be_exists_callback
if ((zret = zpool_iter(g_zfs, be_exists_callback, bt.nbe_name)) > 0) {
if ((zret = zpool_iter(g_zfs, be_exists_callback,
ret = zpool_iter(g_zfs, be_exists_callback,
int be_exists_callback(zpool_handle_t *, void *);