readindir
error = readindir(vp, metalbn, daddr, &bp);
error = readindir(vp, ap->in_lbn, daddr, &bp);
error = readindir(vp, metalbn, daddr, &bp);
error = readindir(vp, ap->in_lbn, daddr, &bp);
static int readindir(struct vnode *, ufs_lbn_t, ufs2_daddr_t, struct buf **);