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+      #
+      #
       # Copyright (C) 2006, 2007, 2010, 2011, 2012 Google Inc.
+      #
       # This program is free software; you can redistribute it and/or modify
       # it under the terms of the GNU General Public License as published by
       # the Free Software Foundation; either version 2 of the License, or
       # (at your option) any later version.
+      #
       # This program is distributed in the hope that it will be useful, but
       # WITHOUT ANY WARRANTY; without even the implied warranty of
       # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
       # General Public License for more details.
+      #
       # You should have received a copy of the GNU General Public License
       # along with this program; if not, write to the Free Software
       # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
       # 02110-1301, USA.
       """Block device abstraction"""
       import re
       import time
       import errno
       import shlex
       import stat
       import pyparsing as pyp
       import os
       import logging
       from ganeti import utils
       from ganeti import errors
       from ganeti import constants
       from ganeti import objects
       from ganeti import compat
       from ganeti import netutils
       from ganeti import pathutils
       # Size of reads in _CanReadDevice
       _DEVICE_READ_SIZE = 128 * 1024
       def _IgnoreError(fn, *args, **kwargs):
         """Executes the given function, ignoring BlockDeviceErrors.
         This is used in order to simplify the execution of cleanup or
         rollback functions.
         @rtype: boolean
         @return: True when fn didn't raise an exception, False otherwise
         """
         try:
           fn(*args, **kwargs)
           return True
         except errors.BlockDeviceError, err:
           logging.warning("Caught BlockDeviceError but ignoring: %s", str(err))
           return False
       def _ThrowError(msg, *args):
         """Log an error to the node daemon and the raise an exception.
         @type msg: string
         @param msg: the text of the exception
         @raise errors.BlockDeviceError
         """
         if args:
           msg = msg % args
         logging.error(msg)
         raise errors.BlockDeviceError(msg)
       def _CheckResult(result):
         """Throws an error if the given result is a failed one.
         @param result: result from RunCmd
         """
         if result.failed:
           _ThrowError("Command: %s error: %s - %s", result.cmd, result.fail_reason,
                       result.output)
       def _CanReadDevice(path):
         """Check if we can read from the given device.
         This tries to read the first 128k of the device.
         """
         try:
           utils.ReadFile(path, size=_DEVICE_READ_SIZE)
           return True
         except EnvironmentError:
           logging.warning("Can't read from device %s", path, exc_info=True)
           return False
       def _GetForbiddenFileStoragePaths():
         """Builds a list of path prefixes which shouldn't be used for file storage.
         @rtype: frozenset
         """
         paths = set([
           "/boot",
           "/dev",
           "/etc",
           "/home",
           "/proc",
           "/root",
           "/sys",
           ])
         for prefix in ["", "/usr", "/usr/local"]:
           paths.update(map(lambda s: "%s/%s" % (prefix, s),
                            ["bin", "lib", "lib32", "lib64", "sbin"]))
         return compat.UniqueFrozenset(map(os.path.normpath, paths))
       def _ComputeWrongFileStoragePaths(paths,
                                         _forbidden=_GetForbiddenFileStoragePaths()):
         """Cross-checks a list of paths for prefixes considered bad.
         Some paths, e.g. "/bin", should not be used for file storage.
         @type paths: list
         @param paths: List of paths to be checked
         @rtype: list
         @return: Sorted list of paths for which the user should be warned
         """
         def _Check(path):
           return (not os.path.isabs(path) or
                   path in _forbidden or
                   filter(lambda p: utils.IsBelowDir(p, path), _forbidden))
         return utils.NiceSort(filter(_Check, map(os.path.normpath, paths)))
       def ComputeWrongFileStoragePaths(_filename=pathutils.FILE_STORAGE_PATHS_FILE):
         """Returns a list of file storage paths whose prefix is considered bad.
         See L{_ComputeWrongFileStoragePaths}.
         """
         return _ComputeWrongFileStoragePaths(_LoadAllowedFileStoragePaths(_filename))
       def _CheckFileStoragePath(path, allowed):
         """Checks if a path is in a list of allowed paths for file storage.
         @type path: string
         @param path: Path to check
         @type allowed: list
         @param allowed: List of allowed paths
         @raise errors.FileStoragePathError: If the path is not allowed
         """
         if not os.path.isabs(path):
           raise errors.FileStoragePathError("File storage path must be absolute,"
                                             " got '%s'" % path)
         for i in allowed:
           if not os.path.isabs(i):
             logging.info("Ignoring relative path '%s' for file storage", i)
             continue
           if utils.IsBelowDir(i, path):
             break
         else:
           raise errors.FileStoragePathError("Path '%s' is not acceptable for file"
                                             " storage" % path)
       def _LoadAllowedFileStoragePaths(filename):
         """Loads file containing allowed file storage paths.
         @rtype: list
         @return: List of allowed paths (can be an empty list)
         """
         try:
           contents = utils.ReadFile(filename)
         except EnvironmentError:
           return []
         else:
           return utils.FilterEmptyLinesAndComments(contents)
       def CheckFileStoragePath(path, _filename=pathutils.FILE_STORAGE_PATHS_FILE):
         """Checks if a path is allowed for file storage.
         @type path: string
         @param path: Path to check
         @raise errors.FileStoragePathError: If the path is not allowed
         """
         allowed = _LoadAllowedFileStoragePaths(_filename)
         if _ComputeWrongFileStoragePaths([path]):
           raise errors.FileStoragePathError("Path '%s' uses a forbidden prefix" %
                                             path)
         _CheckFileStoragePath(path, allowed)
       class BlockDev(object):
         """Block device abstract class.
         A block device can be in the following states:
           - not existing on the system, and by `Create()` it goes into:
           - existing but not setup/not active, and by `Assemble()` goes into:
           - active read-write and by `Open()` it goes into
           - online (=used, or ready for use)
         A device can also be online but read-only, however we are not using
         the readonly state (LV has it, if needed in the future) and we are
         usually looking at this like at a stack, so it's easier to
         conceptualise the transition from not-existing to online and back
         like a linear one.
         The many different states of the device are due to the fact that we
         need to cover many device types:
           - logical volumes are created, lvchange -a y $lv, and used
           - drbd devices are attached to a local disk/remote peer and made primary
         A block device is identified by three items:
           - the /dev path of the device (dynamic)
           - a unique ID of the device (static)
           - it's major/minor pair (dynamic)
         Not all devices implement both the first two as distinct items. LVM
         logical volumes have their unique ID (the pair volume group, logical
         volume name) in a 1-to-1 relation to the dev path. For DRBD devices,
         the /dev path is again dynamic and the unique id is the pair (host1,
         dev1), (host2, dev2).
         You can get to a device in two ways:
           - creating the (real) device, which returns you
             an attached instance (lvcreate)
           - attaching of a python instance to an existing (real) device
         The second point, the attachement to a device, is different
         depending on whether the device is assembled or not. At init() time,
         we search for a device with the same unique_id as us. If found,
         good. It also means that the device is already assembled. If not,
         after assembly we'll have our correct major/minor.
         """
         def __init__(self, unique_id, children, size, params):
           self._children = children
           self.dev_path = None
           self.unique_id = unique_id
           self.major = None
           self.minor = None
           self.attached = False
           self.size = size
           self.params = params
         def Assemble(self):
           """Assemble the device from its components.
           Implementations of this method by child classes must ensure that:
             - after the device has been assembled, it knows its major/minor
               numbers; this allows other devices (usually parents) to probe
               correctly for their children
             - calling this method on an existing, in-use device is safe
             - if the device is already configured (and in an OK state),
               this method is idempotent
           """
           pass
         def Attach(self):
           """Find a device which matches our config and attach to it.
           """
           raise NotImplementedError
         def Close(self):
           """Notifies that the device will no longer be used for I/O.
           """
           raise NotImplementedError
         @classmethod
         def Create(cls, unique_id, children, size, params):
           """Create the device.
           If the device cannot be created, it will return None
           instead. Error messages go to the logging system.
           Note that for some devices, the unique_id is used, and for other,
           the children. The idea is that these two, taken together, are
           enough for both creation and assembly (later).
           """
           raise NotImplementedError
         def Remove(self):
           """Remove this device.
           This makes sense only for some of the device types: LV and file
           storage. Also note that if the device can't attach, the removal
           can't be completed.
           """
           raise NotImplementedError
         def Rename(self, new_id):
           """Rename this device.
           This may or may not make sense for a given device type.
           """
           raise NotImplementedError
         def Open(self, force=False):
           """Make the device ready for use.
           This makes the device ready for I/O. For now, just the DRBD
           devices need this.
           The force parameter signifies that if the device has any kind of
           --force thing, it should be used, we know what we are doing.
           """
           raise NotImplementedError
         def Shutdown(self):
           """Shut down the device, freeing its children.
           This undoes the `Assemble()` work, except for the child
           assembling; as such, the children on the device are still
           assembled after this call.
           """
           raise NotImplementedError
         def SetSyncParams(self, params):
           """Adjust the synchronization parameters of the mirror.
           In case this is not a mirroring device, this is no-op.
           @param params: dictionary of LD level disk parameters related to the
           synchronization.
           @rtype: list
           @return: a list of error messages, emitted both by the current node and by
           children. An empty list means no errors.
           """
           result = []
           if self._children:
             for child in self._children:
               result.extend(child.SetSyncParams(params))
           return result
         def PauseResumeSync(self, pause):
           """Pause/Resume the sync of the mirror.
           In case this is not a mirroring device, this is no-op.
           @param pause: Whether to pause or resume
           """
           result = True
           if self._children:
             for child in self._children:
               result = result and child.PauseResumeSync(pause)
           return result
         def GetSyncStatus(self):
           """Returns the sync status of the device.
           If this device is a mirroring device, this function returns the
           status of the mirror.
           If sync_percent is None, it means the device is not syncing.
           If estimated_time is None, it means we can't estimate
           the time needed, otherwise it's the time left in seconds.
           If is_degraded is True, it means the device is missing
           redundancy. This is usually a sign that something went wrong in
           the device setup, if sync_percent is None.
           The ldisk parameter represents the degradation of the local
           data. This is only valid for some devices, the rest will always
           return False (not degraded).
           @rtype: objects.BlockDevStatus
           """
           return objects.BlockDevStatus(dev_path=self.dev_path,
                                         major=self.major,
                                         minor=self.minor,
                                         sync_percent=None,
                                         estimated_time=None,
                                         is_degraded=False,
                                         ldisk_status=constants.LDS_OKAY)
         def CombinedSyncStatus(self):
           """Calculate the mirror status recursively for our children.
           The return value is the same as for `GetSyncStatus()` except the
           minimum percent and maximum time are calculated across our
           children.
           @rtype: objects.BlockDevStatus
           """
           status = self.GetSyncStatus()
           min_percent = status.sync_percent
           max_time = status.estimated_time
           is_degraded = status.is_degraded
           ldisk_status = status.ldisk_status
           if self._children:
             for child in self._children:
               child_status = child.GetSyncStatus()
               if min_percent is None:
                 min_percent = child_status.sync_percent
               elif child_status.sync_percent is not None:
                 min_percent = min(min_percent, child_status.sync_percent)
               if max_time is None:
                 max_time = child_status.estimated_time
               elif child_status.estimated_time is not None:
                 max_time = max(max_time, child_status.estimated_time)
               is_degraded = is_degraded or child_status.is_degraded
               if ldisk_status is None:
                 ldisk_status = child_status.ldisk_status
               elif child_status.ldisk_status is not None:
                 ldisk_status = max(ldisk_status, child_status.ldisk_status)
           return objects.BlockDevStatus(dev_path=self.dev_path,
                                         major=self.major,
                                         minor=self.minor,
                                         sync_percent=min_percent,
                                         estimated_time=max_time,
                                         is_degraded=is_degraded,
                                         ldisk_status=ldisk_status)
         def SetInfo(self, text):
           """Update metadata with info text.
           Only supported for some device types.
           """
           for child in self._children:
             child.SetInfo(text)
         def Grow(self, amount, dryrun, backingstore):
           """Grow the block device.
           @type amount: integer
           @param amount: the amount (in mebibytes) to grow with
           @type dryrun: boolean
           @param dryrun: whether to execute the operation in simulation mode
               only, without actually increasing the size
           @param backingstore: whether to execute the operation on backing storage
               only, or on "logical" storage only; e.g. DRBD is logical storage,
               whereas LVM, file, RBD are backing storage
           """
           raise NotImplementedError
         def GetActualSize(self):
           """Return the actual disk size.
           @note: the device needs to be active when this is called
           """
           assert self.attached, "BlockDevice not attached in GetActualSize()"
           result = utils.RunCmd(["blockdev", "--getsize64", self.dev_path])
           if result.failed:
             _ThrowError("blockdev failed (%s): %s",
                         result.fail_reason, result.output)
           try:
             sz = int(result.output.strip())
           except (ValueError, TypeError), err:
             _ThrowError("Failed to parse blockdev output: %s", str(err))
           return sz
         def __repr__(self):
           return ("<%s: unique_id: %s, children: %s, %s:%s, %s>" %
                   (self.__class__, self.unique_id, self._children,
                    self.major, self.minor, self.dev_path))
       class LogicalVolume(BlockDev):
         """Logical Volume block device.
         """
         _VALID_NAME_RE = re.compile("^[a-zA-Z0-9+_.-]*$")
         _INVALID_NAMES = compat.UniqueFrozenset([".", "..", "snapshot", "pvmove"])
         _INVALID_SUBSTRINGS = compat.UniqueFrozenset(["_mlog", "_mimage"])
         def __init__(self, unique_id, children, size, params):
           """Attaches to a LV device.
           The unique_id is a tuple (vg_name, lv_name)
           """
           super(LogicalVolume, self).__init__(unique_id, children, size, params)
           if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
             raise ValueError("Invalid configuration data %s" % str(unique_id))
           self._vg_name, self._lv_name = unique_id
           self._ValidateName(self._vg_name)
           self._ValidateName(self._lv_name)
           self.dev_path = utils.PathJoin("/dev", self._vg_name, self._lv_name)
           self._degraded = True
           self.major = self.minor = self.pe_size = self.stripe_count = None
           self.Attach()
         @classmethod
         def Create(cls, unique_id, children, size, params):
           """Create a new logical volume.
           """
           if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
             raise errors.ProgrammerError("Invalid configuration data %s" %
                                          str(unique_id))
           vg_name, lv_name = unique_id
           cls._ValidateName(vg_name)
           cls._ValidateName(lv_name)
           pvs_info = cls.GetPVInfo([vg_name])
           if not pvs_info:
             _ThrowError("Can't compute PV info for vg %s", vg_name)
           pvs_info.sort(key=(lambda pv: pv.free), reverse=True)
           pvlist = [pv.name for pv in pvs_info]
           if compat.any(":" in v for v in pvlist):
             _ThrowError("Some of your PVs have the invalid character ':' in their"
                         " name, this is not supported - please filter them out"
                         " in lvm.conf using either 'filter' or 'preferred_names'")
           free_size = sum([pv.free for pv in pvs_info])
           current_pvs = len(pvlist)
           desired_stripes = params[constants.LDP_STRIPES]
           stripes = min(current_pvs, desired_stripes)
           if stripes < desired_stripes:
             logging.warning("Could not use %d stripes for VG %s, as only %d PVs are"
                             " available.", desired_stripes, vg_name, current_pvs)
           # The size constraint should have been checked from the master before
           # calling the create function.
           if free_size < size:
             _ThrowError("Not enough free space: required %s,"
                         " available %s", size, free_size)
           cmd = ["lvcreate", "-L%dm" % size, "-n%s" % lv_name]
           # If the free space is not well distributed, we won't be able to
           # create an optimally-striped volume; in that case, we want to try
           # with N, N-1, ..., 2, and finally 1 (non-stripped) number of
           # stripes
           for stripes_arg in range(stripes, 0, -1):
             result = utils.RunCmd(cmd + ["-i%d" % stripes_arg] + [vg_name] + pvlist)
             if not result.failed:
               break
           if result.failed:
             _ThrowError("LV create failed (%s): %s",
                         result.fail_reason, result.output)
           return LogicalVolume(unique_id, children, size, params)
         @staticmethod
         def _GetVolumeInfo(lvm_cmd, fields):
           """Returns LVM Volumen infos using lvm_cmd
           @param lvm_cmd: Should be one of "pvs", "vgs" or "lvs"
           @param fields: Fields to return
           @return: A list of dicts each with the parsed fields
           """
           if not fields:
             raise errors.ProgrammerError("No fields specified")
           sep = "|"
           cmd = [lvm_cmd, "--noheadings", "--nosuffix", "--units=m", "--unbuffered",
                  "--separator=%s" % sep, "-o%s" % ",".join(fields)]
           result = utils.RunCmd(cmd)
           if result.failed:
             raise errors.CommandError("Can't get the volume information: %s - %s" %
                                       (result.fail_reason, result.output))
           data = []
           for line in result.stdout.splitlines():
             splitted_fields = line.strip().split(sep)
             if len(fields) != len(splitted_fields):
               raise errors.CommandError("Can't parse %s output: line '%s'" %
                                         (lvm_cmd, line))
             data.append(splitted_fields)
           return data
         @classmethod
         def GetPVInfo(cls, vg_names, filter_allocatable=True):
           """Get the free space info for PVs in a volume group.
           @param vg_names: list of volume group names, if empty all will be returned
           @param filter_allocatable: whether to skip over unallocatable PVs
           @rtype: list
           @return: list of objects.LvmPvInfo objects
           """
           try:
             info = cls._GetVolumeInfo("pvs", ["pv_name", "vg_name", "pv_free",
                                               "pv_attr", "pv_size"])
           except errors.GenericError, err:
             logging.error("Can't get PV information: %s", err)
             return None
           data = []
           for (pv_name, vg_name, pv_free, pv_attr, pv_size) in info:
             # (possibly) skip over pvs which are not allocatable
             if filter_allocatable and pv_attr[0] != "a":
               continue
             # (possibly) skip over pvs which are not in the right volume group(s)
             if vg_names and vg_name not in vg_names:
               continue
             pvi = objects.LvmPvInfo(name=pv_name, vg_name=vg_name,
                                     size=float(pv_size), free=float(pv_free),
                                     attributes=pv_attr)
             data.append(pvi)
           return data
         @classmethod
         def GetVGInfo(cls, vg_names, filter_readonly=True):
           """Get the free space info for specific VGs.
           @param vg_names: list of volume group names, if empty all will be returned
           @param filter_readonly: whether to skip over readonly VGs
           @rtype: list
           @return: list of tuples (free_space, total_size, name) with free_space in
                    MiB
           """
           try:
             info = cls._GetVolumeInfo("vgs", ["vg_name", "vg_free", "vg_attr",
                                               "vg_size"])
           except errors.GenericError, err:
             logging.error("Can't get VG information: %s", err)
             return None
           data = []
           for vg_name, vg_free, vg_attr, vg_size in info:
             # (possibly) skip over vgs which are not writable
             if filter_readonly and vg_attr[0] == "r":
               continue
             # (possibly) skip over vgs which are not in the right volume group(s)
             if vg_names and vg_name not in vg_names:
               continue
             data.append((float(vg_free), float(vg_size), vg_name))
           return data
         @classmethod
         def _ValidateName(cls, name):
           """Validates that a given name is valid as VG or LV name.
           The list of valid characters and restricted names is taken out of
           the lvm(8) manpage, with the simplification that we enforce both
           VG and LV restrictions on the names.
           """
           if (not cls._VALID_NAME_RE.match(name) or
               name in cls._INVALID_NAMES or
               compat.any(substring in name for substring in cls._INVALID_SUBSTRINGS)):
             _ThrowError("Invalid LVM name '%s'", name)
         def Remove(self):
           """Remove this logical volume.
           """
           if not self.minor and not self.Attach():
             # the LV does not exist
             return
           result = utils.RunCmd(["lvremove", "-f", "%s/%s" %
                                  (self._vg_name, self._lv_name)])
           if result.failed:
             _ThrowError("Can't lvremove: %s - %s", result.fail_reason, result.output)
         def Rename(self, new_id):
           """Rename this logical volume.
           """
           if not isinstance(new_id, (tuple, list)) or len(new_id) != 2:
             raise errors.ProgrammerError("Invalid new logical id '%s'" % new_id)
           new_vg, new_name = new_id
           if new_vg != self._vg_name:
             raise errors.ProgrammerError("Can't move a logical volume across"
                                          " volume groups (from %s to to %s)" %
                                          (self._vg_name, new_vg))
           result = utils.RunCmd(["lvrename", new_vg, self._lv_name, new_name])
           if result.failed:
             _ThrowError("Failed to rename the logical volume: %s", result.output)
           self._lv_name = new_name
           self.dev_path = utils.PathJoin("/dev", self._vg_name, self._lv_name)
         def Attach(self):
           """Attach to an existing LV.
           This method will try to see if an existing and active LV exists
           which matches our name. If so, its major/minor will be
           recorded.
           """
           self.attached = False
           result = utils.RunCmd(["lvs", "--noheadings", "--separator=,",
                                  "--units=m", "--nosuffix",
                                  "-olv_attr,lv_kernel_major,lv_kernel_minor,"
                                  "vg_extent_size,stripes", self.dev_path])
           if result.failed:
             logging.error("Can't find LV %s: %s, %s",
                           self.dev_path, result.fail_reason, result.output)
             return False
           # the output can (and will) have multiple lines for multi-segment
           # LVs, as the 'stripes' parameter is a segment one, so we take
           # only the last entry, which is the one we're interested in; note
           # that with LVM2 anyway the 'stripes' value must be constant
           # across segments, so this is a no-op actually
           out = result.stdout.splitlines()
           if not out: # totally empty result? splitlines() returns at least
                       # one line for any non-empty string
             logging.error("Can't parse LVS output, no lines? Got '%s'", str(out))
             return False
           out = out[-1].strip().rstrip(",")
           out = out.split(",")
           if len(out) != 5:
             logging.error("Can't parse LVS output, len(%s) != 5", str(out))
             return False
           status, major, minor, pe_size, stripes = out
           if len(status) < 6:
             logging.error("lvs lv_attr is not at least 6 characters (%s)", status)
             return False
           try:
             major = int(major)
             minor = int(minor)
           except (TypeError, ValueError), err:
             logging.error("lvs major/minor cannot be parsed: %s", str(err))
           try:
             pe_size = int(float(pe_size))
           except (TypeError, ValueError), err:
             logging.error("Can't parse vg extent size: %s", err)
             return False
           try:
             stripes = int(stripes)
           except (TypeError, ValueError), err:
             logging.error("Can't parse the number of stripes: %s", err)
             return False
           self.major = major
           self.minor = minor
           self.pe_size = pe_size
           self.stripe_count = stripes
           self._degraded = status[0] == "v" # virtual volume, i.e. doesn't backing
                                             # storage
           self.attached = True
           return True
         def Assemble(self):
           """Assemble the device.
           We always run `lvchange -ay` on the LV to ensure it's active before
           use, as there were cases when xenvg was not active after boot
           (also possibly after disk issues).
           """
           result = utils.RunCmd(["lvchange", "-ay", self.dev_path])
           if result.failed:
             _ThrowError("Can't activate lv %s: %s", self.dev_path, result.output)
         def Shutdown(self):
           """Shutdown the device.
           This is a no-op for the LV device type, as we don't deactivate the
           volumes on shutdown.
           """
           pass
         def GetSyncStatus(self):
           """Returns the sync status of the device.
           If this device is a mirroring device, this function returns the
           status of the mirror.
           For logical volumes, sync_percent and estimated_time are always
           None (no recovery in progress, as we don't handle the mirrored LV
           case). The is_degraded parameter is the inverse of the ldisk
           parameter.
           For the ldisk parameter, we check if the logical volume has the
           'virtual' type, which means it's not backed by existing storage
           anymore (read from it return I/O error). This happens after a
           physical disk failure and subsequent 'vgreduce --removemissing' on
           the volume group.
           The status was already read in Attach, so we just return it.
           @rtype: objects.BlockDevStatus
           """
           if self._degraded:
             ldisk_status = constants.LDS_FAULTY
           else:
             ldisk_status = constants.LDS_OKAY
           return objects.BlockDevStatus(dev_path=self.dev_path,
                                         major=self.major,
                                         minor=self.minor,
                                         sync_percent=None,
                                         estimated_time=None,
                                         is_degraded=self._degraded,
                                         ldisk_status=ldisk_status)
         def Open(self, force=False):
           """Make the device ready for I/O.
           This is a no-op for the LV device type.
           """
           pass
         def Close(self):
           """Notifies that the device will no longer be used for I/O.
           This is a no-op for the LV device type.
           """
           pass
         def Snapshot(self, size):
           """Create a snapshot copy of an lvm block device.
           @returns: tuple (vg, lv)
           """
           snap_name = self._lv_name + ".snap"
           # remove existing snapshot if found
           snap = LogicalVolume((self._vg_name, snap_name), None, size, self.params)
           _IgnoreError(snap.Remove)
           vg_info = self.GetVGInfo([self._vg_name])
           if not vg_info:
             _ThrowError("Can't compute VG info for vg %s", self._vg_name)
           free_size, _, _ = vg_info[0]
           if free_size < size:
             _ThrowError("Not enough free space: required %s,"
                         " available %s", size, free_size)
           _CheckResult(utils.RunCmd(["lvcreate", "-L%dm" % size, "-s",
                                      "-n%s" % snap_name, self.dev_path]))
           return (self._vg_name, snap_name)
         def _RemoveOldInfo(self):
           """Try to remove old tags from the lv.
           """
           result = utils.RunCmd(["lvs", "-o", "tags", "--noheadings", "--nosuffix",
                                  self.dev_path])
           _CheckResult(result)
           raw_tags = result.stdout.strip()
           if raw_tags:
             for tag in raw_tags.split(","):
               _CheckResult(utils.RunCmd(["lvchange", "--deltag",
                                          tag.strip(), self.dev_path]))
         def SetInfo(self, text):
           """Update metadata with info text.
           """
           BlockDev.SetInfo(self, text)
           self._RemoveOldInfo()
           # Replace invalid characters
           text = re.sub("^[^A-Za-z0-9_+.]", "_", text)
           text = re.sub("[^-A-Za-z0-9_+.]", "_", text)
           # Only up to 128 characters are allowed
           text = text[:128]
           _CheckResult(utils.RunCmd(["lvchange", "--addtag", text, self.dev_path]))
         def Grow(self, amount, dryrun, backingstore):
           """Grow the logical volume.
           """
           if not backingstore:
             return
           if self.pe_size is None or self.stripe_count is None:
             if not self.Attach():
               _ThrowError("Can't attach to LV during Grow()")
           full_stripe_size = self.pe_size * self.stripe_count
           rest = amount % full_stripe_size
           if rest != 0:
             amount += full_stripe_size - rest
           cmd = ["lvextend", "-L", "+%dm" % amount]
           if dryrun:
             cmd.append("--test")
           # we try multiple algorithms since the 'best' ones might not have
           # space available in the right place, but later ones might (since
           # they have less constraints); also note that only recent LVM
           # supports 'cling'
           for alloc_policy in "contiguous", "cling", "normal":
             result = utils.RunCmd(cmd + ["--alloc", alloc_policy, self.dev_path])
             if not result.failed:
               return
           _ThrowError("Can't grow LV %s: %s", self.dev_path, result.output)
       class DRBD8Status(object):
         """A DRBD status representation class.
         Note that this doesn't support unconfigured devices (cs:Unconfigured).
         """
         UNCONF_RE = re.compile(r"\s*[0-9]+:\s*cs:Unconfigured$")
         LINE_RE = re.compile(r"\s*[0-9]+:\s*cs:(\S+)\s+(?:st|ro):([^/]+)/(\S+)"
                              "\s+ds:([^/]+)/(\S+)\s+.*$")
         SYNC_RE = re.compile(r"^.*\ssync'ed:\s*([0-9.]+)%.*"
                              # Due to a bug in drbd in the kernel, introduced in
                              # commit 4b0715f096 (still unfixed as of 2011-08-22)
                              "(?:\s|M)"
                              "finish: ([0-9]+):([0-9]+):([0-9]+)\s.*$")
         CS_UNCONFIGURED = "Unconfigured"
         CS_STANDALONE = "StandAlone"
         CS_WFCONNECTION = "WFConnection"
         CS_WFREPORTPARAMS = "WFReportParams"
         CS_CONNECTED = "Connected"
         CS_STARTINGSYNCS = "StartingSyncS"
         CS_STARTINGSYNCT = "StartingSyncT"
         CS_WFBITMAPS = "WFBitMapS"
         CS_WFBITMAPT = "WFBitMapT"
         CS_WFSYNCUUID = "WFSyncUUID"
         CS_SYNCSOURCE = "SyncSource"
         CS_SYNCTARGET = "SyncTarget"
         CS_PAUSEDSYNCS = "PausedSyncS"
         CS_PAUSEDSYNCT = "PausedSyncT"
         CSET_SYNC = compat.UniqueFrozenset([
           CS_WFREPORTPARAMS,
           CS_STARTINGSYNCS,
           CS_STARTINGSYNCT,
           CS_WFBITMAPS,
           CS_WFBITMAPT,
           CS_WFSYNCUUID,
           CS_SYNCSOURCE,
           CS_SYNCTARGET,
           CS_PAUSEDSYNCS,
           CS_PAUSEDSYNCT,
           ])
         DS_DISKLESS = "Diskless"
         DS_ATTACHING = "Attaching" # transient state
         DS_FAILED = "Failed" # transient state, next: diskless
         DS_NEGOTIATING = "Negotiating" # transient state
         DS_INCONSISTENT = "Inconsistent" # while syncing or after creation
         DS_OUTDATED = "Outdated"
         DS_DUNKNOWN = "DUnknown" # shown for peer disk when not connected
         DS_CONSISTENT = "Consistent"
         DS_UPTODATE = "UpToDate" # normal state
         RO_PRIMARY = "Primary"
         RO_SECONDARY = "Secondary"
         RO_UNKNOWN = "Unknown"
         def __init__(self, procline):
           u = self.UNCONF_RE.match(procline)
           if u:
             self.cstatus = self.CS_UNCONFIGURED
             self.lrole = self.rrole = self.ldisk = self.rdisk = None
           else:
             m = self.LINE_RE.match(procline)
             if not m:
               raise errors.BlockDeviceError("Can't parse input data '%s'" % procline)
             self.cstatus = m.group(1)
             self.lrole = m.group(2)
             self.rrole = m.group(3)
             self.ldisk = m.group(4)
             self.rdisk = m.group(5)
           # end reading of data from the LINE_RE or UNCONF_RE
           self.is_standalone = self.cstatus == self.CS_STANDALONE
           self.is_wfconn = self.cstatus == self.CS_WFCONNECTION
           self.is_connected = self.cstatus == self.CS_CONNECTED
           self.is_primary = self.lrole == self.RO_PRIMARY
           self.is_secondary = self.lrole == self.RO_SECONDARY
           self.peer_primary = self.rrole == self.RO_PRIMARY
           self.peer_secondary = self.rrole == self.RO_SECONDARY
           self.both_primary = self.is_primary and self.peer_primary
           self.both_secondary = self.is_secondary and self.peer_secondary
           self.is_diskless = self.ldisk == self.DS_DISKLESS
           self.is_disk_uptodate = self.ldisk == self.DS_UPTODATE
           self.is_in_resync = self.cstatus in self.CSET_SYNC
           self.is_in_use = self.cstatus != self.CS_UNCONFIGURED
           m = self.SYNC_RE.match(procline)
           if m:
             self.sync_percent = float(m.group(1))
             hours = int(m.group(2))
             minutes = int(m.group(3))
             seconds = int(m.group(4))
             self.est_time = hours * 3600 + minutes * 60 + seconds
           else:
             # we have (in this if branch) no percent information, but if
             # we're resyncing we need to 'fake' a sync percent information,
             # as this is how cmdlib determines if it makes sense to wait for
             # resyncing or not
             if self.is_in_resync:
               self.sync_percent = 0
             else:
               self.sync_percent = None
             self.est_time = None
       class BaseDRBD(BlockDev): # pylint: disable=W0223
         """Base DRBD class.
         This class contains a few bits of common functionality between the
 .7 and 8.x versions of DRBD.
         """
         _VERSION_RE = re.compile(r"^version: (\d+)\.(\d+)\.(\d+)(?:\.\d+)?"
                                  r" \(api:(\d+)/proto:(\d+)(?:-(\d+))?\)")
         _VALID_LINE_RE = re.compile("^ *([0-9]+): cs:([^ ]+).*$")
         _UNUSED_LINE_RE = re.compile("^ *([0-9]+): cs:Unconfigured$")
         _DRBD_MAJOR = 147
         _ST_UNCONFIGURED = "Unconfigured"
         _ST_WFCONNECTION = "WFConnection"
         _ST_CONNECTED = "Connected"
         _STATUS_FILE = constants.DRBD_STATUS_FILE
         _USERMODE_HELPER_FILE = "/sys/module/drbd/parameters/usermode_helper"
         @staticmethod
         def _GetProcData(filename=_STATUS_FILE):
           """Return data from /proc/drbd.
           """
           try:
             data = utils.ReadFile(filename).splitlines()
           except EnvironmentError, err:
             if err.errno == errno.ENOENT:
               _ThrowError("The file %s cannot be opened, check if the module"
                           " is loaded (%s)", filename, str(err))
             else:
               _ThrowError("Can't read the DRBD proc file %s: %s", filename, str(err))
           if not data:
             _ThrowError("Can't read any data from %s", filename)
           return data
         @classmethod
         def _MassageProcData(cls, data):
           """Transform the output of _GetProdData into a nicer form.
           @return: a dictionary of minor: joined lines from /proc/drbd
               for that minor
           """
           results = {}
           old_minor = old_line = None
           for line in data:
             if not line: # completely empty lines, as can be returned by drbd8.0+
               continue
             lresult = cls._VALID_LINE_RE.match(line)
             if lresult is not None:
               if old_minor is not None:
                 results[old_minor] = old_line
               old_minor = int(lresult.group(1))
               old_line = line
             else:
               if old_minor is not None:
                 old_line += " " + line.strip()
           # add last line
           if old_minor is not None:
             results[old_minor] = old_line
           return results
         @classmethod
         def _GetVersion(cls, proc_data):
           """Return the DRBD version.
           This will return a dict with keys:
             - k_major
             - k_minor
             - k_point
             - api
             - proto
             - proto2 (only on drbd > 8.2.X)
           """
           first_line = proc_data[0].strip()
           version = cls._VERSION_RE.match(first_line)
           if not version:
             raise errors.BlockDeviceError("Can't parse DRBD version from '%s'" %
                                           first_line)
           values = version.groups()
           retval = {
             "k_major": int(values[0]),
             "k_minor": int(values[1]),
             "k_point": int(values[2]),
             "api": int(values[3]),
             "proto": int(values[4]),
+            }
           if values[5] is not None:
             retval["proto2"] = values[5]
           return retval
         @staticmethod
         def GetUsermodeHelper(filename=_USERMODE_HELPER_FILE):
           """Returns DRBD usermode_helper currently set.
           """
           try:
             helper = utils.ReadFile(filename).splitlines()[0]
           except EnvironmentError, err:
             if err.errno == errno.ENOENT:
               _ThrowError("The file %s cannot be opened, check if the module"
                           " is loaded (%s)", filename, str(err))
             else:
               _ThrowError("Can't read DRBD helper file %s: %s", filename, str(err))
           if not helper:
             _ThrowError("Can't read any data from %s", filename)
           return helper
         @staticmethod
         def _DevPath(minor):
           """Return the path to a drbd device for a given minor.
           """
           return "/dev/drbd%d" % minor
         @classmethod
         def GetUsedDevs(cls):
           """Compute the list of used DRBD devices.
           """
           data = cls._GetProcData()
           used_devs = {}
           for line in data:
             match = cls._VALID_LINE_RE.match(line)
             if not match:
               continue
             minor = int(match.group(1))
             state = match.group(2)
             if state == cls._ST_UNCONFIGURED:
               continue
             used_devs[minor] = state, line
           return used_devs
         def _SetFromMinor(self, minor):
           """Set our parameters based on the given minor.
           This sets our minor variable and our dev_path.
           """
           if minor is None:
             self.minor = self.dev_path = None
             self.attached = False
           else:
             self.minor = minor
             self.dev_path = self._DevPath(minor)
             self.attached = True
         @staticmethod
         def _CheckMetaSize(meta_device):
           """Check if the given meta device looks like a valid one.
           This currently only checks the size, which must be around
 MiB.
           """
           result = utils.RunCmd(["blockdev", "--getsize", meta_device])
           if result.failed:
             _ThrowError("Failed to get device size: %s - %s",
                         result.fail_reason, result.output)
           try:
             sectors = int(result.stdout)
           except (TypeError, ValueError):
             _ThrowError("Invalid output from blockdev: '%s'", result.stdout)
           num_bytes = sectors * 512
           if num_bytes < 128 * 1024 * 1024: # less than 128MiB
             _ThrowError("Meta device too small (%.2fMib)", (num_bytes / 1024 / 1024))
           # the maximum *valid* size of the meta device when living on top
           # of LVM is hard to compute: it depends on the number of stripes
           # and the PE size; e.g. a 2-stripe, 64MB PE will result in a 128MB
           # (normal size), but an eight-stripe 128MB PE will result in a 1GB
           # size meta device; as such, we restrict it to 1GB (a little bit
           # too generous, but making assumptions about PE size is hard)
           if num_bytes > 1024 * 1024 * 1024:
             _ThrowError("Meta device too big (%.2fMiB)", (num_bytes / 1024 / 1024))
         def Rename(self, new_id):
           """Rename a device.
           This is not supported for drbd devices.
           """
           raise errors.ProgrammerError("Can't rename a drbd device")
       class DRBD8(BaseDRBD):
         """DRBD v8.x block device.
         This implements the local host part of the DRBD device, i.e. it
         doesn't do anything to the supposed peer. If you need a fully
         connected DRBD pair, you need to use this class on both hosts.
         The unique_id for the drbd device is a (local_ip, local_port,
         remote_ip, remote_port, local_minor, secret) tuple, and it must have
         two children: the data device and the meta_device. The meta device
         is checked for valid size and is zeroed on create.
         """
         _MAX_MINORS = 255
         _PARSE_SHOW = None
         # timeout constants
         _NET_RECONFIG_TIMEOUT = 60
         # command line options for barriers
         _DISABLE_DISK_OPTION = "--no-disk-barrier"  # -a
         _DISABLE_DRAIN_OPTION = "--no-disk-drain"   # -D
         _DISABLE_FLUSH_OPTION = "--no-disk-flushes" # -i
         _DISABLE_META_FLUSH_OPTION = "--no-md-flushes"  # -m
         def __init__(self, unique_id, children, size, params):
           if children and children.count(None) > 0:
             children = []
           if len(children) not in (0, 2):
             raise ValueError("Invalid configuration data %s" % str(children))
           if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 6:
             raise ValueError("Invalid configuration data %s" % str(unique_id))
           (self._lhost, self._lport,
            self._rhost, self._rport,
            self._aminor, self._secret) = unique_id
           if children:
             if not _CanReadDevice(children[1].dev_path):
               logging.info("drbd%s: Ignoring unreadable meta device", self._aminor)
               children = []
           super(DRBD8, self).__init__(unique_id, children, size, params)
           self.major = self._DRBD_MAJOR
           version = self._GetVersion(self._GetProcData())
           if version["k_major"] != 8:
             _ThrowError("Mismatch in DRBD kernel version and requested ganeti"
                         " usage: kernel is %s.%s, ganeti wants 8.x",
                         version["k_major"], version["k_minor"])
           if (self._lhost is not None and self._lhost == self._rhost and
               self._lport == self._rport):
             raise ValueError("Invalid configuration data, same local/remote %s" %
                              (unique_id,))
           self.Attach()
         @classmethod
         def _InitMeta(cls, minor, dev_path):
           """Initialize a meta device.
           This will not work if the given minor is in use.
           """
           # Zero the metadata first, in order to make sure drbdmeta doesn't
           # try to auto-detect existing filesystems or similar (see
           # http://code.google.com/p/ganeti/issues/detail?id=182); we only
           # care about the first 128MB of data in the device, even though it
           # can be bigger
           result = utils.RunCmd([constants.DD_CMD,
                                  "if=/dev/zero", "of=%s" % dev_path,
                                  "bs=1048576", "count=128", "oflag=direct"])
           if result.failed:
             _ThrowError("Can't wipe the meta device: %s", result.output)
           result = utils.RunCmd(["drbdmeta", "--force", cls._DevPath(minor),
                                  "v08", dev_path, "0", "create-md"])
           if result.failed:
             _ThrowError("Can't initialize meta device: %s", result.output)
         @classmethod
         def _FindUnusedMinor(cls):
           """Find an unused DRBD device.
           This is specific to 8.x as the minors are allocated dynamically,
           so non-existing numbers up to a max minor count are actually free.
           """
           data = cls._GetProcData()
           highest = None
           for line in data:
             match = cls._UNUSED_LINE_RE.match(line)
             if match:
               return int(match.group(1))
             match = cls._VALID_LINE_RE.match(line)
             if match:
               minor = int(match.group(1))
               highest = max(highest, minor)
           if highest is None: # there are no minors in use at all
             return 0
           if highest >= cls._MAX_MINORS:
             logging.error("Error: no free drbd minors!")
             raise errors.BlockDeviceError("Can't find a free DRBD minor")
           return highest + 1
         @classmethod
         def _GetShowParser(cls):
           """Return a parser for `drbd show` output.
           This will either create or return an already-created parser for the
           output of the command `drbd show`.
           """
           if cls._PARSE_SHOW is not None:
             return cls._PARSE_SHOW
           # pyparsing setup
           lbrace = pyp.Literal("{").suppress()
           rbrace = pyp.Literal("}").suppress()
           lbracket = pyp.Literal("[").suppress()
           rbracket = pyp.Literal("]").suppress()
           semi = pyp.Literal(";").suppress()
           colon = pyp.Literal(":").suppress()
           # this also converts the value to an int
           number = pyp.Word(pyp.nums).setParseAction(lambda s, l, t: int(t[0]))
           comment = pyp.Literal("#") + pyp.Optional(pyp.restOfLine)
           defa = pyp.Literal("_is_default").suppress()
           dbl_quote = pyp.Literal('"').suppress()
           keyword = pyp.Word(pyp.alphanums + "-")
           # value types
           value = pyp.Word(pyp.alphanums + "_-/.:")
           quoted = dbl_quote + pyp.CharsNotIn('"') + dbl_quote
           ipv4_addr = (pyp.Optional(pyp.Literal("ipv4")).suppress() +
                        pyp.Word(pyp.nums + ".") + colon + number)
           ipv6_addr = (pyp.Optional(pyp.Literal("ipv6")).suppress() +
                        pyp.Optional(lbracket) + pyp.Word(pyp.hexnums + ":") +
                        pyp.Optional(rbracket) + colon + number)
           # meta device, extended syntax
           meta_value = ((value ^ quoted) + lbracket + number + rbracket)
           # device name, extended syntax
           device_value = pyp.Literal("minor").suppress() + number
           # a statement
           stmt = (~rbrace + keyword + ~lbrace +
                   pyp.Optional(ipv4_addr ^ ipv6_addr ^ value ^ quoted ^ meta_value ^
                                device_value) +
                   pyp.Optional(defa) + semi +
                   pyp.Optional(pyp.restOfLine).suppress())
           # an entire section
           section_name = pyp.Word(pyp.alphas + "_")
           section = section_name + lbrace + pyp.ZeroOrMore(pyp.Group(stmt)) + rbrace
           bnf = pyp.ZeroOrMore(pyp.Group(section ^ stmt))
           bnf.ignore(comment)
           cls._PARSE_SHOW = bnf
           return bnf
         @classmethod
         def _GetShowData(cls, minor):
           """Return the `drbdsetup show` data for a minor.
           """
           result = utils.RunCmd(["drbdsetup", cls._DevPath(minor), "show"])
           if result.failed:
             logging.error("Can't display the drbd config: %s - %s",
                           result.fail_reason, result.output)
             return None
           return result.stdout
         @classmethod
         def _GetDevInfo(cls, out):
           """Parse details about a given DRBD minor.
           This return, if available, the local backing device (as a path)
           and the local and remote (ip, port) information from a string
           containing the output of the `drbdsetup show` command as returned
           by _GetShowData.
           """
           data = {}
           if not out:
             return data
           bnf = cls._GetShowParser()
           # run pyparse
           try:
             results = bnf.parseString(out)
           except pyp.ParseException, err:
             _ThrowError("Can't parse drbdsetup show output: %s", str(err))
           # and massage the results into our desired format
           for section in results:
             sname = section[0]
             if sname == "_this_host":
               for lst in section[1:]:
                 if lst[0] == "disk":
                   data["local_dev"] = lst[1]
                 elif lst[0] == "meta-disk":
                   data["meta_dev"] = lst[1]
                   data["meta_index"] = lst[2]
                 elif lst[0] == "address":
                   data["local_addr"] = tuple(lst[1:])
             elif sname == "_remote_host":
               for lst in section[1:]:
                 if lst[0] == "address":
                   data["remote_addr"] = tuple(lst[1:])
           return data
         def _MatchesLocal(self, info):
           """Test if our local config matches with an existing device.
           The parameter should be as returned from `_GetDevInfo()`. This
           method tests if our local backing device is the same as the one in
           the info parameter, in effect testing if we look like the given
           device.
           """
           if self._children:
             backend, meta = self._children
           else:
             backend = meta = None
           if backend is not None:
             retval = ("local_dev" in info and info["local_dev"] == backend.dev_path)
           else:
             retval = ("local_dev" not in info)
           if meta is not None:
             retval = retval and ("meta_dev" in info and
                                  info["meta_dev"] == meta.dev_path)
             retval = retval and ("meta_index" in info and
                                  info["meta_index"] == 0)
           else:
             retval = retval and ("meta_dev" not in info and
                                  "meta_index" not in info)
           return retval
         def _MatchesNet(self, info):
           """Test if our network config matches with an existing device.
           The parameter should be as returned from `_GetDevInfo()`. This
           method tests if our network configuration is the same as the one
           in the info parameter, in effect testing if we look like the given
           device.
           """
           if (((self._lhost is None and not ("local_addr" in info)) and
                (self._rhost is None and not ("remote_addr" in info)))):
             return True
           if self._lhost is None:
             return False
           if not ("local_addr" in info and
                   "remote_addr" in info):
             return False
           retval = (info["local_addr"] == (self._lhost, self._lport))
           retval = (retval and
                     info["remote_addr"] == (self._rhost, self._rport))
           return retval
         def _AssembleLocal(self, minor, backend, meta, size):
           """Configure the local part of a DRBD device.
           """
           args = ["drbdsetup", self._DevPath(minor), "disk",
                   backend, meta, "0",
                   "-e", "detach",
                   "--create-device"]
           if size:
             args.extend(["-d", "%sm" % size])
           version = self._GetVersion(self._GetProcData())
           vmaj = version["k_major"]
           vmin = version["k_minor"]
           vrel = version["k_point"]
           barrier_args = \
             self._ComputeDiskBarrierArgs(vmaj, vmin, vrel,
                                          self.params[constants.LDP_BARRIERS],
                                          self.params[constants.LDP_NO_META_FLUSH])
           args.extend(barrier_args)
           if self.params[constants.LDP_DISK_CUSTOM]:
             args.extend(shlex.split(self.params[constants.LDP_DISK_CUSTOM]))
           result = utils.RunCmd(args)
           if result.failed:
             _ThrowError("drbd%d: can't attach local disk: %s", minor, result.output)
         @classmethod
         def _ComputeDiskBarrierArgs(cls, vmaj, vmin, vrel, disabled_barriers,
                                     disable_meta_flush):
           """Compute the DRBD command line parameters for disk barriers
           Returns a list of the disk barrier parameters as requested via the
           disabled_barriers and disable_meta_flush arguments, and according to the
           supported ones in the DRBD version vmaj.vmin.vrel
           If the desired option is unsupported, raises errors.BlockDeviceError.
           """
           disabled_barriers_set = frozenset(disabled_barriers)
           if not disabled_barriers_set in constants.DRBD_VALID_BARRIER_OPT:
             raise errors.BlockDeviceError("%s is not a valid option set for DRBD"
                                           " barriers" % disabled_barriers)
           args = []
           # The following code assumes DRBD 8.x, with x < 4 and x != 1 (DRBD 8.1.x
           # does not exist)
           if not vmaj == 8 and vmin in (0, 2, 3):
             raise errors.BlockDeviceError("Unsupported DRBD version: %d.%d.%d" %
                                           (vmaj, vmin, vrel))
           def _AppendOrRaise(option, min_version):
             """Helper for DRBD options"""
             if min_version is not None and vrel >= min_version:
               args.append(option)
             else:
               raise errors.BlockDeviceError("Could not use the option %s as the"
                                             " DRBD version %d.%d.%d does not support"
                                             " it." % (option, vmaj, vmin, vrel))
           # the minimum version for each feature is encoded via pairs of (minor
           # version -> x) where x is version in which support for the option was
           # introduced.
           meta_flush_supported = disk_flush_supported = {
 : 12,
 : 7,
 : 0,
+            }
           disk_drain_supported = {
 : 7,
 : 0,
+            }
           disk_barriers_supported = {
 : 0,
+            }
           # meta flushes
           if disable_meta_flush:
             _AppendOrRaise(cls._DISABLE_META_FLUSH_OPTION,
                            meta_flush_supported.get(vmin, None))
           # disk flushes
           if constants.DRBD_B_DISK_FLUSH in disabled_barriers_set:
             _AppendOrRaise(cls._DISABLE_FLUSH_OPTION,
                            disk_flush_supported.get(vmin, None))
           # disk drain
           if constants.DRBD_B_DISK_DRAIN in disabled_barriers_set:
             _AppendOrRaise(cls._DISABLE_DRAIN_OPTION,
                            disk_drain_supported.get(vmin, None))
           # disk barriers
           if constants.DRBD_B_DISK_BARRIERS in disabled_barriers_set:
             _AppendOrRaise(cls._DISABLE_DISK_OPTION,
                            disk_barriers_supported.get(vmin, None))
           return args
         def _AssembleNet(self, minor, net_info, protocol,
                          dual_pri=False, hmac=None, secret=None):
           """Configure the network part of the device.
           """
           lhost, lport, rhost, rport = net_info
           if None in net_info:
             # we don't want network connection and actually want to make
             # sure its shutdown
             self._ShutdownNet(minor)
             return
           # Workaround for a race condition. When DRBD is doing its dance to
           # establish a connection with its peer, it also sends the
           # synchronization speed over the wire. In some cases setting the
           # sync speed only after setting up both sides can race with DRBD
           # connecting, hence we set it here before telling DRBD anything
           # about its peer.
           sync_errors = self._SetMinorSyncParams(minor, self.params)
           if sync_errors:
             _ThrowError("drbd%d: can't set the synchronization parameters: %s" %
                         (minor, utils.CommaJoin(sync_errors)))
           if netutils.IP6Address.IsValid(lhost):
             if not netutils.IP6Address.IsValid(rhost):
               _ThrowError("drbd%d: can't connect ip %s to ip %s" %
                           (minor, lhost, rhost))
             family = "ipv6"
           elif netutils.IP4Address.IsValid(lhost):
             if not netutils.IP4Address.IsValid(rhost):
               _ThrowError("drbd%d: can't connect ip %s to ip %s" %
                           (minor, lhost, rhost))
             family = "ipv4"
           else:
             _ThrowError("drbd%d: Invalid ip %s" % (minor, lhost))
           args = ["drbdsetup", self._DevPath(minor), "net",
                   "%s:%s:%s" % (family, lhost, lport),
                   "%s:%s:%s" % (family, rhost, rport), protocol,
                   "-A", "discard-zero-changes",
                   "-B", "consensus",
                   "--create-device",
+                  ]
           if dual_pri:
             args.append("-m")
           if hmac and secret:
             args.extend(["-a", hmac, "-x", secret])
           if self.params[constants.LDP_NET_CUSTOM]:
             args.extend(shlex.split(self.params[constants.LDP_NET_CUSTOM]))
           result = utils.RunCmd(args)
           if result.failed:
             _ThrowError("drbd%d: can't setup network: %s - %s",
                         minor, result.fail_reason, result.output)
           def _CheckNetworkConfig():
             info = self._GetDevInfo(self._GetShowData(minor))
             if not "local_addr" in info or not "remote_addr" in info:
               raise utils.RetryAgain()
             if (info["local_addr"] != (lhost, lport) or
                 info["remote_addr"] != (rhost, rport)):
               raise utils.RetryAgain()
           try:
             utils.Retry(_CheckNetworkConfig, 1.0, 10.0)
           except utils.RetryTimeout:
             _ThrowError("drbd%d: timeout while configuring network", minor)
         def AddChildren(self, devices):
           """Add a disk to the DRBD device.
           """
           if self.minor is None:
             _ThrowError("drbd%d: can't attach to dbrd8 during AddChildren",
                         self._aminor)
           if len(devices) != 2:
             _ThrowError("drbd%d: need two devices for AddChildren", self.minor)
           info = self._GetDevInfo(self._GetShowData(self.minor))
           if "local_dev" in info:
             _ThrowError("drbd%d: already attached to a local disk", self.minor)
           backend, meta = devices
           if backend.dev_path is None or meta.dev_path is None:
             _ThrowError("drbd%d: children not ready during AddChildren", self.minor)
           backend.Open()
           meta.Open()
           self._CheckMetaSize(meta.dev_path)
           self._InitMeta(self._FindUnusedMinor(), meta.dev_path)
           self._AssembleLocal(self.minor, backend.dev_path, meta.dev_path, self.size)
           self._children = devices
         def RemoveChildren(self, devices):
           """Detach the drbd device from local storage.
           """
           if self.minor is None:
             _ThrowError("drbd%d: can't attach to drbd8 during RemoveChildren",
                         self._aminor)
           # early return if we don't actually have backing storage
           info = self._GetDevInfo(self._GetShowData(self.minor))
           if "local_dev" not in info:
             return
           if len(self._children) != 2:
             _ThrowError("drbd%d: we don't have two children: %s", self.minor,
                         self._children)
           if self._children.count(None) == 2: # we don't actually have children :)
             logging.warning("drbd%d: requested detach while detached", self.minor)
             return
           if len(devices) != 2:
             _ThrowError("drbd%d: we need two children in RemoveChildren", self.minor)
           for child, dev in zip(self._children, devices):
             if dev != child.dev_path:
               _ThrowError("drbd%d: mismatch in local storage (%s != %s) in"
                           " RemoveChildren", self.minor, dev, child.dev_path)
           self._ShutdownLocal(self.minor)
           self._children = []
         @classmethod
         def _SetMinorSyncParams(cls, minor, params):
           """Set the parameters of the DRBD syncer.
           This is the low-level implementation.
           @type minor: int
           @param minor: the drbd minor whose settings we change
           @type params: dict
           @param params: LD level disk parameters related to the synchronization
           @rtype: list
           @return: a list of error messages
           """
           args = ["drbdsetup", cls._DevPath(minor), "syncer"]
           if params[constants.LDP_DYNAMIC_RESYNC]:
             version = cls._GetVersion(cls._GetProcData())
             vmin = version["k_minor"]
             vrel = version["k_point"]
             # By definition we are using 8.x, so just check the rest of the version
             # number
             if vmin != 3 or vrel < 9:
               msg = ("The current DRBD version (8.%d.%d) does not support the "
                      "dynamic resync speed controller" % (vmin, vrel))
               logging.error(msg)
               return [msg]
             if params[constants.LDP_PLAN_AHEAD] == 0:
               msg = ("A value of 0 for c-plan-ahead disables the dynamic sync speed"
                      " controller at DRBD level. If you want to disable it, please"
                      " set the dynamic-resync disk parameter to False.")
               logging.error(msg)
               return [msg]
             # add the c-* parameters to args
             args.extend(["--c-plan-ahead", params[constants.LDP_PLAN_AHEAD],
                          "--c-fill-target", params[constants.LDP_FILL_TARGET],
                          "--c-delay-target", params[constants.LDP_DELAY_TARGET],
                          "--c-max-rate", params[constants.LDP_MAX_RATE],
                          "--c-min-rate", params[constants.LDP_MIN_RATE],
                          ])
           else:
             args.extend(["-r", "%d" % params[constants.LDP_RESYNC_RATE]])
           args.append("--create-device")
           result = utils.RunCmd(args)
           if result.failed:
             msg = ("Can't change syncer rate: %s - %s" %
                    (result.fail_reason, result.output))
             logging.error(msg)
             return [msg]
           return []
         def SetSyncParams(self, params):
           """Set the synchronization parameters of the DRBD syncer.
           @type params: dict
           @param params: LD level disk parameters related to the synchronization
           @rtype: list
           @return: a list of error messages, emitted both by the current node and by
           children. An empty list means no errors
           """
           if self.minor is None:
             err = "Not attached during SetSyncParams"
             logging.info(err)
             return [err]
           children_result = super(DRBD8, self).SetSyncParams(params)
           children_result.extend(self._SetMinorSyncParams(self.minor, params))
           return children_result
         def PauseResumeSync(self, pause):
           """Pauses or resumes the sync of a DRBD device.
           @param pause: Wether to pause or resume
           @return: the success of the operation
           """
           if self.minor is None:
             logging.info("Not attached during PauseSync")
             return False
           children_result = super(DRBD8, self).PauseResumeSync(pause)
           if pause:
             cmd = "pause-sync"
           else:
             cmd = "resume-sync"
           result = utils.RunCmd(["drbdsetup", self.dev_path, cmd])
           if result.failed:
             logging.error("Can't %s: %s - %s", cmd,
                           result.fail_reason, result.output)
           return not result.failed and children_result
         def GetProcStatus(self):
           """Return device data from /proc.
           """
           if self.minor is None:
             _ThrowError("drbd%d: GetStats() called while not attached", self._aminor)
           proc_info = self._MassageProcData(self._GetProcData())
           if self.minor not in proc_info:
             _ThrowError("drbd%d: can't find myself in /proc", self.minor)
           return DRBD8Status(proc_info[self.minor])
         def GetSyncStatus(self):
           """Returns the sync status of the device.
           If sync_percent is None, it means all is ok
           If estimated_time is None, it means we can't estimate
           the time needed, otherwise it's the time left in seconds.
           We set the is_degraded parameter to True on two conditions:
           network not connected or local disk missing.
           We compute the ldisk parameter based on whether we have a local
           disk or not.
           @rtype: objects.BlockDevStatus
           """
           if self.minor is None and not self.Attach():
             _ThrowError("drbd%d: can't Attach() in GetSyncStatus", self._aminor)
           stats = self.GetProcStatus()
           is_degraded = not stats.is_connected or not stats.is_disk_uptodate
           if stats.is_disk_uptodate:
             ldisk_status = constants.LDS_OKAY
           elif stats.is_diskless:
             ldisk_status = constants.LDS_FAULTY
           else:
             ldisk_status = constants.LDS_UNKNOWN
           return objects.BlockDevStatus(dev_path=self.dev_path,
                                         major=self.major,
                                         minor=self.minor,
                                         sync_percent=stats.sync_percent,
                                         estimated_time=stats.est_time,
                                         is_degraded=is_degraded,
                                         ldisk_status=ldisk_status)
         def Open(self, force=False):
           """Make the local state primary.
           If the 'force' parameter is given, the '-o' option is passed to
           drbdsetup. Since this is a potentially dangerous operation, the
           force flag should be only given after creation, when it actually
           is mandatory.
           """
           if self.minor is None and not self.Attach():
             logging.error("DRBD cannot attach to a device during open")
             return False
           cmd = ["drbdsetup", self.dev_path, "primary"]
           if force:
             cmd.append("-o")
           result = utils.RunCmd(cmd)
           if result.failed:
             _ThrowError("drbd%d: can't make drbd device primary: %s", self.minor,
                         result.output)
         def Close(self):
           """Make the local state secondary.
           This will, of course, fail if the device is in use.
           """
           if self.minor is None and not self.Attach():
             _ThrowError("drbd%d: can't Attach() in Close()", self._aminor)
           result = utils.RunCmd(["drbdsetup", self.dev_path, "secondary"])
           if result.failed:
             _ThrowError("drbd%d: can't switch drbd device to secondary: %s",
                         self.minor, result.output)
         def DisconnectNet(self):
           """Removes network configuration.
           This method shutdowns the network side of the device.
           The method will wait up to a hardcoded timeout for the device to
           go into standalone after the 'disconnect' command before
           re-configuring it, as sometimes it takes a while for the
           disconnect to actually propagate and thus we might issue a 'net'
           command while the device is still connected. If the device will
           still be attached to the network and we time out, we raise an
           exception.
           """
           if self.minor is None:
             _ThrowError("drbd%d: disk not attached in re-attach net", self._aminor)
           if None in (self._lhost, self._lport, self._rhost, self._rport):
             _ThrowError("drbd%d: DRBD disk missing network info in"
                         " DisconnectNet()", self.minor)
           class _DisconnectStatus:
             def __init__(self, ever_disconnected):
               self.ever_disconnected = ever_disconnected
           dstatus = _DisconnectStatus(_IgnoreError(self._ShutdownNet, self.minor))
           def _WaitForDisconnect():
             if self.GetProcStatus().is_standalone:
               return
             # retry the disconnect, it seems possible that due to a well-time
             # disconnect on the peer, my disconnect command might be ignored and
             # forgotten
             dstatus.ever_disconnected = \
               _IgnoreError(self._ShutdownNet, self.minor) or dstatus.ever_disconnected
             raise utils.RetryAgain()
           # Keep start time
           start_time = time.time()
           try:
             # Start delay at 100 milliseconds and grow up to 2 seconds
             utils.Retry(_WaitForDisconnect, (0.1, 1.5, 2.0),
                         self._NET_RECONFIG_TIMEOUT)
           except utils.RetryTimeout:
             if dstatus.ever_disconnected:
               msg = ("drbd%d: device did not react to the"
                      " 'disconnect' command in a timely manner")
             else:
               msg = "drbd%d: can't shutdown network, even after multiple retries"
             _ThrowError(msg, self.minor)
           reconfig_time = time.time() - start_time
           if reconfig_time > (self._NET_RECONFIG_TIMEOUT * 0.25):
             logging.info("drbd%d: DisconnectNet: detach took %.3f seconds",
                          self.minor, reconfig_time)
         def AttachNet(self, multimaster):
           """Reconnects the network.
           This method connects the network side of the device with a
           specified multi-master flag. The device needs to be 'Standalone'
           but have valid network configuration data.
           Args:
             - multimaster: init the network in dual-primary mode
           """
           if self.minor is None:
             _ThrowError("drbd%d: device not attached in AttachNet", self._aminor)
           if None in (self._lhost, self._lport, self._rhost, self._rport):
             _ThrowError("drbd%d: missing network info in AttachNet()", self.minor)
           status = self.GetProcStatus()
           if not status.is_standalone:
             _ThrowError("drbd%d: device is not standalone in AttachNet", self.minor)
           self._AssembleNet(self.minor,
                             (self._lhost, self._lport, self._rhost, self._rport),
                             constants.DRBD_NET_PROTOCOL, dual_pri=multimaster,
                             hmac=constants.DRBD_HMAC_ALG, secret=self._secret)
         def Attach(self):
           """Check if our minor is configured.
           This doesn't do any device configurations - it only checks if the
           minor is in a state different from Unconfigured.
           Note that this function will not change the state of the system in
           any way (except in case of side-effects caused by reading from
           /proc).
           """
           used_devs = self.GetUsedDevs()
           if self._aminor in used_devs:
             minor = self._aminor
           else:
             minor = None
           self._SetFromMinor(minor)
           return minor is not None
         def Assemble(self):
           """Assemble the drbd.
           Method:
             - if we have a configured device, we try to ensure that it matches
               our config
             - if not, we create it from zero
             - anyway, set the device parameters
           """
           super(DRBD8, self).Assemble()
           self.Attach()
           if self.minor is None:
             # local device completely unconfigured
             self._FastAssemble()
           else:
             # we have to recheck the local and network status and try to fix
             # the device
             self._SlowAssemble()
           sync_errors = self.SetSyncParams(self.params)
           if sync_errors:
             _ThrowError("drbd%d: can't set the synchronization parameters: %s" %
                         (self.minor, utils.CommaJoin(sync_errors)))
         def _SlowAssemble(self):
           """Assembles the DRBD device from a (partially) configured device.
           In case of partially attached (local device matches but no network
           setup), we perform the network attach. If successful, we re-test
           the attach if can return success.
           """
           # TODO: Rewrite to not use a for loop just because there is 'break'
           # pylint: disable=W0631
           net_data = (self._lhost, self._lport, self._rhost, self._rport)
           for minor in (self._aminor,):
             info = self._GetDevInfo(self._GetShowData(minor))
             match_l = self._MatchesLocal(info)
             match_r = self._MatchesNet(info)
             if match_l and match_r:
               # everything matches
               break
             if match_l and not match_r and "local_addr" not in info:
               # disk matches, but not attached to network, attach and recheck
               self._AssembleNet(minor, net_data, constants.DRBD_NET_PROTOCOL,
                                 hmac=constants.DRBD_HMAC_ALG, secret=self._secret)
               if self._MatchesNet(self._GetDevInfo(self._GetShowData(minor))):
                 break
               else:
                 _ThrowError("drbd%d: network attach successful, but 'drbdsetup"
                             " show' disagrees", minor)
             if match_r and "local_dev" not in info:
               # no local disk, but network attached and it matches
               self._AssembleLocal(minor, self._children[0].dev_path,
                                   self._children[1].dev_path, self.size)
               if self._MatchesNet(self._GetDevInfo(self._GetShowData(minor))):
                 break
               else:
                 _ThrowError("drbd%d: disk attach successful, but 'drbdsetup"
                             " show' disagrees", minor)
             # this case must be considered only if we actually have local
             # storage, i.e. not in diskless mode, because all diskless
             # devices are equal from the point of view of local
             # configuration
             if (match_l and "local_dev" in info and
                 not match_r and "local_addr" in info):
               # strange case - the device network part points to somewhere
               # else, even though its local storage is ours; as we own the
               # drbd space, we try to disconnect from the remote peer and
               # reconnect to our correct one
               try:
                 self._ShutdownNet(minor)
               except errors.BlockDeviceError, err:
                 _ThrowError("drbd%d: device has correct local storage, wrong"
                             " remote peer and is unable to disconnect in order"
                             " to attach to the correct peer: %s", minor, str(err))
               # note: _AssembleNet also handles the case when we don't want
               # local storage (i.e. one or more of the _[lr](host|port) is
               # None)
               self._AssembleNet(minor, net_data, constants.DRBD_NET_PROTOCOL,
                                 hmac=constants.DRBD_HMAC_ALG, secret=self._secret)
               if self._MatchesNet(self._GetDevInfo(self._GetShowData(minor))):
                 break
               else:
                 _ThrowError("drbd%d: network attach successful, but 'drbdsetup"
                             " show' disagrees", minor)
           else:
             minor = None
           self._SetFromMinor(minor)
           if minor is None:
             _ThrowError("drbd%d: cannot activate, unknown or unhandled reason",
                         self._aminor)
         def _FastAssemble(self):
           """Assemble the drbd device from zero.
           This is run when in Assemble we detect our minor is unused.
           """
           minor = self._aminor
           if self._children and self._children[0] and self._children[1]:
             self._AssembleLocal(minor, self._children[0].dev_path,
                                 self._children[1].dev_path, self.size)
           if self._lhost and self._lport and self._rhost and self._rport:
             self._AssembleNet(minor,
                               (self._lhost, self._lport, self._rhost, self._rport),
                               constants.DRBD_NET_PROTOCOL,
                               hmac=constants.DRBD_HMAC_ALG, secret=self._secret)
           self._SetFromMinor(minor)
         @classmethod
         def _ShutdownLocal(cls, minor):
           """Detach from the local device.
           I/Os will continue to be served from the remote device. If we
           don't have a remote device, this operation will fail.
           """
           result = utils.RunCmd(["drbdsetup", cls._DevPath(minor), "detach"])
           if result.failed:
             _ThrowError("drbd%d: can't detach local disk: %s", minor, result.output)
         @classmethod
         def _ShutdownNet(cls, minor):
           """Disconnect from the remote peer.
           This fails if we don't have a local device.
           """
           result = utils.RunCmd(["drbdsetup", cls._DevPath(minor), "disconnect"])
           if result.failed:
             _ThrowError("drbd%d: can't shutdown network: %s", minor, result.output)
         @classmethod
         def _ShutdownAll(cls, minor):
           """Deactivate the device.
           This will, of course, fail if the device is in use.
           """
           result = utils.RunCmd(["drbdsetup", cls._DevPath(minor), "down"])
           if result.failed:
             _ThrowError("drbd%d: can't shutdown drbd device: %s",
                         minor, result.output)
         def Shutdown(self):
           """Shutdown the DRBD device.
           """
           if self.minor is None and not self.Attach():
             logging.info("drbd%d: not attached during Shutdown()", self._aminor)
             return
           minor = self.minor
           self.minor = None
           self.dev_path = None
           self._ShutdownAll(minor)
         def Remove(self):
           """Stub remove for DRBD devices.
           """
           self.Shutdown()
         @classmethod
         def Create(cls, unique_id, children, size, params):
           """Create a new DRBD8 device.
           Since DRBD devices are not created per se, just assembled, this
           function only initializes the metadata.
           """
           if len(children) != 2:
             raise errors.ProgrammerError("Invalid setup for the drbd device")
           # check that the minor is unused
           aminor = unique_id[4]
           proc_info = cls._MassageProcData(cls._GetProcData())
           if aminor in proc_info:
             status = DRBD8Status(proc_info[aminor])
             in_use = status.is_in_use
           else:
             in_use = False
           if in_use:
             _ThrowError("drbd%d: minor is already in use at Create() time", aminor)
           meta = children[1]
           meta.Assemble()
           if not meta.Attach():
             _ThrowError("drbd%d: can't attach to meta device '%s'",
                         aminor, meta)
           cls._CheckMetaSize(meta.dev_path)
           cls._InitMeta(aminor, meta.dev_path)
           return cls(unique_id, children, size, params)
         def Grow(self, amount, dryrun, backingstore):
           """Resize the DRBD device and its backing storage.
           """
           if self.minor is None:
             _ThrowError("drbd%d: Grow called while not attached", self._aminor)
           if len(self._children) != 2 or None in self._children:
             _ThrowError("drbd%d: cannot grow diskless device", self.minor)
           self._children[0].Grow(amount, dryrun, backingstore)
           if dryrun or backingstore:
             # DRBD does not support dry-run mode and is not backing storage,
             # so we'll return here
             return
           result = utils.RunCmd(["drbdsetup", self.dev_path, "resize", "-s",
                                  "%dm" % (self.size + amount)])
           if result.failed:
             _ThrowError("drbd%d: resize failed: %s", self.minor, result.output)
       class FileStorage(BlockDev):
         """File device.
         This class represents the a file storage backend device.
         The unique_id for the file device is a (file_driver, file_path) tuple.
         """
         def __init__(self, unique_id, children, size, params):
           """Initalizes a file device backend.
           """
           if children:
             raise errors.BlockDeviceError("Invalid setup for file device")
           super(FileStorage, self).__init__(unique_id, children, size, params)
           if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
             raise ValueError("Invalid configuration data %s" % str(unique_id))
           self.driver = unique_id[0]
           self.dev_path = unique_id[1]
           CheckFileStoragePath(self.dev_path)
           self.Attach()
         def Assemble(self):
           """Assemble the device.
           Checks whether the file device exists, raises BlockDeviceError otherwise.
           """
           if not os.path.exists(self.dev_path):
             _ThrowError("File device '%s' does not exist" % self.dev_path)
         def Shutdown(self):
           """Shutdown the device.
           This is a no-op for the file type, as we don't deactivate
           the file on shutdown.
           """
           pass
         def Open(self, force=False):
           """Make the device ready for I/O.
           This is a no-op for the file type.
           """
           pass
         def Close(self):
           """Notifies that the device will no longer be used for I/O.
           This is a no-op for the file type.
           """
           pass
         def Remove(self):
           """Remove the file backing the block device.
           @rtype: boolean
           @return: True if the removal was successful
           """
           try:
             os.remove(self.dev_path)
           except OSError, err:
             if err.errno != errno.ENOENT:
               _ThrowError("Can't remove file '%s': %s", self.dev_path, err)
         def Rename(self, new_id):
           """Renames the file.
           """
           # TODO: implement rename for file-based storage
           _ThrowError("Rename is not supported for file-based storage")
         def Grow(self, amount, dryrun, backingstore):
           """Grow the file
           @param amount: the amount (in mebibytes) to grow with
           """
           if not backingstore:
             return
           # Check that the file exists
           self.Assemble()
           current_size = self.GetActualSize()
           new_size = current_size + amount * 1024 * 1024
           assert new_size > current_size, "Cannot Grow with a negative amount"
           # We can't really simulate the growth
           if dryrun:
             return
           try:
             f = open(self.dev_path, "a+")
             f.truncate(new_size)
             f.close()
           except EnvironmentError, err:
             _ThrowError("Error in file growth: %", str(err))
         def Attach(self):
           """Attach to an existing file.
           Check if this file already exists.
           @rtype: boolean
           @return: True if file exists
           """
           self.attached = os.path.exists(self.dev_path)
           return self.attached
         def GetActualSize(self):
           """Return the actual disk size.
           @note: the device needs to be active when this is called
           """
           assert self.attached, "BlockDevice not attached in GetActualSize()"
           try:
             st = os.stat(self.dev_path)
             return st.st_size
           except OSError, err:
             _ThrowError("Can't stat %s: %s", self.dev_path, err)
         @classmethod
         def Create(cls, unique_id, children, size, params):
           """Create a new file.
           @param size: the size of file in MiB
           @rtype: L{bdev.FileStorage}
           @return: an instance of FileStorage
           """
           if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
             raise ValueError("Invalid configuration data %s" % str(unique_id))
           dev_path = unique_id[1]
           CheckFileStoragePath(dev_path)
           try:
             fd = os.open(dev_path, os.O_RDWR | os.O_CREAT | os.O_EXCL)
             f = os.fdopen(fd, "w")
             f.truncate(size * 1024 * 1024)
             f.close()
           except EnvironmentError, err:
             if err.errno == errno.EEXIST:
               _ThrowError("File already existing: %s", dev_path)
             _ThrowError("Error in file creation: %", str(err))
           return FileStorage(unique_id, children, size, params)
       class PersistentBlockDevice(BlockDev):
         """A block device with persistent node
         May be either directly attached, or exposed through DM (e.g. dm-multipath).
         udev helpers are probably required to give persistent, human-friendly
         names.
         For the time being, pathnames are required to lie under /dev.
         """
         def __init__(self, unique_id, children, size, params):
           """Attaches to a static block device.
           The unique_id is a path under /dev.
           """
           super(PersistentBlockDevice, self).__init__(unique_id, children, size,
                                                       params)
           if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
             raise ValueError("Invalid configuration data %s" % str(unique_id))
           self.dev_path = unique_id[1]
           if not os.path.realpath(self.dev_path).startswith("/dev/"):
             raise ValueError("Full path '%s' lies outside /dev" %
                                     os.path.realpath(self.dev_path))
           # TODO: this is just a safety guard checking that we only deal with devices
           # we know how to handle. In the future this will be integrated with
           # external storage backends and possible values will probably be collected
           # from the cluster configuration.
           if unique_id[0] != constants.BLOCKDEV_DRIVER_MANUAL:
             raise ValueError("Got persistent block device of invalid type: %s" %
                              unique_id[0])
           self.major = self.minor = None
           self.Attach()
         @classmethod
         def Create(cls, unique_id, children, size, params):
           """Create a new device
           This is a noop, we only return a PersistentBlockDevice instance
           """
           return PersistentBlockDevice(unique_id, children, 0, params)
         def Remove(self):
           """Remove a device
           This is a noop
           """
           pass
         def Rename(self, new_id):
           """Rename this device.
           """
           _ThrowError("Rename is not supported for PersistentBlockDev storage")
         def Attach(self):
           """Attach to an existing block device.
           """
           self.attached = False
           try:
             st = os.stat(self.dev_path)
           except OSError, err:
             logging.error("Error stat()'ing %s: %s", self.dev_path, str(err))
             return False
           if not stat.S_ISBLK(st.st_mode):
             logging.error("%s is not a block device", self.dev_path)
             return False
           self.major = os.major(st.st_rdev)
           self.minor = os.minor(st.st_rdev)
           self.attached = True
           return True
         def Assemble(self):
           """Assemble the device.
           """
           pass
         def Shutdown(self):
           """Shutdown the device.
           """
           pass
         def Open(self, force=False):
           """Make the device ready for I/O.
           """
           pass
         def Close(self):
           """Notifies that the device will no longer be used for I/O.
           """
           pass
         def Grow(self, amount, dryrun, backingstore):
           """Grow the logical volume.
           """
           _ThrowError("Grow is not supported for PersistentBlockDev storage")
       class RADOSBlockDevice(BlockDev):
         """A RADOS Block Device (rbd).
         This class implements the RADOS Block Device for the backend. You need
         the rbd kernel driver, the RADOS Tools and a working RADOS cluster for
         this to be functional.
         """
         def __init__(self, unique_id, children, size, params):
           """Attaches to an rbd device.
           """
           super(RADOSBlockDevice, self).__init__(unique_id, children, size, params)
           if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
             raise ValueError("Invalid configuration data %s" % str(unique_id))
           self.driver, self.rbd_name = unique_id
           self.major = self.minor = None
           self.Attach()
         @classmethod
         def Create(cls, unique_id, children, size, params):
           """Create a new rbd device.
           Provision a new rbd volume inside a RADOS pool.
           """
           if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
             raise errors.ProgrammerError("Invalid configuration data %s" %
                                          str(unique_id))
           rbd_pool = params[constants.LDP_POOL]
           rbd_name = unique_id[1]
           # Provision a new rbd volume (Image) inside the RADOS cluster.
           cmd = [constants.RBD_CMD, "create", "-p", rbd_pool,
                  rbd_name, "--size", "%s" % size]
           result = utils.RunCmd(cmd)
           if result.failed:
             _ThrowError("rbd creation failed (%s): %s",
                         result.fail_reason, result.output)
           return RADOSBlockDevice(unique_id, children, size, params)
         def Remove(self):
           """Remove the rbd device.
           """
           rbd_pool = self.params[constants.LDP_POOL]
           rbd_name = self.unique_id[1]
           if not self.minor and not self.Attach():
             # The rbd device doesn't exist.
             return
           # First shutdown the device (remove mappings).
           self.Shutdown()
           # Remove the actual Volume (Image) from the RADOS cluster.
           cmd = [constants.RBD_CMD, "rm", "-p", rbd_pool, rbd_name]
           result = utils.RunCmd(cmd)
           if result.failed:
             _ThrowError("Can't remove Volume from cluster with rbd rm: %s - %s",
                         result.fail_reason, result.output)
         def Rename(self, new_id):
           """Rename this device.
           """
           pass
         def Attach(self):
           """Attach to an existing rbd device.
           This method maps the rbd volume that matches our name with
           an rbd device and then attaches to this device.
           """
           self.attached = False
           # Map the rbd volume to a block device under /dev
           self.dev_path = self._MapVolumeToBlockdev(self.unique_id)
           try:
             st = os.stat(self.dev_path)
           except OSError, err:
             logging.error("Error stat()'ing %s: %s", self.dev_path, str(err))
             return False
           if not stat.S_ISBLK(st.st_mode):
             logging.error("%s is not a block device", self.dev_path)
             return False
           self.major = os.major(st.st_rdev)
           self.minor = os.minor(st.st_rdev)
           self.attached = True
           return True
         def _MapVolumeToBlockdev(self, unique_id):
           """Maps existing rbd volumes to block devices.
           This method should be idempotent if the mapping already exists.
           @rtype: string
           @return: the block device path that corresponds to the volume
           """
           pool = self.params[constants.LDP_POOL]
           name = unique_id[1]
           # Check if the mapping already exists.
           showmap_cmd = [constants.RBD_CMD, "showmapped", "-p", pool]
           result = utils.RunCmd(showmap_cmd)
           if result.failed:
             _ThrowError("rbd showmapped failed (%s): %s",
                         result.fail_reason, result.output)
           rbd_dev = self._ParseRbdShowmappedOutput(result.output, name)
           if rbd_dev:
             # The mapping exists. Return it.
             return rbd_dev
           # The mapping doesn't exist. Create it.
           map_cmd = [constants.RBD_CMD, "map", "-p", pool, name]
           result = utils.RunCmd(map_cmd)
           if result.failed:
             _ThrowError("rbd map failed (%s): %s",
                         result.fail_reason, result.output)
           # Find the corresponding rbd device.
           showmap_cmd = [constants.RBD_CMD, "showmapped", "-p", pool]
           result = utils.RunCmd(showmap_cmd)
           if result.failed:
             _ThrowError("rbd map succeeded, but showmapped failed (%s): %s",
                         result.fail_reason, result.output)
           rbd_dev = self._ParseRbdShowmappedOutput(result.output, name)
           if not rbd_dev:
             _ThrowError("rbd map succeeded, but could not find the rbd block"
                         " device in output of showmapped, for volume: %s", name)
           # The device was successfully mapped. Return it.
           return rbd_dev
         @staticmethod
         def _ParseRbdShowmappedOutput(output, volume_name):
           """Parse the output of `rbd showmapped'.
           This method parses the output of `rbd showmapped' and returns
           the rbd block device path (e.g. /dev/rbd0) that matches the
           given rbd volume.
           @type output: string
           @param output: the whole output of `rbd showmapped'
           @type volume_name: string
           @param volume_name: the name of the volume whose device we search for
           @rtype: string or None
           @return: block device path if the volume is mapped, else None
           """
           allfields = 5
           volumefield = 2
           devicefield = 4
           field_sep = "\t"
           lines = output.splitlines()
           splitted_lines = map(lambda l: l.split(field_sep), lines)
           # Check empty output.
           if not splitted_lines:
             _ThrowError("rbd showmapped returned empty output")
           # Check showmapped header line, to determine number of fields.
           field_cnt = len(splitted_lines[0])
           if field_cnt != allfields:
             _ThrowError("Cannot parse rbd showmapped output because its format"
                         " seems to have changed; expected %s fields, found %s",
                         allfields, field_cnt)
           matched_lines = \
             filter(lambda l: len(l) == allfields and l[volumefield] == volume_name,
                    splitted_lines)
           if len(matched_lines) > 1:
             _ThrowError("The rbd volume %s is mapped more than once."
                         " This shouldn't happen, try to unmap the extra"
                         " devices manually.", volume_name)
           if matched_lines:
             # rbd block device found. Return it.
             rbd_dev = matched_lines[0][devicefield]
             return rbd_dev
           # The given volume is not mapped.
           return None
         def Assemble(self):
           """Assemble the device.
           """
           pass
         def Shutdown(self):
           """Shutdown the device.
           """
           if not self.minor and not self.Attach():
             # The rbd device doesn't exist.
             return
           # Unmap the block device from the Volume.
           self._UnmapVolumeFromBlockdev(self.unique_id)
           self.minor = None
           self.dev_path = None
         def _UnmapVolumeFromBlockdev(self, unique_id):
           """Unmaps the rbd device from the Volume it is mapped.
           Unmaps the rbd device from the Volume it was previously mapped to.
           This method should be idempotent if the Volume isn't mapped.
           """
           pool = self.params[constants.LDP_POOL]
           name = unique_id[1]
           # Check if the mapping already exists.
           showmap_cmd = [constants.RBD_CMD, "showmapped", "-p", pool]
           result = utils.RunCmd(showmap_cmd)
           if result.failed:
             _ThrowError("rbd showmapped failed [during unmap](%s): %s",
                         result.fail_reason, result.output)
           rbd_dev = self._ParseRbdShowmappedOutput(result.output, name)
           if rbd_dev:
             # The mapping exists. Unmap the rbd device.
             unmap_cmd = [constants.RBD_CMD, "unmap", "%s" % rbd_dev]
             result = utils.RunCmd(unmap_cmd)
             if result.failed:
               _ThrowError("rbd unmap failed (%s): %s",
                           result.fail_reason, result.output)
         def Open(self, force=False):
           """Make the device ready for I/O.
           """
           pass
         def Close(self):
           """Notifies that the device will no longer be used for I/O.
           """
           pass
         def Grow(self, amount, dryrun, backingstore):
           """Grow the Volume.
           @type amount: integer
           @param amount: the amount (in mebibytes) to grow with
           @type dryrun: boolean
           @param dryrun: whether to execute the operation in simulation mode
               only, without actually increasing the size
           """
           if not backingstore:
             return
           if not self.Attach():
             _ThrowError("Can't attach to rbd device during Grow()")
           if dryrun:
             # the rbd tool does not support dry runs of resize operations.
             # Since rbd volumes are thinly provisioned, we assume
             # there is always enough free space for the operation.
             return
           rbd_pool = self.params[constants.LDP_POOL]
           rbd_name = self.unique_id[1]
           new_size = self.size + amount
           # Resize the rbd volume (Image) inside the RADOS cluster.
           cmd = [constants.RBD_CMD, "resize", "-p", rbd_pool,
                  rbd_name, "--size", "%s" % new_size]
           result = utils.RunCmd(cmd)
           if result.failed:
             _ThrowError("rbd resize failed (%s): %s",
                         result.fail_reason, result.output)
       class ExtStorageDevice(BlockDev):
         """A block device provided by an ExtStorage Provider.
         This class implements the External Storage Interface, which means
         handling of the externally provided block devices.
         """
         def __init__(self, unique_id, children, size, params):
           """Attaches to an extstorage block device.
           """
           super(ExtStorageDevice, self).__init__(unique_id, children, size, params)
           if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
             raise ValueError("Invalid configuration data %s" % str(unique_id))
           self.driver, self.vol_name = unique_id
           self.ext_params = params
           self.major = self.minor = None
           self.Attach()
         @classmethod
         def Create(cls, unique_id, children, size, params):
           """Create a new extstorage device.
           Provision a new volume using an extstorage provider, which will
           then be mapped to a block device.
           """
           if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
             raise errors.ProgrammerError("Invalid configuration data %s" %
                                          str(unique_id))
           # Call the External Storage's create script,
           # to provision a new Volume inside the External Storage
           _ExtStorageAction(constants.ES_ACTION_CREATE, unique_id,
                             params, str(size))
           return ExtStorageDevice(unique_id, children, size, params)
         def Remove(self):
           """Remove the extstorage device.
           """
           if not self.minor and not self.Attach():
             # The extstorage device doesn't exist.
             return
           # First shutdown the device (remove mappings).
           self.Shutdown()
           # Call the External Storage's remove script,
           # to remove the Volume from the External Storage
           _ExtStorageAction(constants.ES_ACTION_REMOVE, self.unique_id,
                             self.ext_params)
         def Rename(self, new_id):
           """Rename this device.
           """
           pass
         def Attach(self):
           """Attach to an existing extstorage device.
           This method maps the extstorage volume that matches our name with
           a corresponding block device and then attaches to this device.
           """
           self.attached = False
           # Call the External Storage's attach script,
           # to attach an existing Volume to a block device under /dev
           self.dev_path = _ExtStorageAction(constants.ES_ACTION_ATTACH,
                                             self.unique_id, self.ext_params)
           try:
             st = os.stat(self.dev_path)
           except OSError, err:
             logging.error("Error stat()'ing %s: %s", self.dev_path, str(err))
             return False
           if not stat.S_ISBLK(st.st_mode):
             logging.error("%s is not a block device", self.dev_path)
             return False
           self.major = os.major(st.st_rdev)
           self.minor = os.minor(st.st_rdev)
           self.attached = True
           return True
         def Assemble(self):
           """Assemble the device.
           """
           pass
         def Shutdown(self):
           """Shutdown the device.
           """
           if not self.minor and not self.Attach():
             # The extstorage device doesn't exist.
             return
           # Call the External Storage's detach script,
           # to detach an existing Volume from it's block device under /dev
           _ExtStorageAction(constants.ES_ACTION_DETACH, self.unique_id,
                             self.ext_params)
           self.minor = None
           self.dev_path = None
         def Open(self, force=False):
           """Make the device ready for I/O.
           """
           pass
         def Close(self):
           """Notifies that the device will no longer be used for I/O.
           """
           pass
         def Grow(self, amount, dryrun, backingstore):
           """Grow the Volume.
           @type amount: integer
           @param amount: the amount (in mebibytes) to grow with
           @type dryrun: boolean
           @param dryrun: whether to execute the operation in simulation mode
               only, without actually increasing the size
           """
           if not backingstore:
             return
           if not self.Attach():
             _ThrowError("Can't attach to extstorage device during Grow()")
           if dryrun:
             # we do not support dry runs of resize operations for now.
             return
           new_size = self.size + amount
           # Call the External Storage's grow script,
           # to grow an existing Volume inside the External Storage
           _ExtStorageAction(constants.ES_ACTION_GROW, self.unique_id,
                             self.ext_params, str(self.size), grow=str(new_size))
         def SetInfo(self, text):
           """Update metadata with info text.
           """
           # Replace invalid characters
           text = re.sub("^[^A-Za-z0-9_+.]", "_", text)
           text = re.sub("[^-A-Za-z0-9_+.]", "_", text)
           # Only up to 128 characters are allowed
           text = text[:128]
           # Call the External Storage's setinfo script,
           # to set metadata for an existing Volume inside the External Storage
           _ExtStorageAction(constants.ES_ACTION_SETINFO, self.unique_id,
                             self.ext_params, metadata=text)
       def _ExtStorageAction(action, unique_id, ext_params,
                             size=None, grow=None, metadata=None):
         """Take an External Storage action.
         Take an External Storage action concerning or affecting
         a specific Volume inside the External Storage.
         @type action: string
         @param action: which action to perform. One of:
                        create / remove / grow / attach / detach
         @type unique_id: tuple (driver, vol_name)
         @param unique_id: a tuple containing the type of ExtStorage (driver)
                           and the Volume name
         @type ext_params: dict
         @param ext_params: ExtStorage parameters
         @type size: integer
         @param size: the size of the Volume in mebibytes
         @type grow: integer
         @param grow: the new size in mebibytes (after grow)
         @type metadata: string
         @param metadata: metadata info of the Volume, for use by the provider
         @rtype: None or a block device path (during attach)
         """
         driver, vol_name = unique_id
         # Create an External Storage instance of type `driver'
         status, inst_es = ExtStorageFromDisk(driver)
         if not status:
           _ThrowError("%s" % inst_es)
         # Create the basic environment for the driver's scripts
         create_env = _ExtStorageEnvironment(unique_id, ext_params, size,
                                             grow, metadata)
         # Do not use log file for action `attach' as we need
         # to get the output from RunResult
         # TODO: find a way to have a log file for attach too
         logfile = None
         if action is not constants.ES_ACTION_ATTACH:
           logfile = _VolumeLogName(action, driver, vol_name)
         # Make sure the given action results in a valid script
         if action not in constants.ES_SCRIPTS:
           _ThrowError("Action '%s' doesn't result in a valid ExtStorage script" %
                       action)
         # Find out which external script to run according the given action
         script_name = action + "_script"
         script = getattr(inst_es, script_name)
         # Run the external script
         result = utils.RunCmd([script], env=create_env,
                               cwd=inst_es.path, output=logfile,)
         if result.failed:
           logging.error("External storage's %s command '%s' returned"
                         " error: %s, logfile: %s, output: %s",
                         action, result.cmd, result.fail_reason,
                         logfile, result.output)
           # If logfile is 'None' (during attach), it breaks TailFile
           # TODO: have a log file for attach too
           if action is not constants.ES_ACTION_ATTACH:
             lines = [utils.SafeEncode(val)
                      for val in utils.TailFile(logfile, lines=20)]
           else:
             lines = result.output[-20:]
           _ThrowError("External storage's %s script failed (%s), last"
                       " lines of output:\n%s",
                       action, result.fail_reason, "\n".join(lines))
         if action == constants.ES_ACTION_ATTACH:
           return result.stdout
       def ExtStorageFromDisk(name, base_dir=None):
         """Create an ExtStorage instance from disk.
         This function will return an ExtStorage instance
         if the given name is a valid ExtStorage name.
         @type base_dir: string
         @keyword base_dir: Base directory containing ExtStorage installations.
                            Defaults to a search in all the ES_SEARCH_PATH dirs.
         @rtype: tuple
         @return: True and the ExtStorage instance if we find a valid one, or
             False and the diagnose message on error
         """
         if base_dir is None:
           es_base_dir = pathutils.ES_SEARCH_PATH
         else:
           es_base_dir = [base_dir]
         es_dir = utils.FindFile(name, es_base_dir, os.path.isdir)
         if es_dir is None:
           return False, ("Directory for External Storage Provider %s not"
                          " found in search path" % name)
         # ES Files dictionary, we will populate it with the absolute path
         # names; if the value is True, then it is a required file, otherwise
         # an optional one
         es_files = dict.fromkeys(constants.ES_SCRIPTS, True)
         es_files[constants.ES_PARAMETERS_FILE] = True
         for (filename, _) in es_files.items():
           es_files[filename] = utils.PathJoin(es_dir, filename)
           try:
             st = os.stat(es_files[filename])
           except EnvironmentError, err:
             return False, ("File '%s' under path '%s' is missing (%s)" %
                            (filename, es_dir, utils.ErrnoOrStr(err)))
           if not stat.S_ISREG(stat.S_IFMT(st.st_mode)):
             return False, ("File '%s' under path '%s' is not a regular file" %
                            (filename, es_dir))
           if filename in constants.ES_SCRIPTS:
             if stat.S_IMODE(st.st_mode) & stat.S_IXUSR != stat.S_IXUSR:
               return False, ("File '%s' under path '%s' is not executable" %
                              (filename, es_dir))
         parameters = []
         if constants.ES_PARAMETERS_FILE in es_files:
           parameters_file = es_files[constants.ES_PARAMETERS_FILE]
           try:
             parameters = utils.ReadFile(parameters_file).splitlines()
           except EnvironmentError, err:
             return False, ("Error while reading the EXT parameters file at %s: %s" %
                            (parameters_file, utils.ErrnoOrStr(err)))
           parameters = [v.split(None, 1) for v in parameters]
         es_obj = \
           objects.ExtStorage(name=name, path=es_dir,
                              create_script=es_files[constants.ES_SCRIPT_CREATE],
                              remove_script=es_files[constants.ES_SCRIPT_REMOVE],
                              grow_script=es_files[constants.ES_SCRIPT_GROW],
                              attach_script=es_files[constants.ES_SCRIPT_ATTACH],
                              detach_script=es_files[constants.ES_SCRIPT_DETACH],
                              setinfo_script=es_files[constants.ES_SCRIPT_SETINFO],
                              verify_script=es_files[constants.ES_SCRIPT_VERIFY],
                              supported_parameters=parameters)
         return True, es_obj
       def _ExtStorageEnvironment(unique_id, ext_params,
                                  size=None, grow=None, metadata=None):
         """Calculate the environment for an External Storage script.
         @type unique_id: tuple (driver, vol_name)
         @param unique_id: ExtStorage pool and name of the Volume
         @type ext_params: dict
         @param ext_params: the EXT parameters
         @type size: string
         @param size: size of the Volume (in mebibytes)
         @type grow: string
         @param grow: new size of Volume after grow (in mebibytes)
         @type metadata: string
         @param metadata: metadata info of the Volume
         @rtype: dict
         @return: dict of environment variables
         """
         vol_name = unique_id[1]
         result = {}
         result["VOL_NAME"] = vol_name
         # EXT params
         for pname, pvalue in ext_params.items():
           result["EXTP_%s" % pname.upper()] = str(pvalue)
         if size is not None:
           result["VOL_SIZE"] = size
         if grow is not None:
           result["VOL_NEW_SIZE"] = grow
         if metadata is not None:
           result["VOL_METADATA"] = metadata
         return result
       def _VolumeLogName(kind, es_name, volume):
         """Compute the ExtStorage log filename for a given Volume and operation.
         @type kind: string
         @param kind: the operation type (e.g. create, remove etc.)
         @type es_name: string
         @param es_name: the ExtStorage name
         @type volume: string
         @param volume: the name of the Volume inside the External Storage
         """
         # Check if the extstorage log dir is a valid dir
         if not os.path.isdir(pathutils.LOG_ES_DIR):
           _ThrowError("Cannot find log directory: %s", pathutils.LOG_ES_DIR)
         # TODO: Use tempfile.mkstemp to create unique filename
         base = ("%s-%s-%s-%s.log" %
                 (kind, es_name, volume, utils.TimestampForFilename()))
         return utils.PathJoin(pathutils.LOG_ES_DIR, base)
       DEV_MAP = {
         constants.LD_LV: LogicalVolume,
         constants.LD_DRBD8: DRBD8,
         constants.LD_BLOCKDEV: PersistentBlockDevice,
         constants.LD_RBD: RADOSBlockDevice,
         constants.LD_EXT: ExtStorageDevice,
+        }
       if constants.ENABLE_FILE_STORAGE or constants.ENABLE_SHARED_FILE_STORAGE:
         DEV_MAP[constants.LD_FILE] = FileStorage
       def _VerifyDiskType(dev_type):
         if dev_type not in DEV_MAP:
           raise errors.ProgrammerError("Invalid block device type '%s'" % dev_type)
       def _VerifyDiskParams(disk):
         """Verifies if all disk parameters are set.
         """
         missing = set(constants.DISK_LD_DEFAULTS[disk.dev_type]) - set(disk.params)
         if missing:
           raise errors.ProgrammerError("Block device is missing disk parameters: %s" %
                                        missing)
       def FindDevice(disk, children):
         """Search for an existing, assembled device.
         This will succeed only if the device exists and is assembled, but it
         does not do any actions in order to activate the device.
         @type disk: L{objects.Disk}
         @param disk: the disk object to find
         @type children: list of L{bdev.BlockDev}
         @param children: the list of block devices that are children of the device
                         represented by the disk parameter
         """
         _VerifyDiskType(disk.dev_type)
         device = DEV_MAP[disk.dev_type](disk.physical_id, children, disk.size,
                                         disk.params)
         if not device.attached:
           return None
         return device
       def Assemble(disk, children):
         """Try to attach or assemble an existing device.
         This will attach to assemble the device, as needed, to bring it
         fully up. It must be safe to run on already-assembled devices.
         @type disk: L{objects.Disk}
         @param disk: the disk object to assemble
         @type children: list of L{bdev.BlockDev}
         @param children: the list of block devices that are children of the device
                         represented by the disk parameter
         """
         _VerifyDiskType(disk.dev_type)
         _VerifyDiskParams(disk)
         device = DEV_MAP[disk.dev_type](disk.physical_id, children, disk.size,
                                         disk.params)
         device.Assemble()
         return device
       def Create(disk, children):
         """Create a device.
         @type disk: L{objects.Disk}
         @param disk: the disk object to create
         @type children: list of L{bdev.BlockDev}
         @param children: the list of block devices that are children of the device
                         represented by the disk parameter
         """
         _VerifyDiskType(disk.dev_type)
         _VerifyDiskParams(disk)
         device = DEV_MAP[disk.dev_type].Create(disk.physical_id, children, disk.size,
                                                disk.params)
         return device

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