blist_allocat
swblk_t blk = blist_allocat(bl, count, blkat);
swblk_t blist_allocat(blist_t, swblk_t, swblk_t);
blk = blist_allocat(swapblist, npages, swapiterator);
blk = blist_allocat(swapblist, npages, 0);