Re: [PATCH 09/14] ipv6: hand dst refs to cork setup

[Pavel Begunkov]

On 1/11/22 15:39, Willem de Bruijn wrote:
> On Mon, Jan 10, 2022 at 8:25 PM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote:
> > During cork->dst setup, ip6_make_skb() gets an additional reference to
> > a passed in dst. However, udpv6_sendmsg() doesn't need dst after calling
> > ip6_make_skb(), and so we can save two additional atomics by passing
> > dst references to ip6_make_skb(). udpv6_sendmsg() is the only caller, so
> > it's enough to make sure it doesn't use dst afterwards.
> >
> > Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> > ---
>
> There are two patches 9/14

Weird, thanks for letting know

> >   net/ipv6/ip6_output.c | 9 ++++++---
> >   net/ipv6/udp.c        | 3 ++-
> >   2 files changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> > index 0cc490f2cfbf..6a7bba4dd04d 100644
> > --- a/net/ipv6/ip6_output.c
> > +++ b/net/ipv6/ip6_output.c
> > @@ -1356,6 +1356,8 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,
> >          unsigned int mtu;
> >          struct ipv6_txoptions *nopt, *opt = ipc6->opt;
> >
> > +       cork->base.dst = &rt->dst;
> > +
>
> Is there a reason to move this up from its original location next to
> the other cork initialization assignments?

ip6_setup_cork() consumes a dst ref now even in error cases, moved
it to not patch up all error returns in there. On the other hand
I can add dst_release() to callers when it failed.


> That the reference is taken in ip6_append_data for corked requests
> (once, in setup cork branch) and inherited from udpv6_send_skb
> otherwise is non-trivial. Worth a comment.

Will update in v2, thanks

--
Pavel Begunkov