text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * net/sched/sch_generic.c	Generic packet scheduler routines.
   *
   * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
   *              Jamal Hadi Salim, <hadi@cyberus.ca> 990601
   *              - Ingress support
   */
  
  #include <linux/bitops.h>
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/string.h>
  #include <linux/errno.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>
  #include <linux/rtnetlink.h>
  #include <linux/init.h>
  #include <linux/rcupdate.h>
  #include <linux/list.h>
  #include <linux/slab.h>
  #include <linux/if_vlan.h>
  #include <linux/skb_array.h>
  #include <linux/if_macvlan.h>
  #include <net/sch_generic.h>
  #include <net/pkt_sched.h>
  #include <net/dst.h>
  #include <trace/events/qdisc.h>
  #include <trace/events/net.h>
  #include <net/xfrm.h>
  
  /* Qdisc to use by default */
  const struct Qdisc_ops *default_qdisc_ops = &pfifo_fast_ops;
  EXPORT_SYMBOL(default_qdisc_ops);
  
  static void qdisc_maybe_clear_missed(struct Qdisc *q,
  				     const struct netdev_queue *txq)
  {
  	clear_bit(__QDISC_STATE_MISSED, &q->state);
  
  	/* Make sure the below netif_xmit_frozen_or_stopped()
  	 * checking happens after clearing STATE_MISSED.
  	 */
  	smp_mb__after_atomic();
  
  	/* Checking netif_xmit_frozen_or_stopped() again to
  	 * make sure STATE_MISSED is set if the STATE_MISSED
  	 * set by netif_tx_wake_queue()'s rescheduling of
  	 * net_tx_action() is cleared by the above clear_bit().
  	 */
  	if (!netif_xmit_frozen_or_stopped(txq))
  		set_bit(__QDISC_STATE_MISSED, &q->state);
  	else
  		set_bit(__QDISC_STATE_DRAINING, &q->state);
  }
  
  /* Main transmission queue. */
  
  /* Modifications to data participating in scheduling must be protected with
   * qdisc_lock(qdisc) spinlock.
   *
   * The idea is the following:
   * - enqueue, dequeue are serialized via qdisc root lock
   * - ingress filtering is also serialized via qdisc root lock
   * - updates to tree and tree walking are only done under the rtnl mutex.
   */
  
  #define SKB_XOFF_MAGIC ((struct sk_buff *)1UL)
  
  static inline struct sk_buff *__skb_dequeue_bad_txq(struct Qdisc *q)
  {
  	const struct netdev_queue *txq = q->dev_queue;
  	spinlock_t *lock = NULL;
  	struct sk_buff *skb;
  
  	if (q->flags & TCQ_F_NOLOCK) {
  		lock = qdisc_lock(q);
  		spin_lock(lock);
  	}
  
  	skb = skb_peek(&q->skb_bad_txq);
  	if (skb) {
  		/* check the reason of requeuing without tx lock first */
  		txq = skb_get_tx_queue(txq->dev, skb);
  		if (!netif_xmit_frozen_or_stopped(txq)) {
  			skb = __skb_dequeue(&q->skb_bad_txq);
  			if (qdisc_is_percpu_stats(q)) {
  				qdisc_qstats_cpu_backlog_dec(q, skb);
  				qdisc_qstats_cpu_qlen_dec(q);
  			} else {
  				qdisc_qstats_backlog_dec(q, skb);
  				q->q.qlen--;
  			}
  		} else {
  			skb = SKB_XOFF_MAGIC;
  			qdisc_maybe_clear_missed(q, txq);
  		}
  	}
  
  	if (lock)
  		spin_unlock(lock);
  
  	return skb;
  }
  
  static inline struct sk_buff *qdisc_dequeue_skb_bad_txq(struct Qdisc *q)
  {
  	struct sk_buff *skb = skb_peek(&q->skb_bad_txq);
  
  	if (unlikely(skb))
  		skb = __skb_dequeue_bad_txq(q);
  
  	return skb;
  }
  
  static inline void qdisc_enqueue_skb_bad_txq(struct Qdisc *q,
  					     struct sk_buff *skb)
  {
  	spinlock_t *lock = NULL;
  
  	if (q->flags & TCQ_F_NOLOCK) {
  		lock = qdisc_lock(q);
  		spin_lock(lock);
  	}
  
  	__skb_queue_tail(&q->skb_bad_txq, skb);
  
  	if (qdisc_is_percpu_stats(q)) {
  		qdisc_qstats_cpu_backlog_inc(q, skb);
  		qdisc_qstats_cpu_qlen_inc(q);
  	} else {
  		qdisc_qstats_backlog_inc(q, skb);
  		q->q.qlen++;
  	}
  
  	if (lock)
  		spin_unlock(lock);
  }
  
  static inline void dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
  {
  	spinlock_t *lock = NULL;
  
  	if (q->flags & TCQ_F_NOLOCK) {
  		lock = qdisc_lock(q);
  		spin_lock(lock);
  	}
  
  	while (skb) {
  		struct sk_buff *next = skb->next;
  
  		__skb_queue_tail(&q->gso_skb, skb);
  
  		/* it's still part of the queue */
  		if (qdisc_is_percpu_stats(q)) {
  			qdisc_qstats_cpu_requeues_inc(q);
  			qdisc_qstats_cpu_backlog_inc(q, skb);
  			qdisc_qstats_cpu_qlen_inc(q);
  		} else {
  			q->qstats.requeues++;
  			qdisc_qstats_backlog_inc(q, skb);
  			q->q.qlen++;
  		}
  
  		skb = next;
  	}
  
  	if (lock) {
  		spin_unlock(lock);
  		set_bit(__QDISC_STATE_MISSED, &q->state);
  	} else {
  		__netif_schedule(q);
  	}
  }
  
  static void try_bulk_dequeue_skb(struct Qdisc *q,
  				 struct sk_buff *skb,
  				 const struct netdev_queue *txq,
  				 int *packets)
  {
  	int bytelimit = qdisc_avail_bulklimit(txq) - skb->len;
  
  	while (bytelimit > 0) {
  		struct sk_buff *nskb = q->dequeue(q);
  
  		if (!nskb)
  			break;
  
  		bytelimit -= nskb->len; /* covers GSO len */
  		skb->next = nskb;
  		skb = nskb;
  		(*packets)++; /* GSO counts as one pkt */
  	}
  	skb_mark_not_on_list(skb);
  }
  
  /* This variant of try_bulk_dequeue_skb() makes sure
   * all skbs in the chain are for the same txq
   */
  static void try_bulk_dequeue_skb_slow(struct Qdisc *q,
  				      struct sk_buff *skb,
  				      int *packets)
  {
  	int mapping = skb_get_queue_mapping(skb);
  	struct sk_buff *nskb;
  	int cnt = 0;
  
  	do {
  		nskb = q->dequeue(q);
  		if (!nskb)
  			break;
  		if (unlikely(skb_get_queue_mapping(nskb) != mapping)) {
  			qdisc_enqueue_skb_bad_txq(q, nskb);
  			break;
  		}
  		skb->next = nskb;
  		skb = nskb;
  	} while (++cnt < 8);
  	(*packets) += cnt;
  	skb_mark_not_on_list(skb);
  }
  
  /* Note that dequeue_skb can possibly return a SKB list (via skb->next).
   * A requeued skb (via q->gso_skb) can also be a SKB list.
   */
  static struct sk_buff *dequeue_skb(struct Qdisc *q, bool *validate,
  				   int *packets)
  {
  	const struct netdev_queue *txq = q->dev_queue;
  	struct sk_buff *skb = NULL;
  
  	*packets = 1;
  	if (unlikely(!skb_queue_empty(&q->gso_skb))) {
  		spinlock_t *lock = NULL;
  
  		if (q->flags & TCQ_F_NOLOCK) {
  			lock = qdisc_lock(q);
  			spin_lock(lock);
  		}
  
  		skb = skb_peek(&q->gso_skb);
  
  		/* skb may be null if another cpu pulls gso_skb off in between
  		 * empty check and lock.
  		 */
  		if (!skb) {
  			if (lock)
  				spin_unlock(lock);
  			goto validate;
  		}
  
  		/* skb in gso_skb were already validated */
  		*validate = false;
  		if (xfrm_offload(skb))
  			*validate = true;
  		/* check the reason of requeuing without tx lock first */
  		txq = skb_get_tx_queue(txq->dev, skb);
  		if (!netif_xmit_frozen_or_stopped(txq)) {
  			skb = __skb_dequeue(&q->gso_skb);
  			if (qdisc_is_percpu_stats(q)) {
  				qdisc_qstats_cpu_backlog_dec(q, skb);
  				qdisc_qstats_cpu_qlen_dec(q);
  			} else {
  				qdisc_qstats_backlog_dec(q, skb);
  				q->q.qlen--;
  			}
  		} else {
  			skb = NULL;
  			qdisc_maybe_clear_missed(q, txq);
  		}
  		if (lock)
  			spin_unlock(lock);
  		goto trace;
  	}
  validate:
  	*validate = true;
  
  	if ((q->flags & TCQ_F_ONETXQUEUE) &&
  	    netif_xmit_frozen_or_stopped(txq)) {
  		qdisc_maybe_clear_missed(q, txq);
  		return skb;
  	}
  
  	skb = qdisc_dequeue_skb_bad_txq(q);
  	if (unlikely(skb)) {
  		if (skb == SKB_XOFF_MAGIC)
  			return NULL;
  		goto bulk;
  	}
  	skb = q->dequeue(q);
  	if (skb) {
  bulk:
  		if (qdisc_may_bulk(q))
  			try_bulk_dequeue_skb(q, skb, txq, packets);
  		else
  			try_bulk_dequeue_skb_slow(q, skb, packets);
  	}
  trace:
  	trace_qdisc_dequeue(q, txq, *packets, skb);
  	return skb;
  }
  
  /*
   * Transmit possibly several skbs, and handle the return status as
   * required. Owning running seqcount bit guarantees that
   * only one CPU can execute this function.
   *
   * Returns to the caller:
   *				false  - hardware queue frozen backoff
   *				true   - feel free to send more pkts
   */
  bool sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
  		     struct net_device *dev, struct netdev_queue *txq,
  		     spinlock_t *root_lock, bool validate)
  {
  	int ret = NETDEV_TX_BUSY;
  	bool again = false;
  
  	/* And release qdisc */
  	if (root_lock)
  		spin_unlock(root_lock);
  
  	/* Note that we validate skb (GSO, checksum, ...) outside of locks */
  	if (validate)
  		skb = validate_xmit_skb_list(skb, dev, &again);
  
  #ifdef CONFIG_XFRM_OFFLOAD
  	if (unlikely(again)) {
  		if (root_lock)
  			spin_lock(root_lock);
  
  		dev_requeue_skb(skb, q);
  		return false;
  	}
  #endif
  
  	if (likely(skb)) {
  		HARD_TX_LOCK(dev, txq, smp_processor_id());
  		if (!netif_xmit_frozen_or_stopped(txq))
  			skb = dev_hard_start_xmit(skb, dev, txq, &ret);
  		else
  			qdisc_maybe_clear_missed(q, txq);
  
  		HARD_TX_UNLOCK(dev, txq);
  	} else {
  		if (root_lock)
  			spin_lock(root_lock);
  		return true;
  	}
  
  	if (root_lock)
  		spin_lock(root_lock);
  
  	if (!dev_xmit_complete(ret)) {
  		/* Driver returned NETDEV_TX_BUSY - requeue skb */
  		if (unlikely(ret != NETDEV_TX_BUSY))
  			net_warn_ratelimited("BUG %s code %d qlen %d\n",
  					     dev->name, ret, q->q.qlen);
  
  		dev_requeue_skb(skb, q);
  		return false;
  	}
  
  	return true;
  }
  
  /*
   * NOTE: Called under qdisc_lock(q) with locally disabled BH.
   *
   * running seqcount guarantees only one CPU can process
   * this qdisc at a time. qdisc_lock(q) serializes queue accesses for
   * this queue.
   *
   *  netif_tx_lock serializes accesses to device driver.
   *
   *  qdisc_lock(q) and netif_tx_lock are mutually exclusive,
   *  if one is grabbed, another must be free.
   *
   * Note, that this procedure can be called by a watchdog timer
   *
   * Returns to the caller:
   *				0  - queue is empty or throttled.
   *				>0 - queue is not empty.
   *
   */
  static inline bool qdisc_restart(struct Qdisc *q, int *packets)
  {
  	spinlock_t *root_lock = NULL;
  	struct netdev_queue *txq;
  	struct net_device *dev;
  	struct sk_buff *skb;
  	bool validate;
  
  	/* Dequeue packet */
  	skb = dequeue_skb(q, &validate, packets);
  	if (unlikely(!skb))
  		return false;
  
  	if (!(q->flags & TCQ_F_NOLOCK))
  		root_lock = qdisc_lock(q);
  
  	dev = qdisc_dev(q);
  	txq = skb_get_tx_queue(dev, skb);
  
  	return sch_direct_xmit(skb, q, dev, txq, root_lock, validate);
  }
  
  void __qdisc_run(struct Qdisc *q)
  {
  	int quota = dev_tx_weight;
  	int packets;
  
  	while (qdisc_restart(q, &packets)) {
  		quota -= packets;
  		if (quota <= 0) {
  			if (q->flags & TCQ_F_NOLOCK)
  				set_bit(__QDISC_STATE_MISSED, &q->state);
  			else
  				__netif_schedule(q);
  
  			break;
  		}
  	}
  }
  
  unsigned long dev_trans_start(struct net_device *dev)
  {
  	unsigned long val, res;
  	unsigned int i;
  
  	if (is_vlan_dev(dev))
  		dev = vlan_dev_real_dev(dev);
  	else if (netif_is_macvlan(dev))
  		dev = macvlan_dev_real_dev(dev);
  	res = netdev_get_tx_queue(dev, 0)->trans_start;
  	for (i = 1; i < dev->num_tx_queues; i++) {
  		val = netdev_get_tx_queue(dev, i)->trans_start;
  		if (val && time_after(val, res))
  			res = val;
  	}
  
  	return res;
  }
  EXPORT_SYMBOL(dev_trans_start);
  
  static void dev_watchdog(struct timer_list *t)
  {
  	struct net_device *dev = from_timer(dev, t, watchdog_timer);
  
  	netif_tx_lock(dev);
  	if (!qdisc_tx_is_noop(dev)) {
  		if (netif_device_present(dev) &&
  		    netif_running(dev) &&
  		    netif_carrier_ok(dev)) {
  			int some_queue_timedout = 0;
  			unsigned int i;
  			unsigned long trans_start;
  
  			for (i = 0; i < dev->num_tx_queues; i++) {
  				struct netdev_queue *txq;
  
  				txq = netdev_get_tx_queue(dev, i);
  				trans_start = txq->trans_start;
  				if (netif_xmit_stopped(txq) &&
  				    time_after(jiffies, (trans_start +
  							 dev->watchdog_timeo))) {
  					some_queue_timedout = 1;
  					txq->trans_timeout++;
  					break;
  				}
  			}
  
  			if (some_queue_timedout) {
  				trace_net_dev_xmit_timeout(dev, i);
  				WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s (%s): transmit queue %u timed out\n",
  				       dev->name, netdev_drivername(dev), i);
  				dev->netdev_ops->ndo_tx_timeout(dev, i);
  			}
  			if (!mod_timer(&dev->watchdog_timer,
  				       round_jiffies(jiffies +
  						     dev->watchdog_timeo)))
  				dev_hold(dev);
  		}
  	}
  	netif_tx_unlock(dev);
  
  	dev_put(dev);
  }
  
  void __netdev_watchdog_up(struct net_device *dev)
  {
  	if (dev->netdev_ops->ndo_tx_timeout) {
  		if (dev->watchdog_timeo <= 0)
  			dev->watchdog_timeo = 5*HZ;
  		if (!mod_timer(&dev->watchdog_timer,
  			       round_jiffies(jiffies + dev->watchdog_timeo)))
  			dev_hold(dev);
  	}
  }
  EXPORT_SYMBOL_GPL(__netdev_watchdog_up);
  
  static void dev_watchdog_up(struct net_device *dev)
  {
  	__netdev_watchdog_up(dev);
  }
  
  static void dev_watchdog_down(struct net_device *dev)
  {
  	netif_tx_lock_bh(dev);
  	if (del_timer(&dev->watchdog_timer))
  		dev_put(dev);
  	netif_tx_unlock_bh(dev);
  }
  
  /**
   *	netif_carrier_on - set carrier
   *	@dev: network device
   *
   * Device has detected acquisition of carrier.
   */
  void netif_carrier_on(struct net_device *dev)
  {
  	if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
  		if (dev->reg_state == NETREG_UNINITIALIZED)
  			return;
  		atomic_inc(&dev->carrier_up_count);
  		linkwatch_fire_event(dev);
  		if (netif_running(dev))
  			__netdev_watchdog_up(dev);
  	}
  }
  EXPORT_SYMBOL(netif_carrier_on);
  
  /**
   *	netif_carrier_off - clear carrier
   *	@dev: network device
   *
   * Device has detected loss of carrier.
   */
  void netif_carrier_off(struct net_device *dev)
  {
  	if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
  		if (dev->reg_state == NETREG_UNINITIALIZED)
  			return;
  		atomic_inc(&dev->carrier_down_count);
  		linkwatch_fire_event(dev);
  	}
  }
  EXPORT_SYMBOL(netif_carrier_off);
  
  /**
   *	netif_carrier_event - report carrier state event
   *	@dev: network device
   *
   * Device has detected a carrier event but the carrier state wasn't changed.
   * Use in drivers when querying carrier state asynchronously, to avoid missing
   * events (link flaps) if link recovers before it's queried.
   */
  void netif_carrier_event(struct net_device *dev)
  {
  	if (dev->reg_state == NETREG_UNINITIALIZED)
  		return;
  	atomic_inc(&dev->carrier_up_count);
  	atomic_inc(&dev->carrier_down_count);
  	linkwatch_fire_event(dev);
  }
  EXPORT_SYMBOL_GPL(netif_carrier_event);
  
  /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
     under all circumstances. It is difficult to invent anything faster or
     cheaper.
   */
  
  static int noop_enqueue(struct sk_buff *skb, struct Qdisc *qdisc,
  			struct sk_buff **to_free)
  {
  	__qdisc_drop(skb, to_free);
  	return NET_XMIT_CN;
  }
  
  static struct sk_buff *noop_dequeue(struct Qdisc *qdisc)
  {
  	return NULL;
  }
  
  struct Qdisc_ops noop_qdisc_ops __read_mostly = {
  	.id		=	"noop",
  	.priv_size	=	0,
  	.enqueue	=	noop_enqueue,
  	.dequeue	=	noop_dequeue,
  	.peek		=	noop_dequeue,
  	.owner		=	THIS_MODULE,
  };
  
  static struct netdev_queue noop_netdev_queue = {
  	RCU_POINTER_INITIALIZER(qdisc, &noop_qdisc),
  	.qdisc_sleeping	=	&noop_qdisc,
  };
  
  struct Qdisc noop_qdisc = {
  	.enqueue	=	noop_enqueue,
  	.dequeue	=	noop_dequeue,
  	.flags		=	TCQ_F_BUILTIN,
  	.ops		=	&noop_qdisc_ops,
  	.q.lock		=	__SPIN_LOCK_UNLOCKED(noop_qdisc.q.lock),
  	.dev_queue	=	&noop_netdev_queue,
  	.running	=	SEQCNT_ZERO(noop_qdisc.running),
  	.busylock	=	__SPIN_LOCK_UNLOCKED(noop_qdisc.busylock),
  	.gso_skb = {
  		.next = (struct sk_buff *)&noop_qdisc.gso_skb,
  		.prev = (struct sk_buff *)&noop_qdisc.gso_skb,
  		.qlen = 0,
  		.lock = __SPIN_LOCK_UNLOCKED(noop_qdisc.gso_skb.lock),
  	},
  	.skb_bad_txq = {
  		.next = (struct sk_buff *)&noop_qdisc.skb_bad_txq,
  		.prev = (struct sk_buff *)&noop_qdisc.skb_bad_txq,
  		.qlen = 0,
  		.lock = __SPIN_LOCK_UNLOCKED(noop_qdisc.skb_bad_txq.lock),
  	},
  };
  EXPORT_SYMBOL(noop_qdisc);
  
  static int noqueue_init(struct Qdisc *qdisc, struct nlattr *opt,
  			struct netlink_ext_ack *extack)
  {
  	/* register_qdisc() assigns a default of noop_enqueue if unset,
  	 * but __dev_queue_xmit() treats noqueue only as such
  	 * if this is NULL - so clear it here. */
  	qdisc->enqueue = NULL;
  	return 0;
  }
  
  struct Qdisc_ops noqueue_qdisc_ops __read_mostly = {
  	.id		=	"noqueue",
  	.priv_size	=	0,
  	.init		=	noqueue_init,
  	.enqueue	=	noop_enqueue,
  	.dequeue	=	noop_dequeue,
  	.peek		=	noop_dequeue,
  	.owner		=	THIS_MODULE,
  };
  
  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
  
  /*
   * Private data for a pfifo_fast scheduler containing:
   *	- rings for priority bands
   */
  struct pfifo_fast_priv {
  	struct skb_array q[PFIFO_FAST_BANDS];
  };
  
  static inline struct skb_array *band2list(struct pfifo_fast_priv *priv,
  					  int band)
  {
  	return &priv->q[band];
  }
  
  static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc,
  			      struct sk_buff **to_free)
  {
  	int band = prio2band[skb->priority & TC_PRIO_MAX];
  	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
  	struct skb_array *q = band2list(priv, band);
  	unsigned int pkt_len = qdisc_pkt_len(skb);
  	int err;
  
  	err = skb_array_produce(q, skb);
  
  	if (unlikely(err)) {
  		if (qdisc_is_percpu_stats(qdisc))
  			return qdisc_drop_cpu(skb, qdisc, to_free);
  		else
  			return qdisc_drop(skb, qdisc, to_free);
  	}
  
  	qdisc_update_stats_at_enqueue(qdisc, pkt_len);
  	return NET_XMIT_SUCCESS;
  }
  
  static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc)
  {
  	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
  	struct sk_buff *skb = NULL;
  	bool need_retry = true;
  	int band;
  
  retry:
  	for (band = 0; band < PFIFO_FAST_BANDS && !skb; band++) {
  		struct skb_array *q = band2list(priv, band);
  
  		if (__skb_array_empty(q))
  			continue;
  
  		skb = __skb_array_consume(q);
  	}
  	if (likely(skb)) {
  		qdisc_update_stats_at_dequeue(qdisc, skb);
  	} else if (need_retry &&
  		   READ_ONCE(qdisc->state) & QDISC_STATE_NON_EMPTY) {
  		/* Delay clearing the STATE_MISSED here to reduce
  		 * the overhead of the second spin_trylock() in
  		 * qdisc_run_begin() and __netif_schedule() calling
  		 * in qdisc_run_end().
  		 */
  		clear_bit(__QDISC_STATE_MISSED, &qdisc->state);
  		clear_bit(__QDISC_STATE_DRAINING, &qdisc->state);
  
  		/* Make sure dequeuing happens after clearing
  		 * STATE_MISSED.
  		 */
  		smp_mb__after_atomic();
  
  		need_retry = false;
  
  		goto retry;
  	}
  
  	return skb;
  }
  
  static struct sk_buff *pfifo_fast_peek(struct Qdisc *qdisc)
  {
  	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
  	struct sk_buff *skb = NULL;
  	int band;
  
  	for (band = 0; band < PFIFO_FAST_BANDS && !skb; band++) {
  		struct skb_array *q = band2list(priv, band);
  
  		skb = __skb_array_peek(q);
  	}
  
  	return skb;
  }
  
  static void pfifo_fast_reset(struct Qdisc *qdisc)
  {
  	int i, band;
  	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
  
  	for (band = 0; band < PFIFO_FAST_BANDS; band++) {
  		struct skb_array *q = band2list(priv, band);
  		struct sk_buff *skb;
  
  		/* NULL ring is possible if destroy path is due to a failed
  		 * skb_array_init() in pfifo_fast_init() case.
  		 */
  		if (!q->ring.queue)
  			continue;
  
  		while ((skb = __skb_array_consume(q)) != NULL)
  			kfree_skb(skb);
  	}
  
  	if (qdisc_is_percpu_stats(qdisc)) {
  		for_each_possible_cpu(i) {
  			struct gnet_stats_queue *q;
  
  			q = per_cpu_ptr(qdisc->cpu_qstats, i);
  			q->backlog = 0;
  			q->qlen = 0;
  		}
  	}
  }
  
  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);
  	if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
  		goto nla_put_failure;
  	return skb->len;
  
  nla_put_failure:
  	return -1;
  }
  
  static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt,
  			   struct netlink_ext_ack *extack)
  {
  	unsigned int qlen = qdisc_dev(qdisc)->tx_queue_len;
  	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
  	int prio;
  
  	/* guard against zero length rings */
  	if (!qlen)
  		return -EINVAL;
  
  	for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
  		struct skb_array *q = band2list(priv, prio);
  		int err;
  
  		err = skb_array_init(q, qlen, GFP_KERNEL);
  		if (err)
  			return -ENOMEM;
  	}
  
  	/* Can by-pass the queue discipline */
  	qdisc->flags |= TCQ_F_CAN_BYPASS;
  	return 0;
  }
  
  static void pfifo_fast_destroy(struct Qdisc *sch)
  {
  	struct pfifo_fast_priv *priv = qdisc_priv(sch);
  	int prio;
  
  	for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
  		struct skb_array *q = band2list(priv, prio);
  
  		/* NULL ring is possible if destroy path is due to a failed
  		 * skb_array_init() in pfifo_fast_init() case.
  		 */
  		if (!q->ring.queue)
  			continue;
  		/* Destroy ring but no need to kfree_skb because a call to
  		 * pfifo_fast_reset() has already done that work.
  		 */
  		ptr_ring_cleanup(&q->ring, NULL);
  	}
  }
  
  static int pfifo_fast_change_tx_queue_len(struct Qdisc *sch,
  					  unsigned int new_len)
  {
  	struct pfifo_fast_priv *priv = qdisc_priv(sch);
  	struct skb_array *bands[PFIFO_FAST_BANDS];
  	int prio;
  
  	for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
  		struct skb_array *q = band2list(priv, prio);
  
  		bands[prio] = q;
  	}
  
  	return skb_array_resize_multiple(bands, PFIFO_FAST_BANDS, new_len,
  					 GFP_KERNEL);
  }
  
  struct Qdisc_ops pfifo_fast_ops __read_mostly = {
  	.id		=	"pfifo_fast",
  	.priv_size	=	sizeof(struct pfifo_fast_priv),
  	.enqueue	=	pfifo_fast_enqueue,
  	.dequeue	=	pfifo_fast_dequeue,
  	.peek		=	pfifo_fast_peek,
  	.init		=	pfifo_fast_init,
  	.destroy	=	pfifo_fast_destroy,
  	.reset		=	pfifo_fast_reset,
  	.dump		=	pfifo_fast_dump,
  	.change_tx_queue_len =  pfifo_fast_change_tx_queue_len,
  	.owner		=	THIS_MODULE,
  	.static_flags	=	TCQ_F_NOLOCK | TCQ_F_CPUSTATS,
  };
  EXPORT_SYMBOL(pfifo_fast_ops);
  
  static struct lock_class_key qdisc_tx_busylock;
  static struct lock_class_key qdisc_running_key;
  
  struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
  			  const struct Qdisc_ops *ops,
  			  struct netlink_ext_ack *extack)
  {
  	struct Qdisc *sch;
  	unsigned int size = sizeof(*sch) + ops->priv_size;
  	int err = -ENOBUFS;
  	struct net_device *dev;
  
  	if (!dev_queue) {
  		NL_SET_ERR_MSG(extack, "No device queue given");
  		err = -EINVAL;
  		goto errout;
  	}
  
  	dev = dev_queue->dev;
  	sch = kzalloc_node(size, GFP_KERNEL, netdev_queue_numa_node_read(dev_queue));
  
  	if (!sch)
  		goto errout;
  	__skb_queue_head_init(&sch->gso_skb);
  	__skb_queue_head_init(&sch->skb_bad_txq);
  	qdisc_skb_head_init(&sch->q);
  	spin_lock_init(&sch->q.lock);
  
  	if (ops->static_flags & TCQ_F_CPUSTATS) {
  		sch->cpu_bstats =
  			netdev_alloc_pcpu_stats(struct gnet_stats_basic_cpu);
  		if (!sch->cpu_bstats)
  			goto errout1;
  
  		sch->cpu_qstats = alloc_percpu(struct gnet_stats_queue);
  		if (!sch->cpu_qstats) {
  			free_percpu(sch->cpu_bstats);
  			goto errout1;
  		}
  	}
  
  	spin_lock_init(&sch->busylock);
  	lockdep_set_class(&sch->busylock,
  			  dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);
  
  	/* seqlock has the same scope of busylock, for NOLOCK qdisc */
  	spin_lock_init(&sch->seqlock);
  	lockdep_set_class(&sch->seqlock,
  			  dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);
  
  	seqcount_init(&sch->running);
  	lockdep_set_class(&sch->running,
  			  dev->qdisc_running_key ?: &qdisc_running_key);
  
  	sch->ops = ops;
  	sch->flags = ops->static_flags;
  	sch->enqueue = ops->enqueue;
  	sch->dequeue = ops->dequeue;
  	sch->dev_queue = dev_queue;
  	dev_hold(dev);
  	refcount_set(&sch->refcnt, 1);
  
  	return sch;
  errout1:
  	kfree(sch);
  errout:
  	return ERR_PTR(err);
  }
  
  struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue,
  				const struct Qdisc_ops *ops,
  				unsigned int parentid,
  				struct netlink_ext_ack *extack)
  {
  	struct Qdisc *sch;
  
  	if (!try_module_get(ops->owner)) {
  		NL_SET_ERR_MSG(extack, "Failed to increase module reference counter");
  		return NULL;
  	}
  
  	sch = qdisc_alloc(dev_queue, ops, extack);
  	if (IS_ERR(sch)) {
  		module_put(ops->owner);
  		return NULL;
  	}
  	sch->parent = parentid;
  
  	if (!ops->init || ops->init(sch, NULL, extack) == 0) {
  		trace_qdisc_create(ops, dev_queue->dev, parentid);
  		return sch;
  	}
  
  	qdisc_put(sch);
  	return NULL;
  }
  EXPORT_SYMBOL(qdisc_create_dflt);
  
  /* Under qdisc_lock(qdisc) and BH! */
  
  void qdisc_reset(struct Qdisc *qdisc)
  {
  	const struct Qdisc_ops *ops = qdisc->ops;
  	struct sk_buff *skb, *tmp;
  
  	trace_qdisc_reset(qdisc);
  
  	if (ops->reset)
  		ops->reset(qdisc);
  
  	skb_queue_walk_safe(&qdisc->gso_skb, skb, tmp) {
  		__skb_unlink(skb, &qdisc->gso_skb);
  		kfree_skb_list(skb);
  	}
  
  	skb_queue_walk_safe(&qdisc->skb_bad_txq, skb, tmp) {
  		__skb_unlink(skb, &qdisc->skb_bad_txq);
  		kfree_skb_list(skb);
  	}
  
  	qdisc->q.qlen = 0;
  	qdisc->qstats.backlog = 0;
  }
  EXPORT_SYMBOL(qdisc_reset);
  
  void qdisc_free(struct Qdisc *qdisc)
  {
  	if (qdisc_is_percpu_stats(qdisc)) {
  		free_percpu(qdisc->cpu_bstats);
  		free_percpu(qdisc->cpu_qstats);
  	}
  
  	kfree(qdisc);
  }
  
  static void qdisc_free_cb(struct rcu_head *head)
  {
  	struct Qdisc *q = container_of(head, struct Qdisc, rcu);
  
  	qdisc_free(q);
  }
  
  static void qdisc_destroy(struct Qdisc *qdisc)
  {
  	const struct Qdisc_ops  *ops = qdisc->ops;
  
  #ifdef CONFIG_NET_SCHED
  	qdisc_hash_del(qdisc);
  
  	qdisc_put_stab(rtnl_dereference(qdisc->stab));
  #endif
  	gen_kill_estimator(&qdisc->rate_est);
  
  	qdisc_reset(qdisc);
  
  	if (ops->destroy)
  		ops->destroy(qdisc);
  
  	module_put(ops->owner);
  	dev_put(qdisc_dev(qdisc));
  
  	trace_qdisc_destroy(qdisc);
  
  	call_rcu(&qdisc->rcu, qdisc_free_cb);
  }
  
  void qdisc_put(struct Qdisc *qdisc)
  {
  	if (!qdisc)
  		return;
  
  	if (qdisc->flags & TCQ_F_BUILTIN ||
  	    !refcount_dec_and_test(&qdisc->refcnt))
  		return;
  
  	qdisc_destroy(qdisc);
  }
  EXPORT_SYMBOL(qdisc_put);
  
  /* Version of qdisc_put() that is called with rtnl mutex unlocked.
   * Intended to be used as optimization, this function only takes rtnl lock if
   * qdisc reference counter reached zero.
   */
  
  void qdisc_put_unlocked(struct Qdisc *qdisc)
  {
  	if (qdisc->flags & TCQ_F_BUILTIN ||
  	    !refcount_dec_and_rtnl_lock(&qdisc->refcnt))
  		return;
  
  	qdisc_destroy(qdisc);
  	rtnl_unlock();
  }
  EXPORT_SYMBOL(qdisc_put_unlocked);
  
  /* Attach toplevel qdisc to device queue. */
  struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
  			      struct Qdisc *qdisc)
  {
  	struct Qdisc *oqdisc = dev_queue->qdisc_sleeping;
  	spinlock_t *root_lock;
  
  	root_lock = qdisc_lock(oqdisc);
  	spin_lock_bh(root_lock);
  
  	/* ... and graft new one */
  	if (qdisc == NULL)
  		qdisc = &noop_qdisc;
  	dev_queue->qdisc_sleeping = qdisc;
  	rcu_assign_pointer(dev_queue->qdisc, &noop_qdisc);
  
  	spin_unlock_bh(root_lock);
  
  	return oqdisc;
  }
  EXPORT_SYMBOL(dev_graft_qdisc);
  
  static void attach_one_default_qdisc(struct net_device *dev,
  				     struct netdev_queue *dev_queue,
  				     void *_unused)
  {
  	struct Qdisc *qdisc;
  	const struct Qdisc_ops *ops = default_qdisc_ops;
  
  	if (dev->priv_flags & IFF_NO_QUEUE)
  		ops = &noqueue_qdisc_ops;
  	else if(dev->type == ARPHRD_CAN)
  		ops = &pfifo_fast_ops;
  
  	qdisc = qdisc_create_dflt(dev_queue, ops, TC_H_ROOT, NULL);
  	if (!qdisc)
  		return;
  
  	if (!netif_is_multiqueue(dev))
  		qdisc->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;
  	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->priv_flags & IFF_NO_QUEUE) {
  		netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
  		dev->qdisc = txq->qdisc_sleeping;
  		qdisc_refcount_inc(dev->qdisc);
  	} else {
  		qdisc = qdisc_create_dflt(txq, &mq_qdisc_ops, TC_H_ROOT, NULL);
  		if (qdisc) {
  			dev->qdisc = qdisc;
  			qdisc->ops->attach(qdisc);
  		}
  	}
  
  	/* Detect default qdisc setup/init failed and fallback to "noqueue" */
  	if (dev->qdisc == &noop_qdisc) {
  		netdev_warn(dev, "default qdisc (%s) fail, fallback to %s\n",
  			    default_qdisc_ops->id, noqueue_qdisc_ops.id);
  		dev->priv_flags |= IFF_NO_QUEUE;
  		netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
  		dev->qdisc = txq->qdisc_sleeping;
  		qdisc_refcount_inc(dev->qdisc);
  		dev->priv_flags ^= IFF_NO_QUEUE;
  	}
  
  #ifdef CONFIG_NET_SCHED
  	if (dev->qdisc != &noop_qdisc)
  		qdisc_hash_add(dev->qdisc, false);
  #endif
  }
  
  static void transition_one_qdisc(struct net_device *dev,
  				 struct netdev_queue *dev_queue,
  				 void *_need_watchdog)
  {
  	struct Qdisc *new_qdisc = dev_queue->qdisc_sleeping;
  	int *need_watchdog_p = _need_watchdog;
  
  	if (!(new_qdisc->flags & TCQ_F_BUILTIN))
  		clear_bit(__QDISC_STATE_DEACTIVATED, &new_qdisc->state);
  
  	rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
  	if (need_watchdog_p) {
  		dev_queue->trans_start = 0;
  		*need_watchdog_p = 1;
  	}
  }
  
  void dev_activate(struct net_device *dev)
  {
  	int need_watchdog;
  
  	/* No queueing discipline is attached to device;
  	 * create default one for devices, which need queueing
  	 * and noqueue_qdisc for virtual interfaces
  	 */
  
  	if (dev->qdisc == &noop_qdisc)
  		attach_default_qdiscs(dev);
  
  	if (!netif_carrier_ok(dev))
  		/* Delay activation until next carrier-on event */
  		return;
  
  	need_watchdog = 0;
  	netdev_for_each_tx_queue(dev, transition_one_qdisc, &need_watchdog);
  	if (dev_ingress_queue(dev))
  		transition_one_qdisc(dev, dev_ingress_queue(dev), NULL);
  
  	if (need_watchdog) {
  		netif_trans_update(dev);
  		dev_watchdog_up(dev);
  	}
  }
  EXPORT_SYMBOL(dev_activate);
  
  static void qdisc_deactivate(struct Qdisc *qdisc)
  {
  	if (qdisc->flags & TCQ_F_BUILTIN)
  		return;
  
  	set_bit(__QDISC_STATE_DEACTIVATED, &qdisc->state);
  }
  
  static void dev_deactivate_queue(struct net_device *dev,
  				 struct netdev_queue *dev_queue,
  				 void *_qdisc_default)
  {
  	struct Qdisc *qdisc_default = _qdisc_default;
  	struct Qdisc *qdisc;
  
  	qdisc = rtnl_dereference(dev_queue->qdisc);
  	if (qdisc) {
  		qdisc_deactivate(qdisc);
  		rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
  	}
  }
  
  static void dev_reset_queue(struct net_device *dev,
  			    struct netdev_queue *dev_queue,
  			    void *_unused)
  {
  	struct Qdisc *qdisc;
  	bool nolock;
  
  	qdisc = dev_queue->qdisc_sleeping;
  	if (!qdisc)
  		return;
  
  	nolock = qdisc->flags & TCQ_F_NOLOCK;
  
  	if (nolock)
  		spin_lock_bh(&qdisc->seqlock);
  	spin_lock_bh(qdisc_lock(qdisc));
  
  	qdisc_reset(qdisc);
  
  	spin_unlock_bh(qdisc_lock(qdisc));
  	if (nolock) {
  		clear_bit(__QDISC_STATE_MISSED, &qdisc->state);
  		clear_bit(__QDISC_STATE_DRAINING, &qdisc->state);
  		spin_unlock_bh(&qdisc->seqlock);
  	}
  }
  
  static bool some_qdisc_is_busy(struct net_device *dev)
  {
  	unsigned int i;
  
  	for (i = 0; i < dev->num_tx_queues; i++) {
  		struct netdev_queue *dev_queue;
  		spinlock_t *root_lock;
  		struct Qdisc *q;
  		int val;
  
  		dev_queue = netdev_get_tx_queue(dev, i);
  		q = dev_queue->qdisc_sleeping;
  
  		root_lock = qdisc_lock(q);
  		spin_lock_bh(root_lock);
  
  		val = (qdisc_is_running(q) ||
  		       test_bit(__QDISC_STATE_SCHED, &q->state));
  
  		spin_unlock_bh(root_lock);
  
  		if (val)
  			return true;
  	}
  	return false;
  }
  
  /**
   * 	dev_deactivate_many - deactivate transmissions on several devices
   * 	@head: list of devices to deactivate
   *
   *	This function returns only when all outstanding transmissions
   *	have completed, unless all devices are in dismantle phase.
   */
  void dev_deactivate_many(struct list_head *head)
  {
  	struct net_device *dev;
  
  	list_for_each_entry(dev, head, close_list) {
  		netdev_for_each_tx_queue(dev, dev_deactivate_queue,
  					 &noop_qdisc);
  		if (dev_ingress_queue(dev))
  			dev_deactivate_queue(dev, dev_ingress_queue(dev),
  					     &noop_qdisc);
  
  		dev_watchdog_down(dev);
  	}
  
  	/* Wait for outstanding qdisc-less dev_queue_xmit calls or
  	 * outstanding qdisc enqueuing calls.
  	 * This is avoided if all devices are in dismantle phase :
  	 * Caller will call synchronize_net() for us
  	 */
  	synchronize_net();
  
  	list_for_each_entry(dev, head, close_list) {
  		netdev_for_each_tx_queue(dev, dev_reset_queue, NULL);
  
  		if (dev_ingress_queue(dev))
  			dev_reset_queue(dev, dev_ingress_queue(dev), NULL);
  	}
  
  	/* Wait for outstanding qdisc_run calls. */
  	list_for_each_entry(dev, head, close_list) {
  		while (some_qdisc_is_busy(dev)) {
  			/* wait_event() would avoid this sleep-loop but would
  			 * require expensive checks in the fast paths of packet
  			 * processing which isn't worth it.
  			 */
  			schedule_timeout_uninterruptible(1);
  		}
  	}
  }
  
  void dev_deactivate(struct net_device *dev)
  {
  	LIST_HEAD(single);
  
  	list_add(&dev->close_list, &single);
  	dev_deactivate_many(&single);
  	list_del(&single);
  }
  EXPORT_SYMBOL(dev_deactivate);
  
  static int qdisc_change_tx_queue_len(struct net_device *dev,
  				     struct netdev_queue *dev_queue)
  {
  	struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
  	const struct Qdisc_ops *ops = qdisc->ops;
  
  	if (ops->change_tx_queue_len)
  		return ops->change_tx_queue_len(qdisc, dev->tx_queue_len);
  	return 0;
  }
  
  void dev_qdisc_change_real_num_tx(struct net_device *dev,
  				  unsigned int new_real_tx)
  {
  	struct Qdisc *qdisc = dev->qdisc;
  
  	if (qdisc->ops->change_real_num_tx)
  		qdisc->ops->change_real_num_tx(qdisc, new_real_tx);
  }
  
  int dev_qdisc_change_tx_queue_len(struct net_device *dev)
  {
  	bool up = dev->flags & IFF_UP;
  	unsigned int i;
  	int ret = 0;
  
  	if (up)
  		dev_deactivate(dev);
  
  	for (i = 0; i < dev->num_tx_queues; i++) {
  		ret = qdisc_change_tx_queue_len(dev, &dev->_tx[i]);
  
  		/* TODO: revert changes on a partial failure */
  		if (ret)
  			break;
  	}
  
  	if (up)
  		dev_activate(dev);
  	return ret;
  }
  
  static void dev_init_scheduler_queue(struct net_device *dev,
  				     struct netdev_queue *dev_queue,
  				     void *_qdisc)
  {
  	struct Qdisc *qdisc = _qdisc;
  
  	rcu_assign_pointer(dev_queue->qdisc, qdisc);
  	dev_queue->qdisc_sleeping = qdisc;
  }
  
  void dev_init_scheduler(struct net_device *dev)
  {
  	dev->qdisc = &noop_qdisc;
  	netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
  	if (dev_ingress_queue(dev))
  		dev_init_scheduler_queue(dev, dev_ingress_queue(dev), &noop_qdisc);
  
  	timer_setup(&dev->watchdog_timer, dev_watchdog, 0);
  }
  
  static void shutdown_scheduler_queue(struct net_device *dev,
  				     struct netdev_queue *dev_queue,
  				     void *_qdisc_default)
  {
  	struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
  	struct Qdisc *qdisc_default = _qdisc_default;
  
  	if (qdisc) {
  		rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
  		dev_queue->qdisc_sleeping = qdisc_default;
  
  		qdisc_put(qdisc);
  	}
  }
  
  void dev_shutdown(struct net_device *dev)
  {
  	netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
  	if (dev_ingress_queue(dev))
  		shutdown_scheduler_queue(dev, dev_ingress_queue(dev), &noop_qdisc);
  	qdisc_put(dev->qdisc);
  	dev->qdisc = &noop_qdisc;
  
  	WARN_ON(timer_pending(&dev->watchdog_timer));
  }
  
  /**
   * psched_ratecfg_precompute__() - Pre-compute values for reciprocal division
   * @rate:   Rate to compute reciprocal division values of
   * @mult:   Multiplier for reciprocal division
   * @shift:  Shift for reciprocal division
   *
   * The multiplier and shift for reciprocal division by rate are stored
   * in mult and shift.
   *
   * The deal here is to replace a divide by a reciprocal one
   * in fast path (a reciprocal divide is a multiply and a shift)
   *
   * Normal formula would be :
   *  time_in_ns = (NSEC_PER_SEC * len) / rate_bps
   *
   * We compute mult/shift to use instead :
   *  time_in_ns = (len * mult) >> shift;
   *
   * We try to get the highest possible mult value for accuracy,
   * but have to make sure no overflows will ever happen.
   *
   * reciprocal_value() is not used here it doesn't handle 64-bit values.
   */
  static void psched_ratecfg_precompute__(u64 rate, u32 *mult, u8 *shift)
  {
  	u64 factor = NSEC_PER_SEC;
  
  	*mult = 1;
  	*shift = 0;
  
  	if (rate <= 0)
  		return;
  
  	for (;;) {
  		*mult = div64_u64(factor, rate);
  		if (*mult & (1U << 31) || factor & (1ULL << 63))
  			break;
  		factor <<= 1;
  		(*shift)++;
  	}
  }
  
  void psched_ratecfg_precompute(struct psched_ratecfg *r,
  			       const struct tc_ratespec *conf,
  			       u64 rate64)
  {
  	memset(r, 0, sizeof(*r));
  	r->overhead = conf->overhead;
  	r->rate_bytes_ps = max_t(u64, conf->rate, rate64);
  	r->linklayer = (conf->linklayer & TC_LINKLAYER_MASK);
  	psched_ratecfg_precompute__(r->rate_bytes_ps, &r->mult, &r->shift);
  }
  EXPORT_SYMBOL(psched_ratecfg_precompute);
  
  void psched_ppscfg_precompute(struct psched_pktrate *r, u64 pktrate64)
  {
  	r->rate_pkts_ps = pktrate64;
  	psched_ratecfg_precompute__(r->rate_pkts_ps, &r->mult, &r->shift);
  }
  EXPORT_SYMBOL(psched_ppscfg_precompute);
  
  static void mini_qdisc_rcu_func(struct rcu_head *head)
  {
  }
  
  void mini_qdisc_pair_swap(struct mini_Qdisc_pair *miniqp,
  			  struct tcf_proto *tp_head)
  {
  	/* Protected with chain0->filter_chain_lock.
  	 * Can't access chain directly because tp_head can be NULL.
  	 */
  	struct mini_Qdisc *miniq_old =
  		rcu_dereference_protected(*miniqp->p_miniq, 1);
  	struct mini_Qdisc *miniq;
  
  	if (!tp_head) {
  		RCU_INIT_POINTER(*miniqp->p_miniq, NULL);
  		/* Wait for flying RCU callback before it is freed. */
  		rcu_barrier();
  		return;
  	}
  
  	miniq = !miniq_old || miniq_old == &miniqp->miniq2 ?
  		&miniqp->miniq1 : &miniqp->miniq2;
  
  	/* We need to make sure that readers won't see the miniq
  	 * we are about to modify. So wait until previous call_rcu callback
  	 * is done.
  	 */
  	rcu_barrier();
  	miniq->filter_list = tp_head;
  	rcu_assign_pointer(*miniqp->p_miniq, miniq);
  
  	if (miniq_old)
  		/* This is counterpart of the rcu barriers above. We need to
  		 * block potential new user of miniq_old until all readers
  		 * are not seeing it.
  		 */
  		call_rcu(&miniq_old->rcu, mini_qdisc_rcu_func);
  }
  EXPORT_SYMBOL(mini_qdisc_pair_swap);
  
  void mini_qdisc_pair_block_init(struct mini_Qdisc_pair *miniqp,
  				struct tcf_block *block)
  {
  	miniqp->miniq1.block = block;
  	miniqp->miniq2.block = block;
  }
  EXPORT_SYMBOL(mini_qdisc_pair_block_init);
  
  void mini_qdisc_pair_init(struct mini_Qdisc_pair *miniqp, struct Qdisc *qdisc,
  			  struct mini_Qdisc __rcu **p_miniq)
  {
  	miniqp->miniq1.cpu_bstats = qdisc->cpu_bstats;
  	miniqp->miniq1.cpu_qstats = qdisc->cpu_qstats;
  	miniqp->miniq2.cpu_bstats = qdisc->cpu_bstats;
  	miniqp->miniq2.cpu_qstats = qdisc->cpu_qstats;
  	miniqp->p_miniq = p_miniq;
  }
  EXPORT_SYMBOL(mini_qdisc_pair_init);
  