Messages in this thread | | | From | Willem de Bruijn <> | Date | Tue, 11 Jan 2022 10:39:30 -0500 | Subject | Re: [PATCH 09/14] ipv6: hand dst refs to cork setup |
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On Mon, Jan 10, 2022 at 8:25 PM Pavel Begunkov <asml.silence@gmail.com> 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@gmail.com> > ---
There are two patches 9/14
> 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?
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.
> /* > * setup for corking > */ > @@ -1389,8 +1391,6 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork, > > /* need source address above miyazawa*/ > } > - dst_hold(&rt->dst); > - cork->base.dst = &rt->dst; > v6_cork->hop_limit = ipc6->hlimit; > v6_cork->tclass = ipc6->tclass; > if (rt->dst.flags & DST_XFRM_TUNNEL) > @@ -1784,6 +1784,7 @@ int ip6_append_data(struct sock *sk, > /* > * setup for corking > */ > + dst_hold(&rt->dst); > err = ip6_setup_cork(sk, &inet->cork, &np->cork, > ipc6, rt); > if (err) > @@ -1974,8 +1975,10 @@ struct sk_buff *ip6_make_skb(struct sock *sk, > int exthdrlen = (ipc6->opt ? ipc6->opt->opt_flen : 0); > int err; > > - if (flags & MSG_PROBE) > + if (flags & MSG_PROBE) { > + dst_release(&rt->dst); > return NULL; > + } > > __skb_queue_head_init(&queue); > > diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c > index eec83e34ae27..3039dff7fe64 100644 > --- a/net/ipv6/udp.c > +++ b/net/ipv6/udp.c > @@ -1541,7 +1541,8 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) > err = PTR_ERR(skb); > if (!IS_ERR_OR_NULL(skb)) > err = udp_v6_send_skb(skb, fl6, &cork.base); > - goto out; > + /* ip6_make_skb steals dst reference */ > + goto out_no_dst; > } > > lock_sock(sk); > -- > 2.34.1 >
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