writerp4
error = writerp4(rp, NULL, n, uiop, 0);
error = writerp4(rp, base + pon, n, uiop,
error = writerp4(rp, base + on, n, uiop, 0);
extern int writerp4(rnode4_t *, caddr_t, int, struct uio *, int);