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Linux/net/sched/sch_qfq.c

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  1 /*
  2  * net/sched/sch_qfq.c         Quick Fair Queueing Plus Scheduler.
  3  *
  4  * Copyright (c) 2009 Fabio Checconi, Luigi Rizzo, and Paolo Valente.
  5  * Copyright (c) 2012 Paolo Valente.
  6  *
  7  * This program is free software; you can redistribute it and/or
  8  * modify it under the terms of the GNU General Public License
  9  * version 2 as published by the Free Software Foundation.
 10  */
 11 
 12 #include <linux/module.h>
 13 #include <linux/init.h>
 14 #include <linux/bitops.h>
 15 #include <linux/errno.h>
 16 #include <linux/netdevice.h>
 17 #include <linux/pkt_sched.h>
 18 #include <net/sch_generic.h>
 19 #include <net/pkt_sched.h>
 20 #include <net/pkt_cls.h>
 21 
 22 
 23 /*  Quick Fair Queueing Plus
 24     ========================
 25 
 26     Sources:
 27 
 28     [1] Paolo Valente,
 29     "Reducing the Execution Time of Fair-Queueing Schedulers."
 30     http://algo.ing.unimo.it/people/paolo/agg-sched/agg-sched.pdf
 31 
 32     Sources for QFQ:
 33 
 34     [2] Fabio Checconi, Luigi Rizzo, and Paolo Valente: "QFQ: Efficient
 35     Packet Scheduling with Tight Bandwidth Distribution Guarantees."
 36 
 37     See also:
 38     http://retis.sssup.it/~fabio/linux/qfq/
 39  */
 40 
 41 /*
 42 
 43   QFQ+ divides classes into aggregates of at most MAX_AGG_CLASSES
 44   classes. Each aggregate is timestamped with a virtual start time S
 45   and a virtual finish time F, and scheduled according to its
 46   timestamps. S and F are computed as a function of a system virtual
 47   time function V. The classes within each aggregate are instead
 48   scheduled with DRR.
 49 
 50   To speed up operations, QFQ+ divides also aggregates into a limited
 51   number of groups. Which group a class belongs to depends on the
 52   ratio between the maximum packet length for the class and the weight
 53   of the class. Groups have their own S and F. In the end, QFQ+
 54   schedules groups, then aggregates within groups, then classes within
 55   aggregates. See [1] and [2] for a full description.
 56 
 57   Virtual time computations.
 58 
 59   S, F and V are all computed in fixed point arithmetic with
 60   FRAC_BITS decimal bits.
 61 
 62   QFQ_MAX_INDEX is the maximum index allowed for a group. We need
 63         one bit per index.
 64   QFQ_MAX_WSHIFT is the maximum power of two supported as a weight.
 65 
 66   The layout of the bits is as below:
 67 
 68                    [ MTU_SHIFT ][      FRAC_BITS    ]
 69                    [ MAX_INDEX    ][ MIN_SLOT_SHIFT ]
 70                                  ^.__grp->index = 0
 71                                  *.__grp->slot_shift
 72 
 73   where MIN_SLOT_SHIFT is derived by difference from the others.
 74 
 75   The max group index corresponds to Lmax/w_min, where
 76   Lmax=1<<MTU_SHIFT, w_min = 1 .
 77   From this, and knowing how many groups (MAX_INDEX) we want,
 78   we can derive the shift corresponding to each group.
 79 
 80   Because we often need to compute
 81         F = S + len/w_i  and V = V + len/wsum
 82   instead of storing w_i store the value
 83         inv_w = (1<<FRAC_BITS)/w_i
 84   so we can do F = S + len * inv_w * wsum.
 85   We use W_TOT in the formulas so we can easily move between
 86   static and adaptive weight sum.
 87 
 88   The per-scheduler-instance data contain all the data structures
 89   for the scheduler: bitmaps and bucket lists.
 90 
 91  */
 92 
 93 /*
 94  * Maximum number of consecutive slots occupied by backlogged classes
 95  * inside a group.
 96  */
 97 #define QFQ_MAX_SLOTS   32
 98 
 99 /*
100  * Shifts used for aggregate<->group mapping.  We allow class weights that are
101  * in the range [1, 2^MAX_WSHIFT], and we try to map each aggregate i to the
102  * group with the smallest index that can support the L_i / r_i configured
103  * for the classes in the aggregate.
104  *
105  * grp->index is the index of the group; and grp->slot_shift
106  * is the shift for the corresponding (scaled) sigma_i.
107  */
108 #define QFQ_MAX_INDEX           24
109 #define QFQ_MAX_WSHIFT          10
110 
111 #define QFQ_MAX_WEIGHT          (1<<QFQ_MAX_WSHIFT) /* see qfq_slot_insert */
112 #define QFQ_MAX_WSUM            (64*QFQ_MAX_WEIGHT)
113 
114 #define FRAC_BITS               30      /* fixed point arithmetic */
115 #define ONE_FP                  (1UL << FRAC_BITS)
116 
117 #define QFQ_MTU_SHIFT           16      /* to support TSO/GSO */
118 #define QFQ_MIN_LMAX            512     /* see qfq_slot_insert */
119 
120 #define QFQ_MAX_AGG_CLASSES     8 /* max num classes per aggregate allowed */
121 
122 /*
123  * Possible group states.  These values are used as indexes for the bitmaps
124  * array of struct qfq_queue.
125  */
126 enum qfq_state { ER, IR, EB, IB, QFQ_MAX_STATE };
127 
128 struct qfq_group;
129 
130 struct qfq_aggregate;
131 
132 struct qfq_class {
133         struct Qdisc_class_common common;
134 
135         unsigned int refcnt;
136         unsigned int filter_cnt;
137 
138         struct gnet_stats_basic_packed bstats;
139         struct gnet_stats_queue qstats;
140         struct net_rate_estimator __rcu *rate_est;
141         struct Qdisc *qdisc;
142         struct list_head alist;         /* Link for active-classes list. */
143         struct qfq_aggregate *agg;      /* Parent aggregate. */
144         int deficit;                    /* DRR deficit counter. */
145 };
146 
147 struct qfq_aggregate {
148         struct hlist_node next; /* Link for the slot list. */
149         u64 S, F;               /* flow timestamps (exact) */
150 
151         /* group we belong to. In principle we would need the index,
152          * which is log_2(lmax/weight), but we never reference it
153          * directly, only the group.
154          */
155         struct qfq_group *grp;
156 
157         /* these are copied from the flowset. */
158         u32     class_weight; /* Weight of each class in this aggregate. */
159         /* Max pkt size for the classes in this aggregate, DRR quantum. */
160         int     lmax;
161 
162         u32     inv_w;      /* ONE_FP/(sum of weights of classes in aggr.). */
163         u32     budgetmax;  /* Max budget for this aggregate. */
164         u32     initial_budget, budget;     /* Initial and current budget. */
165 
166         int               num_classes;  /* Number of classes in this aggr. */
167         struct list_head  active;       /* DRR queue of active classes. */
168 
169         struct hlist_node nonfull_next; /* See nonfull_aggs in qfq_sched. */
170 };
171 
172 struct qfq_group {
173         u64 S, F;                       /* group timestamps (approx). */
174         unsigned int slot_shift;        /* Slot shift. */
175         unsigned int index;             /* Group index. */
176         unsigned int front;             /* Index of the front slot. */
177         unsigned long full_slots;       /* non-empty slots */
178 
179         /* Array of RR lists of active aggregates. */
180         struct hlist_head slots[QFQ_MAX_SLOTS];
181 };
182 
183 struct qfq_sched {
184         struct tcf_proto __rcu *filter_list;
185         struct Qdisc_class_hash clhash;
186 
187         u64                     oldV, V;        /* Precise virtual times. */
188         struct qfq_aggregate    *in_serv_agg;   /* Aggregate being served. */
189         u32                     wsum;           /* weight sum */
190         u32                     iwsum;          /* inverse weight sum */
191 
192         unsigned long bitmaps[QFQ_MAX_STATE];       /* Group bitmaps. */
193         struct qfq_group groups[QFQ_MAX_INDEX + 1]; /* The groups. */
194         u32 min_slot_shift;     /* Index of the group-0 bit in the bitmaps. */
195 
196         u32 max_agg_classes;            /* Max number of classes per aggr. */
197         struct hlist_head nonfull_aggs; /* Aggs with room for more classes. */
198 };
199 
200 /*
201  * Possible reasons why the timestamps of an aggregate are updated
202  * enqueue: the aggregate switches from idle to active and must scheduled
203  *          for service
204  * requeue: the aggregate finishes its budget, so it stops being served and
205  *          must be rescheduled for service
206  */
207 enum update_reason {enqueue, requeue};
208 
209 static struct qfq_class *qfq_find_class(struct Qdisc *sch, u32 classid)
210 {
211         struct qfq_sched *q = qdisc_priv(sch);
212         struct Qdisc_class_common *clc;
213 
214         clc = qdisc_class_find(&q->clhash, classid);
215         if (clc == NULL)
216                 return NULL;
217         return container_of(clc, struct qfq_class, common);
218 }
219 
220 static void qfq_purge_queue(struct qfq_class *cl)
221 {
222         unsigned int len = cl->qdisc->q.qlen;
223         unsigned int backlog = cl->qdisc->qstats.backlog;
224 
225         qdisc_reset(cl->qdisc);
226         qdisc_tree_reduce_backlog(cl->qdisc, len, backlog);
227 }
228 
229 static const struct nla_policy qfq_policy[TCA_QFQ_MAX + 1] = {
230         [TCA_QFQ_WEIGHT] = { .type = NLA_U32 },
231         [TCA_QFQ_LMAX] = { .type = NLA_U32 },
232 };
233 
234 /*
235  * Calculate a flow index, given its weight and maximum packet length.
236  * index = log_2(maxlen/weight) but we need to apply the scaling.
237  * This is used only once at flow creation.
238  */
239 static int qfq_calc_index(u32 inv_w, unsigned int maxlen, u32 min_slot_shift)
240 {
241         u64 slot_size = (u64)maxlen * inv_w;
242         unsigned long size_map;
243         int index = 0;
244 
245         size_map = slot_size >> min_slot_shift;
246         if (!size_map)
247                 goto out;
248 
249         index = __fls(size_map) + 1;    /* basically a log_2 */
250         index -= !(slot_size - (1ULL << (index + min_slot_shift - 1)));
251 
252         if (index < 0)
253                 index = 0;
254 out:
255         pr_debug("qfq calc_index: W = %lu, L = %u, I = %d\n",
256                  (unsigned long) ONE_FP/inv_w, maxlen, index);
257 
258         return index;
259 }
260 
261 static void qfq_deactivate_agg(struct qfq_sched *, struct qfq_aggregate *);
262 static void qfq_activate_agg(struct qfq_sched *, struct qfq_aggregate *,
263                              enum update_reason);
264 
265 static void qfq_init_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
266                          u32 lmax, u32 weight)
267 {
268         INIT_LIST_HEAD(&agg->active);
269         hlist_add_head(&agg->nonfull_next, &q->nonfull_aggs);
270 
271         agg->lmax = lmax;
272         agg->class_weight = weight;
273 }
274 
275 static struct qfq_aggregate *qfq_find_agg(struct qfq_sched *q,
276                                           u32 lmax, u32 weight)
277 {
278         struct qfq_aggregate *agg;
279 
280         hlist_for_each_entry(agg, &q->nonfull_aggs, nonfull_next)
281                 if (agg->lmax == lmax && agg->class_weight == weight)
282                         return agg;
283 
284         return NULL;
285 }
286 
287 
288 /* Update aggregate as a function of the new number of classes. */
289 static void qfq_update_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
290                            int new_num_classes)
291 {
292         u32 new_agg_weight;
293 
294         if (new_num_classes == q->max_agg_classes)
295                 hlist_del_init(&agg->nonfull_next);
296 
297         if (agg->num_classes > new_num_classes &&
298             new_num_classes == q->max_agg_classes - 1) /* agg no more full */
299                 hlist_add_head(&agg->nonfull_next, &q->nonfull_aggs);
300 
301         /* The next assignment may let
302          * agg->initial_budget > agg->budgetmax
303          * hold, we will take it into account in charge_actual_service().
304          */
305         agg->budgetmax = new_num_classes * agg->lmax;
306         new_agg_weight = agg->class_weight * new_num_classes;
307         agg->inv_w = ONE_FP/new_agg_weight;
308 
309         if (agg->grp == NULL) {
310                 int i = qfq_calc_index(agg->inv_w, agg->budgetmax,
311                                        q->min_slot_shift);
312                 agg->grp = &q->groups[i];
313         }
314 
315         q->wsum +=
316                 (int) agg->class_weight * (new_num_classes - agg->num_classes);
317         q->iwsum = ONE_FP / q->wsum;
318 
319         agg->num_classes = new_num_classes;
320 }
321 
322 /* Add class to aggregate. */
323 static void qfq_add_to_agg(struct qfq_sched *q,
324                            struct qfq_aggregate *agg,
325                            struct qfq_class *cl)
326 {
327         cl->agg = agg;
328 
329         qfq_update_agg(q, agg, agg->num_classes+1);
330         if (cl->qdisc->q.qlen > 0) { /* adding an active class */
331                 list_add_tail(&cl->alist, &agg->active);
332                 if (list_first_entry(&agg->active, struct qfq_class, alist) ==
333                     cl && q->in_serv_agg != agg) /* agg was inactive */
334                         qfq_activate_agg(q, agg, enqueue); /* schedule agg */
335         }
336 }
337 
338 static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *);
339 
340 static void qfq_destroy_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
341 {
342         hlist_del_init(&agg->nonfull_next);
343         q->wsum -= agg->class_weight;
344         if (q->wsum != 0)
345                 q->iwsum = ONE_FP / q->wsum;
346 
347         if (q->in_serv_agg == agg)
348                 q->in_serv_agg = qfq_choose_next_agg(q);
349         kfree(agg);
350 }
351 
352 /* Deschedule class from within its parent aggregate. */
353 static void qfq_deactivate_class(struct qfq_sched *q, struct qfq_class *cl)
354 {
355         struct qfq_aggregate *agg = cl->agg;
356 
357 
358         list_del(&cl->alist); /* remove from RR queue of the aggregate */
359         if (list_empty(&agg->active)) /* agg is now inactive */
360                 qfq_deactivate_agg(q, agg);
361 }
362 
363 /* Remove class from its parent aggregate. */
364 static void qfq_rm_from_agg(struct qfq_sched *q, struct qfq_class *cl)
365 {
366         struct qfq_aggregate *agg = cl->agg;
367 
368         cl->agg = NULL;
369         if (agg->num_classes == 1) { /* agg being emptied, destroy it */
370                 qfq_destroy_agg(q, agg);
371                 return;
372         }
373         qfq_update_agg(q, agg, agg->num_classes-1);
374 }
375 
376 /* Deschedule class and remove it from its parent aggregate. */
377 static void qfq_deact_rm_from_agg(struct qfq_sched *q, struct qfq_class *cl)
378 {
379         if (cl->qdisc->q.qlen > 0) /* class is active */
380                 qfq_deactivate_class(q, cl);
381 
382         qfq_rm_from_agg(q, cl);
383 }
384 
385 /* Move class to a new aggregate, matching the new class weight and/or lmax */
386 static int qfq_change_agg(struct Qdisc *sch, struct qfq_class *cl, u32 weight,
387                            u32 lmax)
388 {
389         struct qfq_sched *q = qdisc_priv(sch);
390         struct qfq_aggregate *new_agg = qfq_find_agg(q, lmax, weight);
391 
392         if (new_agg == NULL) { /* create new aggregate */
393                 new_agg = kzalloc(sizeof(*new_agg), GFP_ATOMIC);
394                 if (new_agg == NULL)
395                         return -ENOBUFS;
396                 qfq_init_agg(q, new_agg, lmax, weight);
397         }
398         qfq_deact_rm_from_agg(q, cl);
399         qfq_add_to_agg(q, new_agg, cl);
400 
401         return 0;
402 }
403 
404 static int qfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
405                             struct nlattr **tca, unsigned long *arg)
406 {
407         struct qfq_sched *q = qdisc_priv(sch);
408         struct qfq_class *cl = (struct qfq_class *)*arg;
409         bool existing = false;
410         struct nlattr *tb[TCA_QFQ_MAX + 1];
411         struct qfq_aggregate *new_agg = NULL;
412         u32 weight, lmax, inv_w;
413         int err;
414         int delta_w;
415 
416         if (tca[TCA_OPTIONS] == NULL) {
417                 pr_notice("qfq: no options\n");
418                 return -EINVAL;
419         }
420 
421         err = nla_parse_nested(tb, TCA_QFQ_MAX, tca[TCA_OPTIONS], qfq_policy,
422                                NULL);
423         if (err < 0)
424                 return err;
425 
426         if (tb[TCA_QFQ_WEIGHT]) {
427                 weight = nla_get_u32(tb[TCA_QFQ_WEIGHT]);
428                 if (!weight || weight > (1UL << QFQ_MAX_WSHIFT)) {
429                         pr_notice("qfq: invalid weight %u\n", weight);
430                         return -EINVAL;
431                 }
432         } else
433                 weight = 1;
434 
435         if (tb[TCA_QFQ_LMAX]) {
436                 lmax = nla_get_u32(tb[TCA_QFQ_LMAX]);
437                 if (lmax < QFQ_MIN_LMAX || lmax > (1UL << QFQ_MTU_SHIFT)) {
438                         pr_notice("qfq: invalid max length %u\n", lmax);
439                         return -EINVAL;
440                 }
441         } else
442                 lmax = psched_mtu(qdisc_dev(sch));
443 
444         inv_w = ONE_FP / weight;
445         weight = ONE_FP / inv_w;
446 
447         if (cl != NULL &&
448             lmax == cl->agg->lmax &&
449             weight == cl->agg->class_weight)
450                 return 0; /* nothing to change */
451 
452         delta_w = weight - (cl ? cl->agg->class_weight : 0);
453 
454         if (q->wsum + delta_w > QFQ_MAX_WSUM) {
455                 pr_notice("qfq: total weight out of range (%d + %u)\n",
456                           delta_w, q->wsum);
457                 return -EINVAL;
458         }
459 
460         if (cl != NULL) { /* modify existing class */
461                 if (tca[TCA_RATE]) {
462                         err = gen_replace_estimator(&cl->bstats, NULL,
463                                                     &cl->rate_est,
464                                                     NULL,
465                                                     qdisc_root_sleeping_running(sch),
466                                                     tca[TCA_RATE]);
467                         if (err)
468                                 return err;
469                 }
470                 existing = true;
471                 goto set_change_agg;
472         }
473 
474         /* create and init new class */
475         cl = kzalloc(sizeof(struct qfq_class), GFP_KERNEL);
476         if (cl == NULL)
477                 return -ENOBUFS;
478 
479         cl->refcnt = 1;
480         cl->common.classid = classid;
481         cl->deficit = lmax;
482 
483         cl->qdisc = qdisc_create_dflt(sch->dev_queue,
484                                       &pfifo_qdisc_ops, classid);
485         if (cl->qdisc == NULL)
486                 cl->qdisc = &noop_qdisc;
487 
488         if (tca[TCA_RATE]) {
489                 err = gen_new_estimator(&cl->bstats, NULL,
490                                         &cl->rate_est,
491                                         NULL,
492                                         qdisc_root_sleeping_running(sch),
493                                         tca[TCA_RATE]);
494                 if (err)
495                         goto destroy_class;
496         }
497 
498         if (cl->qdisc != &noop_qdisc)
499                 qdisc_hash_add(cl->qdisc, true);
500         sch_tree_lock(sch);
501         qdisc_class_hash_insert(&q->clhash, &cl->common);
502         sch_tree_unlock(sch);
503 
504         qdisc_class_hash_grow(sch, &q->clhash);
505 
506 set_change_agg:
507         sch_tree_lock(sch);
508         new_agg = qfq_find_agg(q, lmax, weight);
509         if (new_agg == NULL) { /* create new aggregate */
510                 sch_tree_unlock(sch);
511                 new_agg = kzalloc(sizeof(*new_agg), GFP_KERNEL);
512                 if (new_agg == NULL) {
513                         err = -ENOBUFS;
514                         gen_kill_estimator(&cl->rate_est);
515                         goto destroy_class;
516                 }
517                 sch_tree_lock(sch);
518                 qfq_init_agg(q, new_agg, lmax, weight);
519         }
520         if (existing)
521                 qfq_deact_rm_from_agg(q, cl);
522         qfq_add_to_agg(q, new_agg, cl);
523         sch_tree_unlock(sch);
524 
525         *arg = (unsigned long)cl;
526         return 0;
527 
528 destroy_class:
529         qdisc_destroy(cl->qdisc);
530         kfree(cl);
531         return err;
532 }
533 
534 static void qfq_destroy_class(struct Qdisc *sch, struct qfq_class *cl)
535 {
536         struct qfq_sched *q = qdisc_priv(sch);
537 
538         qfq_rm_from_agg(q, cl);
539         gen_kill_estimator(&cl->rate_est);
540         qdisc_destroy(cl->qdisc);
541         kfree(cl);
542 }
543 
544 static int qfq_delete_class(struct Qdisc *sch, unsigned long arg)
545 {
546         struct qfq_sched *q = qdisc_priv(sch);
547         struct qfq_class *cl = (struct qfq_class *)arg;
548 
549         if (cl->filter_cnt > 0)
550                 return -EBUSY;
551 
552         sch_tree_lock(sch);
553 
554         qfq_purge_queue(cl);
555         qdisc_class_hash_remove(&q->clhash, &cl->common);
556 
557         BUG_ON(--cl->refcnt == 0);
558         /*
559          * This shouldn't happen: we "hold" one cops->get() when called
560          * from tc_ctl_tclass; the destroy method is done from cops->put().
561          */
562 
563         sch_tree_unlock(sch);
564         return 0;
565 }
566 
567 static unsigned long qfq_get_class(struct Qdisc *sch, u32 classid)
568 {
569         struct qfq_class *cl = qfq_find_class(sch, classid);
570 
571         if (cl != NULL)
572                 cl->refcnt++;
573 
574         return (unsigned long)cl;
575 }
576 
577 static void qfq_put_class(struct Qdisc *sch, unsigned long arg)
578 {
579         struct qfq_class *cl = (struct qfq_class *)arg;
580 
581         if (--cl->refcnt == 0)
582                 qfq_destroy_class(sch, cl);
583 }
584 
585 static struct tcf_proto __rcu **qfq_tcf_chain(struct Qdisc *sch,
586                                               unsigned long cl)
587 {
588         struct qfq_sched *q = qdisc_priv(sch);
589 
590         if (cl)
591                 return NULL;
592 
593         return &q->filter_list;
594 }
595 
596 static unsigned long qfq_bind_tcf(struct Qdisc *sch, unsigned long parent,
597                                   u32 classid)
598 {
599         struct qfq_class *cl = qfq_find_class(sch, classid);
600 
601         if (cl != NULL)
602                 cl->filter_cnt++;
603 
604         return (unsigned long)cl;
605 }
606 
607 static void qfq_unbind_tcf(struct Qdisc *sch, unsigned long arg)
608 {
609         struct qfq_class *cl = (struct qfq_class *)arg;
610 
611         cl->filter_cnt--;
612 }
613 
614 static int qfq_graft_class(struct Qdisc *sch, unsigned long arg,
615                            struct Qdisc *new, struct Qdisc **old)
616 {
617         struct qfq_class *cl = (struct qfq_class *)arg;
618 
619         if (new == NULL) {
620                 new = qdisc_create_dflt(sch->dev_queue,
621                                         &pfifo_qdisc_ops, cl->common.classid);
622                 if (new == NULL)
623                         new = &noop_qdisc;
624         }
625 
626         *old = qdisc_replace(sch, new, &cl->qdisc);
627         return 0;
628 }
629 
630 static struct Qdisc *qfq_class_leaf(struct Qdisc *sch, unsigned long arg)
631 {
632         struct qfq_class *cl = (struct qfq_class *)arg;
633 
634         return cl->qdisc;
635 }
636 
637 static int qfq_dump_class(struct Qdisc *sch, unsigned long arg,
638                           struct sk_buff *skb, struct tcmsg *tcm)
639 {
640         struct qfq_class *cl = (struct qfq_class *)arg;
641         struct nlattr *nest;
642 
643         tcm->tcm_parent = TC_H_ROOT;
644         tcm->tcm_handle = cl->common.classid;
645         tcm->tcm_info   = cl->qdisc->handle;
646 
647         nest = nla_nest_start(skb, TCA_OPTIONS);
648         if (nest == NULL)
649                 goto nla_put_failure;
650         if (nla_put_u32(skb, TCA_QFQ_WEIGHT, cl->agg->class_weight) ||
651             nla_put_u32(skb, TCA_QFQ_LMAX, cl->agg->lmax))
652                 goto nla_put_failure;
653         return nla_nest_end(skb, nest);
654 
655 nla_put_failure:
656         nla_nest_cancel(skb, nest);
657         return -EMSGSIZE;
658 }
659 
660 static int qfq_dump_class_stats(struct Qdisc *sch, unsigned long arg,
661                                 struct gnet_dump *d)
662 {
663         struct qfq_class *cl = (struct qfq_class *)arg;
664         struct tc_qfq_stats xstats;
665 
666         memset(&xstats, 0, sizeof(xstats));
667 
668         xstats.weight = cl->agg->class_weight;
669         xstats.lmax = cl->agg->lmax;
670 
671         if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
672                                   d, NULL, &cl->bstats) < 0 ||
673             gnet_stats_copy_rate_est(d, &cl->rate_est) < 0 ||
674             gnet_stats_copy_queue(d, NULL,
675                                   &cl->qdisc->qstats, cl->qdisc->q.qlen) < 0)
676                 return -1;
677 
678         return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
679 }
680 
681 static void qfq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
682 {
683         struct qfq_sched *q = qdisc_priv(sch);
684         struct qfq_class *cl;
685         unsigned int i;
686 
687         if (arg->stop)
688                 return;
689 
690         for (i = 0; i < q->clhash.hashsize; i++) {
691                 hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
692                         if (arg->count < arg->skip) {
693                                 arg->count++;
694                                 continue;
695                         }
696                         if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
697                                 arg->stop = 1;
698                                 return;
699                         }
700                         arg->count++;
701                 }
702         }
703 }
704 
705 static struct qfq_class *qfq_classify(struct sk_buff *skb, struct Qdisc *sch,
706                                       int *qerr)
707 {
708         struct qfq_sched *q = qdisc_priv(sch);
709         struct qfq_class *cl;
710         struct tcf_result res;
711         struct tcf_proto *fl;
712         int result;
713 
714         if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
715                 pr_debug("qfq_classify: found %d\n", skb->priority);
716                 cl = qfq_find_class(sch, skb->priority);
717                 if (cl != NULL)
718                         return cl;
719         }
720 
721         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
722         fl = rcu_dereference_bh(q->filter_list);
723         result = tc_classify(skb, fl, &res, false);
724         if (result >= 0) {
725 #ifdef CONFIG_NET_CLS_ACT
726                 switch (result) {
727                 case TC_ACT_QUEUED:
728                 case TC_ACT_STOLEN:
729                         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
730                 case TC_ACT_SHOT:
731                         return NULL;
732                 }
733 #endif
734                 cl = (struct qfq_class *)res.class;
735                 if (cl == NULL)
736                         cl = qfq_find_class(sch, res.classid);
737                 return cl;
738         }
739 
740         return NULL;
741 }
742 
743 /* Generic comparison function, handling wraparound. */
744 static inline int qfq_gt(u64 a, u64 b)
745 {
746         return (s64)(a - b) > 0;
747 }
748 
749 /* Round a precise timestamp to its slotted value. */
750 static inline u64 qfq_round_down(u64 ts, unsigned int shift)
751 {
752         return ts & ~((1ULL << shift) - 1);
753 }
754 
755 /* return the pointer to the group with lowest index in the bitmap */
756 static inline struct qfq_group *qfq_ffs(struct qfq_sched *q,
757                                         unsigned long bitmap)
758 {
759         int index = __ffs(bitmap);
760         return &q->groups[index];
761 }
762 /* Calculate a mask to mimic what would be ffs_from(). */
763 static inline unsigned long mask_from(unsigned long bitmap, int from)
764 {
765         return bitmap & ~((1UL << from) - 1);
766 }
767 
768 /*
769  * The state computation relies on ER=0, IR=1, EB=2, IB=3
770  * First compute eligibility comparing grp->S, q->V,
771  * then check if someone is blocking us and possibly add EB
772  */
773 static int qfq_calc_state(struct qfq_sched *q, const struct qfq_group *grp)
774 {
775         /* if S > V we are not eligible */
776         unsigned int state = qfq_gt(grp->S, q->V);
777         unsigned long mask = mask_from(q->bitmaps[ER], grp->index);
778         struct qfq_group *next;
779 
780         if (mask) {
781                 next = qfq_ffs(q, mask);
782                 if (qfq_gt(grp->F, next->F))
783                         state |= EB;
784         }
785 
786         return state;
787 }
788 
789 
790 /*
791  * In principle
792  *      q->bitmaps[dst] |= q->bitmaps[src] & mask;
793  *      q->bitmaps[src] &= ~mask;
794  * but we should make sure that src != dst
795  */
796 static inline void qfq_move_groups(struct qfq_sched *q, unsigned long mask,
797                                    int src, int dst)
798 {
799         q->bitmaps[dst] |= q->bitmaps[src] & mask;
800         q->bitmaps[src] &= ~mask;
801 }
802 
803 static void qfq_unblock_groups(struct qfq_sched *q, int index, u64 old_F)
804 {
805         unsigned long mask = mask_from(q->bitmaps[ER], index + 1);
806         struct qfq_group *next;
807 
808         if (mask) {
809                 next = qfq_ffs(q, mask);
810                 if (!qfq_gt(next->F, old_F))
811                         return;
812         }
813 
814         mask = (1UL << index) - 1;
815         qfq_move_groups(q, mask, EB, ER);
816         qfq_move_groups(q, mask, IB, IR);
817 }
818 
819 /*
820  * perhaps
821  *
822         old_V ^= q->V;
823         old_V >>= q->min_slot_shift;
824         if (old_V) {
825                 ...
826         }
827  *
828  */
829 static void qfq_make_eligible(struct qfq_sched *q)
830 {
831         unsigned long vslot = q->V >> q->min_slot_shift;
832         unsigned long old_vslot = q->oldV >> q->min_slot_shift;
833 
834         if (vslot != old_vslot) {
835                 unsigned long mask;
836                 int last_flip_pos = fls(vslot ^ old_vslot);
837 
838                 if (last_flip_pos > 31) /* higher than the number of groups */
839                         mask = ~0UL;    /* make all groups eligible */
840                 else
841                         mask = (1UL << last_flip_pos) - 1;
842 
843                 qfq_move_groups(q, mask, IR, ER);
844                 qfq_move_groups(q, mask, IB, EB);
845         }
846 }
847 
848 /*
849  * The index of the slot in which the input aggregate agg is to be
850  * inserted must not be higher than QFQ_MAX_SLOTS-2. There is a '-2'
851  * and not a '-1' because the start time of the group may be moved
852  * backward by one slot after the aggregate has been inserted, and
853  * this would cause non-empty slots to be right-shifted by one
854  * position.
855  *
856  * QFQ+ fully satisfies this bound to the slot index if the parameters
857  * of the classes are not changed dynamically, and if QFQ+ never
858  * happens to postpone the service of agg unjustly, i.e., it never
859  * happens that the aggregate becomes backlogged and eligible, or just
860  * eligible, while an aggregate with a higher approximated finish time
861  * is being served. In particular, in this case QFQ+ guarantees that
862  * the timestamps of agg are low enough that the slot index is never
863  * higher than 2. Unfortunately, QFQ+ cannot provide the same
864  * guarantee if it happens to unjustly postpone the service of agg, or
865  * if the parameters of some class are changed.
866  *
867  * As for the first event, i.e., an out-of-order service, the
868  * upper bound to the slot index guaranteed by QFQ+ grows to
869  * 2 +
870  * QFQ_MAX_AGG_CLASSES * ((1<<QFQ_MTU_SHIFT)/QFQ_MIN_LMAX) *
871  * (current_max_weight/current_wsum) <= 2 + 8 * 128 * 1.
872  *
873  * The following function deals with this problem by backward-shifting
874  * the timestamps of agg, if needed, so as to guarantee that the slot
875  * index is never higher than QFQ_MAX_SLOTS-2. This backward-shift may
876  * cause the service of other aggregates to be postponed, yet the
877  * worst-case guarantees of these aggregates are not violated.  In
878  * fact, in case of no out-of-order service, the timestamps of agg
879  * would have been even lower than they are after the backward shift,
880  * because QFQ+ would have guaranteed a maximum value equal to 2 for
881  * the slot index, and 2 < QFQ_MAX_SLOTS-2. Hence the aggregates whose
882  * service is postponed because of the backward-shift would have
883  * however waited for the service of agg before being served.
884  *
885  * The other event that may cause the slot index to be higher than 2
886  * for agg is a recent change of the parameters of some class. If the
887  * weight of a class is increased or the lmax (max_pkt_size) of the
888  * class is decreased, then a new aggregate with smaller slot size
889  * than the original parent aggregate of the class may happen to be
890  * activated. The activation of this aggregate should be properly
891  * delayed to when the service of the class has finished in the ideal
892  * system tracked by QFQ+. If the activation of the aggregate is not
893  * delayed to this reference time instant, then this aggregate may be
894  * unjustly served before other aggregates waiting for service. This
895  * may cause the above bound to the slot index to be violated for some
896  * of these unlucky aggregates.
897  *
898  * Instead of delaying the activation of the new aggregate, which is
899  * quite complex, the above-discussed capping of the slot index is
900  * used to handle also the consequences of a change of the parameters
901  * of a class.
902  */
903 static void qfq_slot_insert(struct qfq_group *grp, struct qfq_aggregate *agg,
904                             u64 roundedS)
905 {
906         u64 slot = (roundedS - grp->S) >> grp->slot_shift;
907         unsigned int i; /* slot index in the bucket list */
908 
909         if (unlikely(slot > QFQ_MAX_SLOTS - 2)) {
910                 u64 deltaS = roundedS - grp->S -
911                         ((u64)(QFQ_MAX_SLOTS - 2)<<grp->slot_shift);
912                 agg->S -= deltaS;
913                 agg->F -= deltaS;
914                 slot = QFQ_MAX_SLOTS - 2;
915         }
916 
917         i = (grp->front + slot) % QFQ_MAX_SLOTS;
918 
919         hlist_add_head(&agg->next, &grp->slots[i]);
920         __set_bit(slot, &grp->full_slots);
921 }
922 
923 /* Maybe introduce hlist_first_entry?? */
924 static struct qfq_aggregate *qfq_slot_head(struct qfq_group *grp)
925 {
926         return hlist_entry(grp->slots[grp->front].first,
927                            struct qfq_aggregate, next);
928 }
929 
930 /*
931  * remove the entry from the slot
932  */
933 static void qfq_front_slot_remove(struct qfq_group *grp)
934 {
935         struct qfq_aggregate *agg = qfq_slot_head(grp);
936 
937         BUG_ON(!agg);
938         hlist_del(&agg->next);
939         if (hlist_empty(&grp->slots[grp->front]))
940                 __clear_bit(0, &grp->full_slots);
941 }
942 
943 /*
944  * Returns the first aggregate in the first non-empty bucket of the
945  * group. As a side effect, adjusts the bucket list so the first
946  * non-empty bucket is at position 0 in full_slots.
947  */
948 static struct qfq_aggregate *qfq_slot_scan(struct qfq_group *grp)
949 {
950         unsigned int i;
951 
952         pr_debug("qfq slot_scan: grp %u full %#lx\n",
953                  grp->index, grp->full_slots);
954 
955         if (grp->full_slots == 0)
956                 return NULL;
957 
958         i = __ffs(grp->full_slots);  /* zero based */
959         if (i > 0) {
960                 grp->front = (grp->front + i) % QFQ_MAX_SLOTS;
961                 grp->full_slots >>= i;
962         }
963 
964         return qfq_slot_head(grp);
965 }
966 
967 /*
968  * adjust the bucket list. When the start time of a group decreases,
969  * we move the index down (modulo QFQ_MAX_SLOTS) so we don't need to
970  * move the objects. The mask of occupied slots must be shifted
971  * because we use ffs() to find the first non-empty slot.
972  * This covers decreases in the group's start time, but what about
973  * increases of the start time ?
974  * Here too we should make sure that i is less than 32
975  */
976 static void qfq_slot_rotate(struct qfq_group *grp, u64 roundedS)
977 {
978         unsigned int i = (grp->S - roundedS) >> grp->slot_shift;
979 
980         grp->full_slots <<= i;
981         grp->front = (grp->front - i) % QFQ_MAX_SLOTS;
982 }
983 
984 static void qfq_update_eligible(struct qfq_sched *q)
985 {
986         struct qfq_group *grp;
987         unsigned long ineligible;
988 
989         ineligible = q->bitmaps[IR] | q->bitmaps[IB];
990         if (ineligible) {
991                 if (!q->bitmaps[ER]) {
992                         grp = qfq_ffs(q, ineligible);
993                         if (qfq_gt(grp->S, q->V))
994                                 q->V = grp->S;
995                 }
996                 qfq_make_eligible(q);
997         }
998 }
999 
1000 /* Dequeue head packet of the head class in the DRR queue of the aggregate. */
1001 static void agg_dequeue(struct qfq_aggregate *agg,
1002                         struct qfq_class *cl, unsigned int len)
1003 {
1004         qdisc_dequeue_peeked(cl->qdisc);
1005 
1006         cl->deficit -= (int) len;
1007 
1008         if (cl->qdisc->q.qlen == 0) /* no more packets, remove from list */
1009                 list_del(&cl->alist);
1010         else if (cl->deficit < qdisc_pkt_len(cl->qdisc->ops->peek(cl->qdisc))) {
1011                 cl->deficit += agg->lmax;
1012                 list_move_tail(&cl->alist, &agg->active);
1013         }
1014 }
1015 
1016 static inline struct sk_buff *qfq_peek_skb(struct qfq_aggregate *agg,
1017                                            struct qfq_class **cl,
1018                                            unsigned int *len)
1019 {
1020         struct sk_buff *skb;
1021 
1022         *cl = list_first_entry(&agg->active, struct qfq_class, alist);
1023         skb = (*cl)->qdisc->ops->peek((*cl)->qdisc);
1024         if (skb == NULL)
1025                 WARN_ONCE(1, "qfq_dequeue: non-workconserving leaf\n");
1026         else
1027                 *len = qdisc_pkt_len(skb);
1028 
1029         return skb;
1030 }
1031 
1032 /* Update F according to the actual service received by the aggregate. */
1033 static inline void charge_actual_service(struct qfq_aggregate *agg)
1034 {
1035         /* Compute the service received by the aggregate, taking into
1036          * account that, after decreasing the number of classes in
1037          * agg, it may happen that
1038          * agg->initial_budget - agg->budget > agg->bugdetmax
1039          */
1040         u32 service_received = min(agg->budgetmax,
1041                                    agg->initial_budget - agg->budget);
1042 
1043         agg->F = agg->S + (u64)service_received * agg->inv_w;
1044 }
1045 
1046 /* Assign a reasonable start time for a new aggregate in group i.
1047  * Admissible values for \hat(F) are multiples of \sigma_i
1048  * no greater than V+\sigma_i . Larger values mean that
1049  * we had a wraparound so we consider the timestamp to be stale.
1050  *
1051  * If F is not stale and F >= V then we set S = F.
1052  * Otherwise we should assign S = V, but this may violate
1053  * the ordering in EB (see [2]). So, if we have groups in ER,
1054  * set S to the F_j of the first group j which would be blocking us.
1055  * We are guaranteed not to move S backward because
1056  * otherwise our group i would still be blocked.
1057  */
1058 static void qfq_update_start(struct qfq_sched *q, struct qfq_aggregate *agg)
1059 {
1060         unsigned long mask;
1061         u64 limit, roundedF;
1062         int slot_shift = agg->grp->slot_shift;
1063 
1064         roundedF = qfq_round_down(agg->F, slot_shift);
1065         limit = qfq_round_down(q->V, slot_shift) + (1ULL << slot_shift);
1066 
1067         if (!qfq_gt(agg->F, q->V) || qfq_gt(roundedF, limit)) {
1068                 /* timestamp was stale */
1069                 mask = mask_from(q->bitmaps[ER], agg->grp->index);
1070                 if (mask) {
1071                         struct qfq_group *next = qfq_ffs(q, mask);
1072                         if (qfq_gt(roundedF, next->F)) {
1073                                 if (qfq_gt(limit, next->F))
1074                                         agg->S = next->F;
1075                                 else /* preserve timestamp correctness */
1076                                         agg->S = limit;
1077                                 return;
1078                         }
1079                 }
1080                 agg->S = q->V;
1081         } else  /* timestamp is not stale */
1082                 agg->S = agg->F;
1083 }
1084 
1085 /* Update the timestamps of agg before scheduling/rescheduling it for
1086  * service.  In particular, assign to agg->F its maximum possible
1087  * value, i.e., the virtual finish time with which the aggregate
1088  * should be labeled if it used all its budget once in service.
1089  */
1090 static inline void
1091 qfq_update_agg_ts(struct qfq_sched *q,
1092                     struct qfq_aggregate *agg, enum update_reason reason)
1093 {
1094         if (reason != requeue)
1095                 qfq_update_start(q, agg);
1096         else /* just charge agg for the service received */
1097                 agg->S = agg->F;
1098 
1099         agg->F = agg->S + (u64)agg->budgetmax * agg->inv_w;
1100 }
1101 
1102 static void qfq_schedule_agg(struct qfq_sched *q, struct qfq_aggregate *agg);
1103 
1104 static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
1105 {
1106         struct qfq_sched *q = qdisc_priv(sch);
1107         struct qfq_aggregate *in_serv_agg = q->in_serv_agg;
1108         struct qfq_class *cl;
1109         struct sk_buff *skb = NULL;
1110         /* next-packet len, 0 means no more active classes in in-service agg */
1111         unsigned int len = 0;
1112 
1113         if (in_serv_agg == NULL)
1114                 return NULL;
1115 
1116         if (!list_empty(&in_serv_agg->active))
1117                 skb = qfq_peek_skb(in_serv_agg, &cl, &len);
1118 
1119         /*
1120          * If there are no active classes in the in-service aggregate,
1121          * or if the aggregate has not enough budget to serve its next
1122          * class, then choose the next aggregate to serve.
1123          */
1124         if (len == 0 || in_serv_agg->budget < len) {
1125                 charge_actual_service(in_serv_agg);
1126 
1127                 /* recharge the budget of the aggregate */
1128                 in_serv_agg->initial_budget = in_serv_agg->budget =
1129                         in_serv_agg->budgetmax;
1130 
1131                 if (!list_empty(&in_serv_agg->active)) {
1132                         /*
1133                          * Still active: reschedule for
1134                          * service. Possible optimization: if no other
1135                          * aggregate is active, then there is no point
1136                          * in rescheduling this aggregate, and we can
1137                          * just keep it as the in-service one. This
1138                          * should be however a corner case, and to
1139                          * handle it, we would need to maintain an
1140                          * extra num_active_aggs field.
1141                         */
1142                         qfq_update_agg_ts(q, in_serv_agg, requeue);
1143                         qfq_schedule_agg(q, in_serv_agg);
1144                 } else if (sch->q.qlen == 0) { /* no aggregate to serve */
1145                         q->in_serv_agg = NULL;
1146                         return NULL;
1147                 }
1148 
1149                 /*
1150                  * If we get here, there are other aggregates queued:
1151                  * choose the new aggregate to serve.
1152                  */
1153                 in_serv_agg = q->in_serv_agg = qfq_choose_next_agg(q);
1154                 skb = qfq_peek_skb(in_serv_agg, &cl, &len);
1155         }
1156         if (!skb)
1157                 return NULL;
1158 
1159         qdisc_qstats_backlog_dec(sch, skb);
1160         sch->q.qlen--;
1161         qdisc_bstats_update(sch, skb);
1162 
1163         agg_dequeue(in_serv_agg, cl, len);
1164         /* If lmax is lowered, through qfq_change_class, for a class
1165          * owning pending packets with larger size than the new value
1166          * of lmax, then the following condition may hold.
1167          */
1168         if (unlikely(in_serv_agg->budget < len))
1169                 in_serv_agg->budget = 0;
1170         else
1171                 in_serv_agg->budget -= len;
1172 
1173         q->V += (u64)len * q->iwsum;
1174         pr_debug("qfq dequeue: len %u F %lld now %lld\n",
1175                  len, (unsigned long long) in_serv_agg->F,
1176                  (unsigned long long) q->V);
1177 
1178         return skb;
1179 }
1180 
1181 static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *q)
1182 {
1183         struct qfq_group *grp;
1184         struct qfq_aggregate *agg, *new_front_agg;
1185         u64 old_F;
1186 
1187         qfq_update_eligible(q);
1188         q->oldV = q->V;
1189 
1190         if (!q->bitmaps[ER])
1191                 return NULL;
1192 
1193         grp = qfq_ffs(q, q->bitmaps[ER]);
1194         old_F = grp->F;
1195 
1196         agg = qfq_slot_head(grp);
1197 
1198         /* agg starts to be served, remove it from schedule */
1199         qfq_front_slot_remove(grp);
1200 
1201         new_front_agg = qfq_slot_scan(grp);
1202 
1203         if (new_front_agg == NULL) /* group is now inactive, remove from ER */
1204                 __clear_bit(grp->index, &q->bitmaps[ER]);
1205         else {
1206                 u64 roundedS = qfq_round_down(new_front_agg->S,
1207                                               grp->slot_shift);
1208                 unsigned int s;
1209 
1210                 if (grp->S == roundedS)
1211                         return agg;
1212                 grp->S = roundedS;
1213                 grp->F = roundedS + (2ULL << grp->slot_shift);
1214                 __clear_bit(grp->index, &q->bitmaps[ER]);
1215                 s = qfq_calc_state(q, grp);
1216                 __set_bit(grp->index, &q->bitmaps[s]);
1217         }
1218 
1219         qfq_unblock_groups(q, grp->index, old_F);
1220 
1221         return agg;
1222 }
1223 
1224 static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
1225                        struct sk_buff **to_free)
1226 {
1227         struct qfq_sched *q = qdisc_priv(sch);
1228         struct qfq_class *cl;
1229         struct qfq_aggregate *agg;
1230         int err = 0;
1231 
1232         cl = qfq_classify(skb, sch, &err);
1233         if (cl == NULL) {
1234                 if (err & __NET_XMIT_BYPASS)
1235                         qdisc_qstats_drop(sch);
1236                 kfree_skb(skb);
1237                 return err;
1238         }
1239         pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);
1240 
1241         if (unlikely(cl->agg->lmax < qdisc_pkt_len(skb))) {
1242                 pr_debug("qfq: increasing maxpkt from %u to %u for class %u",
1243                          cl->agg->lmax, qdisc_pkt_len(skb), cl->common.classid);
1244                 err = qfq_change_agg(sch, cl, cl->agg->class_weight,
1245                                      qdisc_pkt_len(skb));
1246                 if (err) {
1247                         cl->qstats.drops++;
1248                         return qdisc_drop(skb, sch, to_free);
1249                 }
1250         }
1251 
1252         err = qdisc_enqueue(skb, cl->qdisc, to_free);
1253         if (unlikely(err != NET_XMIT_SUCCESS)) {
1254                 pr_debug("qfq_enqueue: enqueue failed %d\n", err);
1255                 if (net_xmit_drop_count(err)) {
1256                         cl->qstats.drops++;
1257                         qdisc_qstats_drop(sch);
1258                 }
1259                 return err;
1260         }
1261 
1262         bstats_update(&cl->bstats, skb);
1263         qdisc_qstats_backlog_inc(sch, skb);
1264         ++sch->q.qlen;
1265 
1266         agg = cl->agg;
1267         /* if the queue was not empty, then done here */
1268         if (cl->qdisc->q.qlen != 1) {
1269                 if (unlikely(skb == cl->qdisc->ops->peek(cl->qdisc)) &&
1270                     list_first_entry(&agg->active, struct qfq_class, alist)
1271                     == cl && cl->deficit < qdisc_pkt_len(skb))
1272                         list_move_tail(&cl->alist, &agg->active);
1273 
1274                 return err;
1275         }
1276 
1277         /* schedule class for service within the aggregate */
1278         cl->deficit = agg->lmax;
1279         list_add_tail(&cl->alist, &agg->active);
1280 
1281         if (list_first_entry(&agg->active, struct qfq_class, alist) != cl ||
1282             q->in_serv_agg == agg)
1283                 return err; /* non-empty or in service, nothing else to do */
1284 
1285         qfq_activate_agg(q, agg, enqueue);
1286 
1287         return err;
1288 }
1289 
1290 /*
1291  * Schedule aggregate according to its timestamps.
1292  */
1293 static void qfq_schedule_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
1294 {
1295         struct qfq_group *grp = agg->grp;
1296         u64 roundedS;
1297         int s;
1298 
1299         roundedS = qfq_round_down(agg->S, grp->slot_shift);
1300 
1301         /*
1302          * Insert agg in the correct bucket.
1303          * If agg->S >= grp->S we don't need to adjust the
1304          * bucket list and simply go to the insertion phase.
1305          * Otherwise grp->S is decreasing, we must make room
1306          * in the bucket list, and also recompute the group state.
1307          * Finally, if there were no flows in this group and nobody
1308          * was in ER make sure to adjust V.
1309          */
1310         if (grp->full_slots) {
1311                 if (!qfq_gt(grp->S, agg->S))
1312                         goto skip_update;
1313 
1314                 /* create a slot for this agg->S */
1315                 qfq_slot_rotate(grp, roundedS);
1316                 /* group was surely ineligible, remove */
1317                 __clear_bit(grp->index, &q->bitmaps[IR]);
1318                 __clear_bit(grp->index, &q->bitmaps[IB]);
1319         } else if (!q->bitmaps[ER] && qfq_gt(roundedS, q->V) &&
1320                    q->in_serv_agg == NULL)
1321                 q->V = roundedS;
1322 
1323         grp->S = roundedS;
1324         grp->F = roundedS + (2ULL << grp->slot_shift);
1325         s = qfq_calc_state(q, grp);
1326         __set_bit(grp->index, &q->bitmaps[s]);
1327 
1328         pr_debug("qfq enqueue: new state %d %#lx S %lld F %lld V %lld\n",
1329                  s, q->bitmaps[s],
1330                  (unsigned long long) agg->S,
1331                  (unsigned long long) agg->F,
1332                  (unsigned long long) q->V);
1333 
1334 skip_update:
1335         qfq_slot_insert(grp, agg, roundedS);
1336 }
1337 
1338 
1339 /* Update agg ts and schedule agg for service */
1340 static void qfq_activate_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
1341                              enum update_reason reason)
1342 {
1343         agg->initial_budget = agg->budget = agg->budgetmax; /* recharge budg. */
1344 
1345         qfq_update_agg_ts(q, agg, reason);
1346         if (q->in_serv_agg == NULL) { /* no aggr. in service or scheduled */
1347                 q->in_serv_agg = agg; /* start serving this aggregate */
1348                  /* update V: to be in service, agg must be eligible */
1349                 q->oldV = q->V = agg->S;
1350         } else if (agg != q->in_serv_agg)
1351                 qfq_schedule_agg(q, agg);
1352 }
1353 
1354 static void qfq_slot_remove(struct qfq_sched *q, struct qfq_group *grp,
1355                             struct qfq_aggregate *agg)
1356 {
1357         unsigned int i, offset;
1358         u64 roundedS;
1359 
1360         roundedS = qfq_round_down(agg->S, grp->slot_shift);
1361         offset = (roundedS - grp->S) >> grp->slot_shift;
1362 
1363         i = (grp->front + offset) % QFQ_MAX_SLOTS;
1364 
1365         hlist_del(&agg->next);
1366         if (hlist_empty(&grp->slots[i]))
1367                 __clear_bit(offset, &grp->full_slots);
1368 }
1369 
1370 /*
1371  * Called to forcibly deschedule an aggregate.  If the aggregate is
1372  * not in the front bucket, or if the latter has other aggregates in
1373  * the front bucket, we can simply remove the aggregate with no other
1374  * side effects.
1375  * Otherwise we must propagate the event up.
1376  */
1377 static void qfq_deactivate_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
1378 {
1379         struct qfq_group *grp = agg->grp;
1380         unsigned long mask;
1381         u64 roundedS;
1382         int s;
1383 
1384         if (agg == q->in_serv_agg) {
1385                 charge_actual_service(agg);
1386                 q->in_serv_agg = qfq_choose_next_agg(q);
1387                 return;
1388         }
1389 
1390         agg->F = agg->S;
1391         qfq_slot_remove(q, grp, agg);
1392 
1393         if (!grp->full_slots) {
1394                 __clear_bit(grp->index, &q->bitmaps[IR]);
1395                 __clear_bit(grp->index, &q->bitmaps[EB]);
1396                 __clear_bit(grp->index, &q->bitmaps[IB]);
1397 
1398                 if (test_bit(grp->index, &q->bitmaps[ER]) &&
1399                     !(q->bitmaps[ER] & ~((1UL << grp->index) - 1))) {
1400                         mask = q->bitmaps[ER] & ((1UL << grp->index) - 1);
1401                         if (mask)
1402                                 mask = ~((1UL << __fls(mask)) - 1);
1403                         else
1404                                 mask = ~0UL;
1405                         qfq_move_groups(q, mask, EB, ER);
1406                         qfq_move_groups(q, mask, IB, IR);
1407                 }
1408                 __clear_bit(grp->index, &q->bitmaps[ER]);
1409         } else if (hlist_empty(&grp->slots[grp->front])) {
1410                 agg = qfq_slot_scan(grp);
1411                 roundedS = qfq_round_down(agg->S, grp->slot_shift);
1412                 if (grp->S != roundedS) {
1413                         __clear_bit(grp->index, &q->bitmaps[ER]);
1414                         __clear_bit(grp->index, &q->bitmaps[IR]);
1415                         __clear_bit(grp->index, &q->bitmaps[EB]);
1416                         __clear_bit(grp->index, &q->bitmaps[IB]);
1417                         grp->S = roundedS;
1418                         grp->F = roundedS + (2ULL << grp->slot_shift);
1419                         s = qfq_calc_state(q, grp);
1420                         __set_bit(grp->index, &q->bitmaps[s]);
1421                 }
1422         }
1423 }
1424 
1425 static void qfq_qlen_notify(struct Qdisc *sch, unsigned long arg)
1426 {
1427         struct qfq_sched *q = qdisc_priv(sch);
1428         struct qfq_class *cl = (struct qfq_class *)arg;
1429 
1430         if (cl->qdisc->q.qlen == 0)
1431                 qfq_deactivate_class(q, cl);
1432 }
1433 
1434 static int qfq_init_qdisc(struct Qdisc *sch, struct nlattr *opt)
1435 {
1436         struct qfq_sched *q = qdisc_priv(sch);
1437         struct qfq_group *grp;
1438         int i, j, err;
1439         u32 max_cl_shift, maxbudg_shift, max_classes;
1440 
1441         err = qdisc_class_hash_init(&q->clhash);
1442         if (err < 0)
1443                 return err;
1444 
1445         if (qdisc_dev(sch)->tx_queue_len + 1 > QFQ_MAX_AGG_CLASSES)
1446                 max_classes = QFQ_MAX_AGG_CLASSES;
1447         else
1448                 max_classes = qdisc_dev(sch)->tx_queue_len + 1;
1449         /* max_cl_shift = floor(log_2(max_classes)) */
1450         max_cl_shift = __fls(max_classes);
1451         q->max_agg_classes = 1<<max_cl_shift;
1452 
1453         /* maxbudg_shift = log2(max_len * max_classes_per_agg) */
1454         maxbudg_shift = QFQ_MTU_SHIFT + max_cl_shift;
1455         q->min_slot_shift = FRAC_BITS + maxbudg_shift - QFQ_MAX_INDEX;
1456 
1457         for (i = 0; i <= QFQ_MAX_INDEX; i++) {
1458                 grp = &q->groups[i];
1459                 grp->index = i;
1460                 grp->slot_shift = q->min_slot_shift + i;
1461                 for (j = 0; j < QFQ_MAX_SLOTS; j++)
1462                         INIT_HLIST_HEAD(&grp->slots[j]);
1463         }
1464 
1465         INIT_HLIST_HEAD(&q->nonfull_aggs);
1466 
1467         return 0;
1468 }
1469 
1470 static void qfq_reset_qdisc(struct Qdisc *sch)
1471 {
1472         struct qfq_sched *q = qdisc_priv(sch);
1473         struct qfq_class *cl;
1474         unsigned int i;
1475 
1476         for (i = 0; i < q->clhash.hashsize; i++) {
1477                 hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
1478                         if (cl->qdisc->q.qlen > 0)
1479                                 qfq_deactivate_class(q, cl);
1480 
1481                         qdisc_reset(cl->qdisc);
1482                 }
1483         }
1484         sch->qstats.backlog = 0;
1485         sch->q.qlen = 0;
1486 }
1487 
1488 static void qfq_destroy_qdisc(struct Qdisc *sch)
1489 {
1490         struct qfq_sched *q = qdisc_priv(sch);
1491         struct qfq_class *cl;
1492         struct hlist_node *next;
1493         unsigned int i;
1494 
1495         tcf_destroy_chain(&q->filter_list);
1496 
1497         for (i = 0; i < q->clhash.hashsize; i++) {
1498                 hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],
1499                                           common.hnode) {
1500                         qfq_destroy_class(sch, cl);
1501                 }
1502         }
1503         qdisc_class_hash_destroy(&q->clhash);
1504 }
1505 
1506 static const struct Qdisc_class_ops qfq_class_ops = {
1507         .change         = qfq_change_class,
1508         .delete         = qfq_delete_class,
1509         .get            = qfq_get_class,
1510         .put            = qfq_put_class,
1511         .tcf_chain      = qfq_tcf_chain,
1512         .bind_tcf       = qfq_bind_tcf,
1513         .unbind_tcf     = qfq_unbind_tcf,
1514         .graft          = qfq_graft_class,
1515         .leaf           = qfq_class_leaf,
1516         .qlen_notify    = qfq_qlen_notify,
1517         .dump           = qfq_dump_class,
1518         .dump_stats     = qfq_dump_class_stats,
1519         .walk           = qfq_walk,
1520 };
1521 
1522 static struct Qdisc_ops qfq_qdisc_ops __read_mostly = {
1523         .cl_ops         = &qfq_class_ops,
1524         .id             = "qfq",
1525         .priv_size      = sizeof(struct qfq_sched),
1526         .enqueue        = qfq_enqueue,
1527         .dequeue        = qfq_dequeue,
1528         .peek           = qdisc_peek_dequeued,
1529         .init           = qfq_init_qdisc,
1530         .reset          = qfq_reset_qdisc,
1531         .destroy        = qfq_destroy_qdisc,
1532         .owner          = THIS_MODULE,
1533 };
1534 
1535 static int __init qfq_init(void)
1536 {
1537         return register_qdisc(&qfq_qdisc_ops);
1538 }
1539 
1540 static void __exit qfq_exit(void)
1541 {
1542         unregister_qdisc(&qfq_qdisc_ops);
1543 }
1544 
1545 module_init(qfq_init);
1546 module_exit(qfq_exit);
1547 MODULE_LICENSE("GPL");
1548 

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