[IPV4]: Replace __in_dev_get with __in_dev_get_rcu/rtnl

The following patch renames __in_dev_get() to __in_dev_get_rtnl() and
introduces __in_dev_get_rcu() to cover the second case.

1) RCU with refcnt should use in_dev_get().
2) RCU without refcnt should use __in_dev_get_rcu().
3) All others must hold RTNL and use __in_dev_get_rtnl().

There is one exception in net/ipv4/route.c which is in fact a pre-existing
race condition.  I've marked it as such so that we remember to fix it.

This patch is based on suggestions and prior work by Suzanne Wood and
Paul McKenney.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 2 deletions

diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index 7e1e15f934f3..fd7af86151b1 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -142,13 +142,21 @@ static __inline__ int bad_mask(u32 mask, u32 addr)
 
 #define endfor_ifa(in_dev) }
 
+static inline struct in_device *__in_dev_get_rcu(const struct net_device *dev)
+{
+	struct in_device *in_dev = dev->ip_ptr;
+	if (in_dev)
+		in_dev = rcu_dereference(in_dev);
+	return in_dev;
+}
+
 static __inline__ struct in_device *
 in_dev_get(const struct net_device *dev)
 {
 	struct in_device *in_dev;
 
 	rcu_read_lock();
-	in_dev = dev->ip_ptr;
+	in_dev = __in_dev_get_rcu(dev);
 	if (in_dev)
 		atomic_inc(&in_dev->refcnt);
 	rcu_read_unlock();
@@ -156,7 +164,7 @@ in_dev_get(const struct net_device *dev)
 }
 
 static __inline__ struct in_device *
-__in_dev_get(const struct net_device *dev)
+__in_dev_get_rtnl(const struct net_device *dev)
 {
 	return (struct in_device*)dev->ip_ptr;
 }