Synnefo » snf-ganeti » Ganeti ExtStorage providers

#!/usr/bin/env python

#

# Copyright (C) 2012 Greek Research and Technology Network

#

# 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.

"""Detach the Image file from the loop device

This program detaches an Image file from the loop device it attached to.

It is idempotent, if the file isn't losetup at all.

It takes it's input from environment variables. Specifically the

following variable should be present:

 - VOL_NAME: The name of the Image file to which the device points

Returns O upon successfull unmapping, 1 upon failure

"""

import os

import sys

sys.path.insert(0, "/etc/ganeti/share")

from ganeti import utils

# Default shared directory

SHARED_DIR = "/srv/ganeti/shared-file-storage"

def ReadEnv():

  """Read the mandatory enviromental variables

  """

  name = os.getenv("VOL_NAME")

  if name is None:

    sys.stderr.write('The environment variable VOL_NAME is missing.\n')

    return None

  shared_dir_param = os.getenv("EXTP_SHARED_DIR")

  if shared_dir_param is not None:

    sys.stderr.write('Found shared dir param, value: %s\n' % shared_dir_param)

  return (name, shared_dir_param)

def _ParseLosetupOutput(output, filename):

  """Parse the output of `losetup -j <filename>`

  This method parses the output of `losetup -j <filename>` and returns

  the corresponding loop device path for this filename

  (e.g. /dev/loop0)

  @type output: string

  @param output: the whole output of `losetup -j filename`

  @type filename: string

  @param filename: the complete file path to the file we search for

  @rtype: string or None

  @return: loop device path if the file is losetup, else None

  """

  # `losetup -j file1` output looks like this

  #   /dev/loop0: [X]:Y (/path/to/file1)

  # if the file has been losetup. If not there is no output.

  # If the file has been losetup more than once, then there will be

  # multiple lines like the one above.

  #

  # We assume the following format (space is the seperator):

  # field0: field1 (field2)

  field0 = 0

  field_sep = " "

  lines = output.splitlines()

  splitted_lines = map(lambda l: l.split(field_sep), lines)

  # Check empty output. If empty, the file is not losetup

  if not splitted_lines:

    return None

  # Check if we have more than one lines in the output

  if len(splitted_lines) > 1:

    sys.stderr.write("The file %s is losetup more than once" % filename)

    sys.exit(1)

  # The file is losetup only once

  # Take field0, remove the ":" at the end and we have our path

  dev_path = splitted_lines[0][field0].split(":")[0]

  return dev_path

def main():

  sys.stderr.write('Detaching started: reading environment...\n')

  # Read environment

  env = ReadEnv()

  if env is None:

    sys.stderr.write('Wrong environment. Aborting\n')

    return 1

  file_name, shared_dir_param = env

  if shared_dir_param is None:

    shared_dir_param = SHARED_DIR

  file_path = utils.PathJoin(shared_dir_param, file_name)

  sys.stderr.write('Read environment successfully: file name: %s\n' % file_path)

  # Check if the file exists

  if not os.path.exists(file_path):

    sys.stderr.write('File %s does not exist. Aborting\n' % file_path)

    return 1

  # Check if the file is losetup

  cmd1 = ["losetup", "-j", "%s" % file_path]

  result = utils.RunCmd(cmd1)

  if result.failed:

    sys.stderr.write('losetup -j %s failed (%s): %s' %

                     (dev_path, result.fail_reason, result.output))

    return 1

  else:

    # Parse the result's output

    dev_path = _ParseLosetupOutput(result.output, file_path)

    if dev_path is None:

      # The file is not losetup (device is not attached). Return.

      sys.stderr.write('File %s successfully detached\n' % file_path)

      return 0

    else:

      # The file is losetup (device attached). Detach it.

      cmd2 = ["losetup", "-d", "%s" % dev_path]

      result = utils.RunCmd(cmd2)

      if result.failed:

        sys.stderr.write('Cannot `losetup -d` device: %s, detachment failed '

                         '(%s): %s\n' %

                          (dev_path, result.fail_reason, result.output))

        return 1

      sys.stderr.write('File %s successfully detached\n' % file_path)

      return 0

if __name__ == "__main__":

    sys.exit(main())