On Mon, Jun 29, 2026 at 06:10:52PM +0000, Kuniyuki Iwashima wrote:

RTM_NEWRULE and RTM_DELRULE acquire rtnl_net_lock(), but this is
only for fib_unmerge() in IPv4.

Since commit d954a67a7dfa ("ipv4: fib_rule: Move fib4_rules_exit()
to ->exit()."), RTM_DELRULE no longer needs RTNL.

fib_unmerge() is one-time event for each netns, so we only need
RTNL for the first IPv4 rule.

This series introduces per-fib_rules_ops mutex and drops RTNL
from fib_rules code except for the first IPv4 RTM_NEWRULE.

LGTM, thanks:

Reviewed-by: Ido Schimmel <idosch@nvidia.com>

A few nits that can be addressed in a follow-up:

1. Patch #3:

The comment at the top of netns_ipv4 suggests that we should document
the new lock in
Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst

Related: Did you consider moving this lock under
CONFIG_IP_MULTIPLE_TABLES?

2. Patch #5:

Sashiko suggests a mutex_destroy() in fib_rules_unregister():

https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260629181226.1929658-1-kuniyu%40google.com?part=5