463 lines
16 KiB
Python
463 lines
16 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 asyncio
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import collections
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import errno
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import fcntl
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import functools
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import glob
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import logging
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import os
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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 # defined in <linux/fs.h>
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LOOP_SET_CAPACITY = 0x4C07 # defined in <linux/loop.h>
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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_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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def included_in(self, app):
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''' Check if there is pool containing this one - either as a
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filesystem or its LVM volume'''
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return qubes.storage.search_pool_containing_dir(
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[pool for pool in app.pools.values() if pool is not self],
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self.dir_path)
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def _unblock(method):
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''' Decorator transforming a synchronous volume method into a
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coroutine that runs the original method in the event loop's
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thread-based default executor, under a per-volume lock.
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'''
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@asyncio.coroutine
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@functools.wraps(method)
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def wrapper(self, *args, **kwargs):
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with (yield from self._lock): # pylint: disable=protected-access
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return (yield from asyncio.get_event_loop().run_in_executor(
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None, functools.partial(method, self, *args, **kwargs)))
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return wrapper
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class ReflinkVolume(qubes.storage.Volume):
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def __init__(self, *args, **kwargs):
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super().__init__(*args, **kwargs)
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self._lock = asyncio.Lock()
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self._path_vid = os.path.join(self.pool.dir_path, self.vid)
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self._path_clean = self._path_vid + '.img'
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self._path_dirty = self._path_vid + '-dirty.img'
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self._path_import = self._path_vid + '-import.img'
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self.path = self._path_dirty
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@_unblock
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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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@_unblock
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def verify(self):
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if self.snap_on_start:
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img = self.source._path_clean # pylint: disable=protected-access
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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 {}'.format(img, self.vid))
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@_unblock
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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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self.pool._volumes.pop(self, None) # pylint: disable=protected-access
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self._cleanup()
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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 _cleanup(self):
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for tmp in glob.iglob(glob.escape(self._path_vid) + '*.img*~*'):
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_remove_file(tmp)
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_remove_file(self._path_import)
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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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@_unblock
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def start(self):
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self._cleanup()
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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.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.snap_on_start or self.save_on_stop:
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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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@_unblock
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def stop(self):
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if self.save_on_stop:
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self._commit(self._path_dirty)
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else:
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_remove_file(self._path_dirty)
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_remove_file(self._path_clean)
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return self
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def _commit(self, path_from):
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self._add_revision()
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self._prune_revisions()
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_rename_file(path_from, 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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ctime = os.path.getctime(self._path_clean)
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timestamp = qubes.storage.isodate(int(ctime))
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_copy_file(self._path_clean,
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self._path_revision(self._next_revision_number, timestamp))
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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 number, timestamp in list(self.revisions.items())[:-keep or None]:
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_remove_file(self._path_revision(number, timestamp))
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@_unblock
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def revert(self, revision=None):
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if self.is_dirty():
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raise qubes.storage.StoragePoolException(
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'Cannot revert: {} is not cleanly stopped'.format(self.vid))
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if revision is None:
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number, timestamp = list(self.revisions.items())[-1]
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else:
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number, timestamp = revision, None
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path_revision = self._path_revision(number, timestamp)
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self._add_revision()
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_rename_file(path_revision, self._path_clean)
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return self
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@_unblock
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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: {} 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 {} is disabled'
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' ({} < {}). 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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self.size = 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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return self
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_update_loopdev_sizes(self._path_dirty)
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return self
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def export(self):
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if not self.save_on_stop:
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raise NotImplementedError(
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'Cannot export: {} is not save_on_stop'.format(self.vid))
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return self._path_clean
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def import_data(self):
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if not self.save_on_stop:
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raise NotImplementedError(
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'Cannot import_data: {} is not save_on_stop'.format(self.vid))
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_create_sparse_file(self._path_import, self.size)
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return self._path_import
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def import_data_end(self, success):
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if success:
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self._commit(self._path_import)
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else:
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_remove_file(self._path_import)
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return self
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@_unblock
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def import_volume(self, src_volume):
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if not self.save_on_stop:
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return self
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try:
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_copy_file(src_volume.export(), self._path_import)
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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, number, timestamp=None):
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if timestamp is None:
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timestamp = self.revisions[number]
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return self._path_clean + '.' + number + '@' + timestamp + 'Z'
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@property
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def _next_revision_number(self):
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numbers = self.revisions.keys()
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if numbers:
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return str(int(list(numbers)[-1]) + 1)
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return '1'
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@property
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def revisions(self):
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prefix = self._path_clean + '.'
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paths = glob.iglob(glob.escape(prefix) + '*@*Z')
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items = (path[len(prefix):-1].split('@') for path in paths)
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return collections.OrderedDict(sorted(items,
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key=lambda item: int(item[0])))
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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 _update_loopdev_sizes(img):
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''' Resolve img; update the size of loop devices backed by it. '''
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needle = os.fsencode(os.path.realpath(img)) + b'\n'
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for sys_path in glob.iglob('/sys/block/loop[0-9]*/loop/backing_file'):
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try:
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with open(sys_path, 'rb') as sys_io:
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if sys_io.read() != needle:
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continue
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except FileNotFoundError:
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continue
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with open('/dev/' + sys_path.split('/')[3]) as dev_io:
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fcntl.ioctl(dev_io.fileno(), LOOP_SET_CAPACITY)
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def _attempt_ficlone(src, dst):
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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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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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with _replace_file(dst) as tmp_io:
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with open(src, 'rb') as src_io:
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if _attempt_ficlone(src_io, tmp_io):
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LOGGER.info('Reflinked file: %s -> %s', src, tmp_io.name)
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return True
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LOGGER.info('Copying file: %s -> %s', src, tmp_io.name)
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cmd = 'cp', '--sparse=always', src, tmp_io.name
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p = subprocess.run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
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if p.returncode != 0:
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raise qubes.storage.StoragePoolException(str(p))
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return False
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def is_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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with tempfile.TemporaryFile(dir=src_dir) as src, \
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tempfile.TemporaryFile(dir=dst_dir) as dst:
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src.write(b'foo') # don't let any fs get clever with empty files
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return _attempt_ficlone(src, dst)
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