Revert "pkt_sched: Make default qdisc nonshared-multiqueue safe."

This reverts commit a0c80b80e0fb48129e4e9d6a9ede914f9ff1850d.

After discussions with Jamal and Herbert on netdev, we should
provide at least minimal prioritization at the qdisc level
even in multiqueue situations.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 77 insertions, 22 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 09dead335805..cb625b4d6da5 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -356,44 +356,99 @@ static struct Qdisc noqueue_qdisc = {
 };
 
 
-static int fifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
+static const u8 prio2band[TC_PRIO_MAX+1] =
+        { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
+
+/* 3-band FIFO queue: old style, but should be a bit faster than
+   generic prio+fifo combination.
+ */
+
+#define PFIFO_FAST_BANDS 3
+
+static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
+                                             struct Qdisc *qdisc)
+{
+        struct sk_buff_head *list = qdisc_priv(qdisc);
+        return list + prio2band[skb->priority & TC_PRIO_MAX];
+}
+
+static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
 {
-        struct sk_buff_head *list = &qdisc->q;
+        struct sk_buff_head *list = prio2list(skb, qdisc);
 
-        if (skb_queue_len(list) < qdisc_dev(qdisc)->tx_queue_len)
+        if (skb_queue_len(list) < qdisc_dev(qdisc)->tx_queue_len) {
+                qdisc->q.qlen++;
                 return __qdisc_enqueue_tail(skb, qdisc, list);
+        }
 
         return qdisc_drop(skb, qdisc);
 }
 
-static struct sk_buff *fifo_fast_dequeue(struct Qdisc* qdisc)
+static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
 {
-        struct sk_buff_head *list = &qdisc->q;
+        int prio;
+        struct sk_buff_head *list = qdisc_priv(qdisc);
 
-        if (!skb_queue_empty(list))
-                return __qdisc_dequeue_head(qdisc, list);
+        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
+                if (!skb_queue_empty(list + prio)) {
+                        qdisc->q.qlen--;
+                        return __qdisc_dequeue_head(qdisc, list + prio);
+                }
+        }
 
         return NULL;
 }
 
-static int fifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
+static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
 {
-        return __qdisc_requeue(skb, qdisc, &qdisc->q);
+        qdisc->q.qlen++;
+        return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
 }
 
-static void fifo_fast_reset(struct Qdisc* qdisc)
+static void pfifo_fast_reset(struct Qdisc* qdisc)
 {
-        __qdisc_reset_queue(qdisc, &qdisc->q);
+        int prio;
+        struct sk_buff_head *list = qdisc_priv(qdisc);
+
+        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
+                __qdisc_reset_queue(qdisc, list + prio);
+
         qdisc->qstats.backlog = 0;
+        qdisc->q.qlen = 0;
 }
 
-static struct Qdisc_ops fifo_fast_ops __read_mostly = {
-        .id             =       "fifo_fast",
-        .priv_size      =       0,
-        .enqueue        =       fifo_fast_enqueue,
-        .dequeue        =       fifo_fast_dequeue,
-        .requeue        =       fifo_fast_requeue,
-        .reset          =       fifo_fast_reset,
+static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
+{
+        struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
+
+        memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
+        NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
+        return skb->len;
+
+nla_put_failure:
+        return -1;
+}
+
+static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
+{
+        int prio;
+        struct sk_buff_head *list = qdisc_priv(qdisc);
+
+        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
+                skb_queue_head_init(list + prio);
+
+        return 0;
+}
+
+static struct Qdisc_ops pfifo_fast_ops __read_mostly = {
+        .id             =       "pfifo_fast",
+        .priv_size      =       PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
+        .enqueue        =       pfifo_fast_enqueue,
+        .dequeue        =       pfifo_fast_dequeue,
+        .requeue        =       pfifo_fast_requeue,
+        .init           =       pfifo_fast_init,
+        .reset          =       pfifo_fast_reset,
+        .dump           =       pfifo_fast_dump,
         .owner          =       THIS_MODULE,
 };
 
@@ -522,7 +577,7 @@ static void attach_one_default_qdisc(struct net_device *dev,
 
         if (dev->tx_queue_len) {
                 qdisc = qdisc_create_dflt(dev, dev_queue,
-                                          &fifo_fast_ops, TC_H_ROOT);
+                                          &pfifo_fast_ops, TC_H_ROOT);
                 if (!qdisc) {
                         printk(KERN_INFO "%s: activation failed\n", dev->name);
                         return;
@@ -550,9 +605,9 @@ void dev_activate(struct net_device *dev)
         int need_watchdog;
 
         /* No queueing discipline is attached to device;
-         * create default one i.e. fifo_fast for devices,
-         * which need queueing and noqueue_qdisc for
-         * virtual interfaces.
+           create default one i.e. pfifo_fast for devices,
+           which need queueing and noqueue_qdisc for
+           virtual interfaces
          */
 
         if (dev_all_qdisc_sleeping_noop(dev))