ext2_getlbns
if (ext2_getlbns(vp, start_lbn, start_ap, &start_lvl) ||
ext2_getlbns(vp, end_lbn, end_ap, &end_lvl))
if ((error = ext2_getlbns(vp, lbn, indirs, &num)) != 0)
error = ext2_getlbns(vp, bn, ap, nump);
error = ext2_getlbns(vp, bn, ap, &num);
int ext2_getlbns(struct vnode *, daddr_t, struct indir *, int *);