91 lines
3.1 KiB
Python
91 lines
3.1 KiB
Python
# Copyright 2010 United States Government as represented by the
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# Administrator of the National Aeronautics and Space Administration.
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# Copyright 2011 Justin Santa Barbara
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# Copyright 2018 Michael Still and Aptira
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# 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, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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# This module is utility methods that privsep depends on. Privsep isn't allowed
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# to depend on anything outside the privsep directory, so these need to be
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# here. That said, other parts of nova can call into these utilities if
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# needed.
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import errno
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import mmap
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import os
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import random
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import sys
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from oslo_log import log as logging
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from oslo_utils import excutils
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# NOTE(mriedem): Avoid importing nova.utils since that can cause a circular
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# import with the privsep code. In fact, avoid importing anything outside
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# of nova/privsep/ if possible.
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LOG = logging.getLogger(__name__)
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def generate_random_string():
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return str(random.randint(0, sys.maxsize))
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def supports_direct_io(dirpath):
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if not hasattr(os, 'O_DIRECT'):
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LOG.debug("This python runtime does not support direct I/O")
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return False
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# Use a random filename to avoid issues with $dirpath being on shared
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# storage.
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file_name = "%s.%s" % (".directio.test", generate_random_string())
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testfile = os.path.join(dirpath, file_name)
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hasDirectIO = True
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fd = None
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try:
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fd = os.open(testfile, os.O_CREAT | os.O_WRONLY | os.O_DIRECT)
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# Check is the write allowed with 4096 byte alignment
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align_size = 4096
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m = mmap.mmap(-1, align_size)
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m.write(b"x" * align_size)
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os.write(fd, m)
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LOG.debug("Path '%(path)s' supports direct I/O",
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{'path': dirpath})
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except OSError as e:
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if e.errno in (errno.EINVAL, errno.ENOENT):
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LOG.debug("Path '%(path)s' does not support direct I/O: "
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"'%(ex)s'", {'path': dirpath, 'ex': e})
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hasDirectIO = False
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else:
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with excutils.save_and_reraise_exception():
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LOG.error("Error on '%(path)s' while checking "
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"direct I/O: '%(ex)s'",
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{'path': dirpath, 'ex': e})
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except Exception as e:
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with excutils.save_and_reraise_exception():
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LOG.error("Error on '%(path)s' while checking direct I/O: "
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"'%(ex)s'", {'path': dirpath, 'ex': e})
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finally:
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# ensure unlink(filepath) will actually remove the file by deleting
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# the remaining link to it in close(fd)
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if fd is not None:
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os.close(fd)
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try:
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os.unlink(testfile)
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except Exception:
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pass
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return hasDirectIO
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