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, 11 insertions, 19 deletions

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index ccccaae50b20..8aa7a134c1f1 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -876,19 +876,16 @@ __be32 inet_select_addr(const struct net_device *dev, __be32 dst, int scope)
                 if (!addr)
                         addr = ifa->ifa_local;
         } endfor_ifa(in_dev);
-no_in_dev:
-        rcu_read_unlock();
 
+no_in_dev:
         if (addr)
-                goto out;
+                goto out_unlock;
 
         /* Not loopback addresses on loopback should be preferred
            in this case. It is importnat that lo is the first interface
            in dev_base list.
          */
-        read_lock(&dev_base_lock);
-        rcu_read_lock();
-        for_each_netdev(net, dev) {
+        for_each_netdev_rcu(net, dev) {
                 if ((in_dev = __in_dev_get_rcu(dev)) == NULL)
                         continue;
 
@@ -896,12 +893,11 @@ no_in_dev:
                         if (ifa->ifa_scope != RT_SCOPE_LINK &&
                             ifa->ifa_scope <= scope) {
                                 addr = ifa->ifa_local;
-                                goto out_unlock_both;
+                                goto out_unlock;
                         }
                 } endfor_ifa(in_dev);
         }
-out_unlock_both:
-        read_unlock(&dev_base_lock);
+out_unlock:
         rcu_read_unlock();
 out:
         return addr;
@@ -962,9 +958,8 @@ __be32 inet_confirm_addr(struct in_device *in_dev,
                 return confirm_addr_indev(in_dev, dst, local, scope);
 
         net = dev_net(in_dev->dev);
-        read_lock(&dev_base_lock);
         rcu_read_lock();
-        for_each_netdev(net, dev) {
+        for_each_netdev_rcu(net, dev) {
                 if ((in_dev = __in_dev_get_rcu(dev))) {
                         addr = confirm_addr_indev(in_dev, dst, local, scope);
                         if (addr)
@@ -972,7 +967,6 @@ __be32 inet_confirm_addr(struct in_device *in_dev,
                 }
         }
         rcu_read_unlock();
-        read_unlock(&dev_base_lock);
 
         return addr;
 }
@@ -1240,18 +1234,18 @@ static void devinet_copy_dflt_conf(struct net *net, int i)
 {
         struct net_device *dev;
 
-        read_lock(&dev_base_lock);
-        for_each_netdev(net, dev) {
+        rcu_read_lock();
+        for_each_netdev_rcu(net, dev) {
                 struct in_device *in_dev;
-                rcu_read_lock();
+
                 in_dev = __in_dev_get_rcu(dev);
                 if (in_dev && !test_bit(i, in_dev->cnf.state))
                         in_dev->cnf.data[i] = net->ipv4.devconf_dflt->data[i];
-                rcu_read_unlock();
         }
-        read_unlock(&dev_base_lock);
+        rcu_read_unlock();
 }
 
+/* called with RTNL locked */
 static void inet_forward_change(struct net *net)
 {
         struct net_device *dev;
@@ -1260,7 +1254,6 @@ static void inet_forward_change(struct net *net)
         IPV4_DEVCONF_ALL(net, ACCEPT_REDIRECTS) = !on;
         IPV4_DEVCONF_DFLT(net, FORWARDING) = on;
 
-        read_lock(&dev_base_lock);
         for_each_netdev(net, dev) {
                 struct in_device *in_dev;
                 if (on)
@@ -1271,7 +1264,6 @@ static void inet_forward_change(struct net *net)
                         IN_DEV_CONF_SET(in_dev, FORWARDING, on);
                 rcu_read_unlock();
         }
-        read_unlock(&dev_base_lock);
 }
 
 static int devinet_conf_proc(ctl_table *ctl, int write,