linux-kernel - [PATCH net-next 0/5] Improve the taprio qdisc's relationship with its children

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Date:   Wed, 31 May 2023 20:39:23 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        linux-kernel@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
        Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@...el.com>,
        Peilin Ye <yepeilin.cs@...il.com>,
        Pedro Tammela <pctammela@...atatu.com>
Subject: [PATCH net-next 0/5] Improve the taprio qdisc's relationship with its children

Prompted by Vinicius' request to consolidate some child Qdisc
dereferences in taprio:
https://lore.kernel.org/netdev/87edmxv7x2.fsf@intel.com/

I remembered that I had left some unfinished work in this Qdisc, namely
commit af7b29b1deaa ("Revert "net/sched: taprio: make qdisc_leaf() see
the per-netdev-queue pfifo child qdiscs"").

This patch set represents another stab at, essentially, what's in the
title. Not only does taprio not properly detect when it's grafted as a
non-root qdisc, but it also returns incorrect per-class stats.
Eventually, Vinicius' request is addressed too, although in a different
form than the one he requested (which was purely cosmetic).

Review from people more experienced with Qdiscs than me would be
appreciated. I tried my best to explain what I consider to be problems.
I am deliberately targeting net-next because the changes are too
invasive for net - they were reverted from stable once already.

Vladimir Oltean (5):
  net/sched: taprio: don't access q->qdiscs[] in unoffloaded mode during
    attach()
  net/sched: taprio: keep child Qdisc refcount elevated at 2 in offload
    mode
  net/sched: taprio: try again to report q->qdiscs[] to qdisc_leaf()
  net/sched: taprio: delete misleading comment about preallocating child
    qdiscs
  net/sched: taprio: dump class stats for the actual q->qdiscs[]

 net/sched/sch_taprio.c | 60 ++++++++++++++++++++++++------------------
 1 file changed, 35 insertions(+), 25 deletions(-)

-- 
2.34.1