net/sched: taprio: try again to report q->qdiscs[] to qdisc_leaf()

This is another stab at commit 1461d212ab27 ("net/sched: taprio: make
qdisc_leaf() see the per-netdev-queue pfifo child qdiscs"), later
reverted in commit af7b29b1deaa ("Revert "net/sched: taprio: make
qdisc_leaf() see the per-netdev-queue pfifo child qdiscs"").

I believe that the problems that caused the revert were fixed, and thus,
this change is identical to the original patch.

Its purpose is to properly reject attaching a software taprio child
qdisc to a software taprio parent. Because unoffloaded taprio currently
reports itself (the root Qdisc) as the return value from qdisc_leaf(),
then the process of attaching another taprio as child to a Qdisc class
of the root will just result in a Qdisc_ops :: change() call for the
root. Whereas that's not we want. We want Qdisc_ops :: init() to be
called for the taprio child, in order to give the taprio child a chance
to check whether its sch->parent is TC_H_ROOT or not (and reject this
configuration).

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20230807193324.4128292-4-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 7c1fc3dc3e55f7b40a13579655c45bc230541990..831e6f3fda2a06c5e37241c44e9cea73b223ab9d 100644 (file)
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -2453,12 +2453,14 @@ static int taprio_dump(struct Qdisc *sch, struct sk_buff *skb)
 
 static struct Qdisc *taprio_leaf(struct Qdisc *sch, unsigned long cl)
 {
-       struct netdev_queue *dev_queue = taprio_queue_get(sch, cl);
+       struct taprio_sched *q = qdisc_priv(sch);
+       struct net_device *dev = qdisc_dev(sch);
+       unsigned int ntx = cl - 1;
 
-       if (!dev_queue)
+       if (ntx >= dev->num_tx_queues)
                return NULL;
 
-       return rtnl_dereference(dev_queue->qdisc_sleeping);
+       return q->qdiscs[ntx];
 }
 
 static unsigned long taprio_find(struct Qdisc *sch, u32 classid)