From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jiri Pirko <jiri@resnulli.us>
Subject: Re: [patch net-next 2/2] net/sched: fix filter flushing
Date: Sun, 21 May 2017 21:19:41 +0200
Message-ID: <20170521191941.GA4278@nanopsycho>
References: <20170520130132.1626-1-jiri@resnulli.us>
 <20170520130132.1626-2-jiri@resnulli.us>
 <CAM_iQpWha6aCV3kOfCEFsBLNiC7LFTh=K=QaL17rH4=PUoeUmQ@mail.gmail.com>
 <20170521055416.GA1848@nanopsycho>
 <CAM_iQpVPuC-FQ3R4QNDCBWxrX5s7Q4bENxMU7+1LooCdHdMZhw@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>,
        David Miller <davem@davemloft.net>,
        Jamal Hadi Salim <jhs@mojatatu.com>,
        Eric Dumazet <edumazet@google.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Simon Horman <simon.horman@netronome.com>, mlxsw@mellanox.com,
        Colin King <colin.king@canonical.com>
To: Cong Wang <xiyou.wangcong@gmail.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mail-wm0-f68.google.com ([74.125.82.68]:33426 "EHLO
        mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751315AbdEUTTo (ORCPT
        <rfc822;netdev@vger.kernel.org>); Sun, 21 May 2017 15:19:44 -0400
Received: by mail-wm0-f68.google.com with SMTP id b84so12413515wmh.0
        for <netdev@vger.kernel.org>; Sun, 21 May 2017 12:19:43 -0700 (PDT)
Content-Disposition: inline
In-Reply-To: <CAM_iQpVPuC-FQ3R4QNDCBWxrX5s7Q4bENxMU7+1LooCdHdMZhw@mail.gmail.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

Sun, May 21, 2017 at 08:27:21PM CEST, xiyou.wangcong@gmail.com wrote:
>On Sat, May 20, 2017 at 10:54 PM, Jiri Pirko <jiri@resnulli.us> wrote:
>> Sun, May 21, 2017 at 02:16:45AM CEST, xiyou.wangcong@gmail.com wrote:
>>>On Sat, May 20, 2017 at 6:01 AM, Jiri Pirko <jiri@resnulli.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.