423 lines
14 KiB
Python
423 lines
14 KiB
Python
#
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# The Qubes OS Project, https://www.qubes-os.org/
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#
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# Copyright (C) 2018 Rusty Bird <rustybird@net-c.com>
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, see <https://www.gnu.org/licenses/>.
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#
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''' Driver for handling VM images as files, without any device-mapper
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involvement. A reflink-capable filesystem is strongly recommended,
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but not required.
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'''
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import collections
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import errno
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import fcntl
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import glob
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import logging
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import os
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import re
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import subprocess
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import tempfile
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from contextlib import contextmanager, suppress
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import qubes.storage
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BLKSIZE = 512
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FICLONE = 1074041865 # see ioctl_ficlone manpage
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LOGGER = logging.getLogger('qubes.storage.reflink')
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class ReflinkPool(qubes.storage.Pool):
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driver = 'file-reflink'
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_known_dir_path_prefixes = ['appvms', 'vm-templates']
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def __init__(self, dir_path, setup_check='yes', revisions_to_keep=1,
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**kwargs):
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super().__init__(revisions_to_keep=revisions_to_keep, **kwargs)
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self._volumes = {}
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self.dir_path = os.path.abspath(dir_path)
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self.setup_check = qubes.property.bool(None, None, setup_check)
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def setup(self):
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created = _make_dir(self.dir_path)
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if self.setup_check and not is_reflink_supported(self.dir_path):
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if created:
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_remove_empty_dir(self.dir_path)
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raise qubes.storage.StoragePoolException(
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'The filesystem for {!r} does not support reflinks. If you'
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' can live with VM startup delays and wasted disk space, pass'
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' the "setup_check=no" option.'.format(self.dir_path))
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for dir_path_prefix in self._known_dir_path_prefixes:
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_make_dir(os.path.join(self.dir_path, dir_path_prefix))
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return self
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def init_volume(self, vm, volume_config):
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# Fail closed on any strange VM dir_path_prefix, just in case
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# /etc/udev/rules/00-qubes-ignore-devices.rules needs updating
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assert vm.dir_path_prefix in self._known_dir_path_prefixes, \
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'Unknown dir_path_prefix {!r}'.format(vm.dir_path_prefix)
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volume_config['pool'] = self
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if 'revisions_to_keep' not in volume_config:
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volume_config['revisions_to_keep'] = self.revisions_to_keep
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if 'vid' not in volume_config:
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volume_config['vid'] = os.path.join(vm.dir_path_prefix, vm.name,
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volume_config['name'])
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volume = ReflinkVolume(**volume_config)
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self._volumes[volume_config['vid']] = volume
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return volume
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def list_volumes(self):
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return list(self._volumes.values())
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def get_volume(self, vid):
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return self._volumes[vid]
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def destroy(self):
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pass
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@property
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def config(self):
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return {
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'name': self.name,
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'dir_path': self.dir_path,
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'driver': ReflinkPool.driver,
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'revisions_to_keep': self.revisions_to_keep
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}
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@property
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def size(self):
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statvfs = os.statvfs(self.dir_path)
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return statvfs.f_frsize * statvfs.f_blocks
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@property
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def usage(self):
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statvfs = os.statvfs(self.dir_path)
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return statvfs.f_frsize * (statvfs.f_blocks - statvfs.f_bfree)
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class ReflinkVolume(qubes.storage.Volume):
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def create(self):
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if self.save_on_stop and not self.snap_on_start:
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_create_sparse_file(self._path_clean, self.size)
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return self
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def verify(self):
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if self.snap_on_start:
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# pylint: disable=protected-access
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img = self.source._path_clean
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elif self.save_on_stop:
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img = self._path_clean
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else:
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img = None
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if img is None or os.path.exists(img):
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return True
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raise qubes.storage.StoragePoolException(
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'Missing image file {!r} for volume {!s}'.format(img, self.vid))
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def remove(self):
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''' Drop volume object from pool; remove volume images from
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oldest to newest; remove empty VM directory.
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'''
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with suppress(KeyError):
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# pylint: disable=protected-access
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del self.pool._volumes[self]
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self._prune_revisions(keep=0)
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_remove_file(self._path_clean)
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_remove_file(self._path_dirty)
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_remove_empty_dir(os.path.dirname(self._path_dirty))
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return self
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def is_outdated(self):
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if self.snap_on_start:
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with suppress(FileNotFoundError):
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# pylint: disable=protected-access
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return (os.path.getmtime(self.source._path_clean) >
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os.path.getmtime(self._path_clean))
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return False
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def is_dirty(self):
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return self.save_on_stop and os.path.exists(self._path_dirty)
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def start(self):
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if self.snap_on_start:
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# pylint: disable=protected-access
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_copy_file(self.source._path_clean, self._path_clean)
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if self.is_dirty(): # implies self.save_on_stop
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return self
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if self.save_on_stop or self.snap_on_start:
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_copy_file(self._path_clean, self._path_dirty)
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else:
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_create_sparse_file(self._path_dirty, self.size)
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return self
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def stop(self):
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if self.save_on_stop:
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self._commit()
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else:
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_remove_file(self._path_dirty)
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if self.snap_on_start:
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_remove_file(self._path_clean)
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return self
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def _commit(self):
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self._add_revision()
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self._prune_revisions()
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_rename_file(self._path_dirty, self._path_clean)
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def _add_revision(self):
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if self.revisions_to_keep == 0:
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return
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if _get_file_disk_usage(self._path_clean) == 0:
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return
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ctime = os.path.getctime(self._path_clean)
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revision = qubes.storage.isodate(int(ctime)) + 'Z'
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_copy_file(self._path_clean, self._path_revision(revision))
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def _prune_revisions(self, keep=None):
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if keep is None:
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keep = self.revisions_to_keep
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# pylint: disable=invalid-unary-operand-type
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for revision in list(self.revisions.keys())[:(-keep) or None]:
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_remove_file(self._path_revision(revision))
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def revert(self, revision=None):
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if revision is None:
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revision = list(self.revisions.keys())[-1]
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elif not os.path.exists(self._path_revision(revision)):
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raise qubes.storage.StoragePoolException(
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'Missing revision {!r} for volume {!s}'.format(
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revision, self.vid))
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self._add_revision()
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_rename_file(self._path_revision(revision), self._path_clean)
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return self
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def resize(self, size):
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''' Expand a read-write volume image; notify any corresponding
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loop devices of the size change.
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'''
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if not self.rw:
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raise qubes.storage.StoragePoolException(
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'Cannot resize: {!s} is read-only'.format(self.vid))
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if size < self.size:
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raise qubes.storage.StoragePoolException(
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'For your own safety, shrinking of {!s} is disabled'
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' ({:d} < {:d}). If you really know what you are doing,'
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' use "truncate" manually.'.format(self.vid, size, self.size))
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try: # assume volume is not (cleanly) stopped ...
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_resize_file(self._path_dirty, size)
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except FileNotFoundError: # ... but it actually is.
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_resize_file(self._path_clean, size)
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self.size = size
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# resize any corresponding loop devices
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out = _cmd('losetup', '--associated', self._path_dirty)
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for match in re.finditer(br'^(/dev/loop[0-9]+): ', out, re.MULTILINE):
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loop_dev = match.group(1).decode('ascii')
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_cmd('losetup', '--set-capacity', loop_dev)
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return self
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def _require_save_on_stop(self, method_name):
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if not self.save_on_stop:
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raise NotImplementedError(
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'Cannot {!s}: {!s} is not save_on_stop'.format(
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method_name, self.vid))
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def export(self):
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self._require_save_on_stop('export')
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return self._path_clean
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def import_data(self):
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self._require_save_on_stop('import_data')
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_create_sparse_file(self._path_dirty, self.size)
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return self._path_dirty
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def import_data_end(self, success):
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if success:
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self._commit()
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else:
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_remove_file(self._path_dirty)
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return self
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def import_volume(self, src_volume):
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self._require_save_on_stop('import_volume')
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try:
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_copy_file(src_volume.export(), self._path_dirty)
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except:
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self.import_data_end(False)
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raise
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self.import_data_end(True)
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return self
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def _path_revision(self, revision):
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return self._path_clean + '@' + revision
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@property
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def _path_clean(self):
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return os.path.join(self.pool.dir_path, self.vid + '.img')
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@property
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def _path_dirty(self):
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return os.path.join(self.pool.dir_path, self.vid + '-dirty.img')
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@property
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def path(self):
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return self._path_dirty
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@property
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def revisions(self):
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revision_to_timestamp = collections.OrderedDict()
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prefix = self._path_revision('')
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for filename in sorted(glob.glob(glob.escape(prefix) + '*Z')):
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revision = filename[len(prefix):]
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timestamp = revision[:-1]
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revision_to_timestamp[revision] = timestamp
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return revision_to_timestamp
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@property
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def usage(self):
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''' Return volume disk usage from the VM's perspective. It is
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usually much lower from the host's perspective due to CoW.
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'''
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with suppress(FileNotFoundError):
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return _get_file_disk_usage(self._path_dirty)
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with suppress(FileNotFoundError):
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return _get_file_disk_usage(self._path_clean)
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return 0
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@contextmanager
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def _replace_file(dst):
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''' Yield a tempfile whose name starts with dst, creating the last
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directory component if necessary. If the block does not raise
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an exception, flush+fsync the tempfile and rename it to dst.
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'''
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tmp_dir, prefix = os.path.split(dst + '~')
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_make_dir(tmp_dir)
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tmp = tempfile.NamedTemporaryFile(dir=tmp_dir, prefix=prefix, delete=False)
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try:
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yield tmp
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tmp.flush()
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os.fsync(tmp.fileno())
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tmp.close()
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_rename_file(tmp.name, dst)
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except:
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tmp.close()
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_remove_file(tmp.name)
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raise
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def _get_file_disk_usage(path):
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''' Return real disk usage (not logical file size) of a file. '''
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return os.stat(path).st_blocks * BLKSIZE
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def _fsync_dir(path):
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dir_fd = os.open(path, os.O_RDONLY | os.O_DIRECTORY)
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try:
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os.fsync(dir_fd)
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finally:
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os.close(dir_fd)
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def _make_dir(path):
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''' mkdir path, ignoring FileExistsError; return whether we
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created it.
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'''
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with suppress(FileExistsError):
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os.mkdir(path)
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_fsync_dir(os.path.dirname(path))
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LOGGER.info('Created directory: %s', path)
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return True
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return False
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def _remove_file(path):
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with suppress(FileNotFoundError):
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os.remove(path)
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_fsync_dir(os.path.dirname(path))
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LOGGER.info('Removed file: %s', path)
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def _remove_empty_dir(path):
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try:
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os.rmdir(path)
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_fsync_dir(os.path.dirname(path))
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LOGGER.info('Removed empty directory: %s', path)
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except OSError as ex:
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if ex.errno not in (errno.ENOENT, errno.ENOTEMPTY):
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raise
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def _rename_file(src, dst):
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os.rename(src, dst)
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dst_dir = os.path.dirname(dst)
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src_dir = os.path.dirname(src)
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_fsync_dir(dst_dir)
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if src_dir != dst_dir:
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_fsync_dir(src_dir)
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LOGGER.info('Renamed file: %s -> %s', src, dst)
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def _resize_file(path, size):
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''' Resize an existing file. '''
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with open(path, 'rb+') as file:
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file.truncate(size)
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os.fsync(file.fileno())
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def _create_sparse_file(path, size):
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''' Create an empty sparse file. '''
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with _replace_file(path) as tmp:
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tmp.truncate(size)
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LOGGER.info('Created sparse file: %s', tmp.name)
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def _copy_file(src, dst):
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''' Copy src to dst as a reflink if possible, sparse if not. '''
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if not os.path.exists(src):
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raise FileNotFoundError(src)
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with _replace_file(dst) as tmp:
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LOGGER.info('Copying file: %s -> %s', src, tmp.name)
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_cmd('cp', '--sparse=always', '--reflink=auto', src, tmp.name)
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def _cmd(*args):
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''' Run command until finished; return stdout (as bytes) if it
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exited 0. Otherwise, raise a detailed StoragePoolException.
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'''
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try:
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return subprocess.run(args, check=True,
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stdout=subprocess.PIPE,
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stderr=subprocess.PIPE).stdout
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except subprocess.CalledProcessError as ex:
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msg = '{!s} err={!r} out={!r}'.format(ex, ex.stderr, ex.stdout)
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raise qubes.storage.StoragePoolException(msg) from ex
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def is_reflink_supported(dst_dir, src_dir=None):
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''' Return whether destination directory supports reflink copies
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from source directory. (A temporary file is created in each
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directory, using O_TMPFILE if possible.)
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'''
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if src_dir is None:
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src_dir = dst_dir
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dst = tempfile.TemporaryFile(dir=dst_dir)
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src = tempfile.TemporaryFile(dir=src_dir)
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src.write(b'foo') # don't let any filesystem get clever with empty files
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try:
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fcntl.ioctl(dst.fileno(), FICLONE, src.fileno())
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return True
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except OSError:
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return False
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