linux-kernel - [PATCH v2 net-next 09/11] ipv6: refactor opts push in __ip6_make

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Message-Id: <c212894e96eebdee39f3ef8a75fc6c1d6b0c1e10.1651153920.git.asml.silence@gmail.com>
Date:   Thu, 28 Apr 2022 14:58:04 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        linux-kernel@...r.kernel.org,
        Pavel Begunkov <asml.silence@...il.com>
Subject: [PATCH v2 net-next 09/11] ipv6: refactor opts push in __ip6_make_skb()

Don't preload v6_cork->opt before we actually need it, it likely to be
saved on the stack and read again for no good reason.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 net/ipv6/ip6_output.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 976554d0fdec..43a541bbcf5f 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1855,7 +1855,6 @@ struct sk_buff *__ip6_make_skb(struct sock *sk,
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct net *net = sock_net(sk);
 	struct ipv6hdr *hdr;
-	struct ipv6_txoptions *opt = v6_cork->opt;
 	struct rt6_info *rt = (struct rt6_info *)cork->base.dst;
 	struct flowi6 *fl6 = &cork->fl.u.ip6;
 	unsigned char proto = fl6->flowi6_proto;
@@ -1884,10 +1883,14 @@ struct sk_buff *__ip6_make_skb(struct sock *sk,
 	__skb_pull(skb, skb_network_header_len(skb));
 
 	final_dst = &fl6->daddr;
-	if (opt && opt->opt_flen)
-		ipv6_push_frag_opts(skb, opt, &proto);
-	if (opt && opt->opt_nflen)
-		ipv6_push_nfrag_opts(skb, opt, &proto, &final_dst, &fl6->saddr);
+	if (v6_cork->opt) {
+		struct ipv6_txoptions *opt = v6_cork->opt;
+
+		if (opt->opt_flen)
+			ipv6_push_frag_opts(skb, opt, &proto);
+		if (opt->opt_nflen)
+			ipv6_push_nfrag_opts(skb, opt, &proto, &final_dst, &fl6->saddr);
+	}
 
 	skb_push(skb, sizeof(struct ipv6hdr));
 	skb_reset_network_header(skb);
-- 
2.36.0