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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * 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.
  */
 
 #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 filter_cnt;
 
     struct gnet_stats_basic_sync bstats;
     struct gnet_stats_queue qstats;
     struct net_rate_estimator __rcu *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 tcf_block    *block;
     struct Qdisc_class_hash clhash;
 
     u64         oldV, V;    /* Precise virtual times. */
     struct qfq_aggregate    *in_serv_agg;   /* Aggregate being served. */
     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 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\n",
          (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)
 {
     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 netlink_ext_ack *extack)
 {
     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\n");
         return -EINVAL;
     }
 
     err = nla_parse_nested_deprecated(tb, TCA_QFQ_MAX, tca[TCA_OPTIONS],
                       qfq_policy, NULL);
     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\n", 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\n", 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)\n",
               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,
                             NULL,
                             true,
                             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;
 
     gnet_stats_basic_sync_init(&cl->bstats);
     cl->common.classid = classid;
     cl->deficit = lmax;
 
     cl->qdisc = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
                       classid, NULL);
     if (cl->qdisc == NULL)
         cl->qdisc = &noop_qdisc;
 
     if (tca[TCA_RATE]) {
         err = gen_new_estimator(&cl->bstats, NULL,
                     &cl->rate_est,
                     NULL,
                     true,
                     tca[TCA_RATE]);
         if (err)
             goto destroy_class;
     }
 
     if (cl->qdisc != &noop_qdisc)
         qdisc_hash_add(cl->qdisc, true);
 
 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->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);
     else
         qdisc_class_hash_insert(&q->clhash, &cl->common);
     qfq_add_to_agg(q, new_agg, cl);
     sch_tree_unlock(sch);
     qdisc_class_hash_grow(sch, &q->clhash);
 
     *arg = (unsigned long)cl;
     return 0;
 
 destroy_class:
     qdisc_put(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->rate_est);
     qdisc_put(cl->qdisc);
     kfree(cl);
 }
 
 static int qfq_delete_class(struct Qdisc *sch, unsigned long arg,
                 struct netlink_ext_ack *extack)
 {
     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);
 
     qdisc_purge_queue(cl->qdisc);
     qdisc_class_hash_remove(&q->clhash, &cl->common);
 
     sch_tree_unlock(sch);
 
     qfq_destroy_class(sch, cl);
     return 0;
 }
 
 static unsigned long qfq_search_class(struct Qdisc *sch, u32 classid)
 {
     return (unsigned long)qfq_find_class(sch, classid);
 }
 
 static struct tcf_block *qfq_tcf_block(struct Qdisc *sch, unsigned long cl,
                        struct netlink_ext_ack *extack)
 {
     struct qfq_sched *q = qdisc_priv(sch);
 
     if (cl)
         return NULL;
 
     return q->block;
 }
 
 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 netlink_ext_ack *extack)
 {
     struct qfq_class *cl = (struct qfq_class *)arg;
 
     if (new == NULL) {
         new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
                     cl->common.classid, NULL);
         if (new == NULL)
             new = &noop_qdisc;
     }
 
     *old = qdisc_replace(sch, new, &cl->qdisc);
     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_noflag(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, true) < 0 ||
         gnet_stats_copy_rate_est(d, &cl->rate_est) < 0 ||
         qdisc_qstats_copy(d, cl->qdisc) < 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\n", 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 = tcf_classify(skb, NULL, fl, &res, false);
     if (result >= 0) {
 #ifdef CONFIG_NET_CLS_ACT
         switch (result) {
         case TC_ACT_QUEUED:
         case TC_ACT_STOLEN:
         case TC_ACT_TRAP:
             *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
             fallthrough;
         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\n",
          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\n");
     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;
 
     qdisc_qstats_backlog_dec(sch, skb);
     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\n",
          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 sk_buff **to_free)
 {
     unsigned int len = qdisc_pkt_len(skb), gso_segs;
     struct qfq_sched *q = qdisc_priv(sch);
     struct qfq_class *cl;
     struct qfq_aggregate *agg;
     int err = 0;
     bool first;
 
     cl = qfq_classify(skb, sch, &err);
     if (cl == NULL) {
         if (err & __NET_XMIT_BYPASS)
             qdisc_qstats_drop(sch);
         __qdisc_drop(skb, to_free);
         return err;
     }
     pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);
 
     if (unlikely(cl->agg->lmax < len)) {
         pr_debug("qfq: increasing maxpkt from %u to %u for class %u",
              cl->agg->lmax, len, cl->common.classid);
         err = qfq_change_agg(sch, cl, cl->agg->class_weight, len);
         if (err) {
             cl->qstats.drops++;
             return qdisc_drop(skb, sch, to_free);
         }
     }
 
     gso_segs = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1;
     first = !cl->qdisc->q.qlen;
     err = qdisc_enqueue(skb, cl->qdisc, to_free);
     if (unlikely(err != NET_XMIT_SUCCESS)) {
         pr_debug("qfq_enqueue: enqueue failed %d\n", err);
         if (net_xmit_drop_count(err)) {
             cl->qstats.drops++;
             qdisc_qstats_drop(sch);
         }
         return err;
     }
 
     _bstats_update(&cl->bstats, len, gso_segs);
     sch->qstats.backlog += len;
     ++sch->q.qlen;
 
     agg = cl->agg;
     /* if the queue was not empty, then done here */
     if (!first) {
         if (unlikely(skb == cl->qdisc->ops->peek(cl->qdisc)) &&
             list_first_entry(&agg->active, struct qfq_class, alist)
             == cl && cl->deficit < len)
             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\n",
          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;
 
     qfq_deactivate_class(q, cl);
 }
 
 static int qfq_init_qdisc(struct Qdisc *sch, struct nlattr *opt,
               struct netlink_ext_ack *extack)
 {
     struct qfq_sched *q = qdisc_priv(sch);
     struct qfq_group *grp;
     int i, j, err;
     u32 max_cl_shift, maxbudg_shift, max_classes;
 
     err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
     if (err)
         return err;
 
     err = qdisc_class_hash_init(&q->clhash);
     if (err < 0)
         return err;
 
     max_classes = min_t(u64, (u64)qdisc_dev(sch)->tx_queue_len + 1,
                 QFQ_MAX_AGG_CLASSES);
     /* 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->qstats.backlog = 0;
     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_block_put(q->block);
 
     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,
     .find       = qfq_search_class,
     .tcf_block  = qfq_tcf_block,
     .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,
     .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");

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