Re: [PATCH net] udp: Remove an unnecessary variable in udp[46]_lib_lookup2().

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

On Fri, Jul 24, 2020 at 3:13 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Fri, Jul 24, 2020 at 6:38 AM Willem de Bruijn
> <willemdebruijn.kernel@gmail.com> wrote:
> >
> > On Fri, Jul 24, 2020 at 2:13 AM Kuniyuki Iwashima <kuniyu@amazon.co.jp> wrote:
> > >
> > > From:   David Miller <davem@davemloft.net>
> > > Date:   Thu, 23 Jul 2020 15:10:51 -0700 (PDT)
> > > > From: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
> > > > Date: Thu, 23 Jul 2020 01:52:27 +0900
> > > >
> > > > > This patch removes an unnecessary variable in udp[46]_lib_lookup2() and
> > > > > makes it easier to resolve a merge conflict with bpf-next reported in
> > > > > the link below.
> > > > >
> > > > > Link: https://lore.kernel.org/linux-next/20200722132143.700a5ccc@canb.auug.org.au/
> > > > > Fixes: efc6b6f6c311 ("udp: Improve load balancing for SO_REUSEPORT.")
> > > > > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
> > > > > Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
> > > > > Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
> > > >
> > > > This doesn't apply to net-next.
> > >
> > > Yes. I think this kind of patch should be submitted to net-next, but this
> > > is for the net tree. Please let me add more description.
> > >
> > > Currently, the net and net-next trees conflict in udp[46]_lib_lookup2()
> > > between
> > >
> > >    efc6b6f6c311 ("udp: Improve load balancing for SO_REUSEPORT.")
> > >
> > > and
> > >
> > >    7629c73a1466 ("udp: Extract helper for selecting socket from reuseport group")
> > >    2a08748cd384 ("udp6: Extract helper for selecting socket from reuseport group")
> > > .
> > >
> > > The conflict is reported in the link[0] and Jakub suggested how to resolve
> > > it[1]. To ease the merge conflict, Jakub and I have to send follow up patches to
> > > the bpf-next and net trees.
> > >
> > > Now, his patchset (7629c73a1466 and 2a08748cd384) to bpf-next is merged
> > > into net-next, and his follow up patch is applied in bpf-next[2].
> > >
> > > I fixed a bug in efc6b6f6c311, but it introduced an unnecessary variable
> > > and made the conflict worse. So I sent this follow up patch to net tree.
> > >
> > > However, I do not know the best way to resolve the conflict, so any comments
> > > are welcome.
> >
> > Perhaps simpler is to apply this change to bpf-next:
>
> I'm fine whichever way.
> Could you please submit an official patch?

http://patchwork.ozlabs.org/project/netdev/patch/20200725025457.1004164-1-willemdebruijn.kernel@gmail.com/

Not sure whether it helps vs doing this as part of the merge conflict
(which remains). Either way after conflict resolution should be

"
static struct sock *udp4_lib_lookup2(struct net *net,
                                     __be32 saddr, __be16 sport,
                                     __be32 daddr, unsigned int hnum,
                                     int dif, int sdif,
                                     struct udp_hslot *hslot2,
                                     struct sk_buff *skb)
{
        struct sock *sk, *result;
        int score, badness;

        result = NULL;
        badness = 0;
        udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
                score = compute_score(sk, net, saddr, sport,
                                      daddr, hnum, dif, sdif);
                if (score > badness) {
                        result = lookup_reuseport(net, sk, skb,
                                                  saddr, sport, daddr, hnum);
                        if (result && !reuseport_has_conns(sk, false))
                                return result;

                        badness = score;
                        if (!result)
                                result = sk;
                }
        }
        return result;
}
"