[PATCH v1 net-next 0/5] ip: Batch flushing uncached routes for dying netns.

[Kuniyuki Iwashima <kuniyu@google.com>]

Chris J Arges reported high RTNL contention during cleanup_net()
caused by rt_flush_dev() and rt6_uncached_list_flush_dev() iterating
over the global per-cpu uncached route lists for every netdev in
dying netns [0].

This series resolves the issue by introducing a new ->pre_exit_batch()
hook in struct pernet_operations and batching the uncached route
cleanup once per cleanup_net() without holding RTNL.

[0]: https://lore.kernel.org/netdev/20260917-hash-bucket-route-lists-v3-0-30493a37b6eb@cloudflare.com/


Kuniyuki Iwashima (5):
  net: Remove net->is_dying.
  net: Add ->pre_exit_batch() to struct pernet_operations.
  net: Track state in ops_undo_list().
  ipv4: Batch rt_flush_dev() for dying netns.
  ipv6: Batch rt6_uncached_list_flush_dev() for dying netns.

 include/net/net_namespace.h | 11 +++++++-
 net/core/net_namespace.c    | 13 +++++++--
 net/ipv4/fib_frontend.c     |  6 +++++
 net/ipv4/route.c            | 28 +++++++++++++++----
 net/ipv6/route.c            | 54 ++++++++++++++++++++++++++-----------
 5 files changed, 89 insertions(+), 23 deletions(-)

-- 
2.56.0.rc1.315.gc6ed9934b7-goog