net: Introduce dev_get_by_name_rcu()

Some workloads hit dev_base_lock rwlock pretty hard.
We can use RCU lookups to avoid touching this rwlock
(and avoid touching netdevice refcount)

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

However, it adds a synchronize_rcu() call in dev_change_name()

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 e5ece8dceaad..bcf1083857fc 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1115,6 +1115,7 @@ extern void		__dev_remove_pack(struct packet_type *pt);
 extern struct net_device        *dev_get_by_flags(struct net *net, unsigned short flags,
                                                   unsigned short mask);
 extern struct net_device        *dev_get_by_name(struct net *net, const char *name);
+extern struct net_device        *dev_get_by_name_rcu(struct net *net, const char *name);
 extern struct net_device        *__dev_get_by_name(struct net *net, const char *name);
 extern int              dev_alloc_name(struct net_device *dev, const char *name);
 extern int              dev_open(struct net_device *dev);