radix_tree_iter_find
bool radix_tree_iter_find(const struct radix_tree_root *, struct radix_tree_iter *, void ***, int);
radix_tree_iter_find(root, iter, &(slot), 0); \
radix_tree_iter_find(root, iter, &(slot), \
return (!radix_tree_iter_find(&xa->xa_head, &iter, &temp, 0));
found = radix_tree_iter_find(&xa->xa_head, &iter, &ppslot, 0);