netdev - Re: [PATCH net] tcp: do not recycle cloned skbs

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Message-ID: <CANn89iLo5rdV2WJyuxwSEC9QntsvuKaLsuE27qvqrYQ1vqvTJg@mail.gmail.com>
Date:   Wed, 15 May 2019 09:47:12 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net] tcp: do not recycle cloned skbs

On Wed, May 15, 2019 at 9:41 AM David Miller <davem@...emloft.net> wrote:
>
> From: Eric Dumazet <edumazet@...gle.com>
> Date: Wed, 15 May 2019 09:26:54 -0700
>
> > On Wed, May 15, 2019 at 9:24 AM David Miller <davem@...emloft.net> wrote:
> >>
> >> From: Eric Dumazet <edumazet@...gle.com>
> >> Date: Wed, 15 May 2019 09:10:15 -0700
> >>
> >> > It is illegal to change arbitrary fields in skb_shared_info if the
> >> > skb is cloned.
> >> >
> >> > Before calling skb_zcopy_clear() we need to ensure this rule,
> >> > therefore we need to move the test from sk_stream_alloc_skb()
> >> > to sk_wmem_free_skb()
> >> >
> >> > Fixes: 4f661542a402 ("tcp: fix zerocopy and notsent_lowat issues")
> >> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> >> > Diagnosed-by: Willem de Bruijn <willemb@...gle.com>
> >>
> >> Applied and queued up for -stable.
> >
> > Note the patch targets current net tree, but does not need to be
> > backported to older kernel versions
> > (4f661542a402 is only in upcoming 5.2)
>
> Doesn't it fix a fix for something in 5.0?

Hmm no, the whole thing is new for 5.2 only.

commit 472c2e07eef045145bc1493cc94a01c87140780a
Author: Eric Dumazet <edumazet@...gle.com>
Date:   Fri Mar 22 08:56:39 2019 -0700

    tcp: add one skb cache for tx