netdev - [PATCH net] ip_tunnel: fix preempt warning in ip tunnel creation/updating

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Message-Id: <b21056e2495c485a2084d058d03e1f95480b3510.1461834203.git.pabeni@redhat.com>
Date:	Thu, 28 Apr 2016 11:04:51 +0200
From:	Paolo Abeni <pabeni@...hat.com>
To:	netdev@...r.kernel.org
Cc:	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>, tgraf@...g.ch,
	pshelar@...ira.com, jbenc@...hat.com, hannes@...essinduktion.org,
	sergei.shtylyov@...entembedded.com,
	Tom Herbert <tom@...bertland.com>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net] ip_tunnel: fix preempt warning in ip tunnel creation/updating

After the commit e09acddf873b ("ip_tunnel: replace dst_cache with generic
implementation"), a preemption debug warning is triggered on ip4
tunnels updating; the dst cache helper needs to be invoked in unpreemptible
context.

We don't need to load the cache on tunnel update, so this commit fixes
the warning replacing the load with a dst cache reset, which is
preempt safe.

Fixes: e09acddf873b ("ip_tunnel: replace dst_cache with generic
implementation")

Reported-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/ipv4/ip_tunnel.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 6aad019..a69ed94 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -326,12 +326,12 @@ static int ip_tunnel_bind_dev(struct net_device *dev)
 
 		if (!IS_ERR(rt)) {
 			tdev = rt->dst.dev;
-			dst_cache_set_ip4(&tunnel->dst_cache, &rt->dst,
-					  fl4.saddr);
 			ip_rt_put(rt);
 		}
 		if (dev->type != ARPHRD_ETHER)
 			dev->flags |= IFF_POINTOPOINT;
+
+		dst_cache_reset(&tunnel->dst_cache);
 	}
 
 	if (!tdev && tunnel->parms.link)
-- 
1.8.3.1