139 lines
4.6 KiB
Python
139 lines
4.6 KiB
Python
# Copyright 2011 Red Hat, Inc.
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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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"""Support for mounting images with qemu-nbd."""
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import os
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import random
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import re
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import time
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from oslo_config import cfg
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from oslo_log import log as logging
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from nova.i18n import _, _LE, _LI, _LW
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from nova import utils
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from nova.virt.disk.mount import api
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LOG = logging.getLogger(__name__)
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nbd_opts = [
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cfg.IntOpt('timeout_nbd',
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default=10,
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help='Amount of time, in seconds, to wait for NBD '
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'device start up.'),
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]
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CONF = cfg.CONF
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CONF.register_opts(nbd_opts)
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NBD_DEVICE_RE = re.compile('nbd[0-9]+')
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class NbdMount(api.Mount):
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"""qemu-nbd support disk images."""
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mode = 'nbd'
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def _detect_nbd_devices(self):
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"""Detect nbd device files."""
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return filter(NBD_DEVICE_RE.match, os.listdir('/sys/block/'))
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def _find_unused(self, devices):
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for device in devices:
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if not os.path.exists(os.path.join('/sys/block/', device, 'pid')):
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if not os.path.exists('/var/lock/qemu-nbd-%s' % device):
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return device
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else:
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LOG.error(_LE('NBD error - previous umount did not '
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'cleanup /var/lock/qemu-nbd-%s.'), device)
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LOG.warning(_LW('No free nbd devices'))
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return None
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def _allocate_nbd(self):
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if not os.path.exists('/sys/block/nbd0'):
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LOG.error(_LE('nbd module not loaded'))
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self.error = _('nbd unavailable: module not loaded')
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return None
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devices = self._detect_nbd_devices()
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random.shuffle(devices)
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device = self._find_unused(devices)
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if not device:
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# really want to log this info, not raise
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self.error = _('No free nbd devices')
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return None
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return os.path.join('/dev', device)
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@utils.synchronized('nbd-allocation-lock')
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def _inner_get_dev(self):
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device = self._allocate_nbd()
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if not device:
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return False
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# NOTE(mikal): qemu-nbd will return an error if the device file is
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# already in use.
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LOG.debug('Get nbd device %(dev)s for %(imgfile)s',
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{'dev': device, 'imgfile': self.image.path})
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_out, err = utils.trycmd('qemu-nbd', '-c', device,
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self.image.path,
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run_as_root=True)
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if err:
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self.error = _('qemu-nbd error: %s') % err
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LOG.info(_LI('NBD mount error: %s'), self.error)
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return False
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# NOTE(vish): this forks into another process, so give it a chance
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# to set up before continuing
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pidfile = "/sys/block/%s/pid" % os.path.basename(device)
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for _i in range(CONF.timeout_nbd):
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if os.path.exists(pidfile):
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self.device = device
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break
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time.sleep(1)
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else:
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self.error = _('nbd device %s did not show up') % device
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LOG.info(_LI('NBD mount error: %s'), self.error)
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# Cleanup
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_out, err = utils.trycmd('qemu-nbd', '-d', device,
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run_as_root=True)
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if err:
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LOG.warning(_LW('Detaching from erroneous nbd device returned '
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'error: %s'), err)
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return False
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self.error = ''
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self.linked = True
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return True
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def get_dev(self):
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"""Retry requests for NBD devices."""
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return self._get_dev_retry_helper()
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def unget_dev(self):
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if not self.linked:
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return
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LOG.debug('Release nbd device %s', self.device)
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utils.execute('qemu-nbd', '-d', self.device, run_as_root=True)
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self.linked = False
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self.device = None
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def flush_dev(self):
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"""flush NBD block device buffer."""
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# Perform an explicit BLKFLSBUF to support older qemu-nbd(s).
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# Without this flush, when a nbd device gets re-used the
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# qemu-nbd intermittently hangs.
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if self.device:
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utils.execute('blockdev', '--flushbufs',
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self.device, run_as_root=True)
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