Source code for

# The Qubes OS Project,
# Copyright (C) 2013-2015  Joanna Rutkowska <[email protected]>
# Copyright (C) 2013-2015  Marek Marczykowski-Górecki
#                              <[email protected]>
# Copyright (C) 2015  Wojtek Porczyk <[email protected]>
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, see <>.

""" Qubes storage system"""

from __future__ import absolute_import

import inspect
import os
import os.path
import string  # pylint: disable=deprecated-module
import subprocess
import time
from datetime import datetime

import asyncio
import lxml.etree
import pkg_resources
import qubes
import qubes.exc
import qubes.utils


[docs]class StoragePoolException(qubes.exc.QubesException): ''' A general storage exception '''
[docs]class BlockDevice: ''' Represents a storage block device. ''' # pylint: disable=too-few-public-methods def __init__(self, path, name, script=None, rw=True, domain=None, devtype='disk'): assert name, 'Missing device name' assert path, 'Missing device path' self.path = path = name = rw self.script = script self.domain = domain self.devtype = devtype
[docs]class Volume: ''' Encapsulates all data about a volume for serialization to qubes.xml and libvirt config. Keep in mind! volatile = not snap_on_start and not save_on_stop snapshot = snap_on_start and not save_on_stop origin = not snap_on_start and save_on_stop origin_snapshot = snap_on_start and save_on_stop ''' devtype = 'disk' domain = None path = None script = None #: disk space used by this volume, can be smaller than :py:attr:`size` #: for sparse volumes usage = 0 def __init__(self, name, pool, vid, revisions_to_keep=0, rw=False, save_on_stop=False, size=0, snap_on_start=False, source=None, **kwargs): ''' Initialize a volume. :param str name: The name of the volume inside owning domain :param Pool pool: The pool object :param str vid: Volume identifier needs to be unique in pool :param int revisions_to_keep: Amount of revisions to keep around :param bool rw: If true volume will be mounted read-write :param bool snap_on_start: Create a snapshot from source on start, instead of using volume own data :param bool save_on_stop: Write changes to the volume in vm.stop(), otherwise - discard :param Volume source: other volume in same pool to make snapshot from, required if *snap_on_start*=`True` :param str/int size: Size of the volume ''' super(Volume, self).__init__(**kwargs) assert isinstance(pool, Pool) assert source is None or (isinstance(source, Volume) and source.pool == pool) if snap_on_start and source is None: msg = "snap_on_start specified on {!r} but no volume source set" msg = msg.format(name) raise StoragePoolException(msg) elif not snap_on_start and source is not None: msg = "source specified on {!r} but no snap_on_start set" msg = msg.format(name) raise StoragePoolException(msg) #: Name of the volume in a domain it's attached to (like `root` or #: `private`). = str(name) #: :py:class:`Pool` instance owning this volume self.pool = pool #: How many revisions of the volume to keep. Each revision is created # at :py:meth:`stop`, if :py:attr:`save_on_stop` is True self.revisions_to_keep = int(revisions_to_keep) #: Should this volume be writable by domain. = rw #: Should volume state be saved or discarded at :py:meth:`stop` self.save_on_stop = save_on_stop self._size = int(size) #: Should the volume state be initialized with a snapshot of #: same-named volume of domain's template. self.snap_on_start = snap_on_start #: source volume for :py:attr:`snap_on_start` volumes self.source = source #: Volume unique (inside given pool) identifier self.vid = vid def __eq__(self, other): if isinstance(other, Volume): return other.pool == self.pool and other.vid == self.vid return NotImplemented def __hash__(self): return hash('%s:%s' % (self.pool, self.vid)) def __neq__(self, other): return not self.__eq__(other) def __repr__(self): return '{!r}'.format(str(self.pool) + ':' + self.vid) def __str__(self): return str(self.vid) def __xml__(self): config = _sanitize_config(self.config) return lxml.etree.Element('volume', **config)
[docs] def create(self): ''' Create the given volume on disk. This method is called only once in the volume lifetime. Before calling this method, no data on disk should be touched (in context of this volume). This can be implemented as a coroutine. ''' raise self._not_implemented("create")
[docs] def remove(self): ''' Remove volume. This can be implemented as a coroutine.''' raise self._not_implemented("remove")
[docs] def export(self): ''' Returns a path to read the volume data from. Reading from this path when domain owning this volume is running (i.e. when :py:meth:`is_dirty` is True) should return the data from before domain startup. Reading from the path returned by this method should return the volume data. If extracting volume data require something more than just reading from file (for example connecting to some other domain, or decompressing the data), the returned path may be a pipe. ''' raise self._not_implemented("export")
[docs] def import_data(self): ''' Returns a path to overwrite volume data. This method is called after volume was already :py:meth:`create`-ed. Writing to this path should overwrite volume data. If importing volume data require something more than just writing to a file ( for example connecting to some other domain, or converting data on the fly), the returned path may be a pipe. This can be implemented as a coroutine. ''' raise self._not_implemented("import_data")
[docs] def import_data_end(self, success): ''' End the data import operation. This may be used by pool implementation to commit changes, cleanup temporary files etc. This method is called regardless the operation was successful or not. This can be implemented as a coroutine. :param success: True if data import was successful, otherwise False '''
# by default do nothing
[docs] def import_volume(self, src_volume): ''' Imports data from a different volume (possibly in a different pool. The volume needs to be create()d first. This can be implemented as a coroutine. ''' # pylint: disable=unused-argument raise self._not_implemented("import_volume")
[docs] def is_dirty(self): ''' Return `True` if volume was not properly shutdown and committed. This include the situation when domain owning the volume is still running. ''' raise self._not_implemented("is_dirty")
[docs] def is_outdated(self): ''' Returns `True` if this snapshot of a source volume (for `snap_on_start`=True) is outdated. ''' raise self._not_implemented("is_outdated")
[docs] def resize(self, size): ''' Expands volume, throws :py:class:`` if given size is less than current_size This can be implemented as a coroutine. :param int size: new size in bytes ''' # pylint: disable=unused-argument raise self._not_implemented("resize")
[docs] def revert(self, revision=None): ''' Revert volume to previous revision This can be implemented as a coroutine. :param revision: revision to revert volume to, see :py:attr:`revisions` ''' # pylint: disable=unused-argument raise self._not_implemented("revert")
[docs] def start(self): ''' Do what ever is needed on start. This include making a snapshot of template's volume if :py:attr:`snap_on_start` is set. This can be implemented as a coroutine.''' raise self._not_implemented("start")
[docs] def stop(self): ''' Do what ever is needed on stop. This include committing data if :py:attr:`save_on_stop` is set. This can be implemented as a coroutine.''' raise self._not_implemented("stop")
[docs] def verify(self): ''' Verifies the volume. This function is supposed to either return :py:obj:`True`, or raise an exception. This can be implemented as a coroutine.''' raise self._not_implemented("verify")
[docs] def block_device(self): ''' Return :py:class:`BlockDevice` for serialization in the libvirt XML template as <disk>. ''' return BlockDevice(self.path,, self.script,, self.domain, self.devtype)
@property def revisions(self): ''' Returns a dict containing revision identifiers and time of their creation ''' msg = "{!s} has revisions not implemented".format(self.__class__) raise NotImplementedError(msg) @property def size(self): ''' Volume size in bytes ''' return self._size @size.setter def size(self, size): # pylint: disable=attribute-defined-outside-init self._size = int(size) @property def config(self): ''' return config data for serialization to qubes.xml ''' result = { 'name':, 'pool': str(self.pool), 'vid': self.vid, 'revisions_to_keep': self.revisions_to_keep, 'rw':, 'save_on_stop': self.save_on_stop, 'snap_on_start': self.snap_on_start, } if self.size: result['size'] = self.size if self.source: result['source'] = str(self.source) return result def _not_implemented(self, method_name): ''' Helper for emitting helpful `NotImplementedError` exceptions ''' msg = "Volume {!s} has {!s}() not implemented" msg = msg.format(str(self.__class__.__name__), method_name) return NotImplementedError(msg)
[docs]class Storage: ''' Class for handling VM virtual disks. This is base class for all other implementations, mostly with Xen on Linux in mind. ''' AVAILABLE_FRONTENDS = {'xvd' + c for c in string.ascii_lowercase} def __init__(self, vm): #: Domain for which we manage storage self.vm = vm self.log = self.vm.log #: Additional drive (currently used only by HVM) = None if hasattr(vm, 'volume_config'): for name, conf in self.vm.volume_config.items(): self.init_volume(name, conf) def _update_volume_config_source(self, name, volume_config): '''Retrieve 'source' volume from VM's template''' template = getattr(self.vm, 'template', None) # recursively lookup source volume - templates may be # chained (TemplateVM -> AppVM -> DispVM, where the # actual source should be used from TemplateVM) while template: source = template.volumes[name] volume_config['source'] = source volume_config['pool'] = source.pool volume_config['size'] = source.size if source.source is not None: template = getattr(template, 'template', None) else: break
[docs] def init_volume(self, name, volume_config): ''' Initialize Volume instance attached to this domain ''' if 'name' not in volume_config: volume_config['name'] = name if 'source' in volume_config: # we have no control over VM load order, # so initialize storage recursively if needed template = getattr(self.vm, 'template', None) if template and is None: = Storage(template) if volume_config['source'] is None: self._update_volume_config_source(name, volume_config) else: # if source is already specified, pool needs to be too pool =['pool']) volume_config['source'] = pool.volumes[volume_config['source']] # if pool still unknown, load default if 'pool' not in volume_config: volume_config['pool'] = \ getattr(, 'default_pool_' + name) pool =['pool']) if 'internal' in volume_config: # migrate old config del volume_config['internal'] volume = pool.init_volume(self.vm, volume_config) self.vm.volumes[name] = volume return volume
[docs] def attach(self, volume, rw=False): ''' Attach a volume to the domain ''' assert self.vm.is_running() if self._is_already_attached(volume):"{!r} already attached".format(volume)) return try: frontend = self.unused_frontend() except IndexError: raise StoragePoolException("No unused frontend found") disk = lxml.etree.Element("disk") disk.set('type', 'block') disk.set('device', 'disk') lxml.etree.SubElement(disk, 'driver').set('name', 'phy') lxml.etree.SubElement(disk, 'source').set('dev', '/dev/%s' % volume.vid) lxml.etree.SubElement(disk, 'target').set('dev', frontend) if not rw: lxml.etree.SubElement(disk, 'readonly') if volume.domain is not None: lxml.etree.SubElement(disk, 'backenddomain').set( 'name', xml_string = lxml.etree.tostring(disk, encoding='utf-8') self.vm.libvirt_domain.attachDevice(xml_string)
# trigger watches to update device status # FIXME: this should be removed once libvirt will report such # events itself # self.vm.untrusted_qdb.write('/qubes-block-devices', '') # ← do we need this? def _is_already_attached(self, volume): ''' Checks if the given volume is already attached ''' parsed_xml = lxml.etree.fromstring(self.vm.libvirt_domain.XMLDesc()) disk_sources = parsed_xml.xpath("//domain/devices/disk/source") for source in disk_sources: if source.get('dev') == '/dev/%s' % volume.vid: return True return False
[docs] def detach(self, volume): ''' Detach a volume from domain ''' parsed_xml = lxml.etree.fromstring(self.vm.libvirt_domain.XMLDesc()) disks = parsed_xml.xpath("//domain/devices/disk") for disk in disks: source = disk.xpath('source')[0] if source.get('dev') == '/dev/%s' % volume.vid: disk_xml = lxml.etree.tostring(disk, encoding='utf-8') self.vm.libvirt_domain.detachDevice(disk_xml) return raise StoragePoolException('Volume {!r} is not attached'.format(volume))
@property def kernels_dir(self): '''Directory where kernel resides. If :py:attr:`self.vm.kernel` is :py:obj:`None`, the this points inside :py:attr:`self.vm.dir_path` ''' assert 'kernel' in self.vm.volumes, "VM has no kernel volume" return self.vm.volumes['kernel'].kernels_dir
[docs] def get_disk_utilization(self): ''' Returns summed up disk utilization for all domain volumes ''' result = 0 for volume in self.vm.volumes.values(): result += volume.usage return result
[docs] @asyncio.coroutine def resize(self, volume, size): ''' Resizes volume a read-writable volume ''' if isinstance(volume, str): volume = self.vm.volumes[volume] ret = volume.resize(size) if asyncio.iscoroutine(ret): yield from ret if self.vm.is_running(): try: yield from self.vm.run_service_for_stdio('qubes.ResizeDisk',, user='root') except subprocess.CalledProcessError as e: service_error = e.stderr.decode('ascii', errors='ignore') service_error = service_error.replace('%', '') raise StoragePoolException( 'Online resize of volume {} failed (you need to resize ' 'filesystem manually): {}'.format(volume, service_error))
[docs] @asyncio.coroutine def create(self): ''' Creates volumes on disk ''' old_umask = os.umask(0o002) coros = [] for volume in self.vm.volumes.values(): # launch the operation, if it's asynchronous, then append to wait # for them at the end ret = volume.create() if asyncio.iscoroutine(ret): coros.append(ret) yield from _wait_and_reraise(coros) os.umask(old_umask)
[docs] @asyncio.coroutine def clone_volume(self, src_vm, name): ''' Clone single volume from the specified vm :param QubesVM src_vm: source VM :param str name: name of volume to clone ('root', 'private' etc) :return cloned volume object ''' config = self.vm.volume_config[name] dst_pool =['pool']) dst = dst_pool.init_volume(self.vm, config) src_volume = src_vm.volumes[name] msg = "Importing volume {!s} from vm {!s}", # First create the destination volume create_op_ret = dst.create() # clone/import functions may be either synchronous or asynchronous # in the later case, we need to wait for them to finish if asyncio.iscoroutine(create_op_ret): yield from create_op_ret # Then import data from source volume clone_op_ret = dst.import_volume(src_volume) # clone/import functions may be either synchronous or asynchronous # in the later case, we need to wait for them to finish if asyncio.iscoroutine(clone_op_ret): yield from clone_op_ret self.vm.volumes[name] = dst return self.vm.volumes[name]
[docs] @asyncio.coroutine def clone(self, src_vm): ''' Clone volumes from the specified vm ''' self.vm.volumes = {} with VmCreationManager(self.vm): yield from _wait_and_reraise([self.clone_volume(src_vm, vol_name) for vol_name in self.vm.volume_config.keys()])
@property def outdated_volumes(self): ''' Returns a list of outdated volumes ''' result = [] if self.vm.is_halted(): return result volumes = self.vm.volumes for volume in volumes.values(): if volume.is_outdated(): result += [volume] return result
[docs] @asyncio.coroutine def verify(self): '''Verify that the storage is sane. On success, returns normally. On failure, raises exception. ''' if not os.path.exists(self.vm.dir_path): raise qubes.exc.QubesVMError( self.vm, 'VM directory does not exist: {}'.format(self.vm.dir_path)) futures = [] for volume in self.vm.volumes.values(): ret = volume.verify() if asyncio.iscoroutine(ret): futures.append(ret) yield from _wait_and_reraise(futures) self.vm.fire_event('domain-verify-files') return True
[docs] @asyncio.coroutine def remove(self): ''' Remove all the volumes. Errors on removal are catched and logged. ''' futures = [] for name, volume in self.vm.volumes.items():'Removing volume %s: %s' % (name, volume.vid)) try: ret = volume.remove() if asyncio.iscoroutine(ret): futures.append(ret) except (IOError, OSError) as e: self.vm.log.exception("Failed to remove volume %s", name, e) try: yield from _wait_and_reraise(futures) except (IOError, OSError) as e: self.vm.log.exception("Failed to remove some volume", e)
[docs] @asyncio.coroutine def start(self): ''' Execute the start method on each volume ''' futures = [] for volume in self.vm.volumes.values(): ret = volume.start() if asyncio.iscoroutine(ret): futures.append(ret) yield from _wait_and_reraise(futures)
[docs] @asyncio.coroutine def stop(self): ''' Execute the stop method on each volume ''' futures = [] for volume in self.vm.volumes.values(): ret = volume.stop() if asyncio.iscoroutine(ret): futures.append(ret) yield from _wait_and_reraise(futures)
[docs] def unused_frontend(self): ''' Find an unused device name ''' unused_frontends = self.AVAILABLE_FRONTENDS.difference( self.used_frontends) return sorted(unused_frontends)[0]
@property def used_frontends(self): ''' Used device names ''' xml = self.vm.libvirt_domain.XMLDesc() parsed_xml = lxml.etree.fromstring(xml) return {target.get('dev', None) for target in parsed_xml.xpath( "//domain/devices/disk/target")}
[docs] def export(self, volume): ''' Helper function to export volume (pool.export(volume))''' assert isinstance(volume, (Volume, str)), \ "You need to pass a Volume or pool name as str" if isinstance(volume, Volume): return volume.export() return self.vm.volumes[volume].export()
[docs] @asyncio.coroutine def import_data(self, volume): ''' Helper function to import volume data (pool.import_data(volume))''' assert isinstance(volume, (Volume, str)), \ "You need to pass a Volume or pool name as str" if isinstance(volume, Volume): ret = volume.import_data() else: ret = self.vm.volumes[volume].import_data() if asyncio.iscoroutine(ret): ret = yield from ret return ret
[docs] @asyncio.coroutine def import_data_end(self, volume, success): ''' Helper function to finish/cleanup data import (pool.import_data_end( volume))''' assert isinstance(volume, (Volume, str)), \ "You need to pass a Volume or pool name as str" if isinstance(volume, Volume): ret = volume.import_data_end(success=success) else: ret = self.vm.volumes[volume].import_data_end(success=success) if asyncio.iscoroutine(ret): ret = yield from ret return ret
[docs]class VolumesCollection: '''Convenient collection wrapper for pool.get_volume and pool.list_volumes ''' def __init__(self, pool): self._pool = pool def __getitem__(self, item): ''' Get a single volume with given Volume ID. You can also a Volume instance to get the same Volume or KeyError if Volume no longer exists. :param item: a Volume ID (str) or a Volume instance ''' if isinstance(item, Volume): if item.pool == self._pool: return self[item.vid] raise KeyError(item) try: return self._pool.get_volume(item) except NotImplementedError: for vol in self: if vol.vid == item: return vol # if list_volumes is not implemented too, it will raise # NotImplementedError again earlier raise KeyError(item) def __iter__(self): ''' Get iterator over pool's volumes ''' return iter(self._pool.list_volumes()) def __contains__(self, item): ''' Check if given volume (either Volume ID or Volume instance) is present in the pool ''' try: return self[item] is not None except KeyError: return False
[docs] def keys(self): ''' Return list of volume IDs ''' return [vol.vid for vol in self]
[docs] def values(self): ''' Return list of Volumes''' return [vol for vol in self]
[docs]class Pool: ''' A Pool is used to manage different kind of volumes (File based/LVM/Btrfs/...). 3rd Parties providing own storage implementations will need to extend this class. ''' # pylint: disable=unused-argument private_img_size = qubes.config.defaults['private_img_size'] root_img_size = qubes.config.defaults['root_img_size'] def __init__(self, name, revisions_to_keep=1, **kwargs): super(Pool, self).__init__(**kwargs) self._volumes_collection = VolumesCollection(self) = name self.revisions_to_keep = revisions_to_keep kwargs['name'] = def __eq__(self, other): if isinstance(other, Pool): return == if isinstance(other, str): return == other return NotImplemented def __neq__(self, other): return not self.__eq__(other) def __str__(self): return def __hash__(self): return hash( def __xml__(self): config = _sanitize_config(self.config) return lxml.etree.Element('pool', **config) @property def config(self): ''' Returns the pool config to be written to qubes.xml ''' raise self._not_implemented("config")
[docs] def destroy(self): ''' Called when removing the pool. Use this for implementation specific clean up. ''' raise self._not_implemented("destroy")
[docs] def init_volume(self, vm, volume_config): ''' Initialize a :py:class:`` from `volume_config`. ''' raise self._not_implemented("init_volume")
[docs] def setup(self): ''' Called when adding a pool to the system. Use this for implementation specific set up. ''' raise self._not_implemented("setup")
@property def volumes(self): ''' Return a collection of volumes managed by this pool ''' return self._volumes_collection
[docs] def list_volumes(self): ''' Return a list of volumes managed by this pool ''' raise self._not_implemented("list_volumes")
[docs] def get_volume(self, vid): ''' Return a volume with *vid* from this pool :raise KeyError: if no volume is found ''' raise self._not_implemented("get_volume")
[docs] def included_in(self, app): ''' Check if this pool is physically included in another one This works on best-effort basis, because one pool driver may not know all the other drivers. :param app: Qubes() object to lookup other pools in :returns pool or None '''
@property def size(self): ''' Storage pool size in bytes, or None if unknown ''' @property def usage(self): ''' Space used in the pool in bytes, or None if unknown ''' def _not_implemented(self, method_name): ''' Helper for emitting helpful `NotImplementedError` exceptions ''' msg = "Pool driver {!s} has {!s}() not implemented" msg = msg.format(str(self.__class__.__name__), method_name) return NotImplementedError(msg)
@asyncio.coroutine def _wait_and_reraise(futures): if futures: done, _ = yield from asyncio.wait(futures) for task in done: # (re-)raise first exception in line task.result() def _sanitize_config(config): ''' Helper function to convert types to appropriate strings ''' # FIXME: find another solution for serializing basic types result = {} for key, value in config.items(): if isinstance(value, bool): if value: result[key] = 'True' else: result[key] = str(value) return result
[docs]def pool_drivers(): """ Return a list of EntryPoints names """ return [ for ep in pkg_resources.iter_entry_points(STORAGE_ENTRY_POINT)]
[docs]def driver_parameters(name): ''' Get __init__ parameters from a driver with out `self` & `name`. ''' init_function = qubes.utils.get_entry_point_one(, name).__init__ signature = inspect.signature(init_function) params = signature.parameters.keys() ignored_params = ['self', 'name', 'kwargs'] return [p for p in params if p not in ignored_params]
[docs]def isodate(seconds): ''' Helper method which returns an iso date ''' return datetime.utcfromtimestamp(seconds).isoformat("T")
[docs]def search_pool_containing_dir(pools, dir_path): ''' Helper function looking for a pool containing given directory. This is useful for implementing Pool.included_in method ''' real_dir_path = os.path.realpath(dir_path) # prefer filesystem pools for pool in pools: if hasattr(pool, 'dir_path'): pool_real_dir_path = os.path.realpath(pool.dir_path) if os.path.commonpath([pool_real_dir_path, real_dir_path]) == \ pool_real_dir_path: return pool # then look for lvm for pool in pools: if hasattr(pool, 'thin_pool') and hasattr(pool, 'volume_group'): if (pool.volume_group, pool.thin_pool) == \ DirectoryThinPool.thin_pool(real_dir_path): return pool return None
[docs]class VmCreationManager: ''' A `ContextManager` which cleans up if volume creation fails. ''' # pylint: disable=too-few-public-methods def __init__(self, vm): self.vm = vm def __enter__(self): pass def __exit__(self, type, value, tb): # pylint: disable=redefined-builtin if type is not None and value is not None and tb is not None: for volume in self.vm.volumes.values(): try: volume.remove() except Exception: # pylint: disable=broad-except pass os.rmdir(self.vm.dir_path)
# pylint: disable=too-few-public-methods
[docs]class DirectoryThinPool: '''The thin pool containing the device of given filesystem''' _thin_pool = {} @classmethod def _init(cls, dir_path): '''Find out the thin pool containing given filesystem''' if dir_path not in cls._thin_pool: cls._thin_pool[dir_path] = None, None try: fs_stat = os.stat(dir_path) fs_major = (fs_stat.st_dev & 0xff00) >> 8 fs_minor = fs_stat.st_dev & 0xff sudo = [] if os.getuid(): sudo = ['sudo'] root_table = subprocess.check_output(sudo + ["dmsetup", "-j", str(fs_major), "-m", str(fs_minor), "table"], stderr=subprocess.DEVNULL) _start, _sectors, target_type, target_args = \ root_table.decode().split(" ", 3) if target_type == "thin": thin_pool_devnum, _thin_pool_id = target_args.split(" ") with open("/sys/dev/block/{}/dm/name" .format(thin_pool_devnum), "r") as thin_pool_tpool_f: thin_pool_tpool ='\n') if thin_pool_tpool.endswith("-tpool"): volume_group, thin_pool, _tpool = \ thin_pool_tpool.rsplit("-", 2) cls._thin_pool[dir_path] = volume_group, thin_pool except: # pylint: disable=bare-except pass
[docs] @classmethod def thin_pool(cls, dir_path): '''Thin tuple (volume group, pool name) containing given filesystem''' cls._init(dir_path) return cls._thin_pool[dir_path]