hlist_nulls_entry_safe
elem = hlist_nulls_entry_safe(n, struct htab_elem, hash_node);
next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_next_rcu(&l->hash_node)),
next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_first_rcu(head)),