netdev - Re: [patch net-next] net: sched: don't dump chains only held by actions

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Message-ID: <CAM_iQpWE1SW44dQGASSwB6UHD_tBCM+K_N2=y6-JcO9ANOSiww@mail.gmail.com>
Date:   Mon, 30 Jul 2018 11:19:56 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>
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>,
        mlxsw@...lanox.com
Subject: Re: [patch net-next] net: sched: don't dump chains only held by actions

On Sun, Jul 29, 2018 at 12:54 AM Jiri Pirko <jiri@...nulli.us> wrote:
>
> Sat, Jul 28, 2018 at 07:39:36PM CEST, xiyou.wangcong@...il.com wrote:
> >On Sat, Jul 28, 2018 at 10:20 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
> >>
> >> On Fri, Jul 27, 2018 at 12:47 AM Jiri Pirko <jiri@...nulli.us> wrote:
> >> >
> >> > From: Jiri Pirko <jiri@...lanox.com>
> >> >
> >> > In case a chain is empty and not explicitly created by a user,
> >> > such chain should not exist. The only exception is if there is
> >> > an action "goto chain" pointing to it. In that case, don't show the
> >> > chain in the dump. Track the chain references held by actions and
> >> > use them to find out if a chain should or should not be shown
> >> > in chain dump.
> >> >
> >> > Signed-off-by: Jiri Pirko <jiri@...lanox.com>
> >>
> >> Looks reasonable to me.
> >>
> >> Acked-by: Cong Wang <xiyou.wangcong@...il.com>
> >
> >Hold on...
> >
> >If you increase the refcnt for a zombie chain on NEWCHAIN path,
> >then it would become a non-zombie, this makes sense. However,
> >if the action_refcnt gets increased again when another action uses it,
> >it become a zombie again because refcnt==action_refcnt??
>
> No. action always increases both refcnt and action_refcnt

Hmm, then the name zombie is confusing, with your definition all
chains implicitly created by actions are zombies, unless touched
by user explicitly. Please find a better name.

Also, tcf_chain_get_by_act() could send out RTM_NEWCHAIN too,
which is confusing too as it is still a "zombie".