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>

2 files changed, 10 insertions, 16 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 918648409612..024bba30de21 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -481,9 +481,8 @@ static void addrconf_forward_change(struct net *net, __s32 newf)
         struct net_device *dev;
         struct inet6_dev *idev;
 
-        read_lock(&dev_base_lock);
-        for_each_netdev(net, dev) {
-                rcu_read_lock();
+        rcu_read_lock();
+        for_each_netdev_rcu(net, dev) {
                 idev = __in6_dev_get(dev);
                 if (idev) {
                         int changed = (!idev->cnf.forwarding) ^ (!newf);
@@ -491,9 +490,8 @@ static void addrconf_forward_change(struct net *net, __s32 newf)
                         if (changed)
                                 dev_forward_change(idev);
                 }
-                rcu_read_unlock();
         }
-        read_unlock(&dev_base_lock);
+        rcu_read_unlock();
 }
 
 static int addrconf_fixup_forwarding(struct ctl_table *table, int *p, int old)
@@ -1137,10 +1135,9 @@ int ipv6_dev_get_saddr(struct net *net, struct net_device *dst_dev,
         hiscore->rule = -1;
         hiscore->ifa = NULL;
 
-        read_lock(&dev_base_lock);
         rcu_read_lock();
 
-        for_each_netdev(net, dev) {
+        for_each_netdev_rcu(net, dev) {
                 struct inet6_dev *idev;
 
                 /* Candidate Source Address (section 4)
@@ -1235,7 +1232,6 @@ try_nextdev:
                 read_unlock_bh(&idev->lock);
         }
         rcu_read_unlock();
-        read_unlock(&dev_base_lock);
 
         if (!hiscore->ifa)
                 return -EADDRNOTAVAIL;
@@ -4052,9 +4048,8 @@ static void addrconf_disable_change(struct net *net, __s32 newf)
         struct net_device *dev;
         struct inet6_dev *idev;
 
-        read_lock(&dev_base_lock);
-        for_each_netdev(net, dev) {
-                rcu_read_lock();
+        rcu_read_lock();
+        for_each_netdev_rcu(net, dev) {
                 idev = __in6_dev_get(dev);
                 if (idev) {
                         int changed = (!idev->cnf.disable_ipv6) ^ (!newf);
@@ -4062,9 +4057,8 @@ static void addrconf_disable_change(struct net *net, __s32 newf)
                         if (changed)
                                 dev_disable_change(idev);
                 }
-                rcu_read_unlock();
         }
-        read_unlock(&dev_base_lock);
+        rcu_read_unlock();
 }
 
 static int addrconf_disable_ipv6(struct ctl_table *table, int *p, int old)
diff --git a/net/ipv6/anycast.c b/net/ipv6/anycast.c
index 1ae58bec1de0..2f00ca83f049 100644
--- a/net/ipv6/anycast.c
+++ b/net/ipv6/anycast.c
@@ -404,13 +404,13 @@ int ipv6_chk_acast_addr(struct net *net, struct net_device *dev,
 
         if (dev)
                 return ipv6_chk_acast_dev(dev, addr);
-        read_lock(&dev_base_lock);
-        for_each_netdev(net, dev)
+        rcu_read_lock();
+        for_each_netdev_rcu(net, dev)
                 if (ipv6_chk_acast_dev(dev, addr)) {
                         found = 1;
                         break;
                 }
-        read_unlock(&dev_base_lock);
+        rcu_read_unlock();
         return found;
 }