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Linux/net/sched/sch_qfq.c

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  1 /*
  2  * net/sched/sch_qfq.c         Quick Fair Queueing Scheduler.
  3  *
  4  * Copyright (c) 2009 Fabio Checconi, Luigi Rizzo, and Paolo Valente.
  5  *
  6  * This program is free software; you can redistribute it and/or
  7  * modify it under the terms of the GNU General Public License
  8  * version 2 as published by the Free Software Foundation.
  9  */
 10 
 11 #include <linux/module.h>
 12 #include <linux/init.h>
 13 #include <linux/bitops.h>
 14 #include <linux/errno.h>
 15 #include <linux/netdevice.h>
 16 #include <linux/pkt_sched.h>
 17 #include <net/sch_generic.h>
 18 #include <net/pkt_sched.h>
 19 #include <net/pkt_cls.h>
 20 
 21 
 22 /*  Quick Fair Queueing
 23     ===================
 24 
 25     Sources:
 26 
 27     Fabio Checconi, Luigi Rizzo, and Paolo Valente: "QFQ: Efficient
 28     Packet Scheduling with Tight Bandwidth Distribution Guarantees."
 29 
 30     See also:
 31     http://retis.sssup.it/~fabio/linux/qfq/
 32  */
 33 
 34 /*
 35 
 36   Virtual time computations.
 37 
 38   S, F and V are all computed in fixed point arithmetic with
 39   FRAC_BITS decimal bits.
 40 
 41   QFQ_MAX_INDEX is the maximum index allowed for a group. We need
 42         one bit per index.
 43   QFQ_MAX_WSHIFT is the maximum power of two supported as a weight.
 44 
 45   The layout of the bits is as below:
 46 
 47                    [ MTU_SHIFT ][      FRAC_BITS    ]
 48                    [ MAX_INDEX    ][ MIN_SLOT_SHIFT ]
 49                                  ^.__grp->index = 0
 50                                  *.__grp->slot_shift
 51 
 52   where MIN_SLOT_SHIFT is derived by difference from the others.
 53 
 54   The max group index corresponds to Lmax/w_min, where
 55   Lmax=1<<MTU_SHIFT, w_min = 1 .
 56   From this, and knowing how many groups (MAX_INDEX) we want,
 57   we can derive the shift corresponding to each group.
 58 
 59   Because we often need to compute
 60         F = S + len/w_i  and V = V + len/wsum
 61   instead of storing w_i store the value
 62         inv_w = (1<<FRAC_BITS)/w_i
 63   so we can do F = S + len * inv_w * wsum.
 64   We use W_TOT in the formulas so we can easily move between
 65   static and adaptive weight sum.
 66 
 67   The per-scheduler-instance data contain all the data structures
 68   for the scheduler: bitmaps and bucket lists.
 69 
 70  */
 71 
 72 /*
 73  * Maximum number of consecutive slots occupied by backlogged classes
 74  * inside a group.
 75  */
 76 #define QFQ_MAX_SLOTS   32
 77 
 78 /*
 79  * Shifts used for class<->group mapping.  We allow class weights that are
 80  * in the range [1, 2^MAX_WSHIFT], and we try to map each class i to the
 81  * group with the smallest index that can support the L_i / r_i configured
 82  * for the class.
 83  *
 84  * grp->index is the index of the group; and grp->slot_shift
 85  * is the shift for the corresponding (scaled) sigma_i.
 86  */
 87 #define QFQ_MAX_INDEX           19
 88 #define QFQ_MAX_WSHIFT          16
 89 
 90 #define QFQ_MAX_WEIGHT          (1<<QFQ_MAX_WSHIFT)
 91 #define QFQ_MAX_WSUM            (2*QFQ_MAX_WEIGHT)
 92 
 93 #define FRAC_BITS               30      /* fixed point arithmetic */
 94 #define ONE_FP                  (1UL << FRAC_BITS)
 95 #define IWSUM                   (ONE_FP/QFQ_MAX_WSUM)
 96 
 97 #define QFQ_MTU_SHIFT           11
 98 #define QFQ_MIN_SLOT_SHIFT      (FRAC_BITS + QFQ_MTU_SHIFT - QFQ_MAX_INDEX)
 99 
100 /*
101  * Possible group states.  These values are used as indexes for the bitmaps
102  * array of struct qfq_queue.
103  */
104 enum qfq_state { ER, IR, EB, IB, QFQ_MAX_STATE };
105 
106 struct qfq_group;
107 
108 struct qfq_class {
109         struct Qdisc_class_common common;
110 
111         unsigned int refcnt;
112         unsigned int filter_cnt;
113 
114         struct gnet_stats_basic_packed bstats;
115         struct gnet_stats_queue qstats;
116         struct gnet_stats_rate_est rate_est;
117         struct Qdisc *qdisc;
118 
119         struct hlist_node next; /* Link for the slot list. */
120         u64 S, F;               /* flow timestamps (exact) */
121 
122         /* group we belong to. In principle we would need the index,
123          * which is log_2(lmax/weight), but we never reference it
124          * directly, only the group.
125          */
126         struct qfq_group *grp;
127 
128         /* these are copied from the flowset. */
129         u32     inv_w;          /* ONE_FP/weight */
130         u32     lmax;           /* Max packet size for this flow. */
131 };
132 
133 struct qfq_group {
134         u64 S, F;                       /* group timestamps (approx). */
135         unsigned int slot_shift;        /* Slot shift. */
136         unsigned int index;             /* Group index. */
137         unsigned int front;             /* Index of the front slot. */
138         unsigned long full_slots;       /* non-empty slots */
139 
140         /* Array of RR lists of active classes. */
141         struct hlist_head slots[QFQ_MAX_SLOTS];
142 };
143 
144 struct qfq_sched {
145         struct tcf_proto *filter_list;
146         struct Qdisc_class_hash clhash;
147 
148         u64             V;              /* Precise virtual time. */
149         u32             wsum;           /* weight sum */
150 
151         unsigned long bitmaps[QFQ_MAX_STATE];       /* Group bitmaps. */
152         struct qfq_group groups[QFQ_MAX_INDEX + 1]; /* The groups. */
153 };
154 
155 static struct qfq_class *qfq_find_class(struct Qdisc *sch, u32 classid)
156 {
157         struct qfq_sched *q = qdisc_priv(sch);
158         struct Qdisc_class_common *clc;
159 
160         clc = qdisc_class_find(&q->clhash, classid);
161         if (clc == NULL)
162                 return NULL;
163         return container_of(clc, struct qfq_class, common);
164 }
165 
166 static void qfq_purge_queue(struct qfq_class *cl)
167 {
168         unsigned int len = cl->qdisc->q.qlen;
169 
170         qdisc_reset(cl->qdisc);
171         qdisc_tree_decrease_qlen(cl->qdisc, len);
172 }
173 
174 static const struct nla_policy qfq_policy[TCA_QFQ_MAX + 1] = {
175         [TCA_QFQ_WEIGHT] = { .type = NLA_U32 },
176         [TCA_QFQ_LMAX] = { .type = NLA_U32 },
177 };
178 
179 /*
180  * Calculate a flow index, given its weight and maximum packet length.
181  * index = log_2(maxlen/weight) but we need to apply the scaling.
182  * This is used only once at flow creation.
183  */
184 static int qfq_calc_index(u32 inv_w, unsigned int maxlen)
185 {
186         u64 slot_size = (u64)maxlen * inv_w;
187         unsigned long size_map;
188         int index = 0;
189 
190         size_map = slot_size >> QFQ_MIN_SLOT_SHIFT;
191         if (!size_map)
192                 goto out;
193 
194         index = __fls(size_map) + 1;    /* basically a log_2 */
195         index -= !(slot_size - (1ULL << (index + QFQ_MIN_SLOT_SHIFT - 1)));
196 
197         if (index < 0)
198                 index = 0;
199 out:
200         pr_debug("qfq calc_index: W = %lu, L = %u, I = %d\n",
201                  (unsigned long) ONE_FP/inv_w, maxlen, index);
202 
203         return index;
204 }
205 
206 /* Length of the next packet (0 if the queue is empty). */
207 static unsigned int qdisc_peek_len(struct Qdisc *sch)
208 {
209         struct sk_buff *skb;
210 
211         skb = sch->ops->peek(sch);
212         return skb ? qdisc_pkt_len(skb) : 0;
213 }
214 
215 static void qfq_deactivate_class(struct qfq_sched *, struct qfq_class *);
216 static void qfq_activate_class(struct qfq_sched *q, struct qfq_class *cl,
217                                unsigned int len);
218 
219 static void qfq_update_class_params(struct qfq_sched *q, struct qfq_class *cl,
220                                     u32 lmax, u32 inv_w, int delta_w)
221 {
222         int i;
223 
224         /* update qfq-specific data */
225         cl->lmax = lmax;
226         cl->inv_w = inv_w;
227         i = qfq_calc_index(cl->inv_w, cl->lmax);
228 
229         cl->grp = &q->groups[i];
230 
231         q->wsum += delta_w;
232 }
233 
234 static int qfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
235                             struct nlattr **tca, unsigned long *arg)
236 {
237         struct qfq_sched *q = qdisc_priv(sch);
238         struct qfq_class *cl = (struct qfq_class *)*arg;
239         struct nlattr *tb[TCA_QFQ_MAX + 1];
240         u32 weight, lmax, inv_w;
241         int i, err;
242         int delta_w;
243 
244         if (tca[TCA_OPTIONS] == NULL) {
245                 pr_notice("qfq: no options\n");
246                 return -EINVAL;
247         }
248 
249         err = nla_parse_nested(tb, TCA_QFQ_MAX, tca[TCA_OPTIONS], qfq_policy);
250         if (err < 0)
251                 return err;
252 
253         if (tb[TCA_QFQ_WEIGHT]) {
254                 weight = nla_get_u32(tb[TCA_QFQ_WEIGHT]);
255                 if (!weight || weight > (1UL << QFQ_MAX_WSHIFT)) {
256                         pr_notice("qfq: invalid weight %u\n", weight);
257                         return -EINVAL;
258                 }
259         } else
260                 weight = 1;
261 
262         inv_w = ONE_FP / weight;
263         weight = ONE_FP / inv_w;
264         delta_w = weight - (cl ? ONE_FP / cl->inv_w : 0);
265         if (q->wsum + delta_w > QFQ_MAX_WSUM) {
266                 pr_notice("qfq: total weight out of range (%u + %u)\n",
267                           delta_w, q->wsum);
268                 return -EINVAL;
269         }
270 
271         if (tb[TCA_QFQ_LMAX]) {
272                 lmax = nla_get_u32(tb[TCA_QFQ_LMAX]);
273                 if (!lmax || lmax > (1UL << QFQ_MTU_SHIFT)) {
274                         pr_notice("qfq: invalid max length %u\n", lmax);
275                         return -EINVAL;
276                 }
277         } else
278                 lmax = 1UL << QFQ_MTU_SHIFT;
279 
280         if (cl != NULL) {
281                 bool need_reactivation = false;
282 
283                 if (tca[TCA_RATE]) {
284                         err = gen_replace_estimator(&cl->bstats, &cl->rate_est,
285                                                     qdisc_root_sleeping_lock(sch),
286                                                     tca[TCA_RATE]);
287                         if (err)
288                                 return err;
289                 }
290 
291                 if (lmax == cl->lmax && inv_w == cl->inv_w)
292                         return 0; /* nothing to update */
293 
294                 i = qfq_calc_index(inv_w, lmax);
295                 sch_tree_lock(sch);
296                 if (&q->groups[i] != cl->grp && cl->qdisc->q.qlen > 0) {
297                         /*
298                          * shift cl->F back, to not charge the
299                          * class for the not-yet-served head
300                          * packet
301                          */
302                         cl->F = cl->S;
303                         /* remove class from its slot in the old group */
304                         qfq_deactivate_class(q, cl);
305                         need_reactivation = true;
306                 }
307 
308                 qfq_update_class_params(q, cl, lmax, inv_w, delta_w);
309 
310                 if (need_reactivation) /* activate in new group */
311                         qfq_activate_class(q, cl, qdisc_peek_len(cl->qdisc));
312                 sch_tree_unlock(sch);
313 
314                 return 0;
315         }
316 
317         cl = kzalloc(sizeof(struct qfq_class), GFP_KERNEL);
318         if (cl == NULL)
319                 return -ENOBUFS;
320 
321         cl->refcnt = 1;
322         cl->common.classid = classid;
323 
324         qfq_update_class_params(q, cl, lmax, inv_w, delta_w);
325 
326         cl->qdisc = qdisc_create_dflt(sch->dev_queue,
327                                       &pfifo_qdisc_ops, classid);
328         if (cl->qdisc == NULL)
329                 cl->qdisc = &noop_qdisc;
330 
331         if (tca[TCA_RATE]) {
332                 err = gen_new_estimator(&cl->bstats, &cl->rate_est,
333                                         qdisc_root_sleeping_lock(sch),
334                                         tca[TCA_RATE]);
335                 if (err) {
336                         qdisc_destroy(cl->qdisc);
337                         kfree(cl);
338                         return err;
339                 }
340         }
341 
342         sch_tree_lock(sch);
343         qdisc_class_hash_insert(&q->clhash, &cl->common);
344         sch_tree_unlock(sch);
345 
346         qdisc_class_hash_grow(sch, &q->clhash);
347 
348         *arg = (unsigned long)cl;
349         return 0;
350 }
351 
352 static void qfq_destroy_class(struct Qdisc *sch, struct qfq_class *cl)
353 {
354         struct qfq_sched *q = qdisc_priv(sch);
355 
356         if (cl->inv_w) {
357                 q->wsum -= ONE_FP / cl->inv_w;
358                 cl->inv_w = 0;
359         }
360 
361         gen_kill_estimator(&cl->bstats, &cl->rate_est);
362         qdisc_destroy(cl->qdisc);
363         kfree(cl);
364 }
365 
366 static int qfq_delete_class(struct Qdisc *sch, unsigned long arg)
367 {
368         struct qfq_sched *q = qdisc_priv(sch);
369         struct qfq_class *cl = (struct qfq_class *)arg;
370 
371         if (cl->filter_cnt > 0)
372                 return -EBUSY;
373 
374         sch_tree_lock(sch);
375 
376         qfq_purge_queue(cl);
377         qdisc_class_hash_remove(&q->clhash, &cl->common);
378 
379         BUG_ON(--cl->refcnt == 0);
380         /*
381          * This shouldn't happen: we "hold" one cops->get() when called
382          * from tc_ctl_tclass; the destroy method is done from cops->put().
383          */
384 
385         sch_tree_unlock(sch);
386         return 0;
387 }
388 
389 static unsigned long qfq_get_class(struct Qdisc *sch, u32 classid)
390 {
391         struct qfq_class *cl = qfq_find_class(sch, classid);
392 
393         if (cl != NULL)
394                 cl->refcnt++;
395 
396         return (unsigned long)cl;
397 }
398 
399 static void qfq_put_class(struct Qdisc *sch, unsigned long arg)
400 {
401         struct qfq_class *cl = (struct qfq_class *)arg;
402 
403         if (--cl->refcnt == 0)
404                 qfq_destroy_class(sch, cl);
405 }
406 
407 static struct tcf_proto **qfq_tcf_chain(struct Qdisc *sch, unsigned long cl)
408 {
409         struct qfq_sched *q = qdisc_priv(sch);
410 
411         if (cl)
412                 return NULL;
413 
414         return &q->filter_list;
415 }
416 
417 static unsigned long qfq_bind_tcf(struct Qdisc *sch, unsigned long parent,
418                                   u32 classid)
419 {
420         struct qfq_class *cl = qfq_find_class(sch, classid);
421 
422         if (cl != NULL)
423                 cl->filter_cnt++;
424 
425         return (unsigned long)cl;
426 }
427 
428 static void qfq_unbind_tcf(struct Qdisc *sch, unsigned long arg)
429 {
430         struct qfq_class *cl = (struct qfq_class *)arg;
431 
432         cl->filter_cnt--;
433 }
434 
435 static int qfq_graft_class(struct Qdisc *sch, unsigned long arg,
436                            struct Qdisc *new, struct Qdisc **old)
437 {
438         struct qfq_class *cl = (struct qfq_class *)arg;
439 
440         if (new == NULL) {
441                 new = qdisc_create_dflt(sch->dev_queue,
442                                         &pfifo_qdisc_ops, cl->common.classid);
443                 if (new == NULL)
444                         new = &noop_qdisc;
445         }
446 
447         sch_tree_lock(sch);
448         qfq_purge_queue(cl);
449         *old = cl->qdisc;
450         cl->qdisc = new;
451         sch_tree_unlock(sch);
452         return 0;
453 }
454 
455 static struct Qdisc *qfq_class_leaf(struct Qdisc *sch, unsigned long arg)
456 {
457         struct qfq_class *cl = (struct qfq_class *)arg;
458 
459         return cl->qdisc;
460 }
461 
462 static int qfq_dump_class(struct Qdisc *sch, unsigned long arg,
463                           struct sk_buff *skb, struct tcmsg *tcm)
464 {
465         struct qfq_class *cl = (struct qfq_class *)arg;
466         struct nlattr *nest;
467 
468         tcm->tcm_parent = TC_H_ROOT;
469         tcm->tcm_handle = cl->common.classid;
470         tcm->tcm_info   = cl->qdisc->handle;
471 
472         nest = nla_nest_start(skb, TCA_OPTIONS);
473         if (nest == NULL)
474                 goto nla_put_failure;
475         if (nla_put_u32(skb, TCA_QFQ_WEIGHT, ONE_FP/cl->inv_w) ||
476             nla_put_u32(skb, TCA_QFQ_LMAX, cl->lmax))
477                 goto nla_put_failure;
478         return nla_nest_end(skb, nest);
479 
480 nla_put_failure:
481         nla_nest_cancel(skb, nest);
482         return -EMSGSIZE;
483 }
484 
485 static int qfq_dump_class_stats(struct Qdisc *sch, unsigned long arg,
486                                 struct gnet_dump *d)
487 {
488         struct qfq_class *cl = (struct qfq_class *)arg;
489         struct tc_qfq_stats xstats;
490 
491         memset(&xstats, 0, sizeof(xstats));
492         cl->qdisc->qstats.qlen = cl->qdisc->q.qlen;
493 
494         xstats.weight = ONE_FP/cl->inv_w;
495         xstats.lmax = cl->lmax;
496 
497         if (gnet_stats_copy_basic(d, &cl->bstats) < 0 ||
498             gnet_stats_copy_rate_est(d, &cl->bstats, &cl->rate_est) < 0 ||
499             gnet_stats_copy_queue(d, &cl->qdisc->qstats) < 0)
500                 return -1;
501 
502         return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
503 }
504 
505 static void qfq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
506 {
507         struct qfq_sched *q = qdisc_priv(sch);
508         struct qfq_class *cl;
509         struct hlist_node *n;
510         unsigned int i;
511 
512         if (arg->stop)
513                 return;
514 
515         for (i = 0; i < q->clhash.hashsize; i++) {
516                 hlist_for_each_entry(cl, n, &q->clhash.hash[i], common.hnode) {
517                         if (arg->count < arg->skip) {
518                                 arg->count++;
519                                 continue;
520                         }
521                         if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
522                                 arg->stop = 1;
523                                 return;
524                         }
525                         arg->count++;
526                 }
527         }
528 }
529 
530 static struct qfq_class *qfq_classify(struct sk_buff *skb, struct Qdisc *sch,
531                                       int *qerr)
532 {
533         struct qfq_sched *q = qdisc_priv(sch);
534         struct qfq_class *cl;
535         struct tcf_result res;
536         int result;
537 
538         if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
539                 pr_debug("qfq_classify: found %d\n", skb->priority);
540                 cl = qfq_find_class(sch, skb->priority);
541                 if (cl != NULL)
542                         return cl;
543         }
544 
545         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
546         result = tc_classify(skb, q->filter_list, &res);
547         if (result >= 0) {
548 #ifdef CONFIG_NET_CLS_ACT
549                 switch (result) {
550                 case TC_ACT_QUEUED:
551                 case TC_ACT_STOLEN:
552                         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
553                 case TC_ACT_SHOT:
554                         return NULL;
555                 }
556 #endif
557                 cl = (struct qfq_class *)res.class;
558                 if (cl == NULL)
559                         cl = qfq_find_class(sch, res.classid);
560                 return cl;
561         }
562 
563         return NULL;
564 }
565 
566 /* Generic comparison function, handling wraparound. */
567 static inline int qfq_gt(u64 a, u64 b)
568 {
569         return (s64)(a - b) > 0;
570 }
571 
572 /* Round a precise timestamp to its slotted value. */
573 static inline u64 qfq_round_down(u64 ts, unsigned int shift)
574 {
575         return ts & ~((1ULL << shift) - 1);
576 }
577 
578 /* return the pointer to the group with lowest index in the bitmap */
579 static inline struct qfq_group *qfq_ffs(struct qfq_sched *q,
580                                         unsigned long bitmap)
581 {
582         int index = __ffs(bitmap);
583         return &q->groups[index];
584 }
585 /* Calculate a mask to mimic what would be ffs_from(). */
586 static inline unsigned long mask_from(unsigned long bitmap, int from)
587 {
588         return bitmap & ~((1UL << from) - 1);
589 }
590 
591 /*
592  * The state computation relies on ER=0, IR=1, EB=2, IB=3
593  * First compute eligibility comparing grp->S, q->V,
594  * then check if someone is blocking us and possibly add EB
595  */
596 static int qfq_calc_state(struct qfq_sched *q, const struct qfq_group *grp)
597 {
598         /* if S > V we are not eligible */
599         unsigned int state = qfq_gt(grp->S, q->V);
600         unsigned long mask = mask_from(q->bitmaps[ER], grp->index);
601         struct qfq_group *next;
602 
603         if (mask) {
604                 next = qfq_ffs(q, mask);
605                 if (qfq_gt(grp->F, next->F))
606                         state |= EB;
607         }
608 
609         return state;
610 }
611 
612 
613 /*
614  * In principle
615  *      q->bitmaps[dst] |= q->bitmaps[src] & mask;
616  *      q->bitmaps[src] &= ~mask;
617  * but we should make sure that src != dst
618  */
619 static inline void qfq_move_groups(struct qfq_sched *q, unsigned long mask,
620                                    int src, int dst)
621 {
622         q->bitmaps[dst] |= q->bitmaps[src] & mask;
623         q->bitmaps[src] &= ~mask;
624 }
625 
626 static void qfq_unblock_groups(struct qfq_sched *q, int index, u64 old_F)
627 {
628         unsigned long mask = mask_from(q->bitmaps[ER], index + 1);
629         struct qfq_group *next;
630 
631         if (mask) {
632                 next = qfq_ffs(q, mask);
633                 if (!qfq_gt(next->F, old_F))
634                         return;
635         }
636 
637         mask = (1UL << index) - 1;
638         qfq_move_groups(q, mask, EB, ER);
639         qfq_move_groups(q, mask, IB, IR);
640 }
641 
642 /*
643  * perhaps
644  *
645         old_V ^= q->V;
646         old_V >>= QFQ_MIN_SLOT_SHIFT;
647         if (old_V) {
648                 ...
649         }
650  *
651  */
652 static void qfq_make_eligible(struct qfq_sched *q, u64 old_V)
653 {
654         unsigned long vslot = q->V >> QFQ_MIN_SLOT_SHIFT;
655         unsigned long old_vslot = old_V >> QFQ_MIN_SLOT_SHIFT;
656 
657         if (vslot != old_vslot) {
658                 unsigned long mask = (1UL << fls(vslot ^ old_vslot)) - 1;
659                 qfq_move_groups(q, mask, IR, ER);
660                 qfq_move_groups(q, mask, IB, EB);
661         }
662 }
663 
664 
665 /*
666  * XXX we should make sure that slot becomes less than 32.
667  * This is guaranteed by the input values.
668  * roundedS is always cl->S rounded on grp->slot_shift bits.
669  */
670 static void qfq_slot_insert(struct qfq_group *grp, struct qfq_class *cl,
671                             u64 roundedS)
672 {
673         u64 slot = (roundedS - grp->S) >> grp->slot_shift;
674         unsigned int i = (grp->front + slot) % QFQ_MAX_SLOTS;
675 
676         hlist_add_head(&cl->next, &grp->slots[i]);
677         __set_bit(slot, &grp->full_slots);
678 }
679 
680 /* Maybe introduce hlist_first_entry?? */
681 static struct qfq_class *qfq_slot_head(struct qfq_group *grp)
682 {
683         return hlist_entry(grp->slots[grp->front].first,
684                            struct qfq_class, next);
685 }
686 
687 /*
688  * remove the entry from the slot
689  */
690 static void qfq_front_slot_remove(struct qfq_group *grp)
691 {
692         struct qfq_class *cl = qfq_slot_head(grp);
693 
694         BUG_ON(!cl);
695         hlist_del(&cl->next);
696         if (hlist_empty(&grp->slots[grp->front]))
697                 __clear_bit(0, &grp->full_slots);
698 }
699 
700 /*
701  * Returns the first full queue in a group. As a side effect,
702  * adjust the bucket list so the first non-empty bucket is at
703  * position 0 in full_slots.
704  */
705 static struct qfq_class *qfq_slot_scan(struct qfq_group *grp)
706 {
707         unsigned int i;
708 
709         pr_debug("qfq slot_scan: grp %u full %#lx\n",
710                  grp->index, grp->full_slots);
711 
712         if (grp->full_slots == 0)
713                 return NULL;
714 
715         i = __ffs(grp->full_slots);  /* zero based */
716         if (i > 0) {
717                 grp->front = (grp->front + i) % QFQ_MAX_SLOTS;
718                 grp->full_slots >>= i;
719         }
720 
721         return qfq_slot_head(grp);
722 }
723 
724 /*
725  * adjust the bucket list. When the start time of a group decreases,
726  * we move the index down (modulo QFQ_MAX_SLOTS) so we don't need to
727  * move the objects. The mask of occupied slots must be shifted
728  * because we use ffs() to find the first non-empty slot.
729  * This covers decreases in the group's start time, but what about
730  * increases of the start time ?
731  * Here too we should make sure that i is less than 32
732  */
733 static void qfq_slot_rotate(struct qfq_group *grp, u64 roundedS)
734 {
735         unsigned int i = (grp->S - roundedS) >> grp->slot_shift;
736 
737         grp->full_slots <<= i;
738         grp->front = (grp->front - i) % QFQ_MAX_SLOTS;
739 }
740 
741 static void qfq_update_eligible(struct qfq_sched *q, u64 old_V)
742 {
743         struct qfq_group *grp;
744         unsigned long ineligible;
745 
746         ineligible = q->bitmaps[IR] | q->bitmaps[IB];
747         if (ineligible) {
748                 if (!q->bitmaps[ER]) {
749                         grp = qfq_ffs(q, ineligible);
750                         if (qfq_gt(grp->S, q->V))
751                                 q->V = grp->S;
752                 }
753                 qfq_make_eligible(q, old_V);
754         }
755 }
756 
757 /*
758  * Updates the class, returns true if also the group needs to be updated.
759  */
760 static bool qfq_update_class(struct qfq_group *grp, struct qfq_class *cl)
761 {
762         unsigned int len = qdisc_peek_len(cl->qdisc);
763 
764         cl->S = cl->F;
765         if (!len)
766                 qfq_front_slot_remove(grp);     /* queue is empty */
767         else {
768                 u64 roundedS;
769 
770                 cl->F = cl->S + (u64)len * cl->inv_w;
771                 roundedS = qfq_round_down(cl->S, grp->slot_shift);
772                 if (roundedS == grp->S)
773                         return false;
774 
775                 qfq_front_slot_remove(grp);
776                 qfq_slot_insert(grp, cl, roundedS);
777         }
778 
779         return true;
780 }
781 
782 static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
783 {
784         struct qfq_sched *q = qdisc_priv(sch);
785         struct qfq_group *grp;
786         struct qfq_class *cl;
787         struct sk_buff *skb;
788         unsigned int len;
789         u64 old_V;
790 
791         if (!q->bitmaps[ER])
792                 return NULL;
793 
794         grp = qfq_ffs(q, q->bitmaps[ER]);
795 
796         cl = qfq_slot_head(grp);
797         skb = qdisc_dequeue_peeked(cl->qdisc);
798         if (!skb) {
799                 WARN_ONCE(1, "qfq_dequeue: non-workconserving leaf\n");
800                 return NULL;
801         }
802 
803         sch->q.qlen--;
804         qdisc_bstats_update(sch, skb);
805 
806         old_V = q->V;
807         len = qdisc_pkt_len(skb);
808         q->V += (u64)len * IWSUM;
809         pr_debug("qfq dequeue: len %u F %lld now %lld\n",
810                  len, (unsigned long long) cl->F, (unsigned long long) q->V);
811 
812         if (qfq_update_class(grp, cl)) {
813                 u64 old_F = grp->F;
814 
815                 cl = qfq_slot_scan(grp);
816                 if (!cl)
817                         __clear_bit(grp->index, &q->bitmaps[ER]);
818                 else {
819                         u64 roundedS = qfq_round_down(cl->S, grp->slot_shift);
820                         unsigned int s;
821 
822                         if (grp->S == roundedS)
823                                 goto skip_unblock;
824                         grp->S = roundedS;
825                         grp->F = roundedS + (2ULL << grp->slot_shift);
826                         __clear_bit(grp->index, &q->bitmaps[ER]);
827                         s = qfq_calc_state(q, grp);
828                         __set_bit(grp->index, &q->bitmaps[s]);
829                 }
830 
831                 qfq_unblock_groups(q, grp->index, old_F);
832         }
833 
834 skip_unblock:
835         qfq_update_eligible(q, old_V);
836 
837         return skb;
838 }
839 
840 /*
841  * Assign a reasonable start time for a new flow k in group i.
842  * Admissible values for \hat(F) are multiples of \sigma_i
843  * no greater than V+\sigma_i . Larger values mean that
844  * we had a wraparound so we consider the timestamp to be stale.
845  *
846  * If F is not stale and F >= V then we set S = F.
847  * Otherwise we should assign S = V, but this may violate
848  * the ordering in ER. So, if we have groups in ER, set S to
849  * the F_j of the first group j which would be blocking us.
850  * We are guaranteed not to move S backward because
851  * otherwise our group i would still be blocked.
852  */
853 static void qfq_update_start(struct qfq_sched *q, struct qfq_class *cl)
854 {
855         unsigned long mask;
856         u64 limit, roundedF;
857         int slot_shift = cl->grp->slot_shift;
858 
859         roundedF = qfq_round_down(cl->F, slot_shift);
860         limit = qfq_round_down(q->V, slot_shift) + (1ULL << slot_shift);
861 
862         if (!qfq_gt(cl->F, q->V) || qfq_gt(roundedF, limit)) {
863                 /* timestamp was stale */
864                 mask = mask_from(q->bitmaps[ER], cl->grp->index);
865                 if (mask) {
866                         struct qfq_group *next = qfq_ffs(q, mask);
867                         if (qfq_gt(roundedF, next->F)) {
868                                 if (qfq_gt(limit, next->F))
869                                         cl->S = next->F;
870                                 else /* preserve timestamp correctness */
871                                         cl->S = limit;
872                                 return;
873                         }
874                 }
875                 cl->S = q->V;
876         } else  /* timestamp is not stale */
877                 cl->S = cl->F;
878 }
879 
880 static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
881 {
882         struct qfq_sched *q = qdisc_priv(sch);
883         struct qfq_class *cl;
884         int err;
885 
886         cl = qfq_classify(skb, sch, &err);
887         if (cl == NULL) {
888                 if (err & __NET_XMIT_BYPASS)
889                         sch->qstats.drops++;
890                 kfree_skb(skb);
891                 return err;
892         }
893         pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);
894 
895         err = qdisc_enqueue(skb, cl->qdisc);
896         if (unlikely(err != NET_XMIT_SUCCESS)) {
897                 pr_debug("qfq_enqueue: enqueue failed %d\n", err);
898                 if (net_xmit_drop_count(err)) {
899                         cl->qstats.drops++;
900                         sch->qstats.drops++;
901                 }
902                 return err;
903         }
904 
905         bstats_update(&cl->bstats, skb);
906         ++sch->q.qlen;
907 
908         /* If the new skb is not the head of queue, then done here. */
909         if (cl->qdisc->q.qlen != 1)
910                 return err;
911 
912         /* If reach this point, queue q was idle */
913         qfq_activate_class(q, cl, qdisc_pkt_len(skb));
914 
915         return err;
916 }
917 
918 /*
919  * Handle class switch from idle to backlogged.
920  */
921 static void qfq_activate_class(struct qfq_sched *q, struct qfq_class *cl,
922                                unsigned int pkt_len)
923 {
924         struct qfq_group *grp = cl->grp;
925         u64 roundedS;
926         int s;
927 
928         qfq_update_start(q, cl);
929 
930         /* compute new finish time and rounded start. */
931         cl->F = cl->S + (u64)pkt_len * cl->inv_w;
932         roundedS = qfq_round_down(cl->S, grp->slot_shift);
933 
934         /*
935          * insert cl in the correct bucket.
936          * If cl->S >= grp->S we don't need to adjust the
937          * bucket list and simply go to the insertion phase.
938          * Otherwise grp->S is decreasing, we must make room
939          * in the bucket list, and also recompute the group state.
940          * Finally, if there were no flows in this group and nobody
941          * was in ER make sure to adjust V.
942          */
943         if (grp->full_slots) {
944                 if (!qfq_gt(grp->S, cl->S))
945                         goto skip_update;
946 
947                 /* create a slot for this cl->S */
948                 qfq_slot_rotate(grp, roundedS);
949                 /* group was surely ineligible, remove */
950                 __clear_bit(grp->index, &q->bitmaps[IR]);
951                 __clear_bit(grp->index, &q->bitmaps[IB]);
952         } else if (!q->bitmaps[ER] && qfq_gt(roundedS, q->V))
953                 q->V = roundedS;
954 
955         grp->S = roundedS;
956         grp->F = roundedS + (2ULL << grp->slot_shift);
957         s = qfq_calc_state(q, grp);
958         __set_bit(grp->index, &q->bitmaps[s]);
959 
960         pr_debug("qfq enqueue: new state %d %#lx S %lld F %lld V %lld\n",
961                  s, q->bitmaps[s],
962                  (unsigned long long) cl->S,
963                  (unsigned long long) cl->F,
964                  (unsigned long long) q->V);
965 
966 skip_update:
967         qfq_slot_insert(grp, cl, roundedS);
968 }
969 
970 
971 static void qfq_slot_remove(struct qfq_sched *q, struct qfq_group *grp,
972                             struct qfq_class *cl)
973 {
974         unsigned int i, offset;
975         u64 roundedS;
976 
977         roundedS = qfq_round_down(cl->S, grp->slot_shift);
978         offset = (roundedS - grp->S) >> grp->slot_shift;
979         i = (grp->front + offset) % QFQ_MAX_SLOTS;
980 
981         hlist_del(&cl->next);
982         if (hlist_empty(&grp->slots[i]))
983                 __clear_bit(offset, &grp->full_slots);
984 }
985 
986 /*
987  * called to forcibly destroy a queue.
988  * If the queue is not in the front bucket, or if it has
989  * other queues in the front bucket, we can simply remove
990  * the queue with no other side effects.
991  * Otherwise we must propagate the event up.
992  */
993 static void qfq_deactivate_class(struct qfq_sched *q, struct qfq_class *cl)
994 {
995         struct qfq_group *grp = cl->grp;
996         unsigned long mask;
997         u64 roundedS;
998         int s;
999 
1000         cl->F = cl->S;
1001         qfq_slot_remove(q, grp, cl);
1002 
1003         if (!grp->full_slots) {
1004                 __clear_bit(grp->index, &q->bitmaps[IR]);
1005                 __clear_bit(grp->index, &q->bitmaps[EB]);
1006                 __clear_bit(grp->index, &q->bitmaps[IB]);
1007 
1008                 if (test_bit(grp->index, &q->bitmaps[ER]) &&
1009                     !(q->bitmaps[ER] & ~((1UL << grp->index) - 1))) {
1010                         mask = q->bitmaps[ER] & ((1UL << grp->index) - 1);
1011                         if (mask)
1012                                 mask = ~((1UL << __fls(mask)) - 1);
1013                         else
1014                                 mask = ~0UL;
1015                         qfq_move_groups(q, mask, EB, ER);
1016                         qfq_move_groups(q, mask, IB, IR);
1017                 }
1018                 __clear_bit(grp->index, &q->bitmaps[ER]);
1019         } else if (hlist_empty(&grp->slots[grp->front])) {
1020                 cl = qfq_slot_scan(grp);
1021                 roundedS = qfq_round_down(cl->S, grp->slot_shift);
1022                 if (grp->S != roundedS) {
1023                         __clear_bit(grp->index, &q->bitmaps[ER]);
1024                         __clear_bit(grp->index, &q->bitmaps[IR]);
1025                         __clear_bit(grp->index, &q->bitmaps[EB]);
1026                         __clear_bit(grp->index, &q->bitmaps[IB]);
1027                         grp->S = roundedS;
1028                         grp->F = roundedS + (2ULL << grp->slot_shift);
1029                         s = qfq_calc_state(q, grp);
1030                         __set_bit(grp->index, &q->bitmaps[s]);
1031                 }
1032         }
1033 
1034         qfq_update_eligible(q, q->V);
1035 }
1036 
1037 static void qfq_qlen_notify(struct Qdisc *sch, unsigned long arg)
1038 {
1039         struct qfq_sched *q = qdisc_priv(sch);
1040         struct qfq_class *cl = (struct qfq_class *)arg;
1041 
1042         if (cl->qdisc->q.qlen == 0)
1043                 qfq_deactivate_class(q, cl);
1044 }
1045 
1046 static unsigned int qfq_drop(struct Qdisc *sch)
1047 {
1048         struct qfq_sched *q = qdisc_priv(sch);
1049         struct qfq_group *grp;
1050         unsigned int i, j, len;
1051 
1052         for (i = 0; i <= QFQ_MAX_INDEX; i++) {
1053                 grp = &q->groups[i];
1054                 for (j = 0; j < QFQ_MAX_SLOTS; j++) {
1055                         struct qfq_class *cl;
1056                         struct hlist_node *n;
1057 
1058                         hlist_for_each_entry(cl, n, &grp->slots[j], next) {
1059 
1060                                 if (!cl->qdisc->ops->drop)
1061                                         continue;
1062 
1063                                 len = cl->qdisc->ops->drop(cl->qdisc);
1064                                 if (len > 0) {
1065                                         sch->q.qlen--;
1066                                         if (!cl->qdisc->q.qlen)
1067                                                 qfq_deactivate_class(q, cl);
1068 
1069                                         return len;
1070                                 }
1071                         }
1072                 }
1073         }
1074 
1075         return 0;
1076 }
1077 
1078 static int qfq_init_qdisc(struct Qdisc *sch, struct nlattr *opt)
1079 {
1080         struct qfq_sched *q = qdisc_priv(sch);
1081         struct qfq_group *grp;
1082         int i, j, err;
1083 
1084         err = qdisc_class_hash_init(&q->clhash);
1085         if (err < 0)
1086                 return err;
1087 
1088         for (i = 0; i <= QFQ_MAX_INDEX; i++) {
1089                 grp = &q->groups[i];
1090                 grp->index = i;
1091                 grp->slot_shift = QFQ_MTU_SHIFT + FRAC_BITS
1092                                    - (QFQ_MAX_INDEX - i);
1093                 for (j = 0; j < QFQ_MAX_SLOTS; j++)
1094                         INIT_HLIST_HEAD(&grp->slots[j]);
1095         }
1096 
1097         return 0;
1098 }
1099 
1100 static void qfq_reset_qdisc(struct Qdisc *sch)
1101 {
1102         struct qfq_sched *q = qdisc_priv(sch);
1103         struct qfq_group *grp;
1104         struct qfq_class *cl;
1105         struct hlist_node *n, *tmp;
1106         unsigned int i, j;
1107 
1108         for (i = 0; i <= QFQ_MAX_INDEX; i++) {
1109                 grp = &q->groups[i];
1110                 for (j = 0; j < QFQ_MAX_SLOTS; j++) {
1111                         hlist_for_each_entry_safe(cl, n, tmp,
1112                                                   &grp->slots[j], next) {
1113                                 qfq_deactivate_class(q, cl);
1114                         }
1115                 }
1116         }
1117 
1118         for (i = 0; i < q->clhash.hashsize; i++) {
1119                 hlist_for_each_entry(cl, n, &q->clhash.hash[i], common.hnode)
1120                         qdisc_reset(cl->qdisc);
1121         }
1122         sch->q.qlen = 0;
1123 }
1124 
1125 static void qfq_destroy_qdisc(struct Qdisc *sch)
1126 {
1127         struct qfq_sched *q = qdisc_priv(sch);
1128         struct qfq_class *cl;
1129         struct hlist_node *n, *next;
1130         unsigned int i;
1131 
1132         tcf_destroy_chain(&q->filter_list);
1133 
1134         for (i = 0; i < q->clhash.hashsize; i++) {
1135                 hlist_for_each_entry_safe(cl, n, next, &q->clhash.hash[i],
1136                                           common.hnode) {
1137                         qfq_destroy_class(sch, cl);
1138                 }
1139         }
1140         qdisc_class_hash_destroy(&q->clhash);
1141 }
1142 
1143 static const struct Qdisc_class_ops qfq_class_ops = {
1144         .change         = qfq_change_class,
1145         .delete         = qfq_delete_class,
1146         .get            = qfq_get_class,
1147         .put            = qfq_put_class,
1148         .tcf_chain      = qfq_tcf_chain,
1149         .bind_tcf       = qfq_bind_tcf,
1150         .unbind_tcf     = qfq_unbind_tcf,
1151         .graft          = qfq_graft_class,
1152         .leaf           = qfq_class_leaf,
1153         .qlen_notify    = qfq_qlen_notify,
1154         .dump           = qfq_dump_class,
1155         .dump_stats     = qfq_dump_class_stats,
1156         .walk           = qfq_walk,
1157 };
1158 
1159 static struct Qdisc_ops qfq_qdisc_ops __read_mostly = {
1160         .cl_ops         = &qfq_class_ops,
1161         .id             = "qfq",
1162         .priv_size      = sizeof(struct qfq_sched),
1163         .enqueue        = qfq_enqueue,
1164         .dequeue        = qfq_dequeue,
1165         .peek           = qdisc_peek_dequeued,
1166         .drop           = qfq_drop,
1167         .init           = qfq_init_qdisc,
1168         .reset          = qfq_reset_qdisc,
1169         .destroy        = qfq_destroy_qdisc,
1170         .owner          = THIS_MODULE,
1171 };
1172 
1173 static int __init qfq_init(void)
1174 {
1175         return register_qdisc(&qfq_qdisc_ops);
1176 }
1177 
1178 static void __exit qfq_exit(void)
1179 {
1180         unregister_qdisc(&qfq_qdisc_ops);
1181 }
1182 
1183 module_init(qfq_init);
1184 module_exit(qfq_exit);
1185 MODULE_LICENSE("GPL");
1186 

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