netdev - Re: [PATCH net-next] ipv6: use DST_NOCOUNT in ip6_rt_pcpu

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Message-ID: <CANn89iJFZCid4eKEx+HW25rLEfyDTzLvPK391aT5tCZzSBCX5w@mail.gmail.com>
Date:   Fri, 8 May 2020 08:13:11 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>, Martin KaFai Lau <kafai@...com>,
        David Ahern <dsahern@...nel.org>, Wei Wang <weiwan@...gle.com>,
        Maciej Żenczykowski <maze@...gle.com>
Subject: Re: [PATCH net-next] ipv6: use DST_NOCOUNT in ip6_rt_pcpu_alloc()

On Fri, May 8, 2020 at 8:04 AM David Ahern <dsahern@...il.com> wrote:
>
> On 5/8/20 8:43 AM, Eric Dumazet wrote:
> > This patch can be backported without any pains ;)
>
> sure, but you tagged it as net-next, not net.

Because it is not a recent regression.
We are late in rc cycle.

I tend to push patches on net-next, then ask later for stable
backports once we are sure no regression was added,
even for patches that look 'very safe'  ;)



>
> >
> > Getting rid of limits, even for exceptions ?
>
> Running through where dst entries are created in IPv6:
> 1. pcpu cache
> 2. uncached_list
> 3. exceptions like pmtu and redirect
>
> All of those match IPv4 and as I recall IPv4 does not have any limits,
> even on exceptions and redirect. If IPv4 does not have limits, why
> should IPv6? And if the argument is uncontrolled memory consumption, is
> there an expectation that IPv6 generates more exceptions?
>
> My argument really just boils down to consistency between them. IPv4
> does not use DST_NOCOUNT, so why put that burden on v6?

That is something that needs further investigation.
Too many fires at this moment on my plate.

My patch stops bleeding right now.

Thanks.