net/sched: Add select_queue() class_ops for mqprio

When replacing a child qdisc from mqprio, tc_modify_qdisc() must fetch
the netdev_queue pointer that the current child qdisc is associated
with before creating the new qdisc.

Currently, when using mqprio as root qdisc, the kernel will end up
getting the queue #0 pointer from the mqprio (root qdisc), which leaves
any new child qdisc with a possibly wrong netdev_queue pointer.

Implementing the Qdisc_class_ops select_queue() on mqprio fixes this
issue and avoid an inconsistent state when child qdiscs are replaced.

Signed-off-by: Jesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Tested-by: Henrik Austad <henrik@austad.us>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
index 51c2b289c69b87e83a8cc80de448b8d968a56d64..4d5ed45123f033d865f56f0217dde763fff136bb 100644 (file)
--- a/net/sched/sch_mqprio.c
+++ b/net/sched/sch_mqprio.c
@@ -575,6 +575,12 @@ static void mqprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
        }
 }
 
+static struct netdev_queue *mqprio_select_queue(struct Qdisc *sch,
+                                               struct tcmsg *tcm)
+{
+       return mqprio_queue_get(sch, TC_H_MIN(tcm->tcm_parent));
+}
+
 static const struct Qdisc_class_ops mqprio_class_ops = {
        .graft          = mqprio_graft,
        .leaf           = mqprio_leaf,
@@ -582,6 +588,7 @@ static const struct Qdisc_class_ops mqprio_class_ops = {
        .walk           = mqprio_walk,
        .dump           = mqprio_dump_class,
        .dump_stats     = mqprio_dump_class_stats,
+       .select_queue   = mqprio_select_queue,
 };
 
 static struct Qdisc_ops mqprio_qdisc_ops __read_mostly = {