netdev - Re: [patch net-next v4 03/12] net: sched: introduce chain object to uapi

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Date:   Thu, 26 Jul 2018 09:38:39 +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>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Simon Horman <simon.horman@...ronome.com>,
        john.hurley@...ronome.com, David Ahern <dsahern@...il.com>,
        mlxsw@...lanox.com, sridhar.samudrala@...el.com
Subject: Re: [patch net-next v4 03/12] net: sched: introduce chain object to
 uapi

Wed, Jul 25, 2018 at 06:40:44PM CEST, xiyou.wangcong@...il.com wrote:
>On Tue, Jul 24, 2018 at 11:49 PM Jiri Pirko <jiri@...nulli.us> wrote:
>>
>> Wed, Jul 25, 2018 at 01:20:08AM CEST, xiyou.wangcong@...il.com wrote:
>> >So, you only send out notification when the last refcnt is gone.
>> >
>> >If the chain that is being deleted by a user is still used by an action,
>> >you return 0 or -EPERM?
>>
>> 0 and the chain stays there until the action is removed. Hmm, do you thing
>> that -EPERM should be returned in that case? The thing is, we have to
>> flush the chain in order to see the action references are there. We would
>> have to have 2 ref counters, one for filter, one for actions.
>> What do you think?
>
>_If_ RTM_DELCHAIN does decrease the chain refcnt, then it is
>broken:
>
># tc chain add X... (refcnt == 1)
># tc action add ... goto chain X (refcnt==2)
># tc chain del X ... (refcnt== 1)
># tc chain del X ... (refcnt==0)
>
>RTM_DELCHAIN should just test if refcnt is 1, if it is, delete it,
>otherwise return -EPERM. This is how we handle tc standalone
>actions, see tcf_idr_delete_index().
>
>Yes, you might need two refcnt's here.

Okay. Sounds good. I'm on it.