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>