wnd_is_used
if (!wnd_is_used(wnd, lcn, len)) {
if (wnd_is_used(wnd, i, 1)) {
if (!wnd_is_used(wnd, rno, 1))
bool wnd_is_used(struct wnd_bitmap *wnd, size_t bit, size_t bits);
ok = !zone && wnd_is_used(wnd, lcn, len);