zfs_btree_add_idx
zfs_btree_add_idx(bt, &randval, &bt_idx);
zfs_btree_add_idx(bt, &randval, &bt_idx);
zfs_btree_add_idx(bt, &i, &bt_idx);
zfs_btree_add_idx(bt, &i, NULL);
zfs_btree_add_idx(tree, node, &where);
zfs_btree_add_idx(&rt->rt_root, rs, &where);
zfs_btree_add_idx(&rt->rt_root, &newseg, &where);
void zfs_btree_add_idx(zfs_btree_t *, const void *, const zfs_btree_index_t *);