RF_FIRSTSHARE
KASSERT((flags & RF_FIRSTSHARE) == 0,
new_rflags = (flags & ~RF_FIRSTSHARE) | RF_ALLOCATED;
s->r_flags |= RF_FIRSTSHARE;
if (r->r_flags & RF_FIRSTSHARE) {
s->r_flags |= RF_FIRSTSHARE;
s->r_flags &= ~RF_FIRSTSHARE;