Function rbd_clone 

pub unsafe extern "C" fn rbd_clone(
    p_ioctx: rados_ioctx_t,
    p_name: *const c_char,
    p_snapname: *const c_char,
    c_ioctx: rados_ioctx_t,
    c_name: *const c_char,
    features: uint64_t,
    c_order: *mut c_int,
) -> c_int

Clone a parent rbd snapshot into a COW sparse child.