netdev - Re: [patch net-next 2/2] net/sched: fix filter flushing

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Message-ID: <20170521191941.GA4278@nanopsycho>
Date:   Sun, 21 May 2017 21:19:41 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Simon Horman <simon.horman@...ronome.com>, mlxsw@...lanox.com,
        Colin King <colin.king@...onical.com>
Subject: Re: [patch net-next 2/2] net/sched: fix filter flushing

Sun, May 21, 2017 at 08:27:21PM CEST, xiyou.wangcong@...il.com wrote:
>On Sat, May 20, 2017 at 10:54 PM, Jiri Pirko <jiri@...nulli.us> wrote:
>> Sun, May 21, 2017 at 02:16:45AM CEST, xiyou.wangcong@...il.com wrote:
>>>On Sat, May 20, 2017 at 6:01 AM, Jiri Pirko <jiri@...nulli.us> wrote:
>>>> +static void tcf_chain_destroy(struct tcf_chain *chain)
>>>> +{
>>>> +       list_del(&chain->list);
>>>> +       tcf_chain_flush(chain);
>>>>         kfree(chain);
>>>>  }
>>>>
>>>> @@ -510,7 +517,7 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
>>>>
>>>>         if (n->nlmsg_type == RTM_DELTFILTER && prio == 0) {
>>>>                 tfilter_notify_chain(net, skb, n, chain, RTM_DELTFILTER);
>>>> -               tcf_chain_destroy(chain);
>>>> +               tcf_chain_flush(chain);
>>>
>>>
>>>I wonder if we should return EBUSY and do nothing in case of busy?
>>>The chain is no longer visual to new actions after your list_del(), but
>>>the old one could still use and see it.
>>
>> No. User request to flush the chain, that is what happens in the past
>> and that is what should happen now.
>> If there is still a reference, the chain_put will keep the empty chain.
>
>But if you dump the actions, this chain is still shown "goto chain"?

Yes, it will be shown there.


>You can't claim you really delete it as long as actions can still
>see it and dump it.

No, user just wants to delete all the filters. That is done. User does
not care if the actual chain structure is there or not.