'Extend an existing volume.
:param volume: volume reference
:param new_size: volume new size in GB'

def extend_volume(self, volume, new_size):

    LOG.info('Extending    volume:    %(id)s    New    size:    %(size)s    GB', {'id': volume['id'], 'size': new_size})
    nfs_share = volume['provider_location']
    nms = self.share2nms[nfs_share]
    volume_path = self.remote_path(volume)
    if getattr(self.configuration, (self.driver_prefix + '_sparsed_volumes')):
        self._create_sparsed_file(nms, volume_path, new_size)
    else:
        block_size_mb = 1
        block_count = (((new_size - volume['size']) * units.Gi) / (block_size_mb * units.Mi))
        nms.appliance.execute(('dd    if=/dev/zero    seek=%(seek)d    of=%(path)s    bs=%(bs)dM    count=%(count)d' % {'seek': ((volume['size'] * units.Gi) / block_size_mb), 'path': volume_path, 'bs': block_size_mb, 'count': block_count}))
