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>

include/net/sch_generic.h

@@ -80,6 +80,7 @@ struct Qdisc
 struct Qdisc_class_ops
 {
 	/* Child qdisc manipulation */
+	unsigned int		(*select_queue)(struct Qdisc *, struct tcmsg *);
 	int			(*graft)(struct Qdisc *, unsigned long cl,
 					struct Qdisc *, struct Qdisc **);
 	struct Qdisc *		(*leaf)(struct Qdisc *, unsigned long cl);
@@ -122,6 +123,7 @@ struct Qdisc_ops
 	void			(*reset)(struct Qdisc *);
 	void			(*destroy)(struct Qdisc *);
 	int			(*change)(struct Qdisc *, struct nlattr *arg);
+	void			(*attach)(struct Qdisc *);
 
 	int			(*dump)(struct Qdisc *, struct sk_buff *);
 	int			(*dump_stats)(struct Qdisc *, struct gnet_dump *);
@@ -255,6 +257,8 @@ static inline void sch_tree_unlock(struct Qdisc *q)
 
 extern struct Qdisc noop_qdisc;
 extern struct Qdisc_ops noop_qdisc_ops;
+extern struct Qdisc_ops pfifo_fast_ops;
+extern struct Qdisc_ops mq_qdisc_ops;
 
 struct Qdisc_class_common
 {

net/sched/Makefile

@@ -2,7 +2,7 @@
 # Makefile for the Linux Traffic Control Unit.
 #
 
-obj-y	:= sch_generic.o
+obj-y	:= sch_generic.o sch_mq.o
 
 obj-$(CONFIG_NET_SCHED)		+= sch_api.o sch_blackhole.o
 obj-$(CONFIG_NET_CLS)		+= cls_api.o

net/sched/sch_api.c

@@ -678,6 +678,11 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
 		if (dev->flags & IFF_UP)
 			dev_deactivate(dev);
 
+		if (new && new->ops->attach) {
+			new->ops->attach(new);
+			num_q = 0;
+		}
+
 		for (i = 0; i < num_q; i++) {
 			struct netdev_queue *dev_queue = &dev->rx_queue;
 
@@ -692,7 +697,7 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
 		}
 
 		notify_and_destroy(skb, n, classid, dev->qdisc, new);
-		if (new)
+		if (new && !new->ops->attach)
 			atomic_inc(&new->refcnt);
 		dev->qdisc = new ? : &noop_qdisc;
 
@@ -1095,10 +1100,16 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
 		q = qdisc_create(dev, &dev->rx_queue,
 				 tcm->tcm_parent, tcm->tcm_parent,
 				 tca, &err);
-	else
-		q = qdisc_create(dev, netdev_get_tx_queue(dev, 0),
+	else {
+		unsigned int ntx = 0;
+
+		if (p && p->ops->cl_ops && p->ops->cl_ops->select_queue)
+			ntx = p->ops->cl_ops->select_queue(p, tcm);
+
+		q = qdisc_create(dev, netdev_get_tx_queue(dev, ntx),
 				 tcm->tcm_parent, tcm->tcm_handle,
 				 tca, &err);
+	}
 	if (q == NULL) {
 		if (err == -EAGAIN)
 			goto replay;
@@ -1674,6 +1685,7 @@ static int __init pktsched_init(void)
 {
 	register_qdisc(&pfifo_qdisc_ops);
 	register_qdisc(&bfifo_qdisc_ops);
+	register_qdisc(&mq_qdisc_ops);
 	proc_net_fops_create(&init_net, "psched", 0, &psched_fops);
 
 	rtnl_register(PF_UNSPEC, RTM_NEWQDISC, tc_modify_qdisc, NULL);

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 */

net/sched/sch_mq.c

+/*
+ * net/sched/sch_mq.c		Classful multiqueue dummy scheduler
+ *
+ * Copyright (c) 2009 Patrick McHardy <kaber@trash.net>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/skbuff.h>
+#include <net/netlink.h>
+#include <net/pkt_sched.h>
+
+struct mq_sched {
+	struct Qdisc		**qdiscs;
+};
+
+static void mq_destroy(struct Qdisc *sch)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct mq_sched *priv = qdisc_priv(sch);
+	unsigned int ntx;
+
+	if (!priv->qdiscs)
+		return;
+	for (ntx = 0; ntx < dev->num_tx_queues && priv->qdiscs[ntx]; ntx++)
+		qdisc_destroy(priv->qdiscs[ntx]);
+	kfree(priv->qdiscs);
+}
+
+static int mq_init(struct Qdisc *sch, struct nlattr *opt)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct mq_sched *priv = qdisc_priv(sch);
+	struct netdev_queue *dev_queue;
+	struct Qdisc *qdisc;
+	unsigned int ntx;
+
+	if (sch->parent != TC_H_ROOT)
+		return -EOPNOTSUPP;
+
+	if (!netif_is_multiqueue(dev))
+		return -EOPNOTSUPP;
+
+	/* pre-allocate qdiscs, attachment can't fail */
+	priv->qdiscs = kcalloc(dev->num_tx_queues, sizeof(priv->qdiscs[0]),
+			       GFP_KERNEL);
+	if (priv->qdiscs == NULL)
+		return -ENOMEM;
+
+	for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
+		dev_queue = netdev_get_tx_queue(dev, ntx);
+		qdisc = qdisc_create_dflt(dev, dev_queue, &pfifo_fast_ops,
+					  TC_H_MAKE(TC_H_MAJ(sch->handle),
+						    TC_H_MIN(ntx + 1)));
+		if (qdisc == NULL)
+			goto err;
+		qdisc->flags |= TCQ_F_CAN_BYPASS;
+		priv->qdiscs[ntx] = qdisc;
+	}
+
+	return 0;
+
+err:
+	mq_destroy(sch);
+	return -ENOMEM;
+}
+
+static void mq_attach(struct Qdisc *sch)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct mq_sched *priv = qdisc_priv(sch);
+	struct Qdisc *qdisc;
+	unsigned int ntx;
+
+	for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
+		qdisc = priv->qdiscs[ntx];
+		qdisc = dev_graft_qdisc(qdisc->dev_queue, qdisc);
+		if (qdisc)
+			qdisc_destroy(qdisc);
+	}
+	kfree(priv->qdiscs);
+	priv->qdiscs = NULL;
+}
+
+static int mq_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct Qdisc *qdisc;
+	unsigned int ntx;
+
+	sch->q.qlen = 0;
+	memset(&sch->bstats, 0, sizeof(sch->bstats));
+	memset(&sch->qstats, 0, sizeof(sch->qstats));
+
+	for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
+		qdisc = netdev_get_tx_queue(dev, ntx)->qdisc_sleeping;
+		spin_lock_bh(qdisc_lock(qdisc));
+		sch->q.qlen		+= qdisc->q.qlen;
+		sch->bstats.bytes	+= qdisc->bstats.bytes;
+		sch->bstats.packets	+= qdisc->bstats.packets;
+		sch->qstats.qlen	+= qdisc->qstats.qlen;
+		sch->qstats.backlog	+= qdisc->qstats.backlog;
+		sch->qstats.drops	+= qdisc->qstats.drops;
+		sch->qstats.requeues	+= qdisc->qstats.requeues;
+		sch->qstats.overlimits	+= qdisc->qstats.overlimits;
+		spin_unlock_bh(qdisc_lock(qdisc));
+	}
+	return 0;
+}
+
+static struct netdev_queue *mq_queue_get(struct Qdisc *sch, unsigned long cl)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	unsigned long ntx = cl - 1;
+
+	if (ntx >= dev->num_tx_queues)
+		return NULL;
+	return netdev_get_tx_queue(dev, ntx);
+}
+
+static unsigned int mq_select_queue(struct Qdisc *sch, struct tcmsg *tcm)
+{
+	unsigned int ntx = TC_H_MIN(tcm->tcm_parent);
+
+	if (!mq_queue_get(sch, ntx))
+		return 0;
+	return ntx - 1;
+}
+
+static int mq_graft(struct Qdisc *sch, unsigned long cl, struct Qdisc *new,
+		    struct Qdisc **old)
+{
+	struct netdev_queue *dev_queue = mq_queue_get(sch, cl);
+	struct net_device *dev = qdisc_dev(sch);
+
+	if (dev->flags & IFF_UP)
+		dev_deactivate(dev);
+
+	*old = dev_graft_qdisc(dev_queue, new);
+
+	if (dev->flags & IFF_UP)
+		dev_activate(dev);
+	return 0;
+}
+
+static struct Qdisc *mq_leaf(struct Qdisc *sch, unsigned long cl)
+{
+	struct netdev_queue *dev_queue = mq_queue_get(sch, cl);
+
+	return dev_queue->qdisc_sleeping;
+}
+
+static unsigned long mq_get(struct Qdisc *sch, u32 classid)
+{
+	unsigned int ntx = TC_H_MIN(classid);
+
+	if (!mq_queue_get(sch, ntx))
+		return 0;
+	return ntx;
+}
+
+static void mq_put(struct Qdisc *sch, unsigned long cl)
+{
+	return;
+}
+
+static int mq_dump_class(struct Qdisc *sch, unsigned long cl,
+			 struct sk_buff *skb, struct tcmsg *tcm)
+{
+	struct netdev_queue *dev_queue = mq_queue_get(sch, cl);
+
+	tcm->tcm_parent = TC_H_ROOT;
+	tcm->tcm_handle |= TC_H_MIN(cl);
+	tcm->tcm_info = dev_queue->qdisc_sleeping->handle;
+	return 0;
+}
+
+static int mq_dump_class_stats(struct Qdisc *sch, unsigned long cl,
+			       struct gnet_dump *d)
+{
+	struct netdev_queue *dev_queue = mq_queue_get(sch, cl);
+
+	sch = dev_queue->qdisc_sleeping;
+	if (gnet_stats_copy_basic(d, &sch->bstats) < 0 ||
+	    gnet_stats_copy_queue(d, &sch->qstats) < 0)
+		return -1;
+	return 0;
+}
+
+static void mq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	unsigned int ntx;
+
+	if (arg->stop)
+		return;
+
+	arg->count = arg->skip;
+	for (ntx = arg->skip; ntx < dev->num_tx_queues; ntx++) {
+		if (arg->fn(sch, ntx + 1, arg) < 0) {
+			arg->stop = 1;
+			break;
+		}
+		arg->count++;
+	}
+}
+
+static const struct Qdisc_class_ops mq_class_ops = {
+	.select_queue	= mq_select_queue,
+	.graft		= mq_graft,
+	.leaf		= mq_leaf,
+	.get		= mq_get,
+	.put		= mq_put,
+	.walk		= mq_walk,
+	.dump		= mq_dump_class,
+	.dump_stats	= mq_dump_class_stats,
+};
+
+struct Qdisc_ops mq_qdisc_ops __read_mostly = {
+	.cl_ops		= &mq_class_ops,
+	.id		= "mq",
+	.priv_size	= sizeof(struct mq_sched),
+	.init		= mq_init,
+	.destroy	= mq_destroy,
+	.attach		= mq_attach,
+	.dump		= mq_dump,
+	.owner		= THIS_MODULE,
+};