Merge branch 'net-prevent-rps-table-overwrite-of-active-flows'

Krishna Kumar says:

====================
net: Prevent RPS table overwrite of active flows

This series splits the original RPS patch [1] into two patches for
net-next. It also addresses a kernel test robot warning by defining
rps_flow_is_active() only when aRFS is enabled. I tested v3 with
four builds and reboots: two for [PATCH 1/2] with aRFS enabled &
disabled, and two for [PATCH 2/2]. There are no code changes in v4
and v5, only documentation. Patch v6 has one line change to keep
'hash' field under #ifdef, and was test built with aRFS=on and
aRFS=off. The same two builds were done for v7, along with 15m load
testing with aRFS=on to ensure the new changes are correct.

The first patch prevents RPS table overwrite for active flows thereby
improving aRFS stability.

The second patch caches hash & flow_id in get_rps_cpu() to avoid
recalculating it in set_rps_cpu().

[1] lore.kernel.org/netdev/20250708081516.53048-1-krikku@gmail.com/
[2] lore.kernel.org/netdev/20250729104109.1687418-1-krikku@gmail.com/
====================

Link: https://patch.msgid.link/20250825031005.3674864-1-krikku@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>