pkt_sched: Fix tx queue selection in tc_modify_qdisc

After the recent mq change there is the new select_queue qdisc class
method used in tc_modify_qdisc, but it works OK only for direct child
qdiscs of mq qdisc. Grandchildren always get the first tx queue, which
would give wrong qdisc_root etc. results (e.g. for sch_htb as child of
sch_prio). This patch fixes it by using parent's dev_queue for such
grandchildren qdiscs. The select_queue method's return type is changed
BTW.

With feedback from: Patrick McHardy <kaber@trash.net>

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 16 insertions, 7 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index c6e4063f698c..1367aa21fad5 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1116,12 +1116,16 @@ create_n_graft:
                                  tcm->tcm_parent, tcm->tcm_parent,
                                  tca, &err);
         else {
-                unsigned int ntx = 0;
+                struct netdev_queue *dev_queue;
 
                 if (p && p->ops->cl_ops && p->ops->cl_ops->select_queue)
-                        ntx = p->ops->cl_ops->select_queue(p, tcm);
+                        dev_queue = p->ops->cl_ops->select_queue(p, tcm);
+                else if (p)
+                        dev_queue = p->dev_queue;
+                else
+                        dev_queue = netdev_get_tx_queue(dev, 0);
 
-                q = qdisc_create(dev, netdev_get_tx_queue(dev, ntx), p,
+                q = qdisc_create(dev, dev_queue, p,
                                  tcm->tcm_parent, tcm->tcm_handle,
                                  tca, &err);
         }
diff --git a/net/sched/sch_mq.c b/net/sched/sch_mq.c
index dd5ee022f1f7..600c50143cc7 100644
--- a/net/sched/sch_mq.c
+++ b/net/sched/sch_mq.c
@@ -125,13 +125,18 @@ static struct netdev_queue *mq_queue_get(struct Qdisc *sch, unsigned long cl)
         return netdev_get_tx_queue(dev, ntx);
 }
 
-static unsigned int mq_select_queue(struct Qdisc *sch, struct tcmsg *tcm)
+static struct netdev_queue *mq_select_queue(struct Qdisc *sch,
+                                            struct tcmsg *tcm)
 {
         unsigned int ntx = TC_H_MIN(tcm->tcm_parent);
+        struct netdev_queue *dev_queue = mq_queue_get(sch, ntx);
 
-        if (!mq_queue_get(sch, ntx))
-                return 0;
-        return ntx - 1;
+        if (!dev_queue) {
+                struct net_device *dev = qdisc_dev(sch);
+
+                return netdev_get_tx_queue(dev, 0);
+        }
+        return dev_queue;
 }
 
 static int mq_graft(struct Qdisc *sch, unsigned long cl, struct Qdisc *new,