net: Introduce for_each_netdev_rcu() iterator

Adds RCU management to the list of netdevices.

Convert some for_each_netdev() users to RCU version, if
it can avoid read_lock-ing dev_base_lock

Ie:
	read_lock(&dev_base_loack);
	for_each_netdev(net, dev)
		some_action();
	read_unlock(&dev_base_lock);

becomes :

	rcu_read_lock();
	for_each_netdev_rcu(net, dev)
		some_action();
	rcu_read_unlock();


Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 7 deletions

diff --git a/net/netrom/nr_route.c b/net/netrom/nr_route.c
index 4eb1ac9a7679..aacba76070fc 100644
--- a/net/netrom/nr_route.c
+++ b/net/netrom/nr_route.c
@@ -597,15 +597,15 @@ struct net_device *nr_dev_first(void)
 {
         struct net_device *dev, *first = NULL;
 
-        read_lock(&dev_base_lock);
-        for_each_netdev(&init_net, dev) {
+        rcu_read_lock();
+        for_each_netdev_rcu(&init_net, dev) {
                 if ((dev->flags & IFF_UP) && dev->type == ARPHRD_NETROM)
                         if (first == NULL || strncmp(dev->name, first->name, 3) < 0)
                                 first = dev;
         }
         if (first)
                 dev_hold(first);
-        read_unlock(&dev_base_lock);
+        rcu_read_unlock();
 
         return first;
 }
@@ -617,16 +617,17 @@ struct net_device *nr_dev_get(ax25_address *addr)
 {
         struct net_device *dev;
 
-        read_lock(&dev_base_lock);
-        for_each_netdev(&init_net, dev) {
-                if ((dev->flags & IFF_UP) && dev->type == ARPHRD_NETROM && ax25cmp(addr, (ax25_address *)dev->dev_addr) == 0) {
+        rcu_read_lock();
+        for_each_netdev_rcu(&init_net, dev) {
+                if ((dev->flags & IFF_UP) && dev->type == ARPHRD_NETROM &&
+                    ax25cmp(addr, (ax25_address *)dev->dev_addr) == 0) {
                         dev_hold(dev);
                         goto out;
                 }
         }
         dev = NULL;
 out:
-        read_unlock(&dev_base_lock);
+        rcu_read_unlock();
         return dev;
 }