From: Jesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Date: Mon, 16 Oct 2017 18:01:25 -0700
Subject: net/sched: Add select_queue() class_ops for mqprio
Patch-mainline: v4.15-rc1
Git-commit: 0f7787b4133fb26b6dc0779e4867408e07711d8e
References: bsc#1109837

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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/sched/sch_mqprio.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/net/sched/sch_mqprio.c
+++ b/net/sched/sch_mqprio.c
@@ -575,6 +575,12 @@ static void mqprio_walk(struct Qdisc *sc
 	}
 }
 
+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 mqpr
 	.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 = {