wnd_set_used
if (wnd_set_used(wnd, fnd, to_alloc))
err = wnd_set_used(wnd, from, len);
err = wnd_set_used(wnd, from, len);
err = wnd_set_used(wnd, lcn, alen);
wnd_set_used(wnd, *rno, 1);
int wnd_set_used(struct wnd_bitmap *wnd, size_t bit, size_t bits);