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>

5 files changed, 34 insertions, 48 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 121cbad0aae5..a44118b1b56c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -832,6 +832,9 @@ struct net_device
         /* Number of TX queues currently active in device  */
         unsigned int            real_num_tx_queues;
 
+        /* root qdisc from userspace point of view */
+        struct Qdisc            *qdisc;
+
         unsigned long           tx_queue_len;   /* Max frames per queue allowed */
         spinlock_t              tx_global_lock;
 /*
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index bbcba2a41018..eb42873f2a3a 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -606,7 +606,6 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
                             int type, u32 pid, u32 seq, u32 change,
                             unsigned int flags)
 {
-        struct netdev_queue *txq;
         struct ifinfomsg *ifm;
         struct nlmsghdr *nlh;
         const struct net_device_stats *stats;
@@ -637,9 +636,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
         if (dev->master)
                 NLA_PUT_U32(skb, IFLA_MASTER, dev->master->ifindex);
 
-        txq = netdev_get_tx_queue(dev, 0);
-        if (txq->qdisc_sleeping)
-                NLA_PUT_STRING(skb, IFLA_QDISC, txq->qdisc_sleeping->ops->id);
+        if (dev->qdisc)
+                NLA_PUT_STRING(skb, IFLA_QDISC, dev->qdisc->ops->id);
 
         if (dev->ifalias)
                 NLA_PUT_STRING(skb, IFLA_IFALIAS, dev->ifalias);
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index bcfbdb4758c9..6a536949cdc0 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -168,8 +168,7 @@ replay:
 
         /* Find qdisc */
         if (!parent) {
-                struct netdev_queue *dev_queue = netdev_get_tx_queue(dev, 0);
-                q = dev_queue->qdisc_sleeping;
+                q = dev->qdisc;
                 parent = q->handle;
         } else {
                 q = qdisc_lookup(dev, TC_H_MAJ(t->tcm_parent));
@@ -408,7 +407,6 @@ static int tcf_node_dump(struct tcf_proto *tp, unsigned long n,
 static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
 {
         struct net *net = sock_net(skb->sk);
-        struct netdev_queue *dev_queue;
         int t;
         int s_t;
         struct net_device *dev;
@@ -427,9 +425,8 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
         if ((dev = dev_get_by_index(&init_net, tcm->tcm_ifindex)) == NULL)
                 return skb->len;
 
-        dev_queue = netdev_get_tx_queue(dev, 0);
         if (!tcm->tcm_parent)
-                q = dev_queue->qdisc_sleeping;
+                q = dev->qdisc;
         else
                 q = qdisc_lookup(dev, TC_H_MAJ(tcm->tcm_parent));
         if (!q)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 166fcca86e7a..8aa9a0c5a9eb 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -207,7 +207,7 @@ static struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle)
 static void qdisc_list_add(struct Qdisc *q)
 {
         if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS))
-                list_add_tail(&q->list, &qdisc_root_sleeping(q)->list);
+                list_add_tail(&q->list, &qdisc_dev(q)->qdisc->list);
 }
 
 void qdisc_list_del(struct Qdisc *q)
@@ -219,17 +219,11 @@ EXPORT_SYMBOL(qdisc_list_del);
 
 struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle)
 {
-        unsigned int i;
         struct Qdisc *q;
 
-        for (i = 0; i < dev->num_tx_queues; i++) {
-                struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
-                struct Qdisc *txq_root = txq->qdisc_sleeping;
-
-                q = qdisc_match_from_root(txq_root, handle);
-                if (q)
-                        goto out;
-        }
+        q = qdisc_match_from_root(dev->qdisc, handle);
+        if (q)
+                goto out;
 
         q = qdisc_match_from_root(dev->rx_queue.qdisc_sleeping, handle);
 out:
@@ -720,9 +714,14 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
                         if (new && i > 0)
                                 atomic_inc(&new->refcnt);
 
-                        notify_and_destroy(skb, n, classid, old, new);
+                        qdisc_destroy(old);
                 }
 
+                notify_and_destroy(skb, n, classid, dev->qdisc, new);
+                if (new)
+                        atomic_inc(&new->refcnt);
+                dev->qdisc = new ? : &noop_qdisc;
+
                 if (dev->flags & IFF_UP)
                         dev_activate(dev);
         } else {
@@ -974,9 +973,7 @@ static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
                                 q = dev->rx_queue.qdisc_sleeping;
                         }
                 } else {
-                        struct netdev_queue *dev_queue;
-                        dev_queue = netdev_get_tx_queue(dev, 0);
-                        q = dev_queue->qdisc_sleeping;
+                        q = dev->qdisc;
                 }
                 if (!q)
                         return -ENOENT;
@@ -1044,9 +1041,7 @@ replay:
                                 q = dev->rx_queue.qdisc_sleeping;
                         }
                 } else {
-                        struct netdev_queue *dev_queue;
-                        dev_queue = netdev_get_tx_queue(dev, 0);
-                        q = dev_queue->qdisc_sleeping;
+                        q = dev->qdisc;
                 }
 
                 /* It may be default qdisc, ignore it */
@@ -1291,8 +1286,7 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
                         s_q_idx = 0;
                 q_idx = 0;
 
-                dev_queue = netdev_get_tx_queue(dev, 0);
-                if (tc_dump_qdisc_root(dev_queue->qdisc_sleeping, skb, cb, &q_idx, s_q_idx) < 0)
+                if (tc_dump_qdisc_root(dev->qdisc, skb, cb, &q_idx, s_q_idx) < 0)
                         goto done;
 
                 dev_queue = &dev->rx_queue;
@@ -1323,7 +1317,6 @@ done:
 static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
 {
         struct net *net = sock_net(skb->sk);
-        struct netdev_queue *dev_queue;
         struct tcmsg *tcm = NLMSG_DATA(n);
         struct nlattr *tca[TCA_MAX + 1];
         struct net_device *dev;
@@ -1361,7 +1354,6 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
 
         /* Step 1. Determine qdisc handle X:0 */
 
-        dev_queue = netdev_get_tx_queue(dev, 0);
         if (pid != TC_H_ROOT) {
                 u32 qid1 = TC_H_MAJ(pid);
 
@@ -1372,7 +1364,7 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
                 } else if (qid1) {
                         qid = qid1;
                 } else if (qid == 0)
-                        qid = dev_queue->qdisc_sleeping->handle;
+                        qid = dev->qdisc->handle;
 
                 /* Now qid is genuine qdisc handle consistent
                    both with parent and child.
@@ -1383,7 +1375,7 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
                         pid = TC_H_MAKE(qid, pid);
         } else {
                 if (qid == 0)
-                        qid = dev_queue->qdisc_sleeping->handle;
+                        qid = dev->qdisc->handle;
         }
 
         /* OK. Locate qdisc */
@@ -1588,8 +1580,7 @@ static int tc_dump_tclass(struct sk_buff *skb, struct netlink_callback *cb)
         s_t = cb->args[0];
         t = 0;
 
-        dev_queue = netdev_get_tx_queue(dev, 0);
-        if (tc_dump_tclass_root(dev_queue->qdisc_sleeping, skb, tcm, cb, &t, s_t) < 0)
+        if (tc_dump_tclass_root(dev->qdisc, skb, tcm, cb, &t, s_t) < 0)
                 goto done;
 
         dev_queue = &dev->rx_queue;
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));
 }