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

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Matthieu Baerts <matttbe@kernel.org>
Date: Wed, 14 Feb 2024 10:32:58 +0100
> 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?

Sounds good!

And I can apply the similar change to the general setsockopt()
not to take lock_sock().


> 
> >  			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.

Thanks!