RFC remove qdisc lock from ingress_qdisc

This series drops the qdisc lock that is currently protecting the ingress qdisc. This can be done after the tcf filters are made lockless and the statistic accounting is safe to run without locks.

To do this the classifiers are converted to use RCU. This requires updating each classifier individually to handle the new copy/update requirement and also to update the core list traversals. This is done in patches 2-11. This also makes the assumption that updates to the tables are infrequent in comparison to the packet per second being classified. On a 10Gbps running near line rate we can easily produce 12+ million packets per second so IMO this is a reasonable assumption. And the updates are serialized by RTNL.

In order to have working statistics patch 13 and 14 convert the bstats and qstats, which do accounting for bytes and packets, into percpu variables and the u64_stats_update_{begin|end} infrastructure is used to maintain consistent 64bit statistics. Because these statistics are also used by the estimators those function calls had to be udpated as well. So that I didn't have to modify all qdiscs at this time many of which don't have an easy path to make lockless the percpu statistics are only used when the TCQ_F_LLQDISC flag is set. Its worth noting that in the mq and mqprio case sub-qdisc's are already mapped 1:1 with TX queues which tend to be equal to the number of CPUs in the system so its not clear that removing locking in these cases would provide any benefit. Most likely a new qdisc written from scratch would be needed to implement a mq-htb or mq-tbf qdisc.

As for some history I wrote what was basically these patches some time ago and then got stalled working on other things. Cong Wang made a proposal to remove the locking around the ingress qdisc which then kicked me to get these patches working again.

I have done some basic testing on this series and do no see any immediate splats or issues. I will continue doing some more testing for the rest of the week before submitting without the RCU tag but any feedback would be good. If someone has a better idea for the percpu union of gnet_stats_basic_* in struct Qdisc or finds it paticularly ugly that would be good to know. At this point I believe the patch set is complete.

My test cases at this point cover all the filters with a tight loop to add/remove filters. Some basic estimator tests where I add an estimator to the qdisc and verify the statistics accurate using pktgen. And finally I have a small script to exercise the 'tc actions' interface. Feel free to send me more tests off list and I can run them.

Performance numbers TBD (working on this).

Also there are still a few checkpatch warnings I need to resolve.

Future work:
- provide metadata such as current cpu for the classifier to match on. this would allow for a multiqueue ingress qdisc strategy.
- provide filter hook on egress before queue is selected to allow a classifier/action to pick the tx queue. This generalizes mqprio and should remove the need for many drivers to implement select_queue() callbacks.
- create a variant of tbf that does not require the qdisc lock using eventually consistent counters.

---

John Fastabend (15):
net: qdisc: use rcu prefix and silence sparse warnings
net: rcu-ify tcf_proto
net: sched: cls_basic use RCU
net: sched: cls_cgroup use RCU
net: sched: cls_flow use RCU
net: sched: fw use RCU
net: sched: RCU cls_route
net: sched: RCU cls_tcindex
net: sched: make cls_u32 lockless
net: sched: rcu'ify cls_rsvp
net: make cls_bpf rcu safe
net: sched: make tc_action safe to walk under RCU
net: sched: make bstats per cpu and estimator RCU safe
net: sched: make qstats per cpu
net: sched: drop ingress qdisc lock

 include/linux/netdevice.h  |   29 +----
 include/linux/rtnetlink.h  |   10 ++
 include/net/act_api.h      |    1 
 include/net/codel.h        |    4 -
 include/net/gen_stats.h    |   17 +++
 include/net/pkt_cls.h      |   12 ++
 include/net/sch_generic.h  |   93 +++++++++++++---
 net/core/dev.c             |   47 +++++++-
 net/core/gen_estimator.c   |   60 ++++++++--
 net/core/gen_stats.c       |   76 +++++++++++++
 net/netfilter/xt_RATEEST.c |    4 -
 net/sched/act_api.c        |   23 ++--
 net/sched/act_police.c     |    4 -
 net/sched/cls_api.c        |   47 ++++----
 net/sched/cls_basic.c      |   80 ++++++++------
 net/sched/cls_bpf.c        |   79 +++++++------
 net/sched/cls_cgroup.c     |   63 +++++++----
 net/sched/cls_flow.c       |  145 ++++++++++++++-----------
 net/sched/cls_fw.c         |  108 +++++++++++++-----
 net/sched/cls_route.c      |  221 ++++++++++++++++++++++----------------
 net/sched/cls_rsvp.h       |  152 +++++++++++++++-----------
 net/sched/cls_tcindex.c    |  240 +++++++++++++++++++++++++----------------
 net/sched/cls_u32.c        |  258 +++++++++++++++++++++++++++++---------------
 net/sched/sch_api.c        |   71 ++++++++++--
 net/sched/sch_atm.c        |   32 +++--
 net/sched/sch_cbq.c        |   40 ++++---
 net/sched/sch_choke.c      |   33 ++++--
 net/sched/sch_codel.c      |    2 
 net/sched/sch_drr.c        |   27 +++--
 net/sched/sch_dsmark.c     |   10 +-
 net/sched/sch_fifo.c       |    6 +
 net/sched/sch_fq.c         |    4 -
 net/sched/sch_fq_codel.c   |   19 ++-
 net/sched/sch_generic.c    |   20 +++
 net/sched/sch_gred.c       |   10 +-
 net/sched/sch_hfsc.c       |   47 +++++---
 net/sched/sch_hhf.c        |    8 +
 net/sched/sch_htb.c        |   45 +++++---
 net/sched/sch_ingress.c    |   20 +++
 net/sched/sch_mq.c         |   31 +++--
 net/sched/sch_mqprio.c     |   54 ++++++---
 net/sched/sch_multiq.c     |   18 ++-
 net/sched/sch_netem.c      |   17 ++-
 net/sched/sch_pie.c        |    8 +
 net/sched/sch_plug.c       |    2 
 net/sched/sch_prio.c       |   21 ++--
 net/sched/sch_qfq.c        |   29 +++--
 net/sched/sch_red.c        |   13 +-
 net/sched/sch_sfb.c        |   28 +++--
 net/sched/sch_sfq.c        |   30 +++--
 net/sched/sch_tbf.c        |   11 +-
 net/sched/sch_teql.c       |    9 +-
 52 files changed, 1552 insertions(+), 886 deletions(-)

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