linux-kernel - Re: [PATCH v2 4.19] tcp: fix TCP socks unreleased in BBR mode

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Date:   Tue, 11 Aug 2020 18:37:46 +0800
From:   Jason Xing <kerneljasonxing@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Neal Cardwell <ncardwell@...gle.com>,
        David Miller <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        liweishi <liweishi@...ishou.com>,
        Shujin Li <lishujin@...ishou.com>
Subject: Re: [PATCH v2 4.19] tcp: fix TCP socks unreleased in BBR mode

Hi everyone,

Could anyone take a look at this issue? I believe it is of high-importance.
Though Eric gave the proper patch a few months ago, the stable branch
still hasn't applied or merged this fix. It seems this patch was
forgotten :(

Thanks,
Jason

On Thu, Jun 4, 2020 at 9:47 PM Jason Xing <kerneljasonxing@...il.com> wrote:
>
> On Thu, Jun 4, 2020 at 9:10 PM Eric Dumazet <edumazet@...gle.com> wrote:
> >
> > On Thu, Jun 4, 2020 at 2:01 AM <kerneljasonxing@...il.com> wrote:
> > >
> > > From: Jason Xing <kerneljasonxing@...il.com>
> > >
> > > When using BBR mode, too many tcp socks cannot be released because of
> > > duplicate use of the sock_hold() in the manner of tcp_internal_pacing()
> > > when RTO happens. Therefore, this situation maddly increases the slab
> > > memory and then constantly triggers the OOM until crash.
> > >
> > > Besides, in addition to BBR mode, if some mode applies pacing function,
> > > it could trigger what we've discussed above,
> > >
> > > Reproduce procedure:
> > > 0) cat /proc/slabinfo | grep TCP
> > > 1) switch net.ipv4.tcp_congestion_control to bbr
> > > 2) using wrk tool something like that to send packages
> > > 3) using tc to increase the delay and loss to simulate the RTO case.
> > > 4) cat /proc/slabinfo | grep TCP
> > > 5) kill the wrk command and observe the number of objects and slabs in
> > > TCP.
> > > 6) at last, you could notice that the number would not decrease.
> > >
> > > v2: extend the timer which could cover all those related potential risks
> > > (suggested by Eric Dumazet and Neal Cardwell)
> > >
> > > Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> > > Signed-off-by: liweishi <liweishi@...ishou.com>
> > > Signed-off-by: Shujin Li <lishujin@...ishou.com>
> >
> > That is not how things work really.
> >
> > I will submit this properly so that stable teams do not have to guess
> > how to backport this to various kernels.
> >
> > Changelog is misleading, this has nothing to do with BBR, we need to be precise.
> >
>
> Thanks for your help. I can finally apply this patch into my kernel.
>
> Looking forward to your patchset :)
>
> Jason
>
> > Thank you.