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Christoph PaaschandGreg Kroah-Hartman
c1d2b289b9
[ Upstream commitb0ac6d3b56] When removing a nexthop, commit90f33bffa3("nexthops: don't modify published nexthop groups") added a call to synchronize_rcu() (later changed to _net()) to make sure everyone sees the new nexthop-group before the rtnl-lock is released. When one wants to delete a large number of groups and nexthops, it is fastest to first flush the groups (ip nexthop flush groups) and then flush the nexthops themselves (ip -6 nexthop flush). As that way the groups don't need to be rebalanced. However, `ip -6 nexthop flush` will still take a long time if there is a very large number of nexthops because of the call to synchronize_net(). Now, if there are no more groups, there is no point in calling synchronize_net(). So, let's skip that entirely by checking if nh->grp_list is empty. This gives us a nice speedup: BEFORE: ======= $ time sudo ip -6 nexthop flush Dump was interrupted and may be inconsistent. Flushed 2097152 nexthops real 1m45.345s user 0m0.001s sys 0m0.005s $ time sudo ip -6 nexthop flush Dump was interrupted and may be inconsistent. Flushed 4194304 nexthops real 3m10.430s user 0m0.002s sys 0m0.004s AFTER: ====== $ time sudo ip -6 nexthop flush Dump was interrupted and may be inconsistent. Flushed 2097152 nexthops real 0m17.545s user 0m0.003s sys 0m0.003s $ time sudo ip -6 nexthop flush Dump was interrupted and may be inconsistent. Flushed 4194304 nexthops real 0m35.823s user 0m0.002s sys 0m0.004s Signed-off-by: Christoph Paasch <cpaasch@openai.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Reviewed-by: David Ahern <dsahern@kernel.org> Link: https://patch.msgid.link/20250816-nexthop_dump-v2-2-491da3462118@openai.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>