[PATCH net-next v2 0/5] Rework ip_ra_chain protection

[Kirill Tkhai <ktkhai@virtuozzo.com>]

Commit 1215e51edad1 "ipv4: fix a deadlock in ip_ra_control"
made rtnl_lock() be used in raw_close(). This function is called
on every RAW socket destruction, so that rtnl_mutex is taken
every time. This scales very sadly. I observe cleanup_net()
spending a lot of time in rtnl_lock() and raw_close() is one
of the biggest rtnl user (since we have percpu net->ipv4.icmp_sk).

Another problem is that commit does not explain actual call path
mrtsock_destruct() takes sk lock and the way to deadlock.
But there is no sk lock taking is visible in mrtsock_destruct().
So, it is a question does we need it at all.

This patchset reworks the locking: reverts the problem commit
and its descendant, and introduces rtnl-independent locking.
This may have a continuation, and someone may work on killing
rtnl_lock() in mrtsock_destruct() in the future.

Thanks,
Kirill

---
v2:  Fix sparse warning (4/5), as reported by kbuild test robot.

Kirill Tkhai (5):
      net: Revert "ipv4: get rid of ip_ra_lock"
      net: Revert "ipv4: fix a deadlock in ip_ra_control"
      net: Move IP_ROUTER_ALERT out of lock_sock(sk)
      net: Make ip_ra_chain per struct net
      net: Replace ip_ra_lock with per-net mutex


 include/net/ip.h         |   13 +++++++++++--
 include/net/netns/ipv4.h |    2 ++
 net/core/net_namespace.c |    1 +
 net/ipv4/ip_input.c      |    5 ++---
 net/ipv4/ip_sockglue.c   |   34 +++++++++++++---------------------
 net/ipv4/ipmr.c          |   11 +++++++++--
 net/ipv4/raw.c           |    2 --
 7 files changed, 38 insertions(+), 30 deletions(-)

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