fw_hash
fp = &head->ht[fw_hash(f->id)];
fp = &head->ht[fw_hash(fnew->id)];
RCU_INIT_POINTER(f->next, head->ht[fw_hash(handle)]);
rcu_assign_pointer(head->ht[fw_hash(handle)], f);
for (f = rcu_dereference_bh(head->ht[fw_hash(id)]); f;
f = rtnl_dereference(head->ht[fw_hash(handle)]);