Re: [PATCH v1 net-next] net: Deprecate SO_DEBUG and reclaim SOCK_DBG bit.

[Matthieu Baerts <matttbe@kernel.org>]

Hi Kuniyuki,

On 13/02/2024 23:31, Kuniyuki Iwashima wrote:
> Recently, commit 8e5443d2b866 ("net: remove SOCK_DEBUG leftovers")
> removed the last users of SOCK_DEBUG(), and commit b1dffcf0da22 ("net:
> remove SOCK_DEBUG macro") removed the macro.
> 
> Now is the time to deprecate the oldest socket option.

Thank you for looking at this!

My review here below is only about the modifications related to MPTCP.

(...)

> diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
> index da37e4541a5d..f6d90eef3d7c 100644
> --- a/net/mptcp/sockopt.c
> +++ b/net/mptcp/sockopt.c
> @@ -81,7 +81,7 @@ static void mptcp_sol_socket_sync_intval(struct mptcp_sock *msk, int optname, in
>  
>  		switch (optname) {
>  		case SO_DEBUG:
> -			sock_valbool_flag(ssk, SOCK_DBG, !!val);
> +			/* deprecated. */

If it is now a NOOP, maybe better to:

 - remove SO_DEBUG from mptcp_sol_socket_sync_intval() and
   mptcp_setsockopt_sol_socket_int()

 - move it just above the "return 0" in mptcp_setsockopt_sol_socket()
with the "deprecated" (or "removed") comment

By doing that, we avoid a lock, plus going through the list of subflows
for nothing.

WDYT?

>  			break;
>  		case SO_KEEPALIVE:
>  			if (ssk->sk_prot->keepalive)
> @@ -1458,8 +1458,6 @@ static void sync_socket_options(struct mptcp_sock *msk, struct sock *ssk)
>  		sk_dst_reset(ssk);
>  	}
>  
> -	sock_valbool_flag(ssk, SOCK_DBG, sock_flag(sk, SOCK_DBG));
> -
>  	if (inet_csk(sk)->icsk_ca_ops != inet_csk(ssk)->icsk_ca_ops)
>  		tcp_set_congestion_control(ssk, msk->ca_name, false, true);
>  	__tcp_sock_set_cork(ssk, !!msk->cork);

The rest looks good to me.

Cheers,
Matt
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