[PATCH net-next v8 0/3] net/sched: sch_fq_pie: add per-flow class statistics

["Hemendra M. Naik" <hemendranaik@gmail.com>]

FQ-PIE runs an independent PIE controller per flow but exposes no
per-flow statistics. This series wires up fq_pie_class_ops to expose
per-flow AQM state (prob, delay, deficit, avg_dq_rate) via
'tc -s class show', following a similar pattern as FQ-CoDel.

This patch series is accompanied by a companion iproute2 patch series that
will be posted on net-next as well.

Both the kernel and iproute2 patches can also be found in GitHub:
- https://github.com/H-N41K/linux-net-next/tree/fq_pie_class_stats/
- https://github.com/H-N41K/iproute2-next/tree/fq_pie_class_stats

---
Changelog:
v8:
- No code changes since v7.
- Reword commit message to reflect usage of div_u64().

v7: https://lore.kernel.org/netdev/20260919060125.38063-1-hemendranaik@gmail.com/
- No code changes since v6.
- Rebased over the latest net-next tree and re-submitted patch.

v6: https://lore.kernel.org/netdev/20260917204225.275251-1-hemendranaik@gmail.com/
- Address Sashiko review comments:
  - Revert the fq_pie flows range to [1..65536]. 
  - Also drop the accompanying selftest 83be change.
  - Compute the per-flow delay with div_u64() on the full 64-bit
    nanosecond value.
  - Widen avg_dq_rate to u64 before scaling it by PSCHED_TICKS_PER_SEC.
  - Document the 36 to 64 byte xstats growth in the patch 1 commit message.
  - Fix selftest 83c0. The ping payload exceeded the TBF burst so no
    packet ever reached fq_pie, and the missing -W left the run waiting
    out ping's default timeout.

v5: https://lore.kernel.org/netdev/20260902035231.81866-1-hemendranaik@gmail.com/
- Addressed Sashiko review comments:
 - Omitted .tcf_block / .bind_tcf / .unbind_tcf from cl_ops (statistics
   only being exported; filter attach to fq_pie is now disabled).
 - Dropped empty tc_fq_pie_xqd_stats placeholder; class_stats is a direct
   struct member.
 - Limited flows to [1..65535] so per-flow class handles fit in a 16-bit
   TC minor.
 - Rewrote selftest 83c0 with TBF + fq_pie, ping traffic, and
   matchCount 1 on per-flow stats output.
 - Updated selftest 83be for the new flows limit.
 - Dropped the tools/include UAPI mirror changes from patch 3/3.

v4: https://lore.kernel.org/netdev/20260727164056.106203-1-hemendranaik@gmail.com/
- Fixed unaligned commit message; moved typo fixes to another patch.

v3: https://lore.kernel.org/netdev/20260630183702.170798-1-hemendranaik@gmail.com/
- No changes since v2.
- Resent after the previous submission was deferred due to the
  net-next tree closing during review.
- Updated corresponding iproute2 patch in response to review comments;
  kernel patches unchanged.

v2: https://lore.kernel.org/netdev/20260614125000.6058-1-hemendranaik@gmail.com/
- Addressed ABI backward compatibility issue for tc_fq_pie_xstats.

v1: https://lore.kernel.org/netdev/20260531125314.22492-1-hemendranaik@gmail.com/
- Initial submission

Hemendra M. Naik (3):
  net/sched: sch_fq_pie: add per-flow statistics via class ops
  selftests: tc-testing: add fq_pie per-flow class stats test
  net/sched: pie: correct tc_pie_xstats field documentation

 include/uapi/linux/pkt_sched.h                | 20 ++++-
 net/sched/sch_fq_pie.c                        | 86 ++++++++++++++++++-
 .../tc-testing/tc-tests/qdiscs/fq_pie.json    | 27 ++++++
 3 files changed, 130 insertions(+), 3 deletions(-)

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2.34.1