VNF_READONLY
if ((ap->a_oflags & FWRITE) && (vn->sc_flags & VNF_READONLY))
vn->sc_flags |= VNF_READONLY;
(vn->sc_flags & VNF_READONLY) ? FREAD : (FREAD|FWRITE),
vn->sc_flags &= ~VNF_READONLY;