net_sched: reintroduce dev->qdisc for use by sch_api

Currently the multiqueue integration with the qdisc API suffers from
a few problems:

- with multiple queues, all root qdiscs use the same handle. This means
  they can't be exposed to userspace in a backwards compatible fashion.

- all API operations always refer to queue number 0. Newly created
  qdiscs are automatically shared between all queues, its not possible
  to address individual queues or restore multiqueue behaviour once a
  shared qdisc has been attached.

- Dumps only contain the root qdisc of queue 0, in case of non-shared
  qdiscs this means the statistics are incomplete.

This patch reintroduces dev->qdisc, which points to the (single) root qdisc
from userspace's point of view. Currently it either points to the first
(non-shared) default qdisc, or a qdisc shared between all queues. The
following patches will introduce a classful dummy qdisc, which will be used
as root qdisc and contain the per-queue qdiscs as children.

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

1 files changed, 11 insertions, 14 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 6128e6f24589..a91f079fb47a 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -623,19 +623,6 @@ void qdisc_destroy(struct Qdisc *qdisc)
 }
 EXPORT_SYMBOL(qdisc_destroy);
 
-static bool dev_all_qdisc_sleeping_noop(struct net_device *dev)
-{
-        unsigned int i;
-
-        for (i = 0; i < dev->num_tx_queues; i++) {
-                struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
-
-                if (txq->qdisc_sleeping != &noop_qdisc)
-                        return false;
-        }
-        return true;
-}
-
 static void attach_one_default_qdisc(struct net_device *dev,
                                      struct netdev_queue *dev_queue,
                                      void *_unused)
@@ -677,6 +664,7 @@ 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;
@@ -685,9 +673,14 @@ void dev_activate(struct net_device *dev)
            virtual interfaces
          */
 
-        if (dev_all_qdisc_sleeping_noop(dev))
+        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 (!netif_carrier_ok(dev))
                 /* Delay activation until next carrier-on event */
                 return;
@@ -777,6 +770,7 @@ static void dev_init_scheduler_queue(struct net_device *dev,
 
 void dev_init_scheduler(struct net_device *dev)
 {
+        dev->qdisc = &noop_qdisc;
         netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
         dev_init_scheduler_queue(dev, &dev->rx_queue, &noop_qdisc);
 
@@ -802,5 +796,8 @@ void dev_shutdown(struct net_device *dev)
 {
         netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
         shutdown_scheduler_queue(dev, &dev->rx_queue, &noop_qdisc);
+        qdisc_destroy(dev->qdisc);
+        dev->qdisc = &noop_qdisc;
+
         WARN_ON(timer_pending(&dev->watchdog_timer));
 }