netdev - [PATCH net-next-2.6] ipv6: RCU changes in ipv6_get_mtu() and ip6_dst

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Message-ID: <1276526780.2478.101.camel@edumazet-laptop>
Date:	Mon, 14 Jun 2010 16:46:20 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next-2.6] ipv6: RCU changes in ipv6_get_mtu() and
 ip6_dst_hoplimit()

Use RCU to avoid atomic ops on idev refcnt in ipv6_get_mtu()
and ip6_dst_hoplimit() 

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 net/ipv6/route.c |   19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f770285..8f2d040 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1084,11 +1084,11 @@ static int ipv6_get_mtu(struct net_device *dev)
 	int mtu = IPV6_MIN_MTU;
 	struct inet6_dev *idev;
 
-	idev = in6_dev_get(dev);
-	if (idev) {
+	rcu_read_lock();
+	idev = __in6_dev_get(dev);
+	if (idev)
 		mtu = idev->cnf.mtu6;
-		in6_dev_put(idev);
-	}
+	rcu_read_unlock();
 	return mtu;
 }
 
@@ -1097,12 +1097,15 @@ int ip6_dst_hoplimit(struct dst_entry *dst)
 	int hoplimit = dst_metric(dst, RTAX_HOPLIMIT);
 	if (hoplimit < 0) {
 		struct net_device *dev = dst->dev;
-		struct inet6_dev *idev = in6_dev_get(dev);
-		if (idev) {
+		struct inet6_dev *idev;
+
+		rcu_read_lock();
+		idev = __in6_dev_get(dev);
+		if (idev)
 			hoplimit = idev->cnf.hop_limit;
-			in6_dev_put(idev);
-		} else
+		else
 			hoplimit = dev_net(dev)->ipv6.devconf_all->hop_limit;
+		rcu_read_unlock();
 	}
 	return hoplimit;
 }


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