net_sched: add classful multiqueue dummy scheduler

This patch adds a classful dummy scheduler which can be used as root qdisc
for multiqueue devices and exposes each device queue as a child class.

This allows to address queues individually and graft them similar to regular
classes. Additionally it presents an accumulated view of the statistics of
all real root qdiscs in the dummy root.

Two new callbacks are added to the qdisc_ops and qdisc_class_ops:

- cl_ops->select_queue selects the tx queue number for new child classes.

- qdisc_ops->attach() overrides root qdisc device grafting to attach
  non-shared qdiscs to the queues.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 23 insertions, 9 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index e7c47ceb0098..4ae6aa562f2b 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -514,7 +514,7 @@ static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
         return 0;
 }
 
-static struct Qdisc_ops pfifo_fast_ops __read_mostly = {
+struct Qdisc_ops pfifo_fast_ops __read_mostly = {
         .id             =       "pfifo_fast",
         .priv_size      =       sizeof(struct pfifo_fast_priv),
         .enqueue        =       pfifo_fast_enqueue,
@@ -670,6 +670,26 @@ static void attach_one_default_qdisc(struct net_device *dev,
         dev_queue->qdisc_sleeping = qdisc;
 }
 
+static void attach_default_qdiscs(struct net_device *dev)
+{
+        struct netdev_queue *txq;
+        struct Qdisc *qdisc;
+
+        txq = netdev_get_tx_queue(dev, 0);
+
+        if (!netif_is_multiqueue(dev) || dev->tx_queue_len == 0) {
+                netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
+                dev->qdisc = txq->qdisc_sleeping;
+                atomic_inc(&dev->qdisc->refcnt);
+        } else {
+                qdisc = qdisc_create_dflt(dev, txq, &mq_qdisc_ops, TC_H_ROOT);
+                if (qdisc) {
+                        qdisc->ops->attach(qdisc);
+                        dev->qdisc = qdisc;
+                }
+        }
+}
+
 static void transition_one_qdisc(struct net_device *dev,
                                  struct netdev_queue *dev_queue,
                                  void *_need_watchdog)
@@ -689,7 +709,6 @@ static void transition_one_qdisc(struct net_device *dev,
 
 void dev_activate(struct net_device *dev)
 {
-        struct netdev_queue *txq;
         int need_watchdog;
 
         /* No queueing discipline is attached to device;
@@ -698,13 +717,8 @@ void dev_activate(struct net_device *dev)
            virtual interfaces
          */
 
-        if (dev->qdisc == &noop_qdisc) {
-                netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
-
-                txq = netdev_get_tx_queue(dev, 0);
-                dev->qdisc = txq->qdisc_sleeping;
-                atomic_inc(&dev->qdisc->refcnt);
-        }
+        if (dev->qdisc == &noop_qdisc)
+                attach_default_qdiscs(dev);
 
         if (!netif_carrier_ok(dev))
                 /* Delay activation until next carrier-on event */