bt_free
m.free = t->bt_free;
t->bt_free = m.free;
t->bt_free = P_INVALID;
h->nextpg = t->bt_free;
t->bt_free = h->pgno;
if (t->bt_free != P_INVALID &&
(h = mpool_get(t->bt_mp, t->bt_free, 0)) != NULL) {
*npg = t->bt_free;
t->bt_free = h->nextpg;
pgno_t bt_free; /* next free page */
bt_free(vm, btnew);
bt_free(vm, btnew);
bt_free(vm, btnew2);
bt_free(vm, btnew);
bt_free(vm, btnew2);
bt_free(vm, t);
bt_free(vm, t);
bt_free(vm, bt);
bt_free(vm, t);
bt_free(vm, btspan);
bt_free(vm, bt);