netdev - [net-next v2 3/6] net/sched: Add select_queue() class

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Message-Id: <20171027165706.85527-4-jeffrey.t.kirsher@intel.com>
Date:   Fri, 27 Oct 2017 09:57:03 -0700
From:   Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:     davem@...emloft.net
Cc:     Jesus Sanchez-Palencia <jesus.sanchez-palencia@...el.com>,
        netdev@...r.kernel.org, nhorman@...hat.com, sassmann@...hat.com,
        jogreene@...hat.com, Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: [net-next v2 3/6] net/sched: Add select_queue() class_ops for mqprio

From: Jesus Sanchez-Palencia <jesus.sanchez-palencia@...el.com>

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@...el.com>
Tested-by: Henrik Austad <henrik@...tad.us>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
---
 net/sched/sch_mqprio.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
index 51c2b289c69b..4d5ed45123f0 100644
--- 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 = {
-- 
2.14.2