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class LibC(object):
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def __init__(self):
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self.linkat_retrieved = False
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@property
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def linkat(self):
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self.linkat_retrieved = True
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raise AttributeError
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libc = LibC()
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mock_cdll = mock.Mock(return_value=libc)
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with mock.patch('ctypes.CDLL', new=mock_cdll):
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# Force re-construction of a `Linkat` instance
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# Something you're not supposed to do in actual code
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new_linkat = type(linkat)()
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self.assertFalse(new_linkat.available)
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libc_name = ctypes.util.find_library('c')
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mock_cdll.assert_called_once_with(libc_name, use_errno=True)
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self.assertTrue(libc.linkat_retrieved)
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@requires_o_tmpfile_support
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def test_linkat_success(self):
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fd = None
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path = None
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ret = -1
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try:
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fd = os.open('/tmp', O_TMPFILE | os.O_WRONLY)
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path = os.path.join('/tmp', uuid4().hex)
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ret = linkat(linkat.AT_FDCWD, "/proc/self/fd/%d" % (fd),
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linkat.AT_FDCWD, path, linkat.AT_SYMLINK_FOLLOW)
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self.assertEqual(ret, 0)
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self.assertTrue(os.path.exists(path))
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finally:
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if fd:
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os.close(fd)
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if path and ret == 0:
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# if linkat succeeded, remove file
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os.unlink(path)
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@mock.patch('swift.common.linkat.linkat._c_linkat')
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def test_linkat_fd_not_integer(self, _mock_linkat):
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self.assertRaises(TypeError, linkat,
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"not_int", None, "not_int", None, 0)
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self.assertFalse(_mock_linkat.called)
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