netdev - [PATCH v2 net-next 03/15] ipv6: addrconf_disable

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Date: Tue, 27 Feb 2024 15:01:48 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: David Ahern <dsahern@...nel.org>, Jiri Pirko <jiri@...dia.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v2 net-next 03/15] ipv6: addrconf_disable_ipv6() optimizations

Writing over /proc/sys/net/ipv6/conf/default/disable_ipv6
does not need to hold RTNL.

When changing /proc/sys/net/ipv6/conf/all/disable_ipv6,
the generic WRITE_ONCE(*p, newf) is enough, no need
to repeat it.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv6/addrconf.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 9c1d141a9a343b45225658ce75f23893ff6c7426..88b129b7884564876a51b359137c33e9b75ee9de 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -6398,25 +6398,23 @@ static void addrconf_disable_change(struct net *net, __s32 newf)
 
 static int addrconf_disable_ipv6(struct ctl_table *table, int *p, int newf)
 {
-	struct net *net;
+	struct net *net = (struct net *)table->extra2;
 	int old;
 
+	if (p == &net->ipv6.devconf_dflt->disable_ipv6) {
+		WRITE_ONCE(*p, newf);
+		return 0;
+	}
+
 	if (!rtnl_trylock())
 		return restart_syscall();
 
-	net = (struct net *)table->extra2;
 	old = *p;
 	WRITE_ONCE(*p, newf);
 
-	if (p == &net->ipv6.devconf_dflt->disable_ipv6) {
-		rtnl_unlock();
-		return 0;
-	}
-
-	if (p == &net->ipv6.devconf_all->disable_ipv6) {
-		WRITE_ONCE(net->ipv6.devconf_dflt->disable_ipv6, newf);
+	if (p == &net->ipv6.devconf_all->disable_ipv6)
 		addrconf_disable_change(net, newf);
-	} else if ((!newf) ^ (!old))
+	else if ((!newf) ^ (!old))
 		dev_disable_change((struct inet6_dev *)table->extra1);
 
 	rtnl_unlock();
-- 
2.44.0.rc1.240.g4c46232300-goog