zfs_iter_root
ret = zfs_iter_root(g_zfs, zfs_callback, &cb);
(void) zfs_iter_root(g_zfs, get_one_dataset, &state);
(void) zfs_iter_root(g_zfs, match_mountpoint, &cb);
(void) zfs_iter_root(g_zfs, be_get_ds_from_dir_callback, &dd);
(void) zfs_iter_root(mp->gm_fs.gf_lzfh, zfs_bootsign, barg);
(void) zfs_iter_root(libzfs, get_one_filesystem, &cb);
(void) zfs_iter_root(impl_handle->zfs_libhandle,
extern int zfs_iter_root(libzfs_handle_t *, zfs_iter_f, void *);