linux/net/sched/sch_qfq.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * net/sched/sch_qfq.c         Quick Fair Queueing Plus Scheduler.
   4 *
   5 * Copyright (c) 2009 Fabio Checconi, Luigi Rizzo, and Paolo Valente.
   6 * Copyright (c) 2012 Paolo Valente.
   7 */
   8
   9#include <linux/module.h>
  10#include <linux/init.h>
  11#include <linux/bitops.h>
  12#include <linux/errno.h>
  13#include <linux/netdevice.h>
  14#include <linux/pkt_sched.h>
  15#include <net/sch_generic.h>
  16#include <net/pkt_sched.h>
  17#include <net/pkt_cls.h>
  18
  19
  20/*  Quick Fair Queueing Plus
  21    ========================
  22
  23    Sources:
  24
  25    [1] Paolo Valente,
  26    "Reducing the Execution Time of Fair-Queueing Schedulers."
  27    http://algo.ing.unimo.it/people/paolo/agg-sched/agg-sched.pdf
  28
  29    Sources for QFQ:
  30
  31    [2] Fabio Checconi, Luigi Rizzo, and Paolo Valente: "QFQ: Efficient
  32    Packet Scheduling with Tight Bandwidth Distribution Guarantees."
  33
  34    See also:
  35    http://retis.sssup.it/~fabio/linux/qfq/
  36 */
  37
  38/*
  39
  40  QFQ+ divides classes into aggregates of at most MAX_AGG_CLASSES
  41  classes. Each aggregate is timestamped with a virtual start time S
  42  and a virtual finish time F, and scheduled according to its
  43  timestamps. S and F are computed as a function of a system virtual
  44  time function V. The classes within each aggregate are instead
  45  scheduled with DRR.
  46
  47  To speed up operations, QFQ+ divides also aggregates into a limited
  48  number of groups. Which group a class belongs to depends on the
  49  ratio between the maximum packet length for the class and the weight
  50  of the class. Groups have their own S and F. In the end, QFQ+
  51  schedules groups, then aggregates within groups, then classes within
  52  aggregates. See [1] and [2] for a full description.
  53
  54  Virtual time computations.
  55
  56  S, F and V are all computed in fixed point arithmetic with
  57  FRAC_BITS decimal bits.
  58
  59  QFQ_MAX_INDEX is the maximum index allowed for a group. We need
  60        one bit per index.
  61  QFQ_MAX_WSHIFT is the maximum power of two supported as a weight.
  62
  63  The layout of the bits is as below:
  64
  65                   [ MTU_SHIFT ][      FRAC_BITS    ]
  66                   [ MAX_INDEX    ][ MIN_SLOT_SHIFT ]
  67                                 ^.__grp->index = 0
  68                                 *.__grp->slot_shift
  69
  70  where MIN_SLOT_SHIFT is derived by difference from the others.
  71
  72  The max group index corresponds to Lmax/w_min, where
  73  Lmax=1<<MTU_SHIFT, w_min = 1 .
  74  From this, and knowing how many groups (MAX_INDEX) we want,
  75  we can derive the shift corresponding to each group.
  76
  77  Because we often need to compute
  78        F = S + len/w_i  and V = V + len/wsum
  79  instead of storing w_i store the value
  80        inv_w = (1<<FRAC_BITS)/w_i
  81  so we can do F = S + len * inv_w * wsum.
  82  We use W_TOT in the formulas so we can easily move between
  83  static and adaptive weight sum.
  84
  85  The per-scheduler-instance data contain all the data structures
  86  for the scheduler: bitmaps and bucket lists.
  87
  88 */
  89
  90/*
  91 * Maximum number of consecutive slots occupied by backlogged classes
  92 * inside a group.
  93 */
  94#define QFQ_MAX_SLOTS   32
  95
  96/*
  97 * Shifts used for aggregate<->group mapping.  We allow class weights that are
  98 * in the range [1, 2^MAX_WSHIFT], and we try to map each aggregate i to the
  99 * group with the smallest index that can support the L_i / r_i configured
 100 * for the classes in the aggregate.
 101 *
 102 * grp->index is the index of the group; and grp->slot_shift
 103 * is the shift for the corresponding (scaled) sigma_i.
 104 */
 105#define QFQ_MAX_INDEX           24
 106#define QFQ_MAX_WSHIFT          10
 107
 108#define QFQ_MAX_WEIGHT          (1<<QFQ_MAX_WSHIFT) /* see qfq_slot_insert */
 109#define QFQ_MAX_WSUM            (64*QFQ_MAX_WEIGHT)
 110
 111#define FRAC_BITS               30      /* fixed point arithmetic */
 112#define ONE_FP                  (1UL << FRAC_BITS)
 113
 114#define QFQ_MTU_SHIFT           16      /* to support TSO/GSO */
 115#define QFQ_MIN_LMAX            512     /* see qfq_slot_insert */
 116
 117#define QFQ_MAX_AGG_CLASSES     8 /* max num classes per aggregate allowed */
 118
 119/*
 120 * Possible group states.  These values are used as indexes for the bitmaps
 121 * array of struct qfq_queue.
 122 */
 123enum qfq_state { ER, IR, EB, IB, QFQ_MAX_STATE };
 124
 125struct qfq_group;
 126
 127struct qfq_aggregate;
 128
 129struct qfq_class {
 130        struct Qdisc_class_common common;
 131
 132        unsigned int filter_cnt;
 133
 134        struct gnet_stats_basic_packed bstats;
 135        struct gnet_stats_queue qstats;
 136        struct net_rate_estimator __rcu *rate_est;
 137        struct Qdisc *qdisc;
 138        struct list_head alist;         /* Link for active-classes list. */
 139        struct qfq_aggregate *agg;      /* Parent aggregate. */
 140        int deficit;                    /* DRR deficit counter. */
 141};
 142
 143struct qfq_aggregate {
 144        struct hlist_node next; /* Link for the slot list. */
 145        u64 S, F;               /* flow timestamps (exact) */
 146
 147        /* group we belong to. In principle we would need the index,
 148         * which is log_2(lmax/weight), but we never reference it
 149         * directly, only the group.
 150         */
 151        struct qfq_group *grp;
 152
 153        /* these are copied from the flowset. */
 154        u32     class_weight; /* Weight of each class in this aggregate. */
 155        /* Max pkt size for the classes in this aggregate, DRR quantum. */
 156        int     lmax;
 157
 158        u32     inv_w;      /* ONE_FP/(sum of weights of classes in aggr.). */
 159        u32     budgetmax;  /* Max budget for this aggregate. */
 160        u32     initial_budget, budget;     /* Initial and current budget. */
 161
 162        int               num_classes;  /* Number of classes in this aggr. */
 163        struct list_head  active;       /* DRR queue of active classes. */
 164
 165        struct hlist_node nonfull_next; /* See nonfull_aggs in qfq_sched. */
 166};
 167
 168struct qfq_group {
 169        u64 S, F;                       /* group timestamps (approx). */
 170        unsigned int slot_shift;        /* Slot shift. */
 171        unsigned int index;             /* Group index. */
 172        unsigned int front;             /* Index of the front slot. */
 173        unsigned long full_slots;       /* non-empty slots */
 174
 175        /* Array of RR lists of active aggregates. */
 176        struct hlist_head slots[QFQ_MAX_SLOTS];
 177};
 178
 179struct qfq_sched {
 180        struct tcf_proto __rcu *filter_list;
 181        struct tcf_block        *block;
 182        struct Qdisc_class_hash clhash;
 183
 184        u64                     oldV, V;        /* Precise virtual times. */
 185        struct qfq_aggregate    *in_serv_agg;   /* Aggregate being served. */
 186        u32                     wsum;           /* weight sum */
 187        u32                     iwsum;          /* inverse weight sum */
 188
 189        unsigned long bitmaps[QFQ_MAX_STATE];       /* Group bitmaps. */
 190        struct qfq_group groups[QFQ_MAX_INDEX + 1]; /* The groups. */
 191        u32 min_slot_shift;     /* Index of the group-0 bit in the bitmaps. */
 192
 193        u32 max_agg_classes;            /* Max number of classes per aggr. */
 194        struct hlist_head nonfull_aggs; /* Aggs with room for more classes. */
 195};
 196
 197/*
 198 * Possible reasons why the timestamps of an aggregate are updated
 199 * enqueue: the aggregate switches from idle to active and must scheduled
 200 *          for service
 201 * requeue: the aggregate finishes its budget, so it stops being served and
 202 *          must be rescheduled for service
 203 */
 204enum update_reason {enqueue, requeue};
 205
 206static struct qfq_class *qfq_find_class(struct Qdisc *sch, u32 classid)
 207{
 208        struct qfq_sched *q = qdisc_priv(sch);
 209        struct Qdisc_class_common *clc;
 210
 211        clc = qdisc_class_find(&q->clhash, classid);
 212        if (clc == NULL)
 213                return NULL;
 214        return container_of(clc, struct qfq_class, common);
 215}
 216
 217static const struct nla_policy qfq_policy[TCA_QFQ_MAX + 1] = {
 218        [TCA_QFQ_WEIGHT] = { .type = NLA_U32 },
 219        [TCA_QFQ_LMAX] = { .type = NLA_U32 },
 220};
 221
 222/*
 223 * Calculate a flow index, given its weight and maximum packet length.
 224 * index = log_2(maxlen/weight) but we need to apply the scaling.
 225 * This is used only once at flow creation.
 226 */
 227static int qfq_calc_index(u32 inv_w, unsigned int maxlen, u32 min_slot_shift)
 228{
 229        u64 slot_size = (u64)maxlen * inv_w;
 230        unsigned long size_map;
 231        int index = 0;
 232
 233        size_map = slot_size >> min_slot_shift;
 234        if (!size_map)
 235                goto out;
 236
 237        index = __fls(size_map) + 1;    /* basically a log_2 */
 238        index -= !(slot_size - (1ULL << (index + min_slot_shift - 1)));
 239
 240        if (index < 0)
 241                index = 0;
 242out:
 243        pr_debug("qfq calc_index: W = %lu, L = %u, I = %d\n",
 244                 (unsigned long) ONE_FP/inv_w, maxlen, index);
 245
 246        return index;
 247}
 248
 249static void qfq_deactivate_agg(struct qfq_sched *, struct qfq_aggregate *);
 250static void qfq_activate_agg(struct qfq_sched *, struct qfq_aggregate *,
 251                             enum update_reason);
 252
 253static void qfq_init_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
 254                         u32 lmax, u32 weight)
 255{
 256        INIT_LIST_HEAD(&agg->active);
 257        hlist_add_head(&agg->nonfull_next, &q->nonfull_aggs);
 258
 259        agg->lmax = lmax;
 260        agg->class_weight = weight;
 261}
 262
 263static struct qfq_aggregate *qfq_find_agg(struct qfq_sched *q,
 264                                          u32 lmax, u32 weight)
 265{
 266        struct qfq_aggregate *agg;
 267
 268        hlist_for_each_entry(agg, &q->nonfull_aggs, nonfull_next)
 269                if (agg->lmax == lmax && agg->class_weight == weight)
 270                        return agg;
 271
 272        return NULL;
 273}
 274
 275
 276/* Update aggregate as a function of the new number of classes. */
 277static void qfq_update_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
 278                           int new_num_classes)
 279{
 280        u32 new_agg_weight;
 281
 282        if (new_num_classes == q->max_agg_classes)
 283                hlist_del_init(&agg->nonfull_next);
 284
 285        if (agg->num_classes > new_num_classes &&
 286            new_num_classes == q->max_agg_classes - 1) /* agg no more full */
 287                hlist_add_head(&agg->nonfull_next, &q->nonfull_aggs);
 288
 289        /* The next assignment may let
 290         * agg->initial_budget > agg->budgetmax
 291         * hold, we will take it into account in charge_actual_service().
 292         */
 293        agg->budgetmax = new_num_classes * agg->lmax;
 294        new_agg_weight = agg->class_weight * new_num_classes;
 295        agg->inv_w = ONE_FP/new_agg_weight;
 296
 297        if (agg->grp == NULL) {
 298                int i = qfq_calc_index(agg->inv_w, agg->budgetmax,
 299                                       q->min_slot_shift);
 300                agg->grp = &q->groups[i];
 301        }
 302
 303        q->wsum +=
 304                (int) agg->class_weight * (new_num_classes - agg->num_classes);
 305        q->iwsum = ONE_FP / q->wsum;
 306
 307        agg->num_classes = new_num_classes;
 308}
 309
 310/* Add class to aggregate. */
 311static void qfq_add_to_agg(struct qfq_sched *q,
 312                           struct qfq_aggregate *agg,
 313                           struct qfq_class *cl)
 314{
 315        cl->agg = agg;
 316
 317        qfq_update_agg(q, agg, agg->num_classes+1);
 318        if (cl->qdisc->q.qlen > 0) { /* adding an active class */
 319                list_add_tail(&cl->alist, &agg->active);
 320                if (list_first_entry(&agg->active, struct qfq_class, alist) ==
 321                    cl && q->in_serv_agg != agg) /* agg was inactive */
 322                        qfq_activate_agg(q, agg, enqueue); /* schedule agg */
 323        }
 324}
 325
 326static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *);
 327
 328static void qfq_destroy_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
 329{
 330        hlist_del_init(&agg->nonfull_next);
 331        q->wsum -= agg->class_weight;
 332        if (q->wsum != 0)
 333                q->iwsum = ONE_FP / q->wsum;
 334
 335        if (q->in_serv_agg == agg)
 336                q->in_serv_agg = qfq_choose_next_agg(q);
 337        kfree(agg);
 338}
 339
 340/* Deschedule class from within its parent aggregate. */
 341static void qfq_deactivate_class(struct qfq_sched *q, struct qfq_class *cl)
 342{
 343        struct qfq_aggregate *agg = cl->agg;
 344
 345
 346        list_del(&cl->alist); /* remove from RR queue of the aggregate */
 347        if (list_empty(&agg->active)) /* agg is now inactive */
 348                qfq_deactivate_agg(q, agg);
 349}
 350
 351/* Remove class from its parent aggregate. */
 352static void qfq_rm_from_agg(struct qfq_sched *q, struct qfq_class *cl)
 353{
 354        struct qfq_aggregate *agg = cl->agg;
 355
 356        cl->agg = NULL;
 357        if (agg->num_classes == 1) { /* agg being emptied, destroy it */
 358                qfq_destroy_agg(q, agg);
 359                return;
 360        }
 361        qfq_update_agg(q, agg, agg->num_classes-1);
 362}
 363
 364/* Deschedule class and remove it from its parent aggregate. */
 365static void qfq_deact_rm_from_agg(struct qfq_sched *q, struct qfq_class *cl)
 366{
 367        if (cl->qdisc->q.qlen > 0) /* class is active */
 368                qfq_deactivate_class(q, cl);
 369
 370        qfq_rm_from_agg(q, cl);
 371}
 372
 373/* Move class to a new aggregate, matching the new class weight and/or lmax */
 374static int qfq_change_agg(struct Qdisc *sch, struct qfq_class *cl, u32 weight,
 375                           u32 lmax)
 376{
 377        struct qfq_sched *q = qdisc_priv(sch);
 378        struct qfq_aggregate *new_agg = qfq_find_agg(q, lmax, weight);
 379
 380        if (new_agg == NULL) { /* create new aggregate */
 381                new_agg = kzalloc(sizeof(*new_agg), GFP_ATOMIC);
 382                if (new_agg == NULL)
 383                        return -ENOBUFS;
 384                qfq_init_agg(q, new_agg, lmax, weight);
 385        }
 386        qfq_deact_rm_from_agg(q, cl);
 387        qfq_add_to_agg(q, new_agg, cl);
 388
 389        return 0;
 390}
 391
 392static int qfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 393                            struct nlattr **tca, unsigned long *arg,
 394                            struct netlink_ext_ack *extack)
 395{
 396        struct qfq_sched *q = qdisc_priv(sch);
 397        struct qfq_class *cl = (struct qfq_class *)*arg;
 398        bool existing = false;
 399        struct nlattr *tb[TCA_QFQ_MAX + 1];
 400        struct qfq_aggregate *new_agg = NULL;
 401        u32 weight, lmax, inv_w;
 402        int err;
 403        int delta_w;
 404
 405        if (tca[TCA_OPTIONS] == NULL) {
 406                pr_notice("qfq: no options\n");
 407                return -EINVAL;
 408        }
 409
 410        err = nla_parse_nested_deprecated(tb, TCA_QFQ_MAX, tca[TCA_OPTIONS],
 411                                          qfq_policy, NULL);
 412        if (err < 0)
 413                return err;
 414
 415        if (tb[TCA_QFQ_WEIGHT]) {
 416                weight = nla_get_u32(tb[TCA_QFQ_WEIGHT]);
 417                if (!weight || weight > (1UL << QFQ_MAX_WSHIFT)) {
 418                        pr_notice("qfq: invalid weight %u\n", weight);
 419                        return -EINVAL;
 420                }
 421        } else
 422                weight = 1;
 423
 424        if (tb[TCA_QFQ_LMAX]) {
 425                lmax = nla_get_u32(tb[TCA_QFQ_LMAX]);
 426                if (lmax < QFQ_MIN_LMAX || lmax > (1UL << QFQ_MTU_SHIFT)) {
 427                        pr_notice("qfq: invalid max length %u\n", lmax);
 428                        return -EINVAL;
 429                }
 430        } else
 431                lmax = psched_mtu(qdisc_dev(sch));
 432
 433        inv_w = ONE_FP / weight;
 434        weight = ONE_FP / inv_w;
 435
 436        if (cl != NULL &&
 437            lmax == cl->agg->lmax &&
 438            weight == cl->agg->class_weight)
 439                return 0; /* nothing to change */
 440
 441        delta_w = weight - (cl ? cl->agg->class_weight : 0);
 442
 443        if (q->wsum + delta_w > QFQ_MAX_WSUM) {
 444                pr_notice("qfq: total weight out of range (%d + %u)\n",
 445                          delta_w, q->wsum);
 446                return -EINVAL;
 447        }
 448
 449        if (cl != NULL) { /* modify existing class */
 450                if (tca[TCA_RATE]) {
 451                        err = gen_replace_estimator(&cl->bstats, NULL,
 452                                                    &cl->rate_est,
 453                                                    NULL,
 454                                                    qdisc_root_sleeping_running(sch),
 455                                                    tca[TCA_RATE]);
 456                        if (err)
 457                                return err;
 458                }
 459                existing = true;
 460                goto set_change_agg;
 461        }
 462
 463        /* create and init new class */
 464        cl = kzalloc(sizeof(struct qfq_class), GFP_KERNEL);
 465        if (cl == NULL)
 466                return -ENOBUFS;
 467
 468        cl->common.classid = classid;
 469        cl->deficit = lmax;
 470
 471        cl->qdisc = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
 472                                      classid, NULL);
 473        if (cl->qdisc == NULL)
 474                cl->qdisc = &noop_qdisc;
 475
 476        if (tca[TCA_RATE]) {
 477                err = gen_new_estimator(&cl->bstats, NULL,
 478                                        &cl->rate_est,
 479                                        NULL,
 480                                        qdisc_root_sleeping_running(sch),
 481                                        tca[TCA_RATE]);
 482                if (err)
 483                        goto destroy_class;
 484        }
 485
 486        if (cl->qdisc != &noop_qdisc)
 487                qdisc_hash_add(cl->qdisc, true);
 488
 489set_change_agg:
 490        sch_tree_lock(sch);
 491        new_agg = qfq_find_agg(q, lmax, weight);
 492        if (new_agg == NULL) { /* create new aggregate */
 493                sch_tree_unlock(sch);
 494                new_agg = kzalloc(sizeof(*new_agg), GFP_KERNEL);
 495                if (new_agg == NULL) {
 496                        err = -ENOBUFS;
 497                        gen_kill_estimator(&cl->rate_est);
 498                        goto destroy_class;
 499                }
 500                sch_tree_lock(sch);
 501                qfq_init_agg(q, new_agg, lmax, weight);
 502        }
 503        if (existing)
 504                qfq_deact_rm_from_agg(q, cl);
 505        else
 506                qdisc_class_hash_insert(&q->clhash, &cl->common);
 507        qfq_add_to_agg(q, new_agg, cl);
 508        sch_tree_unlock(sch);
 509        qdisc_class_hash_grow(sch, &q->clhash);
 510
 511        *arg = (unsigned long)cl;
 512        return 0;
 513
 514destroy_class:
 515        qdisc_put(cl->qdisc);
 516        kfree(cl);
 517        return err;
 518}
 519
 520static void qfq_destroy_class(struct Qdisc *sch, struct qfq_class *cl)
 521{
 522        struct qfq_sched *q = qdisc_priv(sch);
 523
 524        qfq_rm_from_agg(q, cl);
 525        gen_kill_estimator(&cl->rate_est);
 526        qdisc_put(cl->qdisc);
 527        kfree(cl);
 528}
 529
 530static int qfq_delete_class(struct Qdisc *sch, unsigned long arg,
 531                            struct netlink_ext_ack *extack)
 532{
 533        struct qfq_sched *q = qdisc_priv(sch);
 534        struct qfq_class *cl = (struct qfq_class *)arg;
 535
 536        if (cl->filter_cnt > 0)
 537                return -EBUSY;
 538
 539        sch_tree_lock(sch);
 540
 541        qdisc_purge_queue(cl->qdisc);
 542        qdisc_class_hash_remove(&q->clhash, &cl->common);
 543
 544        sch_tree_unlock(sch);
 545
 546        qfq_destroy_class(sch, cl);
 547        return 0;
 548}
 549
 550static unsigned long qfq_search_class(struct Qdisc *sch, u32 classid)
 551{
 552        return (unsigned long)qfq_find_class(sch, classid);
 553}
 554
 555static struct tcf_block *qfq_tcf_block(struct Qdisc *sch, unsigned long cl,
 556                                       struct netlink_ext_ack *extack)
 557{
 558        struct qfq_sched *q = qdisc_priv(sch);
 559
 560        if (cl)
 561                return NULL;
 562
 563        return q->block;
 564}
 565
 566static unsigned long qfq_bind_tcf(struct Qdisc *sch, unsigned long parent,
 567                                  u32 classid)
 568{
 569        struct qfq_class *cl = qfq_find_class(sch, classid);
 570
 571        if (cl != NULL)
 572                cl->filter_cnt++;
 573
 574        return (unsigned long)cl;
 575}
 576
 577static void qfq_unbind_tcf(struct Qdisc *sch, unsigned long arg)
 578{
 579        struct qfq_class *cl = (struct qfq_class *)arg;
 580
 581        cl->filter_cnt--;
 582}
 583
 584static int qfq_graft_class(struct Qdisc *sch, unsigned long arg,
 585                           struct Qdisc *new, struct Qdisc **old,
 586                           struct netlink_ext_ack *extack)
 587{
 588        struct qfq_class *cl = (struct qfq_class *)arg;
 589
 590        if (new == NULL) {
 591                new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
 592                                        cl->common.classid, NULL);
 593                if (new == NULL)
 594                        new = &noop_qdisc;
 595        }
 596
 597        *old = qdisc_replace(sch, new, &cl->qdisc);
 598        return 0;
 599}
 600
 601static struct Qdisc *qfq_class_leaf(struct Qdisc *sch, unsigned long arg)
 602{
 603        struct qfq_class *cl = (struct qfq_class *)arg;
 604
 605        return cl->qdisc;
 606}
 607
 608static int qfq_dump_class(struct Qdisc *sch, unsigned long arg,
 609                          struct sk_buff *skb, struct tcmsg *tcm)
 610{
 611        struct qfq_class *cl = (struct qfq_class *)arg;
 612        struct nlattr *nest;
 613
 614        tcm->tcm_parent = TC_H_ROOT;
 615        tcm->tcm_handle = cl->common.classid;
 616        tcm->tcm_info   = cl->qdisc->handle;
 617
 618        nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
 619        if (nest == NULL)
 620                goto nla_put_failure;
 621        if (nla_put_u32(skb, TCA_QFQ_WEIGHT, cl->agg->class_weight) ||
 622            nla_put_u32(skb, TCA_QFQ_LMAX, cl->agg->lmax))
 623                goto nla_put_failure;
 624        return nla_nest_end(skb, nest);
 625
 626nla_put_failure:
 627        nla_nest_cancel(skb, nest);
 628        return -EMSGSIZE;
 629}
 630
 631static int qfq_dump_class_stats(struct Qdisc *sch, unsigned long arg,
 632                                struct gnet_dump *d)
 633{
 634        struct qfq_class *cl = (struct qfq_class *)arg;
 635        struct tc_qfq_stats xstats;
 636
 637        memset(&xstats, 0, sizeof(xstats));
 638
 639        xstats.weight = cl->agg->class_weight;
 640        xstats.lmax = cl->agg->lmax;
 641
 642        if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
 643                                  d, NULL, &cl->bstats) < 0 ||
 644            gnet_stats_copy_rate_est(d, &cl->rate_est) < 0 ||
 645            qdisc_qstats_copy(d, cl->qdisc) < 0)
 646                return -1;
 647
 648        return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
 649}
 650
 651static void qfq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
 652{
 653        struct qfq_sched *q = qdisc_priv(sch);
 654        struct qfq_class *cl;
 655        unsigned int i;
 656
 657        if (arg->stop)
 658                return;
 659
 660        for (i = 0; i < q->clhash.hashsize; i++) {
 661                hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
 662                        if (arg->count < arg->skip) {
 663                                arg->count++;
 664                                continue;
 665                        }
 666                        if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
 667                                arg->stop = 1;
 668                                return;
 669                        }
 670                        arg->count++;
 671                }
 672        }
 673}
 674
 675static struct qfq_class *qfq_classify(struct sk_buff *skb, struct Qdisc *sch,
 676                                      int *qerr)
 677{
 678        struct qfq_sched *q = qdisc_priv(sch);
 679        struct qfq_class *cl;
 680        struct tcf_result res;
 681        struct tcf_proto *fl;
 682        int result;
 683
 684        if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
 685                pr_debug("qfq_classify: found %d\n", skb->priority);
 686                cl = qfq_find_class(sch, skb->priority);
 687                if (cl != NULL)
 688                        return cl;
 689        }
 690
 691        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 692        fl = rcu_dereference_bh(q->filter_list);
 693        result = tcf_classify(skb, fl, &res, false);
 694        if (result >= 0) {
 695#ifdef CONFIG_NET_CLS_ACT
 696                switch (result) {
 697                case TC_ACT_QUEUED:
 698                case TC_ACT_STOLEN:
 699                case TC_ACT_TRAP:
 700                        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 701                        fallthrough;
 702                case TC_ACT_SHOT:
 703                        return NULL;
 704                }
 705#endif
 706                cl = (struct qfq_class *)res.class;
 707                if (cl == NULL)
 708                        cl = qfq_find_class(sch, res.classid);
 709                return cl;
 710        }
 711
 712        return NULL;
 713}
 714
 715/* Generic comparison function, handling wraparound. */
 716static inline int qfq_gt(u64 a, u64 b)
 717{
 718        return (s64)(a - b) > 0;
 719}
 720
 721/* Round a precise timestamp to its slotted value. */
 722static inline u64 qfq_round_down(u64 ts, unsigned int shift)
 723{
 724        return ts & ~((1ULL << shift) - 1);
 725}
 726
 727/* return the pointer to the group with lowest index in the bitmap */
 728static inline struct qfq_group *qfq_ffs(struct qfq_sched *q,
 729                                        unsigned long bitmap)
 730{
 731        int index = __ffs(bitmap);
 732        return &q->groups[index];
 733}
 734/* Calculate a mask to mimic what would be ffs_from(). */
 735static inline unsigned long mask_from(unsigned long bitmap, int from)
 736{
 737        return bitmap & ~((1UL << from) - 1);
 738}
 739
 740/*
 741 * The state computation relies on ER=0, IR=1, EB=2, IB=3
 742 * First compute eligibility comparing grp->S, q->V,
 743 * then check if someone is blocking us and possibly add EB
 744 */
 745static int qfq_calc_state(struct qfq_sched *q, const struct qfq_group *grp)
 746{
 747        /* if S > V we are not eligible */
 748        unsigned int state = qfq_gt(grp->S, q->V);
 749        unsigned long mask = mask_from(q->bitmaps[ER], grp->index);
 750        struct qfq_group *next;
 751
 752        if (mask) {
 753                next = qfq_ffs(q, mask);
 754                if (qfq_gt(grp->F, next->F))
 755                        state |= EB;
 756        }
 757
 758        return state;
 759}
 760
 761
 762/*
 763 * In principle
 764 *      q->bitmaps[dst] |= q->bitmaps[src] & mask;
 765 *      q->bitmaps[src] &= ~mask;
 766 * but we should make sure that src != dst
 767 */
 768static inline void qfq_move_groups(struct qfq_sched *q, unsigned long mask,
 769                                   int src, int dst)
 770{
 771        q->bitmaps[dst] |= q->bitmaps[src] & mask;
 772        q->bitmaps[src] &= ~mask;
 773}
 774
 775static void qfq_unblock_groups(struct qfq_sched *q, int index, u64 old_F)
 776{
 777        unsigned long mask = mask_from(q->bitmaps[ER], index + 1);
 778        struct qfq_group *next;
 779
 780        if (mask) {
 781                next = qfq_ffs(q, mask);
 782                if (!qfq_gt(next->F, old_F))
 783                        return;
 784        }
 785
 786        mask = (1UL << index) - 1;
 787        qfq_move_groups(q, mask, EB, ER);
 788        qfq_move_groups(q, mask, IB, IR);
 789}
 790
 791/*
 792 * perhaps
 793 *
 794        old_V ^= q->V;
 795        old_V >>= q->min_slot_shift;
 796        if (old_V) {
 797                ...
 798        }
 799 *
 800 */
 801static void qfq_make_eligible(struct qfq_sched *q)
 802{
 803        unsigned long vslot = q->V >> q->min_slot_shift;
 804        unsigned long old_vslot = q->oldV >> q->min_slot_shift;
 805
 806        if (vslot != old_vslot) {
 807                unsigned long mask;
 808                int last_flip_pos = fls(vslot ^ old_vslot);
 809
 810                if (last_flip_pos > 31) /* higher than the number of groups */
 811                        mask = ~0UL;    /* make all groups eligible */
 812                else
 813                        mask = (1UL << last_flip_pos) - 1;
 814
 815                qfq_move_groups(q, mask, IR, ER);
 816                qfq_move_groups(q, mask, IB, EB);
 817        }
 818}
 819
 820/*
 821 * The index of the slot in which the input aggregate agg is to be
 822 * inserted must not be higher than QFQ_MAX_SLOTS-2. There is a '-2'
 823 * and not a '-1' because the start time of the group may be moved
 824 * backward by one slot after the aggregate has been inserted, and
 825 * this would cause non-empty slots to be right-shifted by one
 826 * position.
 827 *
 828 * QFQ+ fully satisfies this bound to the slot index if the parameters
 829 * of the classes are not changed dynamically, and if QFQ+ never
 830 * happens to postpone the service of agg unjustly, i.e., it never
 831 * happens that the aggregate becomes backlogged and eligible, or just
 832 * eligible, while an aggregate with a higher approximated finish time
 833 * is being served. In particular, in this case QFQ+ guarantees that
 834 * the timestamps of agg are low enough that the slot index is never
 835 * higher than 2. Unfortunately, QFQ+ cannot provide the same
 836 * guarantee if it happens to unjustly postpone the service of agg, or
 837 * if the parameters of some class are changed.
 838 *
 839 * As for the first event, i.e., an out-of-order service, the
 840 * upper bound to the slot index guaranteed by QFQ+ grows to
 841 * 2 +
 842 * QFQ_MAX_AGG_CLASSES * ((1<<QFQ_MTU_SHIFT)/QFQ_MIN_LMAX) *
 843 * (current_max_weight/current_wsum) <= 2 + 8 * 128 * 1.
 844 *
 845 * The following function deals with this problem by backward-shifting
 846 * the timestamps of agg, if needed, so as to guarantee that the slot
 847 * index is never higher than QFQ_MAX_SLOTS-2. This backward-shift may
 848 * cause the service of other aggregates to be postponed, yet the
 849 * worst-case guarantees of these aggregates are not violated.  In
 850 * fact, in case of no out-of-order service, the timestamps of agg
 851 * would have been even lower than they are after the backward shift,
 852 * because QFQ+ would have guaranteed a maximum value equal to 2 for
 853 * the slot index, and 2 < QFQ_MAX_SLOTS-2. Hence the aggregates whose
 854 * service is postponed because of the backward-shift would have
 855 * however waited for the service of agg before being served.
 856 *
 857 * The other event that may cause the slot index to be higher than 2
 858 * for agg is a recent change of the parameters of some class. If the
 859 * weight of a class is increased or the lmax (max_pkt_size) of the
 860 * class is decreased, then a new aggregate with smaller slot size
 861 * than the original parent aggregate of the class may happen to be
 862 * activated. The activation of this aggregate should be properly
 863 * delayed to when the service of the class has finished in the ideal
 864 * system tracked by QFQ+. If the activation of the aggregate is not
 865 * delayed to this reference time instant, then this aggregate may be
 866 * unjustly served before other aggregates waiting for service. This
 867 * may cause the above bound to the slot index to be violated for some
 868 * of these unlucky aggregates.
 869 *
 870 * Instead of delaying the activation of the new aggregate, which is
 871 * quite complex, the above-discussed capping of the slot index is
 872 * used to handle also the consequences of a change of the parameters
 873 * of a class.
 874 */
 875static void qfq_slot_insert(struct qfq_group *grp, struct qfq_aggregate *agg,
 876                            u64 roundedS)
 877{
 878        u64 slot = (roundedS - grp->S) >> grp->slot_shift;
 879        unsigned int i; /* slot index in the bucket list */
 880
 881        if (unlikely(slot > QFQ_MAX_SLOTS - 2)) {
 882                u64 deltaS = roundedS - grp->S -
 883                        ((u64)(QFQ_MAX_SLOTS - 2)<<grp->slot_shift);
 884                agg->S -= deltaS;
 885                agg->F -= deltaS;
 886                slot = QFQ_MAX_SLOTS - 2;
 887        }
 888
 889        i = (grp->front + slot) % QFQ_MAX_SLOTS;
 890
 891        hlist_add_head(&agg->next, &grp->slots[i]);
 892        __set_bit(slot, &grp->full_slots);
 893}
 894
 895/* Maybe introduce hlist_first_entry?? */
 896static struct qfq_aggregate *qfq_slot_head(struct qfq_group *grp)
 897{
 898        return hlist_entry(grp->slots[grp->front].first,
 899                           struct qfq_aggregate, next);
 900}
 901
 902/*
 903 * remove the entry from the slot
 904 */
 905static void qfq_front_slot_remove(struct qfq_group *grp)
 906{
 907        struct qfq_aggregate *agg = qfq_slot_head(grp);
 908
 909        BUG_ON(!agg);
 910        hlist_del(&agg->next);
 911        if (hlist_empty(&grp->slots[grp->front]))
 912                __clear_bit(0, &grp->full_slots);
 913}
 914
 915/*
 916 * Returns the first aggregate in the first non-empty bucket of the
 917 * group. As a side effect, adjusts the bucket list so the first
 918 * non-empty bucket is at position 0 in full_slots.
 919 */
 920static struct qfq_aggregate *qfq_slot_scan(struct qfq_group *grp)
 921{
 922        unsigned int i;
 923
 924        pr_debug("qfq slot_scan: grp %u full %#lx\n",
 925                 grp->index, grp->full_slots);
 926
 927        if (grp->full_slots == 0)
 928                return NULL;
 929
 930        i = __ffs(grp->full_slots);  /* zero based */
 931        if (i > 0) {
 932                grp->front = (grp->front + i) % QFQ_MAX_SLOTS;
 933                grp->full_slots >>= i;
 934        }
 935
 936        return qfq_slot_head(grp);
 937}
 938
 939/*
 940 * adjust the bucket list. When the start time of a group decreases,
 941 * we move the index down (modulo QFQ_MAX_SLOTS) so we don't need to
 942 * move the objects. The mask of occupied slots must be shifted
 943 * because we use ffs() to find the first non-empty slot.
 944 * This covers decreases in the group's start time, but what about
 945 * increases of the start time ?
 946 * Here too we should make sure that i is less than 32
 947 */
 948static void qfq_slot_rotate(struct qfq_group *grp, u64 roundedS)
 949{
 950        unsigned int i = (grp->S - roundedS) >> grp->slot_shift;
 951
 952        grp->full_slots <<= i;
 953        grp->front = (grp->front - i) % QFQ_MAX_SLOTS;
 954}
 955
 956static void qfq_update_eligible(struct qfq_sched *q)
 957{
 958        struct qfq_group *grp;
 959        unsigned long ineligible;
 960
 961        ineligible = q->bitmaps[IR] | q->bitmaps[IB];
 962        if (ineligible) {
 963                if (!q->bitmaps[ER]) {
 964                        grp = qfq_ffs(q, ineligible);
 965                        if (qfq_gt(grp->S, q->V))
 966                                q->V = grp->S;
 967                }
 968                qfq_make_eligible(q);
 969        }
 970}
 971
 972/* Dequeue head packet of the head class in the DRR queue of the aggregate. */
 973static void agg_dequeue(struct qfq_aggregate *agg,
 974                        struct qfq_class *cl, unsigned int len)
 975{
 976        qdisc_dequeue_peeked(cl->qdisc);
 977
 978        cl->deficit -= (int) len;
 979
 980        if (cl->qdisc->q.qlen == 0) /* no more packets, remove from list */
 981                list_del(&cl->alist);
 982        else if (cl->deficit < qdisc_pkt_len(cl->qdisc->ops->peek(cl->qdisc))) {
 983                cl->deficit += agg->lmax;
 984                list_move_tail(&cl->alist, &agg->active);
 985        }
 986}
 987
 988static inline struct sk_buff *qfq_peek_skb(struct qfq_aggregate *agg,
 989                                           struct qfq_class **cl,
 990                                           unsigned int *len)
 991{
 992        struct sk_buff *skb;
 993
 994        *cl = list_first_entry(&agg->active, struct qfq_class, alist);
 995        skb = (*cl)->qdisc->ops->peek((*cl)->qdisc);
 996        if (skb == NULL)
 997                WARN_ONCE(1, "qfq_dequeue: non-workconserving leaf\n");
 998        else
 999                *len = qdisc_pkt_len(skb);
1000
1001        return skb;
1002}
1003
1004/* Update F according to the actual service received by the aggregate. */
1005static inline void charge_actual_service(struct qfq_aggregate *agg)
1006{
1007        /* Compute the service received by the aggregate, taking into
1008         * account that, after decreasing the number of classes in
1009         * agg, it may happen that
1010         * agg->initial_budget - agg->budget > agg->bugdetmax
1011         */
1012        u32 service_received = min(agg->budgetmax,
1013                                   agg->initial_budget - agg->budget);
1014
1015        agg->F = agg->S + (u64)service_received * agg->inv_w;
1016}
1017
1018/* Assign a reasonable start time for a new aggregate in group i.
1019 * Admissible values for \hat(F) are multiples of \sigma_i
1020 * no greater than V+\sigma_i . Larger values mean that
1021 * we had a wraparound so we consider the timestamp to be stale.
1022 *
1023 * If F is not stale and F >= V then we set S = F.
1024 * Otherwise we should assign S = V, but this may violate
1025 * the ordering in EB (see [2]). So, if we have groups in ER,
1026 * set S to the F_j of the first group j which would be blocking us.
1027 * We are guaranteed not to move S backward because
1028 * otherwise our group i would still be blocked.
1029 */
1030static void qfq_update_start(struct qfq_sched *q, struct qfq_aggregate *agg)
1031{
1032        unsigned long mask;
1033        u64 limit, roundedF;
1034        int slot_shift = agg->grp->slot_shift;
1035
1036        roundedF = qfq_round_down(agg->F, slot_shift);
1037        limit = qfq_round_down(q->V, slot_shift) + (1ULL << slot_shift);
1038
1039        if (!qfq_gt(agg->F, q->V) || qfq_gt(roundedF, limit)) {
1040                /* timestamp was stale */
1041                mask = mask_from(q->bitmaps[ER], agg->grp->index);
1042                if (mask) {
1043                        struct qfq_group *next = qfq_ffs(q, mask);
1044                        if (qfq_gt(roundedF, next->F)) {
1045                                if (qfq_gt(limit, next->F))
1046                                        agg->S = next->F;
1047                                else /* preserve timestamp correctness */
1048                                        agg->S = limit;
1049                                return;
1050                        }
1051                }
1052                agg->S = q->V;
1053        } else  /* timestamp is not stale */
1054                agg->S = agg->F;
1055}
1056
1057/* Update the timestamps of agg before scheduling/rescheduling it for
1058 * service.  In particular, assign to agg->F its maximum possible
1059 * value, i.e., the virtual finish time with which the aggregate
1060 * should be labeled if it used all its budget once in service.
1061 */
1062static inline void
1063qfq_update_agg_ts(struct qfq_sched *q,
1064                    struct qfq_aggregate *agg, enum update_reason reason)
1065{
1066        if (reason != requeue)
1067                qfq_update_start(q, agg);
1068        else /* just charge agg for the service received */
1069                agg->S = agg->F;
1070
1071        agg->F = agg->S + (u64)agg->budgetmax * agg->inv_w;
1072}
1073
1074static void qfq_schedule_agg(struct qfq_sched *q, struct qfq_aggregate *agg);
1075
1076static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
1077{
1078        struct qfq_sched *q = qdisc_priv(sch);
1079        struct qfq_aggregate *in_serv_agg = q->in_serv_agg;
1080        struct qfq_class *cl;
1081        struct sk_buff *skb = NULL;
1082        /* next-packet len, 0 means no more active classes in in-service agg */
1083        unsigned int len = 0;
1084
1085        if (in_serv_agg == NULL)
1086                return NULL;
1087
1088        if (!list_empty(&in_serv_agg->active))
1089                skb = qfq_peek_skb(in_serv_agg, &cl, &len);
1090
1091        /*
1092         * If there are no active classes in the in-service aggregate,
1093         * or if the aggregate has not enough budget to serve its next
1094         * class, then choose the next aggregate to serve.
1095         */
1096        if (len == 0 || in_serv_agg->budget < len) {
1097                charge_actual_service(in_serv_agg);
1098
1099                /* recharge the budget of the aggregate */
1100                in_serv_agg->initial_budget = in_serv_agg->budget =
1101                        in_serv_agg->budgetmax;
1102
1103                if (!list_empty(&in_serv_agg->active)) {
1104                        /*
1105                         * Still active: reschedule for
1106                         * service. Possible optimization: if no other
1107                         * aggregate is active, then there is no point
1108                         * in rescheduling this aggregate, and we can
1109                         * just keep it as the in-service one. This
1110                         * should be however a corner case, and to
1111                         * handle it, we would need to maintain an
1112                         * extra num_active_aggs field.
1113                        */
1114                        qfq_update_agg_ts(q, in_serv_agg, requeue);
1115                        qfq_schedule_agg(q, in_serv_agg);
1116                } else if (sch->q.qlen == 0) { /* no aggregate to serve */
1117                        q->in_serv_agg = NULL;
1118                        return NULL;
1119                }
1120
1121                /*
1122                 * If we get here, there are other aggregates queued:
1123                 * choose the new aggregate to serve.
1124                 */
1125                in_serv_agg = q->in_serv_agg = qfq_choose_next_agg(q);
1126                skb = qfq_peek_skb(in_serv_agg, &cl, &len);
1127        }
1128        if (!skb)
1129                return NULL;
1130
1131        qdisc_qstats_backlog_dec(sch, skb);
1132        sch->q.qlen--;
1133        qdisc_bstats_update(sch, skb);
1134
1135        agg_dequeue(in_serv_agg, cl, len);
1136        /* If lmax is lowered, through qfq_change_class, for a class
1137         * owning pending packets with larger size than the new value
1138         * of lmax, then the following condition may hold.
1139         */
1140        if (unlikely(in_serv_agg->budget < len))
1141                in_serv_agg->budget = 0;
1142        else
1143                in_serv_agg->budget -= len;
1144
1145        q->V += (u64)len * q->iwsum;
1146        pr_debug("qfq dequeue: len %u F %lld now %lld\n",
1147                 len, (unsigned long long) in_serv_agg->F,
1148                 (unsigned long long) q->V);
1149
1150        return skb;
1151}
1152
1153static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *q)
1154{
1155        struct qfq_group *grp;
1156        struct qfq_aggregate *agg, *new_front_agg;
1157        u64 old_F;
1158
1159        qfq_update_eligible(q);
1160        q->oldV = q->V;
1161
1162        if (!q->bitmaps[ER])
1163                return NULL;
1164
1165        grp = qfq_ffs(q, q->bitmaps[ER]);
1166        old_F = grp->F;
1167
1168        agg = qfq_slot_head(grp);
1169
1170        /* agg starts to be served, remove it from schedule */
1171        qfq_front_slot_remove(grp);
1172
1173        new_front_agg = qfq_slot_scan(grp);
1174
1175        if (new_front_agg == NULL) /* group is now inactive, remove from ER */
1176                __clear_bit(grp->index, &q->bitmaps[ER]);
1177        else {
1178                u64 roundedS = qfq_round_down(new_front_agg->S,
1179                                              grp->slot_shift);
1180                unsigned int s;
1181
1182                if (grp->S == roundedS)
1183                        return agg;
1184                grp->S = roundedS;
1185                grp->F = roundedS + (2ULL << grp->slot_shift);
1186                __clear_bit(grp->index, &q->bitmaps[ER]);
1187                s = qfq_calc_state(q, grp);
1188                __set_bit(grp->index, &q->bitmaps[s]);
1189        }
1190
1191        qfq_unblock_groups(q, grp->index, old_F);
1192
1193        return agg;
1194}
1195
1196static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
1197                       struct sk_buff **to_free)
1198{
1199        unsigned int len = qdisc_pkt_len(skb), gso_segs;
1200        struct qfq_sched *q = qdisc_priv(sch);
1201        struct qfq_class *cl;
1202        struct qfq_aggregate *agg;
1203        int err = 0;
1204        bool first;
1205
1206        cl = qfq_classify(skb, sch, &err);
1207        if (cl == NULL) {
1208                if (err & __NET_XMIT_BYPASS)
1209                        qdisc_qstats_drop(sch);
1210                __qdisc_drop(skb, to_free);
1211                return err;
1212        }
1213        pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);
1214
1215        if (unlikely(cl->agg->lmax < len)) {
1216                pr_debug("qfq: increasing maxpkt from %u to %u for class %u",
1217                         cl->agg->lmax, len, cl->common.classid);
1218                err = qfq_change_agg(sch, cl, cl->agg->class_weight, len);
1219                if (err) {
1220                        cl->qstats.drops++;
1221                        return qdisc_drop(skb, sch, to_free);
1222                }
1223        }
1224
1225        gso_segs = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1;
1226        first = !cl->qdisc->q.qlen;
1227        err = qdisc_enqueue(skb, cl->qdisc, to_free);
1228        if (unlikely(err != NET_XMIT_SUCCESS)) {
1229                pr_debug("qfq_enqueue: enqueue failed %d\n", err);
1230                if (net_xmit_drop_count(err)) {
1231                        cl->qstats.drops++;
1232                        qdisc_qstats_drop(sch);
1233                }
1234                return err;
1235        }
1236
1237        cl->bstats.bytes += len;
1238        cl->bstats.packets += gso_segs;
1239        sch->qstats.backlog += len;
1240        ++sch->q.qlen;
1241
1242        agg = cl->agg;
1243        /* if the queue was not empty, then done here */
1244        if (!first) {
1245                if (unlikely(skb == cl->qdisc->ops->peek(cl->qdisc)) &&
1246                    list_first_entry(&agg->active, struct qfq_class, alist)
1247                    == cl && cl->deficit < len)
1248                        list_move_tail(&cl->alist, &agg->active);
1249
1250                return err;
1251        }
1252
1253        /* schedule class for service within the aggregate */
1254        cl->deficit = agg->lmax;
1255        list_add_tail(&cl->alist, &agg->active);
1256
1257        if (list_first_entry(&agg->active, struct qfq_class, alist) != cl ||
1258            q->in_serv_agg == agg)
1259                return err; /* non-empty or in service, nothing else to do */
1260
1261        qfq_activate_agg(q, agg, enqueue);
1262
1263        return err;
1264}
1265
1266/*
1267 * Schedule aggregate according to its timestamps.
1268 */
1269static void qfq_schedule_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
1270{
1271        struct qfq_group *grp = agg->grp;
1272        u64 roundedS;
1273        int s;
1274
1275        roundedS = qfq_round_down(agg->S, grp->slot_shift);
1276
1277        /*
1278         * Insert agg in the correct bucket.
1279         * If agg->S >= grp->S we don't need to adjust the
1280         * bucket list and simply go to the insertion phase.
1281         * Otherwise grp->S is decreasing, we must make room
1282         * in the bucket list, and also recompute the group state.
1283         * Finally, if there were no flows in this group and nobody
1284         * was in ER make sure to adjust V.
1285         */
1286        if (grp->full_slots) {
1287                if (!qfq_gt(grp->S, agg->S))
1288                        goto skip_update;
1289
1290                /* create a slot for this agg->S */
1291                qfq_slot_rotate(grp, roundedS);
1292                /* group was surely ineligible, remove */
1293                __clear_bit(grp->index, &q->bitmaps[IR]);
1294                __clear_bit(grp->index, &q->bitmaps[IB]);
1295        } else if (!q->bitmaps[ER] && qfq_gt(roundedS, q->V) &&
1296                   q->in_serv_agg == NULL)
1297                q->V = roundedS;
1298
1299        grp->S = roundedS;
1300        grp->F = roundedS + (2ULL << grp->slot_shift);
1301        s = qfq_calc_state(q, grp);
1302        __set_bit(grp->index, &q->bitmaps[s]);
1303
1304        pr_debug("qfq enqueue: new state %d %#lx S %lld F %lld V %lld\n",
1305                 s, q->bitmaps[s],
1306                 (unsigned long long) agg->S,
1307                 (unsigned long long) agg->F,
1308                 (unsigned long long) q->V);
1309
1310skip_update:
1311        qfq_slot_insert(grp, agg, roundedS);
1312}
1313
1314
1315/* Update agg ts and schedule agg for service */
1316static void qfq_activate_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
1317                             enum update_reason reason)
1318{
1319        agg->initial_budget = agg->budget = agg->budgetmax; /* recharge budg. */
1320
1321        qfq_update_agg_ts(q, agg, reason);
1322        if (q->in_serv_agg == NULL) { /* no aggr. in service or scheduled */
1323                q->in_serv_agg = agg; /* start serving this aggregate */
1324                 /* update V: to be in service, agg must be eligible */
1325                q->oldV = q->V = agg->S;
1326        } else if (agg != q->in_serv_agg)
1327                qfq_schedule_agg(q, agg);
1328}
1329
1330static void qfq_slot_remove(struct qfq_sched *q, struct qfq_group *grp,
1331                            struct qfq_aggregate *agg)
1332{
1333        unsigned int i, offset;
1334        u64 roundedS;
1335
1336        roundedS = qfq_round_down(agg->S, grp->slot_shift);
1337        offset = (roundedS - grp->S) >> grp->slot_shift;
1338
1339        i = (grp->front + offset) % QFQ_MAX_SLOTS;
1340
1341        hlist_del(&agg->next);
1342        if (hlist_empty(&grp->slots[i]))
1343                __clear_bit(offset, &grp->full_slots);
1344}
1345
1346/*
1347 * Called to forcibly deschedule an aggregate.  If the aggregate is
1348 * not in the front bucket, or if the latter has other aggregates in
1349 * the front bucket, we can simply remove the aggregate with no other
1350 * side effects.
1351 * Otherwise we must propagate the event up.
1352 */
1353static void qfq_deactivate_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
1354{
1355        struct qfq_group *grp = agg->grp;
1356        unsigned long mask;
1357        u64 roundedS;
1358        int s;
1359
1360        if (agg == q->in_serv_agg) {
1361                charge_actual_service(agg);
1362                q->in_serv_agg = qfq_choose_next_agg(q);
1363                return;
1364        }
1365
1366        agg->F = agg->S;
1367        qfq_slot_remove(q, grp, agg);
1368
1369        if (!grp->full_slots) {
1370                __clear_bit(grp->index, &q->bitmaps[IR]);
1371                __clear_bit(grp->index, &q->bitmaps[EB]);
1372                __clear_bit(grp->index, &q->bitmaps[IB]);
1373
1374                if (test_bit(grp->index, &q->bitmaps[ER]) &&
1375                    !(q->bitmaps[ER] & ~((1UL << grp->index) - 1))) {
1376                        mask = q->bitmaps[ER] & ((1UL << grp->index) - 1);
1377                        if (mask)
1378                                mask = ~((1UL << __fls(mask)) - 1);
1379                        else
1380                                mask = ~0UL;
1381                        qfq_move_groups(q, mask, EB, ER);
1382                        qfq_move_groups(q, mask, IB, IR);
1383                }
1384                __clear_bit(grp->index, &q->bitmaps[ER]);
1385        } else if (hlist_empty(&grp->slots[grp->front])) {
1386                agg = qfq_slot_scan(grp);
1387                roundedS = qfq_round_down(agg->S, grp->slot_shift);
1388                if (grp->S != roundedS) {
1389                        __clear_bit(grp->index, &q->bitmaps[ER]);
1390                        __clear_bit(grp->index, &q->bitmaps[IR]);
1391                        __clear_bit(grp->index, &q->bitmaps[EB]);
1392                        __clear_bit(grp->index, &q->bitmaps[IB]);
1393                        grp->S = roundedS;
1394                        grp->F = roundedS + (2ULL << grp->slot_shift);
1395                        s = qfq_calc_state(q, grp);
1396                        __set_bit(grp->index, &q->bitmaps[s]);
1397                }
1398        }
1399}
1400
1401static void qfq_qlen_notify(struct Qdisc *sch, unsigned long arg)
1402{
1403        struct qfq_sched *q = qdisc_priv(sch);
1404        struct qfq_class *cl = (struct qfq_class *)arg;
1405
1406        qfq_deactivate_class(q, cl);
1407}
1408
1409static int qfq_init_qdisc(struct Qdisc *sch, struct nlattr *opt,
1410                          struct netlink_ext_ack *extack)
1411{
1412        struct qfq_sched *q = qdisc_priv(sch);
1413        struct qfq_group *grp;
1414        int i, j, err;
1415        u32 max_cl_shift, maxbudg_shift, max_classes;
1416
1417        err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
1418        if (err)
1419                return err;
1420
1421        err = qdisc_class_hash_init(&q->clhash);
1422        if (err < 0)
1423                return err;
1424
1425        if (qdisc_dev(sch)->tx_queue_len + 1 > QFQ_MAX_AGG_CLASSES)
1426                max_classes = QFQ_MAX_AGG_CLASSES;
1427        else
1428                max_classes = qdisc_dev(sch)->tx_queue_len + 1;
1429        /* max_cl_shift = floor(log_2(max_classes)) */
1430        max_cl_shift = __fls(max_classes);
1431        q->max_agg_classes = 1<<max_cl_shift;
1432
1433        /* maxbudg_shift = log2(max_len * max_classes_per_agg) */
1434        maxbudg_shift = QFQ_MTU_SHIFT + max_cl_shift;
1435        q->min_slot_shift = FRAC_BITS + maxbudg_shift - QFQ_MAX_INDEX;
1436
1437        for (i = 0; i <= QFQ_MAX_INDEX; i++) {
1438                grp = &q->groups[i];
1439                grp->index = i;
1440                grp->slot_shift = q->min_slot_shift + i;
1441                for (j = 0; j < QFQ_MAX_SLOTS; j++)
1442                        INIT_HLIST_HEAD(&grp->slots[j]);
1443        }
1444
1445        INIT_HLIST_HEAD(&q->nonfull_aggs);
1446
1447        return 0;
1448}
1449
1450static void qfq_reset_qdisc(struct Qdisc *sch)
1451{
1452        struct qfq_sched *q = qdisc_priv(sch);
1453        struct qfq_class *cl;
1454        unsigned int i;
1455
1456        for (i = 0; i < q->clhash.hashsize; i++) {
1457                hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
1458                        if (cl->qdisc->q.qlen > 0)
1459                                qfq_deactivate_class(q, cl);
1460
1461                        qdisc_reset(cl->qdisc);
1462                }
1463        }
1464        sch->qstats.backlog = 0;
1465        sch->q.qlen = 0;
1466}
1467
1468static void qfq_destroy_qdisc(struct Qdisc *sch)
1469{
1470        struct qfq_sched *q = qdisc_priv(sch);
1471        struct qfq_class *cl;
1472        struct hlist_node *next;
1473        unsigned int i;
1474
1475        tcf_block_put(q->block);
1476
1477        for (i = 0; i < q->clhash.hashsize; i++) {
1478                hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],
1479                                          common.hnode) {
1480                        qfq_destroy_class(sch, cl);
1481                }
1482        }
1483        qdisc_class_hash_destroy(&q->clhash);
1484}
1485
1486static const struct Qdisc_class_ops qfq_class_ops = {
1487        .change         = qfq_change_class,
1488        .delete         = qfq_delete_class,
1489        .find           = qfq_search_class,
1490        .tcf_block      = qfq_tcf_block,
1491        .bind_tcf       = qfq_bind_tcf,
1492        .unbind_tcf     = qfq_unbind_tcf,
1493        .graft          = qfq_graft_class,
1494        .leaf           = qfq_class_leaf,
1495        .qlen_notify    = qfq_qlen_notify,
1496        .dump           = qfq_dump_class,
1497        .dump_stats     = qfq_dump_class_stats,
1498        .walk           = qfq_walk,
1499};
1500
1501static struct Qdisc_ops qfq_qdisc_ops __read_mostly = {
1502        .cl_ops         = &qfq_class_ops,
1503        .id             = "qfq",
1504        .priv_size      = sizeof(struct qfq_sched),
1505        .enqueue        = qfq_enqueue,
1506        .dequeue        = qfq_dequeue,
1507        .peek           = qdisc_peek_dequeued,
1508        .init           = qfq_init_qdisc,
1509        .reset          = qfq_reset_qdisc,
1510        .destroy        = qfq_destroy_qdisc,
1511        .owner          = THIS_MODULE,
1512};
1513
1514static int __init qfq_init(void)
1515{
1516        return register_qdisc(&qfq_qdisc_ops);
1517}
1518
1519static void __exit qfq_exit(void)
1520{
1521        unregister_qdisc(&qfq_qdisc_ops);
1522}
1523
1524module_init(qfq_init);
1525module_exit(qfq_exit);
1526MODULE_LICENSE("GPL");
1527