[SCHED]: Qdisc changes and sch_rr added for multiqueue

Add the new sch_rr qdisc for multiqueue network device support.  Allow
sch_prio and sch_rr to be compiled with or without multiqueue hardware
support.

sch_rr is part of sch_prio, and is referenced from MODULE_ALIAS.  This
was done since sch_prio and sch_rr only differ in their dequeue
routine.

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 134 insertions, 15 deletions

diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
index d10f35338507..268c51599eb8 100644
--- a/include/linux/pkt_sched.h
+++ b/include/linux/pkt_sched.h
@@ -101,6 +101,15 @@ struct tc_prio_qopt
         __u8    priomap[TC_PRIO_MAX+1]; /* Map: logical priority -> PRIO band */
 };
 
+enum
+{
+        TCA_PRIO_UNSPEC,
+        TCA_PRIO_MQ,
+        __TCA_PRIO_MAX
+};
+
+#define TCA_PRIO_MAX    (__TCA_PRIO_MAX - 1)
+
 /* TBF section */
 
 struct tc_tbf_qopt
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index 475df8449be9..f3217942ca87 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -111,6 +111,17 @@ config NET_SCH_PRIO
           To compile this code as a module, choose M here: the
           module will be called sch_prio.
 
+config NET_SCH_RR
+        tristate "Multi Band Round Robin Queuing (RR)"
+        select NET_SCH_PRIO
+        ---help---
+          Say Y here if you want to use an n-band round robin packet
+          scheduler.
+
+          The module uses sch_prio for its framework and is aliased as
+          sch_rr, so it will load sch_prio, although it is referred
+          to using sch_rr.
+
 config NET_SCH_RED
         tristate "Random Early Detection (RED)"
         ---help---
diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
index 6d7542c26e47..404522046289 100644
--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -40,9 +40,11 @@
 struct prio_sched_data
 {
         int bands;
+        int curband; /* for round-robin */
         struct tcf_proto *filter_list;
         u8  prio2band[TC_PRIO_MAX+1];
         struct Qdisc *queues[TCQ_PRIO_BANDS];
+        int mq;
 };
 
 
@@ -70,14 +72,17 @@ prio_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)
 #endif
                         if (TC_H_MAJ(band))
                                 band = 0;
-                        return q->queues[q->prio2band[band&TC_PRIO_MAX]];
+                        band = q->prio2band[band&TC_PRIO_MAX];
+                        goto out;
                 }
                 band = res.classid;
         }
         band = TC_H_MIN(band) - 1;
         if (band >= q->bands)
-                return q->queues[q->prio2band[0]];
-
+                band = q->prio2band[0];
+out:
+        if (q->mq)
+                skb_set_queue_mapping(skb, band);
         return q->queues[band];
 }
 
@@ -144,17 +149,58 @@ prio_dequeue(struct Qdisc* sch)
         struct Qdisc *qdisc;
 
         for (prio = 0; prio < q->bands; prio++) {
-                qdisc = q->queues[prio];
-                skb = qdisc->dequeue(qdisc);
-                if (skb) {
-                        sch->q.qlen--;
-                        return skb;
+                /* Check if the target subqueue is available before
+                 * pulling an skb.  This way we avoid excessive requeues
+                 * for slower queues.
+                 */
+                if (!netif_subqueue_stopped(sch->dev, (q->mq ? prio : 0))) {
+                        qdisc = q->queues[prio];
+                        skb = qdisc->dequeue(qdisc);
+                        if (skb) {
+                                sch->q.qlen--;
+                                return skb;
+                        }
                 }
         }
         return NULL;
 
 }
 
+static struct sk_buff *rr_dequeue(struct Qdisc* sch)
+{
+        struct sk_buff *skb;
+        struct prio_sched_data *q = qdisc_priv(sch);
+        struct Qdisc *qdisc;
+        int bandcount;
+
+        /* Only take one pass through the queues.  If nothing is available,
+         * return nothing.
+         */
+        for (bandcount = 0; bandcount < q->bands; bandcount++) {
+                /* Check if the target subqueue is available before
+                 * pulling an skb.  This way we avoid excessive requeues
+                 * for slower queues.  If the queue is stopped, try the
+                 * next queue.
+                 */
+                if (!netif_subqueue_stopped(sch->dev,
+                                            (q->mq ? q->curband : 0))) {
+                        qdisc = q->queues[q->curband];
+                        skb = qdisc->dequeue(qdisc);
+                        if (skb) {
+                                sch->q.qlen--;
+                                q->curband++;
+                                if (q->curband >= q->bands)
+                                        q->curband = 0;
+                                return skb;
+                        }
+                }
+                q->curband++;
+                if (q->curband >= q->bands)
+                        q->curband = 0;
+        }
+        return NULL;
+}
+
 static unsigned int prio_drop(struct Qdisc* sch)
 {
         struct prio_sched_data *q = qdisc_priv(sch);
@@ -198,21 +244,41 @@ prio_destroy(struct Qdisc* sch)
 static int prio_tune(struct Qdisc *sch, struct rtattr *opt)
 {
         struct prio_sched_data *q = qdisc_priv(sch);
-        struct tc_prio_qopt *qopt = RTA_DATA(opt);
+        struct tc_prio_qopt *qopt;
+        struct rtattr *tb[TCA_PRIO_MAX];
         int i;
 
-        if (opt->rta_len < RTA_LENGTH(sizeof(*qopt)))
+        if (rtattr_parse_nested_compat(tb, TCA_PRIO_MAX, opt, qopt,
+                                       sizeof(*qopt)))
                 return -EINVAL;
-        if (qopt->bands > TCQ_PRIO_BANDS || qopt->bands < 2)
+        q->bands = qopt->bands;
+        /* If we're multiqueue, make sure the number of incoming bands
+         * matches the number of queues on the device we're associating with.
+         * If the number of bands requested is zero, then set q->bands to
+         * dev->egress_subqueue_count.
+         */
+        q->mq = RTA_GET_FLAG(tb[TCA_PRIO_MQ - 1]);
+        if (q->mq) {
+                if (sch->handle != TC_H_ROOT)
+                        return -EINVAL;
+                if (netif_is_multiqueue(sch->dev)) {
+                        if (q->bands == 0)
+                                q->bands = sch->dev->egress_subqueue_count;
+                        else if (q->bands != sch->dev->egress_subqueue_count)
+                                return -EINVAL;
+                } else
+                        return -EOPNOTSUPP;
+        }
+
+        if (q->bands > TCQ_PRIO_BANDS || q->bands < 2)
                 return -EINVAL;
 
         for (i=0; i<=TC_PRIO_MAX; i++) {
-                if (qopt->priomap[i] >= qopt->bands)
+                if (qopt->priomap[i] >= q->bands)
                         return -EINVAL;
         }
 
         sch_tree_lock(sch);
-        q->bands = qopt->bands;
         memcpy(q->prio2band, qopt->priomap, TC_PRIO_MAX+1);
 
         for (i=q->bands; i<TCQ_PRIO_BANDS; i++) {
@@ -268,11 +334,17 @@ static int prio_dump(struct Qdisc *sch, struct sk_buff *skb)
 {
         struct prio_sched_data *q = qdisc_priv(sch);
         unsigned char *b = skb_tail_pointer(skb);
+        struct rtattr *nest;
         struct tc_prio_qopt opt;
 
         opt.bands = q->bands;
         memcpy(&opt.priomap, q->prio2band, TC_PRIO_MAX+1);
-        RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
+
+        nest = RTA_NEST_COMPAT(skb, TCA_OPTIONS, sizeof(opt), &opt);
+        if (q->mq)
+                RTA_PUT_FLAG(skb, TCA_PRIO_MQ);
+        RTA_NEST_COMPAT_END(skb, nest);
+
         return skb->len;
 
 rtattr_failure:
@@ -443,17 +515,44 @@ static struct Qdisc_ops prio_qdisc_ops = {
         .owner          =       THIS_MODULE,
 };
 
+static struct Qdisc_ops rr_qdisc_ops = {
+        .next           =       NULL,
+        .cl_ops         =       &prio_class_ops,
+        .id             =       "rr",
+        .priv_size      =       sizeof(struct prio_sched_data),
+        .enqueue        =       prio_enqueue,
+        .dequeue        =       rr_dequeue,
+        .requeue        =       prio_requeue,
+        .drop           =       prio_drop,
+        .init           =       prio_init,
+        .reset          =       prio_reset,
+        .destroy        =       prio_destroy,
+        .change         =       prio_tune,
+        .dump           =       prio_dump,
+        .owner          =       THIS_MODULE,
+};
+
 static int __init prio_module_init(void)
 {
-        return register_qdisc(&prio_qdisc_ops);
+        int err;
+
+        err = register_qdisc(&prio_qdisc_ops);
+        if (err < 0)
+                return err;
+        err = register_qdisc(&rr_qdisc_ops);
+        if (err < 0)
+                unregister_qdisc(&prio_qdisc_ops);
+        return err;
 }
 
 static void __exit prio_module_exit(void)
 {
         unregister_qdisc(&prio_qdisc_ops);
+        unregister_qdisc(&rr_qdisc_ops);
 }
 
 module_init(prio_module_init)
 module_exit(prio_module_exit)
 
 MODULE_LICENSE("GPL");
+MODULE_ALIAS("sch_rr");