/*

   * net/sched/sch_qfq.c         Quick Fair Queueing Plus Scheduler.

   *
   * Copyright (c) 2009 Fabio Checconi, Luigi Rizzo, and Paolo Valente.

   * Copyright (c) 2012 Paolo Valente.

   *
   * 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/module.h>
  #include <linux/init.h>
  #include <linux/bitops.h>
  #include <linux/errno.h>
  #include <linux/netdevice.h>
  #include <linux/pkt_sched.h>
  #include <net/sch_generic.h>
  #include <net/pkt_sched.h>
  #include <net/pkt_cls.h>

  /*  Quick Fair Queueing Plus
      ========================

  
      Sources:

      [1] Paolo Valente,
      "Reducing the Execution Time of Fair-Queueing Schedulers."
      http://algo.ing.unimo.it/people/paolo/agg-sched/agg-sched.pdf
  
      Sources for QFQ:
  
      [2] Fabio Checconi, Luigi Rizzo, and Paolo Valente: "QFQ: Efficient

      Packet Scheduling with Tight Bandwidth Distribution Guarantees."
  
      See also:
      http://retis.sssup.it/~fabio/linux/qfq/
   */
  
  /*

    QFQ+ divides classes into aggregates of at most MAX_AGG_CLASSES
    classes. Each aggregate is timestamped with a virtual start time S
    and a virtual finish time F, and scheduled according to its
    timestamps. S and F are computed as a function of a system virtual
    time function V. The classes within each aggregate are instead
    scheduled with DRR.
  
    To speed up operations, QFQ+ divides also aggregates into a limited
    number of groups. Which group a class belongs to depends on the
    ratio between the maximum packet length for the class and the weight
    of the class. Groups have their own S and F. In the end, QFQ+
    schedules groups, then aggregates within groups, then classes within
    aggregates. See [1] and [2] for a full description.

    Virtual time computations.
  
    S, F and V are all computed in fixed point arithmetic with
    FRAC_BITS decimal bits.
  
    QFQ_MAX_INDEX is the maximum index allowed for a group. We need
  	one bit per index.
    QFQ_MAX_WSHIFT is the maximum power of two supported as a weight.
  
    The layout of the bits is as below:
  
                     [ MTU_SHIFT ][      FRAC_BITS    ]
                     [ MAX_INDEX    ][ MIN_SLOT_SHIFT ]
  				 ^.__grp->index = 0
  				 *.__grp->slot_shift
  
    where MIN_SLOT_SHIFT is derived by difference from the others.
  
    The max group index corresponds to Lmax/w_min, where
    Lmax=1<<MTU_SHIFT, w_min = 1 .
    From this, and knowing how many groups (MAX_INDEX) we want,
    we can derive the shift corresponding to each group.
  
    Because we often need to compute
  	F = S + len/w_i  and V = V + len/wsum
    instead of storing w_i store the value
  	inv_w = (1<<FRAC_BITS)/w_i
    so we can do F = S + len * inv_w * wsum.
    We use W_TOT in the formulas so we can easily move between
    static and adaptive weight sum.
  
    The per-scheduler-instance data contain all the data structures
    for the scheduler: bitmaps and bucket lists.
  
   */
  
  /*
   * Maximum number of consecutive slots occupied by backlogged classes
   * inside a group.
   */
  #define QFQ_MAX_SLOTS	32
  
  /*

   * Shifts used for aggregate<->group mapping.  We allow class weights that are
   * in the range [1, 2^MAX_WSHIFT], and we try to map each aggregate i to the

   * group with the smallest index that can support the L_i / r_i configured

   * for the classes in the aggregate.

   *
   * grp->index is the index of the group; and grp->slot_shift
   * is the shift for the corresponding (scaled) sigma_i.
   */

  #define QFQ_MAX_INDEX		24

  #define QFQ_MAX_WSHIFT		10

  #define	QFQ_MAX_WEIGHT		(1<<QFQ_MAX_WSHIFT) /* see qfq_slot_insert */
  #define QFQ_MAX_WSUM		(64*QFQ_MAX_WEIGHT)

  
  #define FRAC_BITS		30	/* fixed point arithmetic */
  #define ONE_FP			(1UL << FRAC_BITS)

  #define QFQ_MTU_SHIFT		16	/* to support TSO/GSO */

  #define QFQ_MIN_LMAX		512	/* see qfq_slot_insert */
  
  #define QFQ_MAX_AGG_CLASSES	8 /* max num classes per aggregate allowed */

  
  /*
   * Possible group states.  These values are used as indexes for the bitmaps
   * array of struct qfq_queue.
   */
  enum qfq_state { ER, IR, EB, IB, QFQ_MAX_STATE };
  
  struct qfq_group;

  struct qfq_aggregate;

  struct qfq_class {
  	struct Qdisc_class_common common;
  
  	unsigned int refcnt;
  	unsigned int filter_cnt;
  
  	struct gnet_stats_basic_packed bstats;
  	struct gnet_stats_queue qstats;

  	struct gnet_stats_rate_est64 rate_est;

  	struct Qdisc *qdisc;

  	struct list_head alist;		/* Link for active-classes list. */
  	struct qfq_aggregate *agg;	/* Parent aggregate. */
  	int deficit;			/* DRR deficit counter. */
  };

  struct qfq_aggregate {

  	struct hlist_node next;	/* Link for the slot list. */
  	u64 S, F;		/* flow timestamps (exact) */
  
  	/* group we belong to. In principle we would need the index,
  	 * which is log_2(lmax/weight), but we never reference it
  	 * directly, only the group.
  	 */
  	struct qfq_group *grp;
  
  	/* these are copied from the flowset. */

  	u32	class_weight; /* Weight of each class in this aggregate. */
  	/* Max pkt size for the classes in this aggregate, DRR quantum. */
  	int	lmax;
  
  	u32	inv_w;	    /* ONE_FP/(sum of weights of classes in aggr.). */
  	u32	budgetmax;  /* Max budget for this aggregate. */
  	u32	initial_budget, budget;     /* Initial and current budget. */
  
  	int		  num_classes;	/* Number of classes in this aggr. */
  	struct list_head  active;	/* DRR queue of active classes. */
  
  	struct hlist_node nonfull_next;	/* See nonfull_aggs in qfq_sched. */

  };
  
  struct qfq_group {
  	u64 S, F;			/* group timestamps (approx). */
  	unsigned int slot_shift;	/* Slot shift. */
  	unsigned int index;		/* Group index. */
  	unsigned int front;		/* Index of the front slot. */
  	unsigned long full_slots;	/* non-empty slots */

  	/* Array of RR lists of active aggregates. */

  	struct hlist_head slots[QFQ_MAX_SLOTS];
  };
  
  struct qfq_sched {

  	struct tcf_proto __rcu *filter_list;

  	struct Qdisc_class_hash clhash;

  	u64			oldV, V;	/* Precise virtual times. */
  	struct qfq_aggregate	*in_serv_agg;   /* Aggregate being served. */
  	u32			num_active_agg; /* Num. of active aggregates */
  	u32			wsum;		/* weight sum */

  	u32			iwsum;		/* inverse weight sum */

  
  	unsigned long bitmaps[QFQ_MAX_STATE];	    /* Group bitmaps. */
  	struct qfq_group groups[QFQ_MAX_INDEX + 1]; /* The groups. */

  	u32 min_slot_shift;	/* Index of the group-0 bit in the bitmaps. */
  
  	u32 max_agg_classes;		/* Max number of classes per aggr. */
  	struct hlist_head nonfull_aggs; /* Aggs with room for more classes. */

  };

  /*
   * Possible reasons why the timestamps of an aggregate are updated
   * enqueue: the aggregate switches from idle to active and must scheduled
   *	    for service
   * requeue: the aggregate finishes its budget, so it stops being served and
   *	    must be rescheduled for service
   */
  enum update_reason {enqueue, requeue};

  static struct qfq_class *qfq_find_class(struct Qdisc *sch, u32 classid)
  {
  	struct qfq_sched *q = qdisc_priv(sch);
  	struct Qdisc_class_common *clc;
  
  	clc = qdisc_class_find(&q->clhash, classid);
  	if (clc == NULL)
  		return NULL;
  	return container_of(clc, struct qfq_class, common);
  }
  
  static void qfq_purge_queue(struct qfq_class *cl)
  {
  	unsigned int len = cl->qdisc->q.qlen;
  
  	qdisc_reset(cl->qdisc);
  	qdisc_tree_decrease_qlen(cl->qdisc, len);
  }
  
  static const struct nla_policy qfq_policy[TCA_QFQ_MAX + 1] = {
  	[TCA_QFQ_WEIGHT] = { .type = NLA_U32 },
  	[TCA_QFQ_LMAX] = { .type = NLA_U32 },
  };
  
  /*
   * Calculate a flow index, given its weight and maximum packet length.
   * index = log_2(maxlen/weight) but we need to apply the scaling.
   * This is used only once at flow creation.
   */

  static int qfq_calc_index(u32 inv_w, unsigned int maxlen, u32 min_slot_shift)

  {
  	u64 slot_size = (u64)maxlen * inv_w;
  	unsigned long size_map;
  	int index = 0;

  	size_map = slot_size >> min_slot_shift;

  	if (!size_map)
  		goto out;
  
  	index = __fls(size_map) + 1;	/* basically a log_2 */

  	index -= !(slot_size - (1ULL << (index + min_slot_shift - 1)));

  
  	if (index < 0)
  		index = 0;
  out:
  	pr_debug("qfq calc_index: W = %lu, L = %u, I = %d
  ",
  		 (unsigned long) ONE_FP/inv_w, maxlen, index);
  
  	return index;
  }

  static void qfq_deactivate_agg(struct qfq_sched *, struct qfq_aggregate *);
  static void qfq_activate_agg(struct qfq_sched *, struct qfq_aggregate *,
  			     enum update_reason);
  
  static void qfq_init_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
  			 u32 lmax, u32 weight)

  {

  	INIT_LIST_HEAD(&agg->active);
  	hlist_add_head(&agg->nonfull_next, &q->nonfull_aggs);
  
  	agg->lmax = lmax;
  	agg->class_weight = weight;
  }
  
  static struct qfq_aggregate *qfq_find_agg(struct qfq_sched *q,
  					  u32 lmax, u32 weight)
  {
  	struct qfq_aggregate *agg;

  	hlist_for_each_entry(agg, &q->nonfull_aggs, nonfull_next)

  		if (agg->lmax == lmax && agg->class_weight == weight)
  			return agg;
  
  	return NULL;
  }

  /* Update aggregate as a function of the new number of classes. */
  static void qfq_update_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
  			   int new_num_classes)
  {
  	u32 new_agg_weight;
  
  	if (new_num_classes == q->max_agg_classes)
  		hlist_del_init(&agg->nonfull_next);
  
  	if (agg->num_classes > new_num_classes &&
  	    new_num_classes == q->max_agg_classes - 1) /* agg no more full */
  		hlist_add_head(&agg->nonfull_next, &q->nonfull_aggs);

  	/* The next assignment may let
  	 * agg->initial_budget > agg->budgetmax
  	 * hold, we will take it into account in charge_actual_service().
  	 */

  	agg->budgetmax = new_num_classes * agg->lmax;
  	new_agg_weight = agg->class_weight * new_num_classes;
  	agg->inv_w = ONE_FP/new_agg_weight;
  
  	if (agg->grp == NULL) {
  		int i = qfq_calc_index(agg->inv_w, agg->budgetmax,
  				       q->min_slot_shift);
  		agg->grp = &q->groups[i];
  	}
  
  	q->wsum +=
  		(int) agg->class_weight * (new_num_classes - agg->num_classes);

  	q->iwsum = ONE_FP / q->wsum;

  
  	agg->num_classes = new_num_classes;
  }
  
  /* Add class to aggregate. */
  static void qfq_add_to_agg(struct qfq_sched *q,
  			   struct qfq_aggregate *agg,
  			   struct qfq_class *cl)
  {
  	cl->agg = agg;
  
  	qfq_update_agg(q, agg, agg->num_classes+1);
  	if (cl->qdisc->q.qlen > 0) { /* adding an active class */
  		list_add_tail(&cl->alist, &agg->active);
  		if (list_first_entry(&agg->active, struct qfq_class, alist) ==
  		    cl && q->in_serv_agg != agg) /* agg was inactive */
  			qfq_activate_agg(q, agg, enqueue); /* schedule agg */
  	}

  }

  static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *);

  static void qfq_destroy_agg(struct qfq_sched *q, struct qfq_aggregate *agg)

  {

  	if (!hlist_unhashed(&agg->nonfull_next))
  		hlist_del_init(&agg->nonfull_next);

  	q->wsum -= agg->class_weight;
  	if (q->wsum != 0)
  		q->iwsum = ONE_FP / q->wsum;

  	if (q->in_serv_agg == agg)
  		q->in_serv_agg = qfq_choose_next_agg(q);
  	kfree(agg);
  }

  /* Deschedule class from within its parent aggregate. */
  static void qfq_deactivate_class(struct qfq_sched *q, struct qfq_class *cl)
  {
  	struct qfq_aggregate *agg = cl->agg;

  	list_del(&cl->alist); /* remove from RR queue of the aggregate */
  	if (list_empty(&agg->active)) /* agg is now inactive */
  		qfq_deactivate_agg(q, agg);

  }

  /* Remove class from its parent aggregate. */
  static void qfq_rm_from_agg(struct qfq_sched *q, struct qfq_class *cl)

  {

  	struct qfq_aggregate *agg = cl->agg;

  	cl->agg = NULL;
  	if (agg->num_classes == 1) { /* agg being emptied, destroy it */
  		qfq_destroy_agg(q, agg);
  		return;

  	}

  	qfq_update_agg(q, agg, agg->num_classes-1);
  }

  /* Deschedule class and remove it from its parent aggregate. */
  static void qfq_deact_rm_from_agg(struct qfq_sched *q, struct qfq_class *cl)
  {
  	if (cl->qdisc->q.qlen > 0) /* class is active */
  		qfq_deactivate_class(q, cl);

  	qfq_rm_from_agg(q, cl);

  }

  /* Move class to a new aggregate, matching the new class weight and/or lmax */
  static int qfq_change_agg(struct Qdisc *sch, struct qfq_class *cl, u32 weight,
  			   u32 lmax)
  {
  	struct qfq_sched *q = qdisc_priv(sch);
  	struct qfq_aggregate *new_agg = qfq_find_agg(q, lmax, weight);
  
  	if (new_agg == NULL) { /* create new aggregate */
  		new_agg = kzalloc(sizeof(*new_agg), GFP_ATOMIC);
  		if (new_agg == NULL)
  			return -ENOBUFS;
  		qfq_init_agg(q, new_agg, lmax, weight);
  	}
  	qfq_deact_rm_from_agg(q, cl);
  	qfq_add_to_agg(q, new_agg, cl);
  
  	return 0;
  }

  static int qfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
  			    struct nlattr **tca, unsigned long *arg)
  {
  	struct qfq_sched *q = qdisc_priv(sch);
  	struct qfq_class *cl = (struct qfq_class *)*arg;

  	bool existing = false;

  	struct nlattr *tb[TCA_QFQ_MAX + 1];

  	struct qfq_aggregate *new_agg = NULL;

  	u32 weight, lmax, inv_w;

  	int err;

  	int delta_w;

  
  	if (tca[TCA_OPTIONS] == NULL) {
  		pr_notice("qfq: no options
  ");
  		return -EINVAL;
  	}
  
  	err = nla_parse_nested(tb, TCA_QFQ_MAX, tca[TCA_OPTIONS], qfq_policy);
  	if (err < 0)
  		return err;
  
  	if (tb[TCA_QFQ_WEIGHT]) {
  		weight = nla_get_u32(tb[TCA_QFQ_WEIGHT]);
  		if (!weight || weight > (1UL << QFQ_MAX_WSHIFT)) {
  			pr_notice("qfq: invalid weight %u
  ", weight);
  			return -EINVAL;
  		}
  	} else
  		weight = 1;

  	if (tb[TCA_QFQ_LMAX]) {
  		lmax = nla_get_u32(tb[TCA_QFQ_LMAX]);

  		if (lmax < QFQ_MIN_LMAX || lmax > (1UL << QFQ_MTU_SHIFT)) {

  			pr_notice("qfq: invalid max length %u
  ", lmax);
  			return -EINVAL;
  		}
  	} else

  		lmax = psched_mtu(qdisc_dev(sch));

  	inv_w = ONE_FP / weight;
  	weight = ONE_FP / inv_w;
  
  	if (cl != NULL &&
  	    lmax == cl->agg->lmax &&
  	    weight == cl->agg->class_weight)
  		return 0; /* nothing to change */
  
  	delta_w = weight - (cl ? cl->agg->class_weight : 0);
  
  	if (q->wsum + delta_w > QFQ_MAX_WSUM) {
  		pr_notice("qfq: total weight out of range (%d + %u)
  ",
  			  delta_w, q->wsum);
  		return -EINVAL;
  	}
  
  	if (cl != NULL) { /* modify existing class */

  		if (tca[TCA_RATE]) {

  			err = gen_replace_estimator(&cl->bstats, NULL,
  						    &cl->rate_est,

  						    qdisc_root_sleeping_lock(sch),
  						    tca[TCA_RATE]);
  			if (err)
  				return err;
  		}

  		existing = true;
  		goto set_change_agg;

  	}

  	/* create and init new class */

  	cl = kzalloc(sizeof(struct qfq_class), GFP_KERNEL);
  	if (cl == NULL)
  		return -ENOBUFS;
  
  	cl->refcnt = 1;
  	cl->common.classid = classid;

  	cl->deficit = lmax;

  
  	cl->qdisc = qdisc_create_dflt(sch->dev_queue,
  				      &pfifo_qdisc_ops, classid);
  	if (cl->qdisc == NULL)
  		cl->qdisc = &noop_qdisc;
  
  	if (tca[TCA_RATE]) {

  		err = gen_new_estimator(&cl->bstats, NULL,
  					&cl->rate_est,

  					qdisc_root_sleeping_lock(sch),
  					tca[TCA_RATE]);

  		if (err)
  			goto destroy_class;

  	}
  
  	sch_tree_lock(sch);
  	qdisc_class_hash_insert(&q->clhash, &cl->common);
  	sch_tree_unlock(sch);
  
  	qdisc_class_hash_grow(sch, &q->clhash);

  set_change_agg:
  	sch_tree_lock(sch);
  	new_agg = qfq_find_agg(q, lmax, weight);
  	if (new_agg == NULL) { /* create new aggregate */
  		sch_tree_unlock(sch);
  		new_agg = kzalloc(sizeof(*new_agg), GFP_KERNEL);
  		if (new_agg == NULL) {
  			err = -ENOBUFS;
  			gen_kill_estimator(&cl->bstats, &cl->rate_est);
  			goto destroy_class;
  		}
  		sch_tree_lock(sch);
  		qfq_init_agg(q, new_agg, lmax, weight);
  	}
  	if (existing)
  		qfq_deact_rm_from_agg(q, cl);
  	qfq_add_to_agg(q, new_agg, cl);
  	sch_tree_unlock(sch);

  	*arg = (unsigned long)cl;
  	return 0;

  
  destroy_class:
  	qdisc_destroy(cl->qdisc);
  	kfree(cl);
  	return err;

  }
  
  static void qfq_destroy_class(struct Qdisc *sch, struct qfq_class *cl)
  {
  	struct qfq_sched *q = qdisc_priv(sch);

  	qfq_rm_from_agg(q, cl);

  	gen_kill_estimator(&cl->bstats, &cl->rate_est);
  	qdisc_destroy(cl->qdisc);
  	kfree(cl);
  }
  
  static int qfq_delete_class(struct Qdisc *sch, unsigned long arg)
  {
  	struct qfq_sched *q = qdisc_priv(sch);
  	struct qfq_class *cl = (struct qfq_class *)arg;
  
  	if (cl->filter_cnt > 0)
  		return -EBUSY;
  
  	sch_tree_lock(sch);
  
  	qfq_purge_queue(cl);
  	qdisc_class_hash_remove(&q->clhash, &cl->common);
  
  	BUG_ON(--cl->refcnt == 0);
  	/*
  	 * This shouldn't happen: we "hold" one cops->get() when called
  	 * from tc_ctl_tclass; the destroy method is done from cops->put().
  	 */
  
  	sch_tree_unlock(sch);
  	return 0;
  }
  
  static unsigned long qfq_get_class(struct Qdisc *sch, u32 classid)
  {
  	struct qfq_class *cl = qfq_find_class(sch, classid);
  
  	if (cl != NULL)
  		cl->refcnt++;
  
  	return (unsigned long)cl;
  }
  
  static void qfq_put_class(struct Qdisc *sch, unsigned long arg)
  {
  	struct qfq_class *cl = (struct qfq_class *)arg;
  
  	if (--cl->refcnt == 0)
  		qfq_destroy_class(sch, cl);
  }

  static struct tcf_proto __rcu **qfq_tcf_chain(struct Qdisc *sch,
  					      unsigned long cl)

  {
  	struct qfq_sched *q = qdisc_priv(sch);
  
  	if (cl)
  		return NULL;
  
  	return &q->filter_list;
  }
  
  static unsigned long qfq_bind_tcf(struct Qdisc *sch, unsigned long parent,
  				  u32 classid)
  {
  	struct qfq_class *cl = qfq_find_class(sch, classid);
  
  	if (cl != NULL)
  		cl->filter_cnt++;
  
  	return (unsigned long)cl;
  }
  
  static void qfq_unbind_tcf(struct Qdisc *sch, unsigned long arg)
  {
  	struct qfq_class *cl = (struct qfq_class *)arg;
  
  	cl->filter_cnt--;
  }
  
  static int qfq_graft_class(struct Qdisc *sch, unsigned long arg,
  			   struct Qdisc *new, struct Qdisc **old)
  {
  	struct qfq_class *cl = (struct qfq_class *)arg;
  
  	if (new == NULL) {
  		new = qdisc_create_dflt(sch->dev_queue,
  					&pfifo_qdisc_ops, cl->common.classid);
  		if (new == NULL)
  			new = &noop_qdisc;
  	}
  
  	sch_tree_lock(sch);
  	qfq_purge_queue(cl);
  	*old = cl->qdisc;
  	cl->qdisc = new;
  	sch_tree_unlock(sch);
  	return 0;
  }
  
  static struct Qdisc *qfq_class_leaf(struct Qdisc *sch, unsigned long arg)
  {
  	struct qfq_class *cl = (struct qfq_class *)arg;
  
  	return cl->qdisc;
  }
  
  static int qfq_dump_class(struct Qdisc *sch, unsigned long arg,
  			  struct sk_buff *skb, struct tcmsg *tcm)
  {
  	struct qfq_class *cl = (struct qfq_class *)arg;
  	struct nlattr *nest;
  
  	tcm->tcm_parent	= TC_H_ROOT;
  	tcm->tcm_handle	= cl->common.classid;
  	tcm->tcm_info	= cl->qdisc->handle;
  
  	nest = nla_nest_start(skb, TCA_OPTIONS);
  	if (nest == NULL)
  		goto nla_put_failure;

  	if (nla_put_u32(skb, TCA_QFQ_WEIGHT, cl->agg->class_weight) ||
  	    nla_put_u32(skb, TCA_QFQ_LMAX, cl->agg->lmax))

  		goto nla_put_failure;

  	return nla_nest_end(skb, nest);
  
  nla_put_failure:
  	nla_nest_cancel(skb, nest);
  	return -EMSGSIZE;
  }
  
  static int qfq_dump_class_stats(struct Qdisc *sch, unsigned long arg,
  				struct gnet_dump *d)
  {
  	struct qfq_class *cl = (struct qfq_class *)arg;
  	struct tc_qfq_stats xstats;
  
  	memset(&xstats, 0, sizeof(xstats));

  	xstats.weight = cl->agg->class_weight;
  	xstats.lmax = cl->agg->lmax;

  	if (gnet_stats_copy_basic(d, NULL, &cl->bstats) < 0 ||

  	    gnet_stats_copy_rate_est(d, &cl->bstats, &cl->rate_est) < 0 ||

  	    gnet_stats_copy_queue(d, NULL,
  				  &cl->qdisc->qstats, cl->qdisc->q.qlen) < 0)

  		return -1;
  
  	return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
  }
  
  static void qfq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
  {
  	struct qfq_sched *q = qdisc_priv(sch);
  	struct qfq_class *cl;

  	unsigned int i;
  
  	if (arg->stop)
  		return;
  
  	for (i = 0; i < q->clhash.hashsize; i++) {

  		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {

  			if (arg->count < arg->skip) {
  				arg->count++;
  				continue;
  			}
  			if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
  				arg->stop = 1;
  				return;
  			}
  			arg->count++;
  		}
  	}
  }
  
  static struct qfq_class *qfq_classify(struct sk_buff *skb, struct Qdisc *sch,
  				      int *qerr)
  {
  	struct qfq_sched *q = qdisc_priv(sch);
  	struct qfq_class *cl;
  	struct tcf_result res;

  	struct tcf_proto *fl;

  	int result;
  
  	if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
  		pr_debug("qfq_classify: found %d
  ", skb->priority);
  		cl = qfq_find_class(sch, skb->priority);
  		if (cl != NULL)
  			return cl;
  	}
  
  	*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;

  	fl = rcu_dereference_bh(q->filter_list);
  	result = tc_classify(skb, fl, &res);

  	if (result >= 0) {
  #ifdef CONFIG_NET_CLS_ACT
  		switch (result) {
  		case TC_ACT_QUEUED:
  		case TC_ACT_STOLEN:
  			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
  		case TC_ACT_SHOT:
  			return NULL;
  		}
  #endif
  		cl = (struct qfq_class *)res.class;
  		if (cl == NULL)
  			cl = qfq_find_class(sch, res.classid);
  		return cl;
  	}
  
  	return NULL;
  }
  
  /* Generic comparison function, handling wraparound. */
  static inline int qfq_gt(u64 a, u64 b)
  {
  	return (s64)(a - b) > 0;
  }
  
  /* Round a precise timestamp to its slotted value. */
  static inline u64 qfq_round_down(u64 ts, unsigned int shift)
  {
  	return ts & ~((1ULL << shift) - 1);
  }
  
  /* return the pointer to the group with lowest index in the bitmap */
  static inline struct qfq_group *qfq_ffs(struct qfq_sched *q,
  					unsigned long bitmap)
  {
  	int index = __ffs(bitmap);
  	return &q->groups[index];
  }
  /* Calculate a mask to mimic what would be ffs_from(). */
  static inline unsigned long mask_from(unsigned long bitmap, int from)
  {
  	return bitmap & ~((1UL << from) - 1);
  }
  
  /*
   * The state computation relies on ER=0, IR=1, EB=2, IB=3
   * First compute eligibility comparing grp->S, q->V,
   * then check if someone is blocking us and possibly add EB
   */
  static int qfq_calc_state(struct qfq_sched *q, const struct qfq_group *grp)
  {
  	/* if S > V we are not eligible */
  	unsigned int state = qfq_gt(grp->S, q->V);
  	unsigned long mask = mask_from(q->bitmaps[ER], grp->index);
  	struct qfq_group *next;
  
  	if (mask) {
  		next = qfq_ffs(q, mask);
  		if (qfq_gt(grp->F, next->F))
  			state |= EB;
  	}
  
  	return state;
  }
  
  
  /*
   * In principle
   *	q->bitmaps[dst] |= q->bitmaps[src] & mask;
   *	q->bitmaps[src] &= ~mask;
   * but we should make sure that src != dst
   */
  static inline void qfq_move_groups(struct qfq_sched *q, unsigned long mask,
  				   int src, int dst)
  {
  	q->bitmaps[dst] |= q->bitmaps[src] & mask;
  	q->bitmaps[src] &= ~mask;
  }
  
  static void qfq_unblock_groups(struct qfq_sched *q, int index, u64 old_F)
  {
  	unsigned long mask = mask_from(q->bitmaps[ER], index + 1);
  	struct qfq_group *next;
  
  	if (mask) {
  		next = qfq_ffs(q, mask);
  		if (!qfq_gt(next->F, old_F))
  			return;
  	}
  
  	mask = (1UL << index) - 1;
  	qfq_move_groups(q, mask, EB, ER);
  	qfq_move_groups(q, mask, IB, IR);
  }
  
  /*
   * perhaps
   *
  	old_V ^= q->V;

  	old_V >>= q->min_slot_shift;

  	if (old_V) {
  		...
  	}
   *
   */

  static void qfq_make_eligible(struct qfq_sched *q)

  {

  	unsigned long vslot = q->V >> q->min_slot_shift;
  	unsigned long old_vslot = q->oldV >> q->min_slot_shift;

  
  	if (vslot != old_vslot) {

  		unsigned long mask;
  		int last_flip_pos = fls(vslot ^ old_vslot);
  
  		if (last_flip_pos > 31) /* higher than the number of groups */
  			mask = ~0UL;    /* make all groups eligible */
  		else
  			mask = (1UL << last_flip_pos) - 1;

  		qfq_move_groups(q, mask, IR, ER);
  		qfq_move_groups(q, mask, IB, EB);
  	}
  }

  /*

   * The index of the slot in which the input aggregate agg is to be
   * inserted must not be higher than QFQ_MAX_SLOTS-2. There is a '-2'
   * and not a '-1' because the start time of the group may be moved
   * backward by one slot after the aggregate has been inserted, and
   * this would cause non-empty slots to be right-shifted by one
   * position.
   *
   * QFQ+ fully satisfies this bound to the slot index if the parameters
   * of the classes are not changed dynamically, and if QFQ+ never
   * happens to postpone the service of agg unjustly, i.e., it never
   * happens that the aggregate becomes backlogged and eligible, or just
   * eligible, while an aggregate with a higher approximated finish time
   * is being served. In particular, in this case QFQ+ guarantees that
   * the timestamps of agg are low enough that the slot index is never
   * higher than 2. Unfortunately, QFQ+ cannot provide the same
   * guarantee if it happens to unjustly postpone the service of agg, or
   * if the parameters of some class are changed.
   *
   * As for the first event, i.e., an out-of-order service, the
   * upper bound to the slot index guaranteed by QFQ+ grows to
   * 2 +
   * QFQ_MAX_AGG_CLASSES * ((1<<QFQ_MTU_SHIFT)/QFQ_MIN_LMAX) *
   * (current_max_weight/current_wsum) <= 2 + 8 * 128 * 1.

   *

   * The following function deals with this problem by backward-shifting
   * the timestamps of agg, if needed, so as to guarantee that the slot
   * index is never higher than QFQ_MAX_SLOTS-2. This backward-shift may
   * cause the service of other aggregates to be postponed, yet the
   * worst-case guarantees of these aggregates are not violated.  In
   * fact, in case of no out-of-order service, the timestamps of agg
   * would have been even lower than they are after the backward shift,
   * because QFQ+ would have guaranteed a maximum value equal to 2 for
   * the slot index, and 2 < QFQ_MAX_SLOTS-2. Hence the aggregates whose
   * service is postponed because of the backward-shift would have
   * however waited for the service of agg before being served.

   *

   * The other event that may cause the slot index to be higher than 2
   * for agg is a recent change of the parameters of some class. If the
   * weight of a class is increased or the lmax (max_pkt_size) of the
   * class is decreased, then a new aggregate with smaller slot size
   * than the original parent aggregate of the class may happen to be
   * activated. The activation of this aggregate should be properly
   * delayed to when the service of the class has finished in the ideal
   * system tracked by QFQ+. If the activation of the aggregate is not
   * delayed to this reference time instant, then this aggregate may be
   * unjustly served before other aggregates waiting for service. This
   * may cause the above bound to the slot index to be violated for some
   * of these unlucky aggregates.

   *

   * Instead of delaying the activation of the new aggregate, which is

   * quite complex, the above-discussed capping of the slot index is
   * used to handle also the consequences of a change of the parameters
   * of a class.

   */

  static void qfq_slot_insert(struct qfq_group *grp, struct qfq_aggregate *agg,

  			    u64 roundedS)
  {
  	u64 slot = (roundedS - grp->S) >> grp->slot_shift;

  	unsigned int i; /* slot index in the bucket list */
  
  	if (unlikely(slot > QFQ_MAX_SLOTS - 2)) {
  		u64 deltaS = roundedS - grp->S -
  			((u64)(QFQ_MAX_SLOTS - 2)<<grp->slot_shift);

  		agg->S -= deltaS;
  		agg->F -= deltaS;

  		slot = QFQ_MAX_SLOTS - 2;
  	}
  
  	i = (grp->front + slot) % QFQ_MAX_SLOTS;

  	hlist_add_head(&agg->next, &grp->slots[i]);

  	__set_bit(slot, &grp->full_slots);
  }
  
  /* Maybe introduce hlist_first_entry?? */

  static struct qfq_aggregate *qfq_slot_head(struct qfq_group *grp)

  {
  	return hlist_entry(grp->slots[grp->front].first,

  			   struct qfq_aggregate, next);

  }
  
  /*
   * remove the entry from the slot
   */
  static void qfq_front_slot_remove(struct qfq_group *grp)
  {

  	struct qfq_aggregate *agg = qfq_slot_head(grp);

  	BUG_ON(!agg);
  	hlist_del(&agg->next);

  	if (hlist_empty(&grp->slots[grp->front]))
  		__clear_bit(0, &grp->full_slots);
  }
  
  /*

   * Returns the first aggregate in the first non-empty bucket of the
   * group. As a side effect, adjusts the bucket list so the first
   * non-empty bucket is at position 0 in full_slots.

   */

  static struct qfq_aggregate *qfq_slot_scan(struct qfq_group *grp)

  {
  	unsigned int i;
  
  	pr_debug("qfq slot_scan: grp %u full %#lx
  ",
  		 grp->index, grp->full_slots);
  
  	if (grp->full_slots == 0)
  		return NULL;
  
  	i = __ffs(grp->full_slots);  /* zero based */
  	if (i > 0) {
  		grp->front = (grp->front + i) % QFQ_MAX_SLOTS;
  		grp->full_slots >>= i;
  	}
  
  	return qfq_slot_head(grp);
  }
  
  /*
   * adjust the bucket list. When the start time of a group decreases,
   * we move the index down (modulo QFQ_MAX_SLOTS) so we don't need to
   * move the objects. The mask of occupied slots must be shifted
   * because we use ffs() to find the first non-empty slot.
   * This covers decreases in the group's start time, but what about
   * increases of the start time ?
   * Here too we should make sure that i is less than 32
   */
  static void qfq_slot_rotate(struct qfq_group *grp, u64 roundedS)
  {
  	unsigned int i = (grp->S - roundedS) >> grp->slot_shift;
  
  	grp->full_slots <<= i;
  	grp->front = (grp->front - i) % QFQ_MAX_SLOTS;
  }

  static void qfq_update_eligible(struct qfq_sched *q)

  {
  	struct qfq_group *grp;
  	unsigned long ineligible;
  
  	ineligible = q->bitmaps[IR] | q->bitmaps[IB];
  	if (ineligible) {
  		if (!q->bitmaps[ER]) {
  			grp = qfq_ffs(q, ineligible);
  			if (qfq_gt(grp->S, q->V))
  				q->V = grp->S;
  		}

  		qfq_make_eligible(q);

  	}
  }

  /* Dequeue head packet of the head class in the DRR queue of the aggregate. */
  static void agg_dequeue(struct qfq_aggregate *agg,
  			struct qfq_class *cl, unsigned int len)

  {

  	qdisc_dequeue_peeked(cl->qdisc);

  	cl->deficit -= (int) len;

  	if (cl->qdisc->q.qlen == 0) /* no more packets, remove from list */
  		list_del(&cl->alist);
  	else if (cl->deficit < qdisc_pkt_len(cl->qdisc->ops->peek(cl->qdisc))) {
  		cl->deficit += agg->lmax;
  		list_move_tail(&cl->alist, &agg->active);

  	}

  }
  
  static inline struct sk_buff *qfq_peek_skb(struct qfq_aggregate *agg,
  					   struct qfq_class **cl,
  					   unsigned int *len)
  {
  	struct sk_buff *skb;

  	*cl = list_first_entry(&agg->active, struct qfq_class, alist);
  	skb = (*cl)->qdisc->ops->peek((*cl)->qdisc);
  	if (skb == NULL)
  		WARN_ONCE(1, "qfq_dequeue: non-workconserving leaf
  ");
  	else
  		*len = qdisc_pkt_len(skb);
  
  	return skb;
  }
  
  /* Update F according to the actual service received by the aggregate. */
  static inline void charge_actual_service(struct qfq_aggregate *agg)
  {

  	/* Compute the service received by the aggregate, taking into
  	 * account that, after decreasing the number of classes in
  	 * agg, it may happen that
  	 * agg->initial_budget - agg->budget > agg->bugdetmax
  	 */
  	u32 service_received = min(agg->budgetmax,
  				   agg->initial_budget - agg->budget);

  
  	agg->F = agg->S + (u64)service_received * agg->inv_w;

  }

  /* Assign a reasonable start time for a new aggregate in group i.
   * Admissible values for \hat(F) are multiples of \sigma_i
   * no greater than V+\sigma_i . Larger values mean that
   * we had a wraparound so we consider the timestamp to be stale.
   *
   * If F is not stale and F >= V then we set S = F.
   * Otherwise we should assign S = V, but this may violate
   * the ordering in EB (see [2]). So, if we have groups in ER,
   * set S to the F_j of the first group j which would be blocking us.
   * We are guaranteed not to move S backward because
   * otherwise our group i would still be blocked.
   */
  static void qfq_update_start(struct qfq_sched *q, struct qfq_aggregate *agg)
  {
  	unsigned long mask;
  	u64 limit, roundedF;
  	int slot_shift = agg->grp->slot_shift;
  
  	roundedF = qfq_round_down(agg->F, slot_shift);
  	limit = qfq_round_down(q->V, slot_shift) + (1ULL << slot_shift);
  
  	if (!qfq_gt(agg->F, q->V) || qfq_gt(roundedF, limit)) {
  		/* timestamp was stale */
  		mask = mask_from(q->bitmaps[ER], agg->grp->index);
  		if (mask) {
  			struct qfq_group *next = qfq_ffs(q, mask);
  			if (qfq_gt(roundedF, next->F)) {
  				if (qfq_gt(limit, next->F))
  					agg->S = next->F;
  				else /* preserve timestamp correctness */
  					agg->S = limit;
  				return;
  			}
  		}
  		agg->S = q->V;
  	} else  /* timestamp is not stale */
  		agg->S = agg->F;
  }
  
  /* Update the timestamps of agg before scheduling/rescheduling it for
   * service.  In particular, assign to agg->F its maximum possible
   * value, i.e., the virtual finish time with which the aggregate
   * should be labeled if it used all its budget once in service.
   */
  static inline void
  qfq_update_agg_ts(struct qfq_sched *q,
  		    struct qfq_aggregate *agg, enum update_reason reason)
  {
  	if (reason != requeue)
  		qfq_update_start(q, agg);
  	else /* just charge agg for the service received */
  		agg->S = agg->F;
  
  	agg->F = agg->S + (u64)agg->budgetmax * agg->inv_w;
  }

  
  static void qfq_schedule_agg(struct qfq_sched *q, struct qfq_aggregate *agg);

  static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
  {
  	struct qfq_sched *q = qdisc_priv(sch);

  	struct qfq_aggregate *in_serv_agg = q->in_serv_agg;

  	struct qfq_class *cl;

  	struct sk_buff *skb = NULL;
  	/* next-packet len, 0 means no more active classes in in-service agg */
  	unsigned int len = 0;

  	if (in_serv_agg == NULL)

  		return NULL;

  	if (!list_empty(&in_serv_agg->active))
  		skb = qfq_peek_skb(in_serv_agg, &cl, &len);

  	/*
  	 * If there are no active classes in the in-service aggregate,
  	 * or if the aggregate has not enough budget to serve its next
  	 * class, then choose the next aggregate to serve.
  	 */
  	if (len == 0 || in_serv_agg->budget < len) {
  		charge_actual_service(in_serv_agg);
  
  		/* recharge the budget of the aggregate */
  		in_serv_agg->initial_budget = in_serv_agg->budget =
  			in_serv_agg->budgetmax;

  		if (!list_empty(&in_serv_agg->active)) {

  			/*
  			 * Still active: reschedule for
  			 * service. Possible optimization: if no other
  			 * aggregate is active, then there is no point
  			 * in rescheduling this aggregate, and we can
  			 * just keep it as the in-service one. This
  			 * should be however a corner case, and to
  			 * handle it, we would need to maintain an
  			 * extra num_active_aggs field.
  			*/

  			qfq_update_agg_ts(q, in_serv_agg, requeue);
  			qfq_schedule_agg(q, in_serv_agg);
  		} else if (sch->q.qlen == 0) { /* no aggregate to serve */

  			q->in_serv_agg = NULL;
  			return NULL;
  		}
  
  		/*
  		 * If we get here, there are other aggregates queued:
  		 * choose the new aggregate to serve.
  		 */
  		in_serv_agg = q->in_serv_agg = qfq_choose_next_agg(q);
  		skb = qfq_peek_skb(in_serv_agg, &cl, &len);

  	}

  	if (!skb)
  		return NULL;

  
  	sch->q.qlen--;
  	qdisc_bstats_update(sch, skb);

  	agg_dequeue(in_serv_agg, cl, len);

  	/* If lmax is lowered, through qfq_change_class, for a class
  	 * owning pending packets with larger size than the new value
  	 * of lmax, then the following condition may hold.
  	 */
  	if (unlikely(in_serv_agg->budget < len))
  		in_serv_agg->budget = 0;
  	else
  		in_serv_agg->budget -= len;

  	q->V += (u64)len * q->iwsum;

  	pr_debug("qfq dequeue: len %u F %lld now %lld
  ",

  		 len, (unsigned long long) in_serv_agg->F,
  		 (unsigned long long) q->V);

  	return skb;
  }

  static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *q)
  {
  	struct qfq_group *grp;
  	struct qfq_aggregate *agg, *new_front_agg;
  	u64 old_F;

  	qfq_update_eligible(q);
  	q->oldV = q->V;
  
  	if (!q->bitmaps[ER])
  		return NULL;
  
  	grp = qfq_ffs(q, q->bitmaps[ER]);
  	old_F = grp->F;
  
  	agg = qfq_slot_head(grp);

  	/* agg starts to be served, remove it from schedule */
  	qfq_front_slot_remove(grp);
  
  	new_front_agg = qfq_slot_scan(grp);
  
  	if (new_front_agg == NULL) /* group is now inactive, remove from ER */
  		__clear_bit(grp->index, &q->bitmaps[ER]);
  	else {
  		u64 roundedS = qfq_round_down(new_front_agg->S,
  					      grp->slot_shift);
  		unsigned int s;
  
  		if (grp->S == roundedS)
  			return agg;
  		grp->S = roundedS;
  		grp->F = roundedS + (2ULL << grp->slot_shift);
  		__clear_bit(grp->index, &q->bitmaps[ER]);
  		s = qfq_calc_state(q, grp);
  		__set_bit(grp->index, &q->bitmaps[s]);

  	}

  	qfq_unblock_groups(q, grp->index, old_F);

  	return agg;

  }

  static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
  {
  	struct qfq_sched *q = qdisc_priv(sch);

  	struct qfq_class *cl;

  	struct qfq_aggregate *agg;

  	int err = 0;

  
  	cl = qfq_classify(skb, sch, &err);
  	if (cl == NULL) {
  		if (err & __NET_XMIT_BYPASS)

  			qdisc_qstats_drop(sch);

  		kfree_skb(skb);
  		return err;
  	}
  	pr_debug("qfq_enqueue: cl = %x
  ", cl->common.classid);

  	if (unlikely(cl->agg->lmax < qdisc_pkt_len(skb))) {

  		pr_debug("qfq: increasing maxpkt from %u to %u for class %u",

  			 cl->agg->lmax, qdisc_pkt_len(skb), cl->common.classid);
  		err = qfq_change_agg(sch, cl, cl->agg->class_weight,
  				     qdisc_pkt_len(skb));
  		if (err)
  			return err;

  	}

  	err = qdisc_enqueue(skb, cl->qdisc);
  	if (unlikely(err != NET_XMIT_SUCCESS)) {
  		pr_debug("qfq_enqueue: enqueue failed %d
  ", err);
  		if (net_xmit_drop_count(err)) {
  			cl->qstats.drops++;

  			qdisc_qstats_drop(sch);

  		}
  		return err;
  	}
  
  	bstats_update(&cl->bstats, skb);
  	++sch->q.qlen;

  	agg = cl->agg;
  	/* if the queue was not empty, then done here */
  	if (cl->qdisc->q.qlen != 1) {
  		if (unlikely(skb == cl->qdisc->ops->peek(cl->qdisc)) &&
  		    list_first_entry(&agg->active, struct qfq_class, alist)
  		    == cl && cl->deficit < qdisc_pkt_len(skb))
  			list_move_tail(&cl->alist, &agg->active);

  		return err;

  	}
  
  	/* schedule class for service within the aggregate */
  	cl->deficit = agg->lmax;
  	list_add_tail(&cl->alist, &agg->active);

  	if (list_first_entry(&agg->active, struct qfq_class, alist) != cl ||
  	    q->in_serv_agg == agg)
  		return err; /* non-empty or in service, nothing else to do */

  	qfq_activate_agg(q, agg, enqueue);

  
  	return err;
  }
  
  /*

   * Schedule aggregate according to its timestamps.

   */

  static void qfq_schedule_agg(struct qfq_sched *q, struct qfq_aggregate *agg)

  {

  	struct qfq_group *grp = agg->grp;

  	u64 roundedS;
  	int s;

  	roundedS = qfq_round_down(agg->S, grp->slot_shift);

  
  	/*

  	 * Insert agg in the correct bucket.
  	 * If agg->S >= grp->S we don't need to adjust the

  	 * bucket list and simply go to the insertion phase.
  	 * Otherwise grp->S is decreasing, we must make room
  	 * in the bucket list, and also recompute the group state.
  	 * Finally, if there were no flows in this group and nobody
  	 * was in ER make sure to adjust V.
  	 */
  	if (grp->full_slots) {

  		if (!qfq_gt(grp->S, agg->S))

  			goto skip_update;

  		/* create a slot for this agg->S */

  		qfq_slot_rotate(grp, roundedS);
  		/* group was surely ineligible, remove */
  		__clear_bit(grp->index, &q->bitmaps[IR]);
  		__clear_bit(grp->index, &q->bitmaps[IB]);

  	} else if (!q->bitmaps[ER] && qfq_gt(roundedS, q->V) &&
  		   q->in_serv_agg == NULL)

  		q->V = roundedS;
  
  	grp->S = roundedS;
  	grp->F = roundedS + (2ULL << grp->slot_shift);
  	s = qfq_calc_state(q, grp);
  	__set_bit(grp->index, &q->bitmaps[s]);
  
  	pr_debug("qfq enqueue: new state %d %#lx S %lld F %lld V %lld
  ",
  		 s, q->bitmaps[s],

  		 (unsigned long long) agg->S,
  		 (unsigned long long) agg->F,

  		 (unsigned long long) q->V);
  
  skip_update:

  	qfq_slot_insert(grp, agg, roundedS);

  }

  /* Update agg ts and schedule agg for service */
  static void qfq_activate_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
  			     enum update_reason reason)
  {

  	agg->initial_budget = agg->budget = agg->budgetmax; /* recharge budg. */

  	qfq_update_agg_ts(q, agg, reason);

  	if (q->in_serv_agg == NULL) { /* no aggr. in service or scheduled */
  		q->in_serv_agg = agg; /* start serving this aggregate */
  		 /* update V: to be in service, agg must be eligible */
  		q->oldV = q->V = agg->S;
  	} else if (agg != q->in_serv_agg)
  		qfq_schedule_agg(q, agg);

  }

  static void qfq_slot_remove(struct qfq_sched *q, struct qfq_group *grp,

  			    struct qfq_aggregate *agg)

  {
  	unsigned int i, offset;
  	u64 roundedS;

  	roundedS = qfq_round_down(agg->S, grp->slot_shift);

  	offset = (roundedS - grp->S) >> grp->slot_shift;

  	i = (grp->front + offset) % QFQ_MAX_SLOTS;

  	hlist_del(&agg->next);

  	if (hlist_empty(&grp->slots[i]))
  		__clear_bit(offset, &grp->full_slots);
  }
  
  /*

   * Called to forcibly deschedule an aggregate.  If the aggregate is
   * not in the front bucket, or if the latter has other aggregates in
   * the front bucket, we can simply remove the aggregate with no other
   * side effects.

   * Otherwise we must propagate the event up.
   */

  static void qfq_deactivate_agg(struct qfq_sched *q, struct qfq_aggregate *agg)

  {

  	struct qfq_group *grp = agg->grp;

  	unsigned long mask;
  	u64 roundedS;
  	int s;

  	if (agg == q->in_serv_agg) {
  		charge_actual_service(agg);
  		q->in_serv_agg = qfq_choose_next_agg(q);
  		return;
  	}
  
  	agg->F = agg->S;
  	qfq_slot_remove(q, grp, agg);

  
  	if (!grp->full_slots) {
  		__clear_bit(grp->index, &q->bitmaps[IR]);
  		__clear_bit(grp->index, &q->bitmaps[EB]);
  		__clear_bit(grp->index, &q->bitmaps[IB]);
  
  		if (test_bit(grp->index, &q->bitmaps[ER]) &&
  		    !(q->bitmaps[ER] & ~((1UL << grp->index) - 1))) {
  			mask = q->bitmaps[ER] & ((1UL << grp->index) - 1);
  			if (mask)
  				mask = ~((1UL << __fls(mask)) - 1);
  			else
  				mask = ~0UL;
  			qfq_move_groups(q, mask, EB, ER);
  			qfq_move_groups(q, mask, IB, IR);
  		}
  		__clear_bit(grp->index, &q->bitmaps[ER]);
  	} else if (hlist_empty(&grp->slots[grp->front])) {

  		agg = qfq_slot_scan(grp);
  		roundedS = qfq_round_down(agg->S, grp->slot_shift);

  		if (grp->S != roundedS) {
  			__clear_bit(grp->index, &q->bitmaps[ER]);
  			__clear_bit(grp->index, &q->bitmaps[IR]);
  			__clear_bit(grp->index, &q->bitmaps[EB]);
  			__clear_bit(grp->index, &q->bitmaps[IB]);
  			grp->S = roundedS;
  			grp->F = roundedS + (2ULL << grp->slot_shift);
  			s = qfq_calc_state(q, grp);
  			__set_bit(grp->index, &q->bitmaps[s]);
  		}
  	}

  }
  
  static void qfq_qlen_notify(struct Qdisc *sch, unsigned long arg)
  {
  	struct qfq_sched *q = qdisc_priv(sch);
  	struct qfq_class *cl = (struct qfq_class *)arg;
  
  	if (cl->qdisc->q.qlen == 0)
  		qfq_deactivate_class(q, cl);
  }

  static unsigned int qfq_drop_from_slot(struct qfq_sched *q,
  				       struct hlist_head *slot)
  {
  	struct qfq_aggregate *agg;

  	struct qfq_class *cl;
  	unsigned int len;

  	hlist_for_each_entry(agg, slot, next) {

  		list_for_each_entry(cl, &agg->active, alist) {
  
  			if (!cl->qdisc->ops->drop)
  				continue;
  
  			len = cl->qdisc->ops->drop(cl->qdisc);
  			if (len > 0) {
  				if (cl->qdisc->q.qlen == 0)
  					qfq_deactivate_class(q, cl);
  
  				return len;
  			}
  		}
  	}
  	return 0;
  }

  static unsigned int qfq_drop(struct Qdisc *sch)
  {
  	struct qfq_sched *q = qdisc_priv(sch);
  	struct qfq_group *grp;
  	unsigned int i, j, len;
  
  	for (i = 0; i <= QFQ_MAX_INDEX; i++) {
  		grp = &q->groups[i];
  		for (j = 0; j < QFQ_MAX_SLOTS; j++) {

  			len = qfq_drop_from_slot(q, &grp->slots[j]);
  			if (len > 0) {
  				sch->q.qlen--;
  				return len;

  			}
  		}

  	}
  
  	return 0;
  }
  
  static int qfq_init_qdisc(struct Qdisc *sch, struct nlattr *opt)
  {
  	struct qfq_sched *q = qdisc_priv(sch);
  	struct qfq_group *grp;
  	int i, j, err;

  	u32 max_cl_shift, maxbudg_shift, max_classes;

  
  	err = qdisc_class_hash_init(&q->clhash);
  	if (err < 0)
  		return err;

  	if (qdisc_dev(sch)->tx_queue_len + 1 > QFQ_MAX_AGG_CLASSES)
  		max_classes = QFQ_MAX_AGG_CLASSES;
  	else
  		max_classes = qdisc_dev(sch)->tx_queue_len + 1;
  	/* max_cl_shift = floor(log_2(max_classes)) */
  	max_cl_shift = __fls(max_classes);
  	q->max_agg_classes = 1<<max_cl_shift;
  
  	/* maxbudg_shift = log2(max_len * max_classes_per_agg) */
  	maxbudg_shift = QFQ_MTU_SHIFT + max_cl_shift;
  	q->min_slot_shift = FRAC_BITS + maxbudg_shift - QFQ_MAX_INDEX;

  	for (i = 0; i <= QFQ_MAX_INDEX; i++) {
  		grp = &q->groups[i];
  		grp->index = i;

  		grp->slot_shift = q->min_slot_shift + i;

  		for (j = 0; j < QFQ_MAX_SLOTS; j++)
  			INIT_HLIST_HEAD(&grp->slots[j]);
  	}

  	INIT_HLIST_HEAD(&q->nonfull_aggs);

  	return 0;
  }
  
  static void qfq_reset_qdisc(struct Qdisc *sch)
  {
  	struct qfq_sched *q = qdisc_priv(sch);

  	struct qfq_class *cl;

  	unsigned int i;

  	for (i = 0; i < q->clhash.hashsize; i++) {

  		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {

  			if (cl->qdisc->q.qlen > 0)

  				qfq_deactivate_class(q, cl);

  			qdisc_reset(cl->qdisc);

  		}

  	}
  	sch->q.qlen = 0;
  }
  
  static void qfq_destroy_qdisc(struct Qdisc *sch)
  {
  	struct qfq_sched *q = qdisc_priv(sch);
  	struct qfq_class *cl;

  	struct hlist_node *next;

  	unsigned int i;
  
  	tcf_destroy_chain(&q->filter_list);
  
  	for (i = 0; i < q->clhash.hashsize; i++) {

  		hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],

  					  common.hnode) {
  			qfq_destroy_class(sch, cl);
  		}
  	}
  	qdisc_class_hash_destroy(&q->clhash);
  }
  
  static const struct Qdisc_class_ops qfq_class_ops = {
  	.change		= qfq_change_class,
  	.delete		= qfq_delete_class,
  	.get		= qfq_get_class,
  	.put		= qfq_put_class,
  	.tcf_chain	= qfq_tcf_chain,
  	.bind_tcf	= qfq_bind_tcf,
  	.unbind_tcf	= qfq_unbind_tcf,
  	.graft		= qfq_graft_class,
  	.leaf		= qfq_class_leaf,
  	.qlen_notify	= qfq_qlen_notify,
  	.dump		= qfq_dump_class,
  	.dump_stats	= qfq_dump_class_stats,
  	.walk		= qfq_walk,
  };
  
  static struct Qdisc_ops qfq_qdisc_ops __read_mostly = {
  	.cl_ops		= &qfq_class_ops,
  	.id		= "qfq",
  	.priv_size	= sizeof(struct qfq_sched),
  	.enqueue	= qfq_enqueue,
  	.dequeue	= qfq_dequeue,
  	.peek		= qdisc_peek_dequeued,
  	.drop		= qfq_drop,
  	.init		= qfq_init_qdisc,
  	.reset		= qfq_reset_qdisc,
  	.destroy	= qfq_destroy_qdisc,
  	.owner		= THIS_MODULE,
  };
  
  static int __init qfq_init(void)
  {
  	return register_qdisc(&qfq_qdisc_ops);
  }
  
  static void __exit qfq_exit(void)
  {
  	unregister_qdisc(&qfq_qdisc_ops);
  }
  
  module_init(qfq_init);
  module_exit(qfq_exit);
  MODULE_LICENSE("GPL");