net: Introduce dev_get_by_index_rcu()

Some workloads hit dev_base_lock rwlock pretty hard.
We can use RCU lookups to avoid touching this rwlock.

netdevices are already freed after a RCU grace period, so this patch
adds no penalty at device dismantle time.

dev_ifname() converted to dev_get_by_index_rcu()

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

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 656110a46e96..ffc3106cc037 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1139,6 +1139,7 @@ extern void		netdev_resync_ops(struct net_device *dev);
 extern int call_netdevice_notifiers(unsigned long val, struct net_device *dev);
 extern struct net_device        *dev_get_by_index(struct net *net, int ifindex);
 extern struct net_device        *__dev_get_by_index(struct net *net, int ifindex);
+extern struct net_device        *dev_get_by_index_rcu(struct net *net, int ifindex);
 extern int              dev_restart(struct net_device *dev);
 #ifdef CONFIG_NETPOLL_TRAP
 extern int              netpoll_trap(void);