netdev - Re: [Patch net] ipv4: restore rt->fi for reference counting

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Message-ID: <CAM_iQpWAjTJL54h_Pdg3DigjEK4kQdSz0pmAks6ByoP67ROOFg@mail.gmail.com>
Date:   Mon, 15 May 2017 15:13:24 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Julian Anastasov <ja@....bg>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [Patch net] ipv4: restore rt->fi for reference counting

On Mon, May 15, 2017 at 1:37 PM, Julian Anastasov <ja@....bg> wrote:
>         Any user that does not set FIB_LOOKUP_NOREF
> will need nh_dev refcounts. The assumption is that the
> NHs are accessed, who knows, may be even after RCU grace
> period. As result, we can not use dev_put on NETDEV_UNREGISTER.
> So, we should check if there are users that do not
> set FIB_LOOKUP_NOREF, at first look, I don't see such ones
> for IPv4.

I see, although we do have FIB_LOOKUP_NOREF set all the times,
there are other places we hold fib_clntref too, for example
mlxsw_sp_router_fib_event_work(), it actually uses nh_dev too...

So I am afraid moving dev_put() to fib_release_info() is not a solution
here. I have to rethink about it.