Merge branch 'Introduce-net_rwsem-to-protect-net_namespace_list'

Kirill Tkhai says:

====================
Introduce net_rwsem to protect net_namespace_list

The series introduces fine grained rw_semaphore, which will be used
instead of rtnl_lock() to protect net_namespace_list.

This improves scalability and allows to do non-exclusive sleepable
iteration for_each_net(), which is enough for most cases.

scripts/get_maintainer.pl gives enormous list of people, and I add
all to CC.

Note, that this patch is independent of "Close race between
{un, }register_netdevice_notifier and pernet_operations":
https://patchwork.ozlabs.org/project/netdev/list/?series=36495

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/core/fib_notifier.c b/net/core/fib_notifier.c
index 0c048bdeb016..614b985c92a4 100644
--- a/net/core/fib_notifier.c
+++ b/net/core/fib_notifier.c
@@ -33,6 +33,7 @@ static unsigned int fib_seq_sum(void)
 	struct net *net;
 
 	rtnl_lock();
+	down_read(&net_rwsem);
 	for_each_net(net) {
 		rcu_read_lock();
 		list_for_each_entry_rcu(ops, &net->fib_notifier_ops, list) {
@@ -43,6 +44,7 @@ static unsigned int fib_seq_sum(void)
 		}
 		rcu_read_unlock();
 	}
+	up_read(&net_rwsem);
 	rtnl_unlock();
 
 	return fib_seq;