netdev - Re: [PATCH net] tcp: fix page frag corruption on page fault

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Message-ID: <CANn89iJx9b=Z=40TGhNtc7fRQSd=9MeG1x1PnJv2S5PYdYUoyw@mail.gmail.com>
Date:   Fri, 26 Nov 2021 07:32:59 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, Steffen Froemer <sfroemer@...hat.com>
Subject: Re: [PATCH net] tcp: fix page frag corruption on page fault

On Fri, Nov 26, 2021 at 7:27 AM Eric Dumazet <edumazet@...gle.com> wrote:

> We need to find one flag that can ask  gfpflags_normal_context() to
> return false for this case.
>
> Or if too difficult, stop only using sk->sk_allocation to decide
> between the per-thread frag, or the per socket one.
>
> I presume there are few active CIFS sockets on a host. They should use
> a per socket sk_frag.
>

A pure networking change could be to use a new MSG_  flag to force sendmsg()
to use the sk->sk_frag, but that would add yet another test in TCP fast path.

About gfpflags_normal_context being used by dlm : we can simply add our own
helper with a new name describing that we want:

Both being in process context, and not from page fault handler .