'Extend volume backing\'s virtual disk.
:param backing: volume backing
:param new_size_in_gb: new size of virtual disk'

def _extend_backing(self, backing, new_size_in_gb):

    root_vmdk_path = self.volumeops.get_vmdk_path(backing)
    datacenter = self.volumeops.get_dc(backing)
    self.volumeops.extend_virtual_disk(new_size_in_gb, root_vmdk_path, datacenter)
