linux-kernel - RE: [PATCH bpf-next 1/6] net: sk_msg: simplify sk

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Date:   Wed, 19 Aug 2020 13:05:36 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Lorenz Bauer <lmb@...udflare.com>, jakub@...udflare.com,
        john.fastabend@...il.com, Daniel Borkmann <daniel@...earbox.net>,
        Lorenz Bauer <lmb@...udflare.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     kernel-team@...udflare.com, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: RE: [PATCH bpf-next 1/6] net: sk_msg: simplify sk_psock
 initialization

Lorenz Bauer wrote:
> Initializing psock->sk_proto and other saved callbacks is only
> done in sk_psock_update_proto, after sk_psock_init has returned.
> The logic for this is difficult to follow, and needlessly complex.
> 
> Instead, initialize psock->sk_proto whenever we allocate a new
> psock. Additionally, assert the following invariants:
> 
> * The SK has no ULP: ULP does it's own finagling of sk->sk_prot
> * sk_user_data is unused: we need it to store sk_psock
> 
> Protect our access to sk_user_data with sk_callback_lock, which
> is what other users like reuseport arrays, etc. do.
> 
> The result is that an sk_psock is always fully initialized, and
> that psock->sk_proto is always the "original" struct proto.
> The latter allows us to use psock->sk_proto when initializing
> IPv6 TCP / UDP callbacks for sockmap.
> 
> Signed-off-by: Lorenz Bauer <lmb@...udflare.com>
> ---

Looks like a nice bit of cleanup thanks. I think we might be able to fold
up more of this code as well, but I'll take a look in a bit.

Acked-by: John Fastabend <john.fastabend@...il.com>