diff options
Diffstat (limited to 'charms/trusty/contrail-control/hooks/charmhelpers/contrib/storage/linux/loopback.py')
-rw-r--r-- | charms/trusty/contrail-control/hooks/charmhelpers/contrib/storage/linux/loopback.py | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/charms/trusty/contrail-control/hooks/charmhelpers/contrib/storage/linux/loopback.py b/charms/trusty/contrail-control/hooks/charmhelpers/contrib/storage/linux/loopback.py new file mode 100644 index 0000000..c296f09 --- /dev/null +++ b/charms/trusty/contrail-control/hooks/charmhelpers/contrib/storage/linux/loopback.py @@ -0,0 +1,78 @@ +# Copyright 2014-2015 Canonical Limited. +# +# This file is part of charm-helpers. +# +# charm-helpers is free software: you can redistribute it and/or modify +# it under the terms of the GNU Lesser General Public License version 3 as +# published by the Free Software Foundation. +# +# charm-helpers 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 Lesser General Public License for more details. +# +# You should have received a copy of the GNU Lesser General Public License +# along with charm-helpers. If not, see <http://www.gnu.org/licenses/>. + +import os +import re +from subprocess import ( + check_call, + check_output, +) + +import six + + +################################################## +# loopback device helpers. +################################################## +def loopback_devices(): + ''' + Parse through 'losetup -a' output to determine currently mapped + loopback devices. Output is expected to look like: + + /dev/loop0: [0807]:961814 (/tmp/my.img) + + :returns: dict: a dict mapping {loopback_dev: backing_file} + ''' + loopbacks = {} + cmd = ['losetup', '-a'] + devs = [d.strip().split(' ') for d in + check_output(cmd).splitlines() if d != ''] + for dev, _, f in devs: + loopbacks[dev.replace(':', '')] = re.search('\((\S+)\)', f).groups()[0] + return loopbacks + + +def create_loopback(file_path): + ''' + Create a loopback device for a given backing file. + + :returns: str: Full path to new loopback device (eg, /dev/loop0) + ''' + file_path = os.path.abspath(file_path) + check_call(['losetup', '--find', file_path]) + for d, f in six.iteritems(loopback_devices()): + if f == file_path: + return d + + +def ensure_loopback_device(path, size): + ''' + Ensure a loopback device exists for a given backing file path and size. + If it a loopback device is not mapped to file, a new one will be created. + + TODO: Confirm size of found loopback device. + + :returns: str: Full path to the ensured loopback device (eg, /dev/loop0) + ''' + for d, f in six.iteritems(loopback_devices()): + if f == path: + return d + + if not os.path.exists(path): + cmd = ['truncate', '--size', size, path] + check_call(cmd) + + return create_loopback(path) |