# Copyright (c) 2012 NetApp, Inc.
# Copyright (c) 2014 Red Hat, Inc.
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import hashlib
import inspect
import json
import os
import re
import tempfile
import time

from oslo_config import cfg
from oslo_log import log as logging
from oslo_utils import units
import six

from cinder import compute
from cinder import db
from cinder import exception
from cinder import utils
from cinder.i18n import _, _LE, _LI, _LW
from cinder.image import image_utils
from cinder.volume import driver

LOG = logging.getLogger(__name__)

nas_opts = [
    # TODO(eharney): deprecate nas_ip and change this to nas_host
    cfg.StrOpt('nas_ip',
               default='',
               help='IP address or Hostname of NAS system.'),
    cfg.StrOpt('nas_login',
               default='admin',
               help='User name to connect to NAS system.'),
    cfg.StrOpt('nas_password',
               default='',
               help='Password to connect to NAS system.',
               secret=True),
    cfg.IntOpt('nas_ssh_port',
               default=22,
               min=1, max=65535,
               help='SSH port to use to connect to NAS system.'),
    cfg.StrOpt('nas_private_key',
               default='',
               help='Filename of private key to use for SSH authentication.'),
    cfg.StrOpt('nas_secure_file_operations',
               default='auto',
               help=('Allow network-attached storage systems to operate in a '
                     'secure environment where root level access is not '
                     'permitted. If set to False, access is as the root user '
                     'and insecure. If set to True, access is not as root. '
                     'If set to auto, a check is done to determine if this is '
                     'a new installation: True is used if so, otherwise '
                     'False. Default is auto.')),
    cfg.StrOpt('nas_secure_file_permissions',
               default='auto',
               help=('Set more secure file permissions on network-attached '
                     'storage volume files to restrict broad other/world '
                     'access. If set to False, volumes are created with open '
                     'permissions. If set to True, volumes are created with '
                     'permissions for the cinder user and group (660). If '
                     'set to auto, a check is done to determine if '
                     'this is a new installation: True is used if so, '
                     'otherwise False. Default is auto.')),
    cfg.StrOpt('nas_share_path',
               default='',
               help=('Path to the share to use for storing Cinder volumes. '
                     'For example:  "/srv/export1" for an NFS server export '
                     'available at 10.0.5.10:/srv/export1 .')),
    cfg.StrOpt('nas_mount_options',
               default=None,
               help=('Options used to mount the storage backend file system '
                     'where Cinder volumes are stored.')),
]

old_vol_type_opts = [cfg.DeprecatedOpt('glusterfs_sparsed_volumes'),
                     cfg.DeprecatedOpt('glusterfs_qcow2_volumes')]

volume_opts = [
    cfg.StrOpt('nas_volume_prov_type',
               default='thin',
               choices=['thin', 'thick'],
               deprecated_opts=old_vol_type_opts,
               help=('Provisioning type that will be used when '
                     'creating volumes.')),
]

CONF = cfg.CONF
CONF.register_opts(nas_opts)
CONF.register_opts(volume_opts)


def locked_volume_id_operation(f, external=False):
    """Lock decorator for volume operations.

       Takes a named lock prior to executing the operation. The lock is named
       with the id of the volume. This lock can be used by driver methods
       to prevent conflicts with other operations modifying the same volume.

       May be applied to methods that take a 'volume' or 'snapshot' argument.
    """

    def lvo_inner1(inst, *args, **kwargs):
        lock_tag = inst.driver_prefix
        call_args = inspect.getcallargs(f, inst, *args, **kwargs)

        if call_args.get('volume'):
            volume_id = call_args['volume']['id']
        elif call_args.get('snapshot'):
            volume_id = call_args['snapshot']['volume']['id']
        else:
            err_msg = _('The decorated method must accept either a volume or '
                        'a snapshot object')
            raise exception.VolumeBackendAPIException(data=err_msg)

        @utils.synchronized('%s-%s' % (lock_tag, volume_id),
                            external=external)
        def lvo_inner2():
            return f(inst, *args, **kwargs)
        return lvo_inner2()
    return lvo_inner1


class RemoteFSDriver(driver.LocalVD, driver.TransferVD, driver.BaseVD):
    """Common base for drivers that work like NFS."""

    driver_volume_type = None
    driver_prefix = 'remotefs'
    volume_backend_name = None
    SHARE_FORMAT_REGEX = r'.+:/.+'

    def __init__(self, *args, **kwargs):
        super(RemoteFSDriver, self).__init__(*args, **kwargs)
        self.shares = {}
        self._mounted_shares = []
        self._execute_as_root = True
        self._is_voldb_empty_at_startup = kwargs.pop('is_vol_db_empty', None)

        if self.configuration:
            self.configuration.append_config_values(nas_opts)
            self.configuration.append_config_values(volume_opts)

    def check_for_setup_error(self):
        """Just to override parent behavior."""
        pass

    def initialize_connection(self, volume, connector):
        """Allow connection to connector and return connection info.

        :param volume: volume reference
        :param connector: connector reference
        """
        data = {'export': volume['provider_location'],
                'name': volume['name']}
        if volume['provider_location'] in self.shares:
            data['options'] = self.shares[volume['provider_location']]
        return {
            'driver_volume_type': self.driver_volume_type,
            'data': data,
            'mount_point_base': self._get_mount_point_base()
        }

    def do_setup(self, context):
        """Any initialization the volume driver does while starting."""
        super(RemoteFSDriver, self).do_setup(context)

        # Validate the settings for our secure file options.
        self.configuration.nas_secure_file_permissions = \
            self.configuration.nas_secure_file_permissions.lower()
        self.configuration.nas_secure_file_operations = \
            self.configuration.nas_secure_file_operations.lower()
        valid_secure_opts = ['auto', 'true', 'false']
        secure_options = {'nas_secure_file_permissions':
                          self.configuration.nas_secure_file_permissions,
                          'nas_secure_file_operations':
                          self.configuration.nas_secure_file_operations}
        for opt_name, opt_value in secure_options.items():
            if opt_value not in valid_secure_opts:
                err_parms = {'name': opt_name, 'value': opt_value}
                msg = _("NAS config '%(name)s=%(value)s' invalid. Must be "
                        "'auto', 'true', or 'false'") % err_parms
                LOG.error(msg)
                raise exception.InvalidConfigurationValue(msg)

    def _get_provisioned_capacity(self):
        """Returns the provisioned capacity.

        Get the sum of sizes of volumes, snapshots and any other
        files on the mountpoint.
        """
        provisioned_size = 0.0
        for share in self.shares.keys():
            mount_path = self._get_mount_point_for_share(share)
            out, _ = self._execute('du', '--bytes', mount_path,
                                   run_as_root=True)
            provisioned_size += int(out.split()[0])
        return round(provisioned_size / units.Gi, 2)

    def _get_mount_point_base(self):
        """Returns the mount point base for the remote fs.

           This method facilitates returning mount point base
           for the specific remote fs. Override this method
           in the respective driver to return the entry to be
           used while attach/detach using brick in cinder.
           If not overridden then it returns None without
           raising exception to continue working for cases
           when not used with brick.
        """
        LOG.debug("Driver specific implementation needs to return"
                  " mount_point_base.")
        return None

    def create_volume(self, volume):
        """Creates a volume.

        :param volume: volume reference
        :returns: provider_location update dict for database
        """
        self._ensure_shares_mounted()

        volume['provider_location'] = self._find_share(volume['size'])

        LOG.info(_LI('casted to %s'), volume['provider_location'])

        self._do_create_volume(volume)

        return {'provider_location': volume['provider_location']}

    def _do_create_volume(self, volume):
        """Create a volume on given remote share.

        :param volume: volume reference
        """
        volume_path = self.local_path(volume)
        volume_size = volume['size']

        if getattr(self.configuration,
                   self.driver_prefix + '_sparsed_volumes'):
            # If touch file exist, set the bootable flag for the volume
            if (os.path.isfile('/etc/cinder/recogimage')):
                LOG.debug('DEBUG : setting bootable flag for the volume')
                	volume['bootable'] = 1
                self._create_sparsed_file(volume_path, volume_size, volume)
				# Do not try to change permissions of the file here, as we are operating on a sym-link that is not local 
	    	else:
                self._create_sparsed_file(volume_path, volume_size)
                self._set_rw_permissions(volume_path)
        else:
            self._create_regular_file(volume_path, volume_size)
            self._set_rw_permissions(volume_path)

    def _ensure_shares_mounted(self):
        """Look for remote shares in the flags and mount them locally."""
        mounted_shares = []

        self._load_shares_config(getattr(self.configuration,
                                         self.driver_prefix +
                                         '_shares_config'))

        for share in self.shares.keys():
            try:
                self._ensure_share_mounted(share)
                mounted_shares.append(share)
            except Exception as exc:
                LOG.error(_LE('Exception during mounting %s'), exc)

        self._mounted_shares = mounted_shares

        LOG.debug('Available shares %s', self._mounted_shares)

    def delete_volume(self, volume):
        """Deletes a logical volume.

        :param volume: volume reference
        """
        if not volume['provider_location']:
            LOG.warning(_LW('Volume %s does not have '
                            'provider_location specified, '
                            'skipping'), volume['name'])
            return

        self._ensure_share_mounted(volume['provider_location'])

        mounted_path = self.local_path(volume)

        self._delete(mounted_path)

    def ensure_export(self, ctx, volume):
        """Synchronously recreates an export for a logical volume."""
        self._ensure_share_mounted(volume['provider_location'])

    def create_export(self, ctx, volume, connector):
        """Exports the volume.

        Can optionally return a dictionary of changes
        to the volume object to be persisted.
        """
        pass

    def remove_export(self, ctx, volume):
        """Removes an export for a logical volume."""
        pass

    def delete_snapshot(self, snapshot):
        """Delete snapshot.

        Do nothing for this driver, but allow manager to handle deletion
        of snapshot in error state.
        """
        pass

    def _delete(self, path):
        # Note(lpetrut): this method is needed in order to provide
        # interoperability with Windows as it will be overridden.
        self._execute('rm', '-f', path, run_as_root=self._execute_as_root)

    def _create_sparsed_file(self, path, size):
        """Creates a sparse file of a given size in GiB."""
        self._execute('truncate', '-s', '%sG' % size,
                      path, run_as_root=self._execute_as_root)

    def _create_regular_file(self, path, size):
        """Creates a regular file of given size in GiB."""

        block_size_mb = 1
        block_count = size * units.Gi / (block_size_mb * units.Mi)

        self._execute('dd', 'if=/dev/zero', 'of=%s' % path,
                      'bs=%dM' % block_size_mb,
                      'count=%d' % block_count,
                      run_as_root=self._execute_as_root)

    def _fallocate(self, path, size):
        """Creates a raw file of given size in GiB using fallocate."""
        self._execute('fallocate', '--length=%sG' % size,
                      path, run_as_root=True)

    def _create_qcow2_file(self, path, size_gb):
        """Creates a QCOW2 file of a given size in GiB."""

        self._execute('qemu-img', 'create', '-f', 'qcow2',
                      '-o', 'preallocation=metadata',
                      path, str(size_gb * units.Gi),
                      run_as_root=self._execute_as_root)

    def _set_rw_permissions(self, path):
        """Sets access permissions for given NFS path.

        Volume file permissions are set based upon the value of
        secure_file_permissions: 'true' sets secure access permissions and
        'false' sets more open (insecure) access permissions.

        :param path: the volume file path.
        """
        if self.configuration.nas_secure_file_permissions == 'true':
            permissions = '660'
            LOG.debug('File path %(path)s is being set with permissions: '
                      '%(permissions)s',
                      {'path': path, 'permissions': permissions})
        else:
            permissions = 'ugo+rw'
            LOG.warning(_LW('%(path)s is being set with open permissions: '
                            '%(perm)s'), {'path': path, 'perm': permissions})

        self._execute('chmod', permissions, path,
                      run_as_root=self._execute_as_root)

    def _set_rw_permissions_for_all(self, path):
        """Sets 666 permissions for the path."""
        self._execute('chmod', 'ugo+rw', path,
                      run_as_root=self._execute_as_root)

    def _set_rw_permissions_for_owner(self, path):
        """Sets read-write permissions to the owner for the path."""
        self._execute('chmod', 'u+rw', path,
                      run_as_root=self._execute_as_root)

    def local_path(self, volume):
        """Get volume path (mounted locally fs path) for given volume.

        :param volume: volume reference
        """
        remotefs_share = volume['provider_location']
        return os.path.join(self._get_mount_point_for_share(remotefs_share),
                            volume['name'])

    def copy_image_to_volume(self, context, volume, image_service, image_id):
        """Fetch the image from image_service and write it to the volume."""
        run_as_root = self._execute_as_root

        image_utils.fetch_to_raw(context,
                                 image_service,
                                 image_id,
                                 self.local_path(volume),
                                 self.configuration.volume_dd_blocksize,
                                 size=volume['size'],
                                 run_as_root=run_as_root)

        # NOTE (leseb): Set the virtual size of the image
        # the raw conversion overwrote the destination file
        # (which had the correct size)
        # with the fetched glance image size,
        # thus the initial 'size' parameter is not honored
        # this sets the size to the one asked in the first place by the user
        # and then verify the final virtual size
        image_utils.resize_image(self.local_path(volume), volume['size'],
                                 run_as_root=run_as_root)

        data = image_utils.qemu_img_info(self.local_path(volume),
                                         run_as_root=run_as_root)
        virt_size = data.virtual_size / units.Gi
        if virt_size != volume['size']:
            raise exception.ImageUnacceptable(
                image_id=image_id,
                reason=(_("Expected volume size was %d") % volume['size'])
                + (_(" but size is now %d") % virt_size))

    def copy_volume_to_image(self, context, volume, image_service, image_meta):
        """Copy the volume to the specified image."""
        image_utils.upload_volume(context,
                                  image_service,
                                  image_meta,
                                  self.local_path(volume))

    def _read_config_file(self, config_file):
        # Returns list of lines in file
        with open(config_file) as f:
            return f.readlines()

    def _load_shares_config(self, share_file=None):
        self.shares = {}

        if all((self.configuration.nas_ip,
                self.configuration.nas_share_path)):
            LOG.debug('Using nas_ip and nas_share_path configuration.')

            nas_ip = self.configuration.nas_ip
            nas_share_path = self.configuration.nas_share_path

            share_address = '%s:%s' % (nas_ip, nas_share_path)

            if not re.match(self.SHARE_FORMAT_REGEX, share_address):
                msg = (_("Share %s ignored due to invalid format. Must "
                         "be of form address:/export. Please check the "
                         "nas_ip and nas_share_path settings."),
                       share_address)
                raise exception.InvalidConfigurationValue(msg)

            self.shares[share_address] = self.configuration.nas_mount_options

        elif share_file is not None:
            LOG.debug('Loading shares from %s.', share_file)

            for share in self._read_config_file(share_file):
                # A configuration line may be either:
                #  host:/vol_name
                # or
                #  host:/vol_name -o options=123,rw --other
                if not share.strip():
                    # Skip blank or whitespace-only lines
                    continue
                if share.startswith('#'):
                    continue

                share_info = share.split(' ', 1)
                # results in share_info =
                #  [ 'address:/vol', '-o options=123,rw --other' ]

                share_address = share_info[0].strip()
                # Replace \040 with a space, to support paths with spaces
                share_address = share_address.replace("\\040", " ")
                share_opts = None
                if len(share_info) > 1:
                    share_opts = share_info[1].strip()

                if not re.match(self.SHARE_FORMAT_REGEX, share_address):
                    LOG.error(_LE("Share %s ignored due to invalid format. "
                                  "Must be of form address:/export."),
                              share_address)
                    continue

                self.shares[share_address] = share_opts

        LOG.debug("shares loaded: %s", self.shares)

    def _get_mount_point_for_share(self, path):
        raise NotImplementedError()

    def terminate_connection(self, volume, connector, **kwargs):
        """Disallow connection from connector."""
        pass

    def get_volume_stats(self, refresh=False):
        """Get volume stats.

        If 'refresh' is True, update the stats first.
        """
        if refresh or not self._stats:
            self._update_volume_stats()

        return self._stats

    def _update_volume_stats(self):
        """Retrieve stats info from volume group."""

        data = {}
        backend_name = self.configuration.safe_get('volume_backend_name')
        data['volume_backend_name'] = backend_name or self.volume_backend_name
        data['vendor_name'] = 'Open Source'
        data['driver_version'] = self.get_version()
        data['storage_protocol'] = self.driver_volume_type

        self._ensure_shares_mounted()

        global_capacity = 0
        global_free = 0
        for share in self._mounted_shares:
            capacity, free, used = self._get_capacity_info(share)
            global_capacity += capacity
            global_free += free

        data['total_capacity_gb'] = global_capacity / float(units.Gi)
        data['free_capacity_gb'] = global_free / float(units.Gi)
        data['reserved_percentage'] = self.configuration.reserved_percentage
        data['QoS_support'] = False
        self._stats = data

    def _get_capacity_info(self, share):
        raise NotImplementedError()

    def _find_share(self, volume_size_in_gib):
        raise NotImplementedError()

    def _ensure_share_mounted(self, share):
        raise NotImplementedError()

    def secure_file_operations_enabled(self):
        """Determine if driver is operating in Secure File Operations mode.

        The Cinder Volume driver needs to query if this driver is operating
        in a secure file mode; check our nas_secure_file_operations flag.
        """
        if self.configuration.nas_secure_file_operations == 'true':
            return True
        return False

    def set_nas_security_options(self, is_new_cinder_install):
        """Determine the setting to use for Secure NAS options.

        This method must be overridden by child wishing to use secure
        NAS file operations. This base method will set the NAS security
        options to false.
        """
        doc_html = "http://docs.openstack.org/admin-guide-cloud" \
                   "/blockstorage_nfs_backend.html"
        self.configuration.nas_secure_file_operations = 'false'
        LOG.warning(_LW("The NAS file operations will be run as root: "
                        "allowing root level access at the storage backend. "
                        "This is considered an insecure NAS environment. "
                        "Please see %s for information on a secure NAS "
                        "configuration."),
                    doc_html)
        self.configuration.nas_secure_file_permissions = 'false'
        LOG.warning(_LW("The NAS file permissions mode will be 666 (allowing "
                        "other/world read & write access). This is considered "
                        "an insecure NAS environment. Please see %s for "
                        "information on a secure NFS configuration."),
                    doc_html)

    def _determine_nas_security_option_setting(self, nas_option, mount_point,
                                               is_new_cinder_install):
        """Determine NAS security option setting when 'auto' is assigned.

        This method determines the final 'true'/'false' setting of an NAS
        security option when the default value of 'auto' has been detected.
        If the nas option isn't 'auto' then its current value is used.

        :param nas_option: The NAS security option value loaded from config.
        :param mount_point: Mount where indicator file is written.
        :param is_new_cinder_install: boolean for new Cinder installation.
        :return string: 'true' or 'false' for new option setting.
        """
        if nas_option == 'auto':
            # For auto detection, we first check to see if we have been
            # through this process before by checking for the existence of
            # the Cinder secure environment indicator file.
            file_name = '.cinderSecureEnvIndicator'
            file_path = os.path.join(mount_point, file_name)
            if os.path.isfile(file_path):
                nas_option = 'true'
                LOG.info(_LI('Cinder secure environment '
                             'indicator file exists.'))
            else:
                # The indicator file does not exist. If it is a new
                # installation, set to 'true' and create the indicator file.
                if is_new_cinder_install:
                    nas_option = 'true'
                    try:
                        with open(file_path, 'w') as fh:
                            fh.write('Detector file for Cinder secure '
                                     'environment usage.\n')
                            fh.write('Do not delete this file.\n')

                        # Set the permissions on our special marker file to
                        # protect from accidental removal (owner write only).
                        self._execute('chmod', '640', file_path,
                                      run_as_root=False)
                        LOG.info(_LI('New Cinder secure environment indicator'
                                     ' file created at path %s.'), file_path)
                    except IOError as err:
                        LOG.error(_LE('Failed to created Cinder secure '
                                      'environment indicator file: %s'),
                                  err)
                else:
                    # For existing installs, we default to 'false'. The
                    # admin can always set the option at the driver config.
                    nas_option = 'false'

        return nas_option


class RemoteFSSnapDriver(RemoteFSDriver, driver.SnapshotVD):
    """Base class for remotefs drivers implementing qcow2 snapshots.

       Driver must implement:
         _local_volume_dir(self, volume)
    """

    def __init__(self, *args, **kwargs):
        self._remotefsclient = None
        self.base = None
        self._nova = None
        super(RemoteFSSnapDriver, self).__init__(*args, **kwargs)

    def do_setup(self, context):
        super(RemoteFSSnapDriver, self).do_setup(context)

        self._nova = compute.API()

    def _local_volume_dir(self, volume):
        share = volume['provider_location']
        local_dir = self._get_mount_point_for_share(share)
        return local_dir

    def _local_path_volume(self, volume):
        path_to_disk = os.path.join(
            self._local_volume_dir(volume),
            volume['name'])

        return path_to_disk

    def _get_new_snap_path(self, snapshot):
        vol_path = self.local_path(snapshot['volume'])
        snap_path = '%s.%s' % (vol_path, snapshot['id'])
        return snap_path

    def _local_path_volume_info(self, volume):
        return '%s%s' % (self.local_path(volume), '.info')

    def _read_file(self, filename):
        """This method is to make it easier to stub out code for testing.

        Returns a string representing the contents of the file.
        """

        with open(filename, 'r') as f:
            return f.read()

    def _write_info_file(self, info_path, snap_info):
        if 'active' not in snap_info.keys():
            msg = _("'active' must be present when writing snap_info.")
            raise exception.RemoteFSException(msg)

        with open(info_path, 'w') as f:
            json.dump(snap_info, f, indent=1, sort_keys=True)

    def _qemu_img_info_base(self, path, volume_name, basedir):
        """Sanitize image_utils' qemu_img_info.

        This code expects to deal only with relative filenames.
        """

        info = image_utils.qemu_img_info(path)
        if info.image:
            info.image = os.path.basename(info.image)
        if info.backing_file:
            backing_file_template = \
                "(%(basedir)s/[0-9a-f]+/)?%" \
                "(volname)s(.(tmp-snap-)?[0-9a-f-]+)?$" % {
                    'basedir': basedir,
                    'volname': volume_name
                }
            if not re.match(backing_file_template, info.backing_file):
                msg = _("File %(path)s has invalid backing file "
                        "%(bfile)s, aborting.") % {'path': path,
                                                   'bfile': info.backing_file}
                raise exception.RemoteFSException(msg)

            info.backing_file = os.path.basename(info.backing_file)

        return info

    def _qemu_img_info(self, path, volume_name):
        raise NotImplementedError()

    def _img_commit(self, path):
        self._execute('qemu-img', 'commit', path,
                      run_as_root=self._execute_as_root)
        self._delete(path)

    def _rebase_img(self, image, backing_file, volume_format):
        self._execute('qemu-img', 'rebase', '-u', '-b', backing_file, image,
                      '-F', volume_format, run_as_root=self._execute_as_root)

    def _read_info_file(self, info_path, empty_if_missing=False):
        """Return dict of snapshot information.

           :param: info_path: path to file
           :param: empty_if_missing: True=return empty dict if no file
        """

        if not os.path.exists(info_path):
            if empty_if_missing is True:
                return {}

        return json.loads(self._read_file(info_path))

    def _get_backing_chain_for_path(self, volume, path):
        """Returns list of dicts containing backing-chain information.

        Includes 'filename', and 'backing-filename' for each
        applicable entry.

        Consider converting this to use --backing-chain and --output=json
        when environment supports qemu-img 1.5.0.

        :param volume: volume reference
        :param path: path to image file at top of chain

        """

        output = []

        info = self._qemu_img_info(path, volume['name'])
        new_info = {}
        new_info['filename'] = os.path.basename(path)
        new_info['backing-filename'] = info.backing_file

        output.append(new_info)

        while new_info['backing-filename']:
            filename = new_info['backing-filename']
            path = os.path.join(self._local_volume_dir(volume), filename)
            info = self._qemu_img_info(path, volume['name'])
            backing_filename = info.backing_file
            new_info = {}
            new_info['filename'] = filename
            new_info['backing-filename'] = backing_filename

            output.append(new_info)

        return output

    def _get_hash_str(self, base_str):
        """Return a string that represents hash of base_str.

        Returns string in a hex format.
        """
        if isinstance(base_str, six.text_type):
            base_str = base_str.encode('utf-8')
        return hashlib.md5(base_str).hexdigest()

    def _get_mount_point_for_share(self, share):
        """Return mount point for share.

        :param share: example 172.18.194.100:/var/fs
        """
        return self._remotefsclient.get_mount_point(share)

    def _get_available_capacity(self, share):
        """Calculate available space on the share.

        :param share: example 172.18.194.100:/var/fs
        """
        mount_point = self._get_mount_point_for_share(share)

        out, _ = self._execute('df', '--portability', '--block-size', '1',
                               mount_point,
                               run_as_root=self._execute_as_root)
        out = out.splitlines()[1]

        size = int(out.split()[1])
        available = int(out.split()[3])

        return available, size

    def _get_capacity_info(self, remotefs_share):
        available, size = self._get_available_capacity(remotefs_share)
        return size, available, size - available

    def _get_mount_point_base(self):
        return self.base

    def _ensure_share_writable(self, path):
        """Ensure that the Cinder user can write to the share.

        If not, raise an exception.

        :param path: path to test
        :raises: RemoteFSException
        :returns: None
        """

        prefix = '.cinder-write-test-' + str(os.getpid()) + '-'

        try:
            tempfile.NamedTemporaryFile(prefix=prefix, dir=path)
        except OSError:
            msg = _('Share at %(dir)s is not writable by the '
                    'Cinder volume service. Snapshot operations will not be '
                    'supported.') % {'dir': path}
            raise exception.RemoteFSException(msg)

    def _copy_volume_to_image(self, context, volume, image_service,
                              image_meta):
        """Copy the volume to the specified image."""

        # If snapshots exist, flatten to a temporary image, and upload it

        active_file = self.get_active_image_from_info(volume)
        active_file_path = os.path.join(self._local_volume_dir(volume),
                                        active_file)
        info = self._qemu_img_info(active_file_path, volume['name'])
        backing_file = info.backing_file

        root_file_fmt = info.file_format

        tmp_params = {
            'prefix': '%s.temp_image.%s' % (volume['id'], image_meta['id']),
            'suffix': '.img'
        }
        with image_utils.temporary_file(**tmp_params) as temp_path:
            if backing_file or (root_file_fmt != 'raw'):
                # Convert due to snapshots
                # or volume data not being stored in raw format
                #  (upload_volume assumes raw format input)
                image_utils.convert_image(active_file_path, temp_path, 'raw')
                upload_path = temp_path
            else:
                upload_path = active_file_path

            image_utils.upload_volume(context,
                                      image_service,
                                      image_meta,
                                      upload_path)

    def get_active_image_from_info(self, volume):
        """Returns filename of the active image from the info file."""

        info_file = self._local_path_volume_info(volume)

        snap_info = self._read_info_file(info_file, empty_if_missing=True)

        if not snap_info:
            # No info file = no snapshots exist
            vol_path = os.path.basename(self.local_path(volume))
            return vol_path

        return snap_info['active']

    def _create_cloned_volume(self, volume, src_vref):
        LOG.info(_LI('Cloning volume %(src)s to volume %(dst)s'),
                 {'src': src_vref['id'],
                  'dst': volume['id']})

        if src_vref['status'] != 'available':
            msg = _("Volume status must be 'available'.")
            raise exception.InvalidVolume(msg)

        volume_name = CONF.volume_name_template % volume['id']

        volume_info = {'provider_location': src_vref['provider_location'],
                       'size': src_vref['size'],
                       'id': volume['id'],
                       'name': volume_name,
                       'status': src_vref['status']}
        temp_snapshot = {'volume_name': volume_name,
                         'size': src_vref['size'],
                         'volume_size': src_vref['size'],
                         'name': 'clone-snap-%s' % src_vref['id'],
                         'volume_id': src_vref['id'],
                         'id': 'tmp-snap-%s' % src_vref['id'],
                         'volume': src_vref}
        self._create_snapshot(temp_snapshot)
        try:
            self._copy_volume_from_snapshot(temp_snapshot,
                                            volume_info,
                                            volume['size'])

        finally:
            self._delete_snapshot(temp_snapshot)

        return {'provider_location': src_vref['provider_location']}

    def _delete_stale_snapshot(self, snapshot):
        info_path = self._local_path_volume_info(snapshot['volume'])
        snap_info = self._read_info_file(info_path)

        snapshot_file = snap_info[snapshot['id']]
        active_file = self.get_active_image_from_info(snapshot['volume'])
        snapshot_path = os.path.join(
            self._local_volume_dir(snapshot['volume']), snapshot_file)
        if (snapshot_file == active_file):
            return

        LOG.info(_LI('Deleting stale snapshot: %s'), snapshot['id'])
        self._delete(snapshot_path)
        del(snap_info[snapshot['id']])
        self._write_info_file(info_path, snap_info)

    def _delete_snapshot(self, snapshot):
        """Delete a snapshot.

        If volume status is 'available', delete snapshot here in Cinder
        using qemu-img.

        If volume status is 'in-use', calculate what qcow2 files need to
        merge, and call to Nova to perform this operation.

        :raises: InvalidVolume if status not acceptable
        :raises: RemoteFSException(msg) if operation fails
        :returns: None

        """

        LOG.debug('Deleting snapshot %s:', snapshot['id'])

        volume_status = snapshot['volume']['status']
        if volume_status not in ['available', 'in-use']:
            msg = _('Volume status must be "available" or "in-use".')
            raise exception.InvalidVolume(msg)

        vol_path = self._local_volume_dir(snapshot['volume'])
        self._ensure_share_writable(vol_path)

        # Determine the true snapshot file for this snapshot
        # based on the .info file
        info_path = self._local_path_volume_info(snapshot['volume'])
        snap_info = self._read_info_file(info_path, empty_if_missing=True)

        if snapshot['id'] not in snap_info:
            # If snapshot info file is present, but snapshot record does not
            # exist, do not attempt to delete.
            # (This happens, for example, if snapshot_create failed due to lack
            # of permission to write to the share.)
            LOG.info(_LI('Snapshot record for %s is not present, allowing '
                         'snapshot_delete to proceed.'), snapshot['id'])
            return

        snapshot_file = snap_info[snapshot['id']]
        LOG.debug('snapshot_file for this snap is: %s', snapshot_file)
        snapshot_path = os.path.join(
            self._local_volume_dir(snapshot['volume']),
            snapshot_file)

        snapshot_path_img_info = self._qemu_img_info(
            snapshot_path,
            snapshot['volume']['name'])

        base_file = snapshot_path_img_info.backing_file
        if base_file is None:
            # There should always be at least the original volume
            # file as base.
            LOG.warning(_LW('No backing file found for %s, allowing '
                            'snapshot to be deleted.'), snapshot_path)

            # Snapshot may be stale, so just delete it and update the
            # info file instead of blocking
            return self._delete_stale_snapshot(snapshot)

        base_path = os.path.join(vol_path, base_file)
        base_file_img_info = self._qemu_img_info(base_path,
                                                 snapshot['volume']['name'])

        # Find what file has this as its backing file
        active_file = self.get_active_image_from_info(snapshot['volume'])
        active_file_path = os.path.join(vol_path, active_file)

        if volume_status == 'in-use':
            # Online delete
            context = snapshot['context']

            new_base_file = base_file_img_info.backing_file

            base_id = None
            for key, value in snap_info.items():
                if value == base_file and key != 'active':
                    base_id = key
                    break
            if base_id is None:
                # This means we are deleting the oldest snapshot
                LOG.debug('No %(base_id)s found for %(file)s',
                          {'base_id': 'base_id', 'file': snapshot_file})

            online_delete_info = {
                'active_file': active_file,
                'snapshot_file': snapshot_file,
                'base_file': base_file,
                'base_id': base_id,
                'new_base_file': new_base_file
            }

            return self._delete_snapshot_online(context,
                                                snapshot,
                                                online_delete_info)

        if snapshot_file == active_file:
            # There is no top file
            #      T0       |        T1         |
            #     base      |   snapshot_file   | None
            # (guaranteed to|  (being deleted,  |
            #    exist)     |   commited down)  |

            self._img_commit(snapshot_path)
            # Active file has changed
            snap_info['active'] = base_file
        else:
            #      T0        |      T1         |     T2         |      T3
            #     base       |  snapshot_file  |  higher_file   | highest_file
            # (guaranteed to | (being deleted, | (guaranteed to |  (may exist)
            #   exist, not   |  commited down) |  exist, needs  |
            #   used here)   |                 |   ptr update)  |

            backing_chain = self._get_backing_chain_for_path(
                snapshot['volume'], active_file_path)
            # This file is guaranteed to exist since we aren't operating on
            # the active file.
            higher_file = next((os.path.basename(f['filename'])
                                for f in backing_chain
                                if f.get('backing-filename', '') ==
                                snapshot_file),
                               None)
            if higher_file is None:
                msg = _('No file found with %s as backing file.') %\
                    snapshot_file
                raise exception.RemoteFSException(msg)

            higher_id = next((i for i in snap_info
                              if snap_info[i] == higher_file
                              and i != 'active'),
                             None)
            if higher_id is None:
                msg = _('No snap found with %s as backing file.') %\
                    higher_file
                raise exception.RemoteFSException(msg)

            self._img_commit(snapshot_path)

            higher_file_path = os.path.join(vol_path, higher_file)
            base_file_fmt = base_file_img_info.file_format
            self._rebase_img(higher_file_path, base_file, base_file_fmt)

        # Remove snapshot_file from info
        del(snap_info[snapshot['id']])
        self._write_info_file(info_path, snap_info)

    def _create_volume_from_snapshot(self, volume, snapshot):
        """Creates a volume from a snapshot.

        Snapshot must not be the active snapshot. (offline)
        """

        if snapshot['status'] != 'available':
            msg = _('Snapshot status must be "available" to clone.')
            raise exception.InvalidSnapshot(msg)

        self._ensure_shares_mounted()

        volume['provider_location'] = self._find_share(volume['size'])

        self._do_create_volume(volume)

        self._copy_volume_from_snapshot(snapshot,
                                        volume,
                                        volume['size'])

        return {'provider_location': volume['provider_location']}

    def _copy_volume_from_snapshot(self, snapshot, volume, volume_size):
        raise NotImplementedError()

    def _do_create_snapshot(self, snapshot, backing_filename,
                            new_snap_path):
        """Create a QCOW2 file backed by another file.

        :param snapshot: snapshot reference
        :param backing_filename: filename of file that will back the
            new qcow2 file
        :param new_snap_path: filename of new qcow2 file
        """

        backing_path_full_path = os.path.join(
            self._local_volume_dir(snapshot['volume']),
            backing_filename)

        command = ['qemu-img', 'create', '-f', 'qcow2', '-o',
                   'backing_file=%s' % backing_path_full_path, new_snap_path]
        self._execute(*command, run_as_root=self._execute_as_root)

        info = self._qemu_img_info(backing_path_full_path,
                                   snapshot['volume']['name'])
        backing_fmt = info.file_format

        command = ['qemu-img', 'rebase', '-u',
                   '-b', backing_filename,
                   '-F', backing_fmt,
                   new_snap_path]
        self._execute(*command, run_as_root=self._execute_as_root)

        self._set_rw_permissions(new_snap_path)

    def _create_snapshot(self, snapshot):
        """Create a snapshot.

        If volume is attached, call to Nova to create snapshot, providing a
        qcow2 file. Cinder creates and deletes qcow2 files, but Nova is
        responsible for transitioning the VM between them and handling live
        transfers of data between files as required.

        If volume is detached, create locally with qemu-img. Cinder handles
        manipulation of qcow2 files.

        A file named volume-<uuid>.info is stored with the volume
        data and is a JSON table which contains a mapping between
        Cinder snapshot UUIDs and filenames, as these associations
        will change as snapshots are deleted.


        Basic snapshot operation:

        1. Initial volume file:
            volume-1234

        2. Snapshot created:
            volume-1234  <- volume-1234.aaaa

            volume-1234.aaaa becomes the new "active" disk image.
            If the volume is not attached, this filename will be used to
            attach the volume to a VM at volume-attach time.
            If the volume is attached, the VM will switch to this file as
            part of the snapshot process.

            Note that volume-1234.aaaa represents changes after snapshot
            'aaaa' was created.  So the data for snapshot 'aaaa' is actually
            in the backing file(s) of volume-1234.aaaa.

            This file has a qcow2 header recording the fact that volume-1234 is
            its backing file.  Delta changes since the snapshot was created are
            stored in this file, and the backing file (volume-1234) does not
            change.

            info file: { 'active': 'volume-1234.aaaa',
                         'aaaa':   'volume-1234.aaaa' }

        3. Second snapshot created:
            volume-1234 <- volume-1234.aaaa <- volume-1234.bbbb

            volume-1234.bbbb now becomes the "active" disk image, recording
            changes made to the volume.

            info file: { 'active': 'volume-1234.bbbb',  (* changed!)
                         'aaaa':   'volume-1234.aaaa',
                         'bbbb':   'volume-1234.bbbb' } (* added!)

        4. Snapshot deletion when volume is attached ('in-use' state):

            * When first snapshot is deleted, Cinder calls Nova for online
              snapshot deletion. Nova deletes snapshot with id "aaaa" and
              makes snapshot with id "bbbb" point to the base image.
              Snapshot with id "bbbb" is the active image.

              volume-1234 <- volume-1234.bbbb

              info file: { 'active': 'volume-1234.bbbb',
                           'bbbb':   'volume-1234.bbbb'
                         }

             * When second snapshot is deleted, Cinder calls Nova for online
               snapshot deletion. Nova deletes snapshot with id "bbbb" by
               pulling volume-1234's data into volume-1234.bbbb. This
               (logically) removes snapshot with id "bbbb" and the active
               file remains the same.

               volume-1234.bbbb

               info file: { 'active': 'volume-1234.bbbb' }

           TODO (deepakcs): Change this once Nova supports blockCommit for
                            in-use volumes.

        5. Snapshot deletion when volume is detached ('available' state):

            * When first snapshot is deleted, Cinder does the snapshot
              deletion. volume-1234.aaaa is removed from the snapshot chain.
              The data from it is merged into its parent.

              volume-1234.bbbb is rebased, having volume-1234 as its new
              parent.

              volume-1234 <- volume-1234.bbbb

              info file: { 'active': 'volume-1234.bbbb',
                           'bbbb':   'volume-1234.bbbb'
                         }

            * When second snapshot is deleted, Cinder does the snapshot
              deletion. volume-1234.aaaa is removed from the snapshot chain.
              The base image, volume-1234 becomes the active image for this
              volume again.

              volume-1234

              info file: { 'active': 'volume-1234' }  (* changed!)
        """

        status = snapshot['volume']['status']
        if status not in ['available', 'in-use']:
            msg = _('Volume status must be "available" or "in-use"'
                    ' for snapshot. (is %s)') % status
            raise exception.InvalidVolume(msg)

        info_path = self._local_path_volume_info(snapshot['volume'])
        snap_info = self._read_info_file(info_path, empty_if_missing=True)
        backing_filename = self.get_active_image_from_info(
            snapshot['volume'])
        new_snap_path = self._get_new_snap_path(snapshot)

        if status == 'in-use':
            self._create_snapshot_online(snapshot,
                                         backing_filename,
                                         new_snap_path)
        else:
            self._do_create_snapshot(snapshot,
                                     backing_filename,
                                     new_snap_path)

        snap_info['active'] = os.path.basename(new_snap_path)
        snap_info[snapshot['id']] = os.path.basename(new_snap_path)
        self._write_info_file(info_path, snap_info)

    def _create_snapshot_online(self, snapshot, backing_filename,
                                new_snap_path):
        # Perform online snapshot via Nova
        context = snapshot['context']

        self._do_create_snapshot(snapshot,
                                 backing_filename,
                                 new_snap_path)

        connection_info = {
            'type': 'qcow2',
            'new_file': os.path.basename(new_snap_path),
            'snapshot_id': snapshot['id']
        }

        try:
            result = self._nova.create_volume_snapshot(
                context,
                snapshot['volume_id'],
                connection_info)
            LOG.debug('nova call result: %s', result)
        except Exception:
            LOG.exception(_LE('Call to Nova to create snapshot failed'))
            raise

        # Loop and wait for result
        # Nova will call Cinderclient to update the status in the database
        # An update of progress = '90%' means that Nova is done
        seconds_elapsed = 0
        increment = 1
        timeout = 600
        while True:
            s = db.snapshot_get(context, snapshot['id'])

            if s['status'] == 'creating':
                if s['progress'] == '90%':
                    # Nova tasks completed successfully
                    break

                time.sleep(increment)
                seconds_elapsed += increment
            elif s['status'] == 'error':

                msg = _('Nova returned "error" status '
                        'while creating snapshot.')
                raise exception.RemoteFSException(msg)

            LOG.debug('Status of snapshot %(id)s is now %(status)s',
                      {'id': snapshot['id'],
                       'status': s['status']})

            if 10 < seconds_elapsed <= 20:
                increment = 2
            elif 20 < seconds_elapsed <= 60:
                increment = 5
            elif 60 < seconds_elapsed:
                increment = 10

            if seconds_elapsed > timeout:
                msg = _('Timed out while waiting for Nova update '
                        'for creation of snapshot %s.') % snapshot['id']
                raise exception.RemoteFSException(msg)

    def _delete_snapshot_online(self, context, snapshot, info):
        # Update info over the course of this method
        # active file never changes
        info_path = self._local_path_volume(snapshot['volume']) + '.info'
        snap_info = self._read_info_file(info_path)

        if info['active_file'] == info['snapshot_file']:
            # blockRebase/Pull base into active
            # info['base'] => snapshot_file

            file_to_delete = info['base_file']
            if info['base_id'] is None:
                # Passing base=none to blockRebase ensures that
                # libvirt blanks out the qcow2 backing file pointer
                new_base = None
            else:
                new_base = info['new_base_file']
                snap_info[info['base_id']] = info['snapshot_file']

            delete_info = {'file_to_merge': new_base,
                           'merge_target_file': None,  # current
                           'type': 'qcow2',
                           'volume_id': snapshot['volume']['id']}

            del(snap_info[snapshot['id']])
        else:
            # blockCommit snapshot into base
            # info['base'] <= snapshot_file
            # delete record of snapshot
            file_to_delete = info['snapshot_file']

            delete_info = {'file_to_merge': info['snapshot_file'],
                           'merge_target_file': info['base_file'],
                           'type': 'qcow2',
                           'volume_id': snapshot['volume']['id']}

            del(snap_info[snapshot['id']])

        try:
            self._nova.delete_volume_snapshot(
                context,
                snapshot['id'],
                delete_info)
        except Exception:
            LOG.exception(_LE('Call to Nova delete snapshot failed'))
            raise

        # Loop and wait for result
        # Nova will call Cinderclient to update the status in the database
        # An update of progress = '90%' means that Nova is done
        seconds_elapsed = 0
        increment = 1
        timeout = 7200
        while True:
            s = db.snapshot_get(context, snapshot['id'])

            if s['status'] == 'deleting':
                if s['progress'] == '90%':
                    # Nova tasks completed successfully
                    break
                else:
                    LOG.debug('status of snapshot %s is still "deleting"... '
                              'waiting', snapshot['id'])
                    time.sleep(increment)
                    seconds_elapsed += increment
            else:
                msg = _('Unable to delete snapshot %(id)s, '
                        'status: %(status)s.') % {'id': snapshot['id'],
                                                  'status': s['status']}
                raise exception.RemoteFSException(msg)

            if 10 < seconds_elapsed <= 20:
                increment = 2
            elif 20 < seconds_elapsed <= 60:
                increment = 5
            elif 60 < seconds_elapsed:
                increment = 10

            if seconds_elapsed > timeout:
                msg = _('Timed out while waiting for Nova update '
                        'for deletion of snapshot %(id)s.') %\
                    {'id': snapshot['id']}
                raise exception.RemoteFSException(msg)

        # Write info file updated above
        self._write_info_file(info_path, snap_info)

        # Delete stale file
        path_to_delete = os.path.join(
            self._local_volume_dir(snapshot['volume']), file_to_delete)
        self._execute('rm', '-f', path_to_delete, run_as_root=True)

    @locked_volume_id_operation
    def create_snapshot(self, snapshot):
        """Apply locking to the create snapshot operation."""

        return self._create_snapshot(snapshot)

    @locked_volume_id_operation
    def delete_snapshot(self, snapshot):
        """Apply locking to the delete snapshot operation."""

        return self._delete_snapshot(snapshot)

    @locked_volume_id_operation
    def create_volume_from_snapshot(self, volume, snapshot):
        return self._create_volume_from_snapshot(volume, snapshot)

    @locked_volume_id_operation
    def create_cloned_volume(self, volume, src_vref):
        """Creates a clone of the specified volume."""
        return self._create_cloned_volume(volume, src_vref)

    @locked_volume_id_operation
    def copy_volume_to_image(self, context, volume, image_service, image_meta):
        """Copy the volume to the specified image."""

        return self._copy_volume_to_image(context,
                                          volume,
                                          image_service,
                                          image_meta)
