RTRUNCATE
if ((rp->r_flags & RTRUNCATE) && pp->p_offset >= rp->r_truncaddr) {
while (rp->r_flags & RTRUNCATE)
rp->r_flags |= RTRUNCATE;
rp->r_flags &= ~RTRUNCATE;
while (np->r_flags & RTRUNCATE)
np->r_flags |= RTRUNCATE;
np->r_flags &= ~RTRUNCATE;