summaryrefslogtreecommitdiff
path: root/net/sched/sch_qfq.c
blob: 6335230a971e21233bb1758b57ae72fff41ce6fc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
// SPDX-License-Identifier: GPL-2.0-only
/*
 * net/sched/sch_qfq.c         Quick Fair Queueing Plus Scheduler.
 *
 * Copyright (c) 2009 Fabio Checconi, Luigi Rizzo, and Paolo Valente.
 * Copyright (c) 2012 Paolo Valente.
 */

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


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

    Sources:

    [1] Paolo Valente,
    "Reducing the Execution Time of Fair-Queueing Schedulers."
    http://algo.ing.unimo.it/people/paolo/agg-sched/agg-sched.pdf

    Sources for QFQ:

    [2] Fabio Checconi, Luigi Rizzo, and Paolo Valente: "QFQ: Efficient
    Packet Scheduling with Tight Bandwidth Distribution Guarantees."

    See also:
    http://retis.sssup.it/~fabio/linux/qfq/
 */

/*

  QFQ+ divides classes into aggregates of at most MAX_AGG_CLASSES
  classes. Each aggregate is timestamped with a virtual start time S
  and a virtual finish time F, and scheduled according to its
  timestamps. S and F are computed as a function of a system virtual
  time function V. The classes within each aggregate are instead
  scheduled with DRR.

  To speed up operations, QFQ+ divides also aggregates into a limited
  number of groups. Which group a class belongs to depends on the
  ratio between the maximum packet length for the class and the weight
  of the class. Groups have their own S and F. In the end, QFQ+
  schedules groups, then aggregates within groups, then classes within
  aggregates. See [1] and [2] for a full description.

  Virtual time computations.

  S, F and V are all computed in fixed point arithmetic with
  FRAC_BITS decimal bits.

  QFQ_MAX_INDEX is the maximum index allowed for a group. We need
	one bit per index.
  QFQ_MAX_WSHIFT is the maximum power of two supported as a weight.

  The layout of the bits is as below:

                   [ MTU_SHIFT ][      FRAC_BITS    ]
                   [ MAX_INDEX    ][ MIN_SLOT_SHIFT ]
				 ^.__grp->index = 0
				 *.__grp->slot_shift

  where MIN_SLOT_SHIFT is derived by difference from the others.

  The max group index corresponds to Lmax/w_min, where
  Lmax=1<<MTU_SHIFT, w_min = 1 .
  From this, and knowing how many groups (MAX_INDEX) we want,
  we can derive the shift corresponding to each group.

  Because we often need to compute
	F = S + len/w_i  and V = V + len/wsum
  instead of storing w_i store the value
	inv_w = (1<<FRAC_BITS)/w_i
  so we can do F = S + len * inv_w * wsum.
  We use W_TOT in the formulas so we can easily move between
  static and adaptive weight sum.

  The per-scheduler-instance data contain all the data structures
  for the scheduler: bitmaps and bucket lists.

 */

/*
 * Maximum number of consecutive slots occupied by backlogged classes
 * inside a group.
 */
#define QFQ_MAX_SLOTS	32

/*
 * Shifts used for aggregate<->group mapping.  We allow class weights that are
 * in the range [1, 2^MAX_WSHIFT], and we try to map each aggregate i to the
 * group with the smallest index that can support the L_i / r_i configured
 * for the classes in the aggregate.
 *
 * grp->index is the index of the group; and grp->slot_shift
 * is the shift for the corresponding (scaled) sigma_i.
 */
#define QFQ_MAX_INDEX		24
#define QFQ_MAX_WSHIFT		10

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

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

#define QFQ_MTU_SHIFT		16	/* to support TSO/GSO */
#define QFQ_MIN_LMAX		512	/* see qfq_slot_insert */

#define QFQ_MAX_AGG_CLASSES	8 /* max num classes per aggregate allowed */

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

struct qfq_group;

struct qfq_aggregate;

struct qfq_class {
	struct Qdisc_class_common common;

	unsigned int filter_cnt;

	struct gnet_stats_basic_packed bstats;
	struct gnet_stats_queue qstats;
	struct net_rate_estimator __rcu *rate_est;
	struct Qdisc *qdisc;
	struct list_head alist;		/* Link for active-classes list. */
	struct qfq_aggregate *agg;	/* Parent aggregate. */
	int deficit;			/* DRR deficit counter. */
};

struct qfq_aggregate {
	struct hlist_node next;	/* Link for the slot list. */
	u64 S, F;		/* flow timestamps (exact) */

	/* group we belong to. In principle we would need the index,
	 * which is log_2(lmax/weight), but we never reference it
	 * directly, only the group.
	 */
	struct qfq_group *grp;

	/* these are copied from the flowset. */
	u32	class_weight; /* Weight of each class in this aggregate. */
	/* Max pkt size for the classes in this aggregate, DRR quantum. */
	int	lmax;

	u32	inv_w;	    /* ONE_FP/(sum of weights of classes in aggr.). */
	u32	budgetmax;  /* Max budget for this aggregate. */
	u32	initial_budget, budget;     /* Initial and current budget. */

	int		  num_classes;	/* Number of classes in this aggr. */
	struct list_head  active;	/* DRR queue of active classes. */

	struct hlist_node nonfull_next;	/* See nonfull_aggs in qfq_sched. */
};

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

	/* Array of RR lists of active aggregates. */
	struct hlist_head slots[QFQ_MAX_SLOTS];
};

struct qfq_sched {
	struct tcf_proto __rcu *filter_list;
	struct tcf_block	*block;
	struct Qdisc_class_hash clhash;

	u64			oldV, V;	/* Precise virtual times. */
	struct qfq_aggregate	*in_serv_agg;   /* Aggregate being served. */
	u32			wsum;		/* weight sum */
	u32			iwsum;		/* inverse weight sum */

	unsigned long bitmaps[QFQ_MAX_STATE];	    /* Group bitmaps. */
	struct qfq_group groups[QFQ_MAX_INDEX + 1]; /* The groups. */
	u32 min_slot_shift;	/* Index of the group-0 bit in the bitmaps. */

	u32 max_agg_classes;		/* Max number of classes per aggr. */
	struct hlist_head nonfull_aggs; /* Aggs with room for more classes. */
};

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

static struct qfq_class *qfq_find_class(struct Qdisc *sch, u32 classid)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct Qdisc_class_common *clc;

	clc = qdisc_class_find(&q->clhash, classid);
	if (clc == NULL)
		return NULL;
	return container_of(clc, struct qfq_class, common);
}

static const struct nla_policy qfq_policy[TCA_QFQ_MAX + 1] = {
	[TCA_QFQ_WEIGHT] = { .type = NLA_U32 },
	[TCA_QFQ_LMAX] = { .type = NLA_U32 },
};

/*
 * Calculate a flow index, given its weight and maximum packet length.
 * index = log_2(maxlen/weight) but we need to apply the scaling.
 * This is used only once at flow creation.
 */
static int qfq_calc_index(u32 inv_w, unsigned int maxlen, u32 min_slot_shift)
{
	u64 slot_size = (u64)maxlen * inv_w;
	unsigned long size_map;
	int index = 0;

	size_map = slot_size >> min_slot_shift;
	if (!size_map)
		goto out;

	index = __fls(size_map) + 1;	/* basically a log_2 */
	index -= !(slot_size - (1ULL << (index + min_slot_shift - 1)));

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

	return index;
}

static void qfq_deactivate_agg(struct qfq_sched *, struct qfq_aggregate *);
static void qfq_activate_agg(struct qfq_sched *, struct qfq_aggregate *,
			     enum update_reason);

static void qfq_init_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
			 u32 lmax, u32 weight)
{
	INIT_LIST_HEAD(&agg->active);
	hlist_add_head(&agg->nonfull_next, &q->nonfull_aggs);

	agg->lmax = lmax;
	agg->class_weight = weight;
}

static struct qfq_aggregate *qfq_find_agg(struct qfq_sched *q,
					  u32 lmax, u32 weight)
{
	struct qfq_aggregate *agg;

	hlist_for_each_entry(agg, &q->nonfull_aggs, nonfull_next)
		if (agg->lmax == lmax && agg->class_weight == weight)
			return agg;

	return NULL;
}


/* Update aggregate as a function of the new number of classes. */
static void qfq_update_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
			   int new_num_classes)
{
	u32 new_agg_weight;

	if (new_num_classes == q->max_agg_classes)
		hlist_del_init(&agg->nonfull_next);

	if (agg->num_classes > new_num_classes &&
	    new_num_classes == q->max_agg_classes - 1) /* agg no more full */
		hlist_add_head(&agg->nonfull_next, &q->nonfull_aggs);

	/* The next assignment may let
	 * agg->initial_budget > agg->budgetmax
	 * hold, we will take it into account in charge_actual_service().
	 */
	agg->budgetmax = new_num_classes * agg->lmax;
	new_agg_weight = agg->class_weight * new_num_classes;
	agg->inv_w = ONE_FP/new_agg_weight;

	if (agg->grp == NULL) {
		int i = qfq_calc_index(agg->inv_w, agg->budgetmax,
				       q->min_slot_shift);
		agg->grp = &q->groups[i];
	}

	q->wsum +=
		(int) agg->class_weight * (new_num_classes - agg->num_classes);
	q->iwsum = ONE_FP / q->wsum;

	agg->num_classes = new_num_classes;
}

/* Add class to aggregate. */
static void qfq_add_to_agg(struct qfq_sched *q,
			   struct qfq_aggregate *agg,
			   struct qfq_class *cl)
{
	cl->agg = agg;

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

static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *);

static void qfq_destroy_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
{
	hlist_del_init(&agg->nonfull_next);
	q->wsum -= agg->class_weight;
	if (q->wsum != 0)
		q->iwsum = ONE_FP / q->wsum;

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

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


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

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

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

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

	qfq_rm_from_agg(q, cl);
}

/* Move class to a new aggregate, matching the new class weight and/or lmax */
static int qfq_change_agg(struct Qdisc *sch, struct qfq_class *cl, u32 weight,
			   u32 lmax)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_aggregate *new_agg = qfq_find_agg(q, lmax, weight);

	if (new_agg == NULL) { /* create new aggregate */
		new_agg = kzalloc(sizeof(*new_agg), GFP_ATOMIC);
		if (new_agg == NULL)
			return -ENOBUFS;
		qfq_init_agg(q, new_agg, lmax, weight);
	}
	qfq_deact_rm_from_agg(q, cl);
	qfq_add_to_agg(q, new_agg, cl);

	return 0;
}

static int qfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
			    struct nlattr **tca, unsigned long *arg,
			    struct netlink_ext_ack *extack)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_class *cl = (struct qfq_class *)*arg;
	bool existing = false;
	struct nlattr *tb[TCA_QFQ_MAX + 1];
	struct qfq_aggregate *new_agg = NULL;
	u32 weight, lmax, inv_w;
	int err;
	int delta_w;

	if (tca[TCA_OPTIONS] == NULL) {
		pr_notice("qfq: no options\n");
		return -EINVAL;
	}

	err = nla_parse_nested_deprecated(tb, TCA_QFQ_MAX, tca[TCA_OPTIONS],
					  qfq_policy, NULL);
	if (err < 0)
		return err;

	if (tb[TCA_QFQ_WEIGHT]) {
		weight = nla_get_u32(tb[TCA_QFQ_WEIGHT]);
		if (!weight || weight > (1UL << QFQ_MAX_WSHIFT)) {
			pr_notice("qfq: invalid weight %u\n", weight);
			return -EINVAL;
		}
	} else
		weight = 1;

	if (tb[TCA_QFQ_LMAX]) {
		lmax = nla_get_u32(tb[TCA_QFQ_LMAX]);
		if (lmax < QFQ_MIN_LMAX || lmax > (1UL << QFQ_MTU_SHIFT)) {
			pr_notice("qfq: invalid max length %u\n", lmax);
			return -EINVAL;
		}
	} else
		lmax = psched_mtu(qdisc_dev(sch));

	inv_w = ONE_FP / weight;
	weight = ONE_FP / inv_w;

	if (cl != NULL &&
	    lmax == cl->agg->lmax &&
	    weight == cl->agg->class_weight)
		return 0; /* nothing to change */

	delta_w = weight - (cl ? cl->agg->class_weight : 0);

	if (q->wsum + delta_w > QFQ_MAX_WSUM) {
		pr_notice("qfq: total weight out of range (%d + %u)\n",
			  delta_w, q->wsum);
		return -EINVAL;
	}

	if (cl != NULL) { /* modify existing class */
		if (tca[TCA_RATE]) {
			err = gen_replace_estimator(&cl->bstats, NULL,
						    &cl->rate_est,
						    NULL,
						    qdisc_root_sleeping_running(sch),
						    tca[TCA_RATE]);
			if (err)
				return err;
		}
		existing = true;
		goto set_change_agg;
	}

	/* create and init new class */
	cl = kzalloc(sizeof(struct qfq_class), GFP_KERNEL);
	if (cl == NULL)
		return -ENOBUFS;

	cl->common.classid = classid;
	cl->deficit = lmax;

	cl->qdisc = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
				      classid, NULL);
	if (cl->qdisc == NULL)
		cl->qdisc = &noop_qdisc;

	if (tca[TCA_RATE]) {
		err = gen_new_estimator(&cl->bstats, NULL,
					&cl->rate_est,
					NULL,
					qdisc_root_sleeping_running(sch),
					tca[TCA_RATE]);
		if (err)
			goto destroy_class;
	}

	if (cl->qdisc != &noop_qdisc)
		qdisc_hash_add(cl->qdisc, true);
	sch_tree_lock(sch);
	qdisc_class_hash_insert(&q->clhash, &cl->common);
	sch_tree_unlock(sch);

	qdisc_class_hash_grow(sch, &q->clhash);

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

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

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

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

	qfq_rm_from_agg(q, cl);
	gen_kill_estimator(&cl->rate_est);
	qdisc_put(cl->qdisc);
	kfree(cl);
}

static int qfq_delete_class(struct Qdisc *sch, unsigned long arg)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_class *cl = (struct qfq_class *)arg;

	if (cl->filter_cnt > 0)
		return -EBUSY;

	sch_tree_lock(sch);

	qdisc_purge_queue(cl->qdisc);
	qdisc_class_hash_remove(&q->clhash, &cl->common);

	sch_tree_unlock(sch);

	qfq_destroy_class(sch, cl);
	return 0;
}

static unsigned long qfq_search_class(struct Qdisc *sch, u32 classid)
{
	return (unsigned long)qfq_find_class(sch, classid);
}

static struct tcf_block *qfq_tcf_block(struct Qdisc *sch, unsigned long cl,
				       struct netlink_ext_ack *extack)
{
	struct qfq_sched *q = qdisc_priv(sch);

	if (cl)
		return NULL;

	return q->block;
}

static unsigned long qfq_bind_tcf(struct Qdisc *sch, unsigned long parent,
				  u32 classid)
{
	struct qfq_class *cl = qfq_find_class(sch, classid);

	if (cl != NULL)
		cl->filter_cnt++;

	return (unsigned long)cl;
}

static void qfq_unbind_tcf(struct Qdisc *sch, unsigned long arg)
{
	struct qfq_class *cl = (struct qfq_class *)arg;

	cl->filter_cnt--;
}

static int qfq_graft_class(struct Qdisc *sch, unsigned long arg,
			   struct Qdisc *new, struct Qdisc **old,
			   struct netlink_ext_ack *extack)
{
	struct qfq_class *cl = (struct qfq_class *)arg;

	if (new == NULL) {
		new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
					cl->common.classid, NULL);
		if (new == NULL)
			new = &noop_qdisc;
	}

	*old = qdisc_replace(sch, new, &cl->qdisc);
	return 0;
}

static struct Qdisc *qfq_class_leaf(struct Qdisc *sch, unsigned long arg)
{
	struct qfq_class *cl = (struct qfq_class *)arg;

	return cl->qdisc;
}

static int qfq_dump_class(struct Qdisc *sch, unsigned long arg,
			  struct sk_buff *skb, struct tcmsg *tcm)
{
	struct qfq_class *cl = (struct qfq_class *)arg;
	struct nlattr *nest;

	tcm->tcm_parent	= TC_H_ROOT;
	tcm->tcm_handle	= cl->common.classid;
	tcm->tcm_info	= cl->qdisc->handle;

	nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
	if (nest == NULL)
		goto nla_put_failure;
	if (nla_put_u32(skb, TCA_QFQ_WEIGHT, cl->agg->class_weight) ||
	    nla_put_u32(skb, TCA_QFQ_LMAX, cl->agg->lmax))
		goto nla_put_failure;
	return nla_nest_end(skb, nest);

nla_put_failure:
	nla_nest_cancel(skb, nest);
	return -EMSGSIZE;
}

static int qfq_dump_class_stats(struct Qdisc *sch, unsigned long arg,
				struct gnet_dump *d)
{
	struct qfq_class *cl = (struct qfq_class *)arg;
	struct tc_qfq_stats xstats;

	memset(&xstats, 0, sizeof(xstats));

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

	if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
				  d, NULL, &cl->bstats) < 0 ||
	    gnet_stats_copy_rate_est(d, &cl->rate_est) < 0 ||
	    qdisc_qstats_copy(d, cl->qdisc) < 0)
		return -1;

	return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
}

static void qfq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_class *cl;
	unsigned int i;

	if (arg->stop)
		return;

	for (i = 0; i < q->clhash.hashsize; i++) {
		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
			if (arg->count < arg->skip) {
				arg->count++;
				continue;
			}
			if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
				arg->stop = 1;
				return;
			}
			arg->count++;
		}
	}
}

static struct qfq_class *qfq_classify(struct sk_buff *skb, struct Qdisc *sch,
				      int *qerr)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_class *cl;
	struct tcf_result res;
	struct tcf_proto *fl;
	int result;

	if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
		pr_debug("qfq_classify: found %d\n", skb->priority);
		cl = qfq_find_class(sch, skb->priority);
		if (cl != NULL)
			return cl;
	}

	*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
	fl = rcu_dereference_bh(q->filter_list);
	result = tcf_classify(skb, fl, &res, false);
	if (result >= 0) {
#ifdef CONFIG_NET_CLS_ACT
		switch (result) {
		case TC_ACT_QUEUED:
		case TC_ACT_STOLEN:
		case TC_ACT_TRAP:
			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
			fallthrough;
		case TC_ACT_SHOT:
			return NULL;
		}
#endif
		cl = (struct qfq_class *)res.class;
		if (cl == NULL)
			cl = qfq_find_class(sch, res.classid);
		return cl;
	}

	return NULL;
}

/* Generic comparison function, handling wraparound. */
static inline int qfq_gt(u64 a, u64 b)
{
	return (s64)(a - b) > 0;
}

/* Round a precise timestamp to its slotted value. */
static inline u64 qfq_round_down(u64 ts, unsigned int shift)
{
	return ts & ~((1ULL << shift) - 1);
}

/* return the pointer to the group with lowest index in the bitmap */
static inline struct qfq_group *qfq_ffs(struct qfq_sched *q,
					unsigned long bitmap)
{
	int index = __ffs(bitmap);
	return &q->groups[index];
}
/* Calculate a mask to mimic what would be ffs_from(). */
static inline unsigned long mask_from(unsigned long bitmap, int from)
{
	return bitmap & ~((1UL << from) - 1);
}

/*
 * The state computation relies on ER=0, IR=1, EB=2, IB=3
 * First compute eligibility comparing grp->S, q->V,
 * then check if someone is blocking us and possibly add EB
 */
static int qfq_calc_state(struct qfq_sched *q, const struct qfq_group *grp)
{
	/* if S > V we are not eligible */
	unsigned int state = qfq_gt(grp->S, q->V);
	unsigned long mask = mask_from(q->bitmaps[ER], grp->index);
	struct qfq_group *next;

	if (mask) {
		next = qfq_ffs(q, mask);
		if (qfq_gt(grp->F, next->F))
			state |= EB;
	}

	return state;
}


/*
 * In principle
 *	q->bitmaps[dst] |= q->bitmaps[src] & mask;
 *	q->bitmaps[src] &= ~mask;
 * but we should make sure that src != dst
 */
static inline void qfq_move_groups(struct qfq_sched *q, unsigned long mask,
				   int src, int dst)
{
	q->bitmaps[dst] |= q->bitmaps[src] & mask;
	q->bitmaps[src] &= ~mask;
}

static void qfq_unblock_groups(struct qfq_sched *q, int index, u64 old_F)
{
	unsigned long mask = mask_from(q->bitmaps[ER], index + 1);
	struct qfq_group *next;

	if (mask) {
		next = qfq_ffs(q, mask);
		if (!qfq_gt(next->F, old_F))
			return;
	}

	mask = (1UL << index) - 1;
	qfq_move_groups(q, mask, EB, ER);
	qfq_move_groups(q, mask, IB, IR);
}

/*
 * perhaps
 *
	old_V ^= q->V;
	old_V >>= q->min_slot_shift;
	if (old_V) {
		...
	}
 *
 */
static void qfq_make_eligible(struct qfq_sched *q)
{
	unsigned long vslot = q->V >> q->min_slot_shift;
	unsigned long old_vslot = q->oldV >> q->min_slot_shift;

	if (vslot != old_vslot) {
		unsigned long mask;
		int last_flip_pos = fls(vslot ^ old_vslot);

		if (last_flip_pos > 31) /* higher than the number of groups */
			mask = ~0UL;    /* make all groups eligible */
		else
			mask = (1UL << last_flip_pos) - 1;

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

/*
 * The index of the slot in which the input aggregate agg is to be
 * inserted must not be higher than QFQ_MAX_SLOTS-2. There is a '-2'
 * and not a '-1' because the start time of the group may be moved
 * backward by one slot after the aggregate has been inserted, and
 * this would cause non-empty slots to be right-shifted by one
 * position.
 *
 * QFQ+ fully satisfies this bound to the slot index if the parameters
 * of the classes are not changed dynamically, and if QFQ+ never
 * happens to postpone the service of agg unjustly, i.e., it never
 * happens that the aggregate becomes backlogged and eligible, or just
 * eligible, while an aggregate with a higher approximated finish time
 * is being served. In particular, in this case QFQ+ guarantees that
 * the timestamps of agg are low enough that the slot index is never
 * higher than 2. Unfortunately, QFQ+ cannot provide the same
 * guarantee if it happens to unjustly postpone the service of agg, or
 * if the parameters of some class are changed.
 *
 * As for the first event, i.e., an out-of-order service, the
 * upper bound to the slot index guaranteed by QFQ+ grows to
 * 2 +
 * QFQ_MAX_AGG_CLASSES * ((1<<QFQ_MTU_SHIFT)/QFQ_MIN_LMAX) *
 * (current_max_weight/current_wsum) <= 2 + 8 * 128 * 1.
 *
 * The following function deals with this problem by backward-shifting
 * the timestamps of agg, if needed, so as to guarantee that the slot
 * index is never higher than QFQ_MAX_SLOTS-2. This backward-shift may
 * cause the service of other aggregates to be postponed, yet the
 * worst-case guarantees of these aggregates are not violated.  In
 * fact, in case of no out-of-order service, the timestamps of agg
 * would have been even lower than they are after the backward shift,
 * because QFQ+ would have guaranteed a maximum value equal to 2 for
 * the slot index, and 2 < QFQ_MAX_SLOTS-2. Hence the aggregates whose
 * service is postponed because of the backward-shift would have
 * however waited for the service of agg before being served.
 *
 * The other event that may cause the slot index to be higher than 2
 * for agg is a recent change of the parameters of some class. If the
 * weight of a class is increased or the lmax (max_pkt_size) of the
 * class is decreased, then a new aggregate with smaller slot size
 * than the original parent aggregate of the class may happen to be
 * activated. The activation of this aggregate should be properly
 * delayed to when the service of the class has finished in the ideal
 * system tracked by QFQ+. If the activation of the aggregate is not
 * delayed to this reference time instant, then this aggregate may be
 * unjustly served before other aggregates waiting for service. This
 * may cause the above bound to the slot index to be violated for some
 * of these unlucky aggregates.
 *
 * Instead of delaying the activation of the new aggregate, which is
 * quite complex, the above-discussed capping of the slot index is
 * used to handle also the consequences of a change of the parameters
 * of a class.
 */
static void qfq_slot_insert(struct qfq_group *grp, struct qfq_aggregate *agg,
			    u64 roundedS)
{
	u64 slot = (roundedS - grp->S) >> grp->slot_shift;
	unsigned int i; /* slot index in the bucket list */

	if (unlikely(slot > QFQ_MAX_SLOTS - 2)) {
		u64 deltaS = roundedS - grp->S -
			((u64)(QFQ_MAX_SLOTS - 2)<<grp->slot_shift);
		agg->S -= deltaS;
		agg->F -= deltaS;
		slot = QFQ_MAX_SLOTS - 2;
	}

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

	hlist_add_head(&agg->next, &grp->slots[i]);
	__set_bit(slot, &grp->full_slots);
}

/* Maybe introduce hlist_first_entry?? */
static struct qfq_aggregate *qfq_slot_head(struct qfq_group *grp)
{
	return hlist_entry(grp->slots[grp->front].first,
			   struct qfq_aggregate, next);
}

/*
 * remove the entry from the slot
 */
static void qfq_front_slot_remove(struct qfq_group *grp)
{
	struct qfq_aggregate *agg = qfq_slot_head(grp);

	BUG_ON(!agg);
	hlist_del(&agg->next);
	if (hlist_empty(&grp->slots[grp->front]))
		__clear_bit(0, &grp->full_slots);
}

/*
 * Returns the first aggregate in the first non-empty bucket of the
 * group. As a side effect, adjusts the bucket list so the first
 * non-empty bucket is at position 0 in full_slots.
 */
static struct qfq_aggregate *qfq_slot_scan(struct qfq_group *grp)
{
	unsigned int i;

	pr_debug("qfq slot_scan: grp %u full %#lx\n",
		 grp->index, grp->full_slots);

	if (grp->full_slots == 0)
		return NULL;

	i = __ffs(grp->full_slots);  /* zero based */
	if (i > 0) {
		grp->front = (grp->front + i) % QFQ_MAX_SLOTS;
		grp->full_slots >>= i;
	}

	return qfq_slot_head(grp);
}

/*
 * adjust the bucket list. When the start time of a group decreases,
 * we move the index down (modulo QFQ_MAX_SLOTS) so we don't need to
 * move the objects. The mask of occupied slots must be shifted
 * because we use ffs() to find the first non-empty slot.
 * This covers decreases in the group's start time, but what about
 * increases of the start time ?
 * Here too we should make sure that i is less than 32
 */
static void qfq_slot_rotate(struct qfq_group *grp, u64 roundedS)
{
	unsigned int i = (grp->S - roundedS) >> grp->slot_shift;

	grp->full_slots <<= i;
	grp->front = (grp->front - i) % QFQ_MAX_SLOTS;
}

static void qfq_update_eligible(struct qfq_sched *q)
{
	struct qfq_group *grp;
	unsigned long ineligible;

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

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

	cl->deficit -= (int) len;

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

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

	*cl = list_first_entry(&agg->active, struct qfq_class, alist);
	skb = (*cl)->qdisc->ops->peek((*cl)->qdisc);
	if (skb == NULL)
		WARN_ONCE(1, "qfq_dequeue: non-workconserving leaf\n");
	else
		*len = qdisc_pkt_len(skb);

	return skb;
}

/* Update F according to the actual service received by the aggregate. */
static inline void charge_actual_service(struct qfq_aggregate *agg)
{
	/* Compute the service received by the aggregate, taking into
	 * account that, after decreasing the number of classes in
	 * agg, it may happen that
	 * agg->initial_budget - agg->budget > agg->bugdetmax
	 */
	u32 service_received = min(agg->budgetmax,
				   agg->initial_budget - agg->budget);

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

/* Assign a reasonable start time for a new aggregate in group i.
 * Admissible values for \hat(F) are multiples of \sigma_i
 * no greater than V+\sigma_i . Larger values mean that
 * we had a wraparound so we consider the timestamp to be stale.
 *
 * If F is not stale and F >= V then we set S = F.
 * Otherwise we should assign S = V, but this may violate
 * the ordering in EB (see [2]). So, if we have groups in ER,
 * set S to the F_j of the first group j which would be blocking us.
 * We are guaranteed not to move S backward because
 * otherwise our group i would still be blocked.
 */
static void qfq_update_start(struct qfq_sched *q, struct qfq_aggregate *agg)
{
	unsigned long mask;
	u64 limit, roundedF;
	int slot_shift = agg->grp->slot_shift;

	roundedF = qfq_round_down(agg->F, slot_shift);
	limit = qfq_round_down(q->V, slot_shift) + (1ULL << slot_shift);

	if (!qfq_gt(agg->F, q->V) || qfq_gt(roundedF, limit)) {
		/* timestamp was stale */
		mask = mask_from(q->bitmaps[ER], agg->grp->index);
		if (mask) {
			struct qfq_group *next = qfq_ffs(q, mask);
			if (qfq_gt(roundedF, next->F)) {
				if (qfq_gt(limit, next->F))
					agg->S = next->F;
				else /* preserve timestamp correctness */
					agg->S = limit;
				return;
			}
		}
		agg->S = q->V;
	} else  /* timestamp is not stale */
		agg->S = agg->F;
}

/* Update the timestamps of agg before scheduling/rescheduling it for
 * service.  In particular, assign to agg->F its maximum possible
 * value, i.e., the virtual finish time with which the aggregate
 * should be labeled if it used all its budget once in service.
 */
static inline void
qfq_update_agg_ts(struct qfq_sched *q,
		    struct qfq_aggregate *agg, enum update_reason reason)
{
	if (reason != requeue)
		qfq_update_start(q, agg);
	else /* just charge agg for the service received */
		agg->S = agg->F;

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

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

static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_aggregate *in_serv_agg = q->in_serv_agg;
	struct qfq_class *cl;
	struct sk_buff *skb = NULL;
	/* next-packet len, 0 means no more active classes in in-service agg */
	unsigned int len = 0;

	if (in_serv_agg == NULL)
		return NULL;

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

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

		/* recharge the budget of the aggregate */
		in_serv_agg->initial_budget = in_serv_agg->budget =
			in_serv_agg->budgetmax;

		if (!list_empty(&in_serv_agg->active)) {
			/*
			 * Still active: reschedule for
			 * service. Possible optimization: if no other
			 * aggregate is active, then there is no point
			 * in rescheduling this aggregate, and we can
			 * just keep it as the in-service one. This
			 * should be however a corner case, and to
			 * handle it, we would need to maintain an
			 * extra num_active_aggs field.
			*/
			qfq_update_agg_ts(q, in_serv_agg, requeue);
			qfq_schedule_agg(q, in_serv_agg);
		} else if (sch->q.qlen == 0) { /* no aggregate to serve */
			q->in_serv_agg = NULL;
			return NULL;
		}

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

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

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

	q->V += (u64)len * q->iwsum;
	pr_debug("qfq dequeue: len %u F %lld now %lld\n",
		 len, (unsigned long long) in_serv_agg->F,
		 (unsigned long long) q->V);

	return skb;
}

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

	qfq_update_eligible(q);
	q->oldV = q->V;

	if (!q->bitmaps[ER])
		return NULL;

	grp = qfq_ffs(q, q->bitmaps[ER]);
	old_F = grp->F;

	agg = qfq_slot_head(grp);

	/* agg starts to be served, remove it from schedule */
	qfq_front_slot_remove(grp);

	new_front_agg = qfq_slot_scan(grp);

	if (new_front_agg == NULL) /* group is now inactive, remove from ER */
		__clear_bit(grp->index, &q->bitmaps[ER]);
	else {
		u64 roundedS = qfq_round_down(new_front_agg->S,
					      grp->slot_shift);
		unsigned int s;

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

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

	return agg;
}

static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
		       struct sk_buff **to_free)
{
	unsigned int len = qdisc_pkt_len(skb), gso_segs;
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_class *cl;
	struct qfq_aggregate *agg;
	int err = 0;
	bool first;

	cl = qfq_classify(skb, sch, &err);
	if (cl == NULL) {
		if (err & __NET_XMIT_BYPASS)
			qdisc_qstats_drop(sch);
		__qdisc_drop(skb, to_free);
		return err;
	}
	pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);

	if (unlikely(cl->agg->lmax < len)) {
		pr_debug("qfq: increasing maxpkt from %u to %u for class %u",
			 cl->agg->lmax, len, cl->common.classid);
		err = qfq_change_agg(sch, cl, cl->agg->class_weight, len);
		if (err) {
			cl->qstats.drops++;
			return qdisc_drop(skb, sch, to_free);
		}
	}

	gso_segs = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1;
	first = !cl->qdisc->q.qlen;
	err = qdisc_enqueue(skb, cl->qdisc, to_free);
	if (unlikely(err != NET_XMIT_SUCCESS)) {
		pr_debug("qfq_enqueue: enqueue failed %d\n", err);
		if (net_xmit_drop_count(err)) {
			cl->qstats.drops++;
			qdisc_qstats_drop(sch);
		}
		return err;
	}

	cl->bstats.bytes += len;
	cl->bstats.packets += gso_segs;
	sch->qstats.backlog += len;
	++sch->q.qlen;

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

		return err;
	}

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

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

	qfq_activate_agg(q, agg, enqueue);

	return err;
}

/*
 * Schedule aggregate according to its timestamps.
 */
static void qfq_schedule_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
{
	struct qfq_group *grp = agg->grp;
	u64 roundedS;
	int s;

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

	/*
	 * Insert agg in the correct bucket.
	 * If agg->S >= grp->S we don't need to adjust the
	 * bucket list and simply go to the insertion phase.
	 * Otherwise grp->S is decreasing, we must make room
	 * in the bucket list, and also recompute the group state.
	 * Finally, if there were no flows in this group and nobody
	 * was in ER make sure to adjust V.
	 */
	if (grp->full_slots) {
		if (!qfq_gt(grp->S, agg->S))
			goto skip_update;

		/* create a slot for this agg->S */
		qfq_slot_rotate(grp, roundedS);
		/* group was surely ineligible, remove */
		__clear_bit(grp->index, &q->bitmaps[IR]);
		__clear_bit(grp->index, &q->bitmaps[IB]);
	} else if (!q->bitmaps[ER] && qfq_gt(roundedS, q->V) &&
		   q->in_serv_agg == NULL)
		q->V = roundedS;

	grp->S = roundedS;
	grp->F = roundedS + (2ULL << grp->slot_shift);
	s = qfq_calc_state(q, grp);
	__set_bit(grp->index, &q->bitmaps[s]);

	pr_debug("qfq enqueue: new state %d %#lx S %lld F %lld V %lld\n",
		 s, q->bitmaps[s],
		 (unsigned long long) agg->S,
		 (unsigned long long) agg->F,
		 (unsigned long long) q->V);

skip_update:
	qfq_slot_insert(grp, agg, roundedS);
}


/* Update agg ts and schedule agg for service */
static void qfq_activate_agg(struct qfq_sched *q, struct qfq_aggregate *agg,
			     enum update_reason reason)
{
	agg->initial_budget = agg->budget = agg->budgetmax; /* recharge budg. */

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

static void qfq_slot_remove(struct qfq_sched *q, struct qfq_group *grp,
			    struct qfq_aggregate *agg)
{
	unsigned int i, offset;
	u64 roundedS;

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

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

	hlist_del(&agg->next);
	if (hlist_empty(&grp->slots[i]))
		__clear_bit(offset, &grp->full_slots);
}

/*
 * Called to forcibly deschedule an aggregate.  If the aggregate is
 * not in the front bucket, or if the latter has other aggregates in
 * the front bucket, we can simply remove the aggregate with no other
 * side effects.
 * Otherwise we must propagate the event up.
 */
static void qfq_deactivate_agg(struct qfq_sched *q, struct qfq_aggregate *agg)
{
	struct qfq_group *grp = agg->grp;
	unsigned long mask;
	u64 roundedS;
	int s;

	if (agg == q->in_serv_agg) {
		charge_actual_service(agg);
		q->in_serv_agg = qfq_choose_next_agg(q);
		return;
	}

	agg->F = agg->S;
	qfq_slot_remove(q, grp, agg);

	if (!grp->full_slots) {
		__clear_bit(grp->index, &q->bitmaps[IR]);
		__clear_bit(grp->index, &q->bitmaps[EB]);
		__clear_bit(grp->index, &q->bitmaps[IB]);

		if (test_bit(grp->index, &q->bitmaps[ER]) &&
		    !(q->bitmaps[ER] & ~((1UL << grp->index) - 1))) {
			mask = q->bitmaps[ER] & ((1UL << grp->index) - 1);
			if (mask)
				mask = ~((1UL << __fls(mask)) - 1);
			else
				mask = ~0UL;
			qfq_move_groups(q, mask, EB, ER);
			qfq_move_groups(q, mask, IB, IR);
		}
		__clear_bit(grp->index, &q->bitmaps[ER]);
	} else if (hlist_empty(&grp->slots[grp->front])) {
		agg = qfq_slot_scan(grp);
		roundedS = qfq_round_down(agg->S, grp->slot_shift);
		if (grp->S != roundedS) {
			__clear_bit(grp->index, &q->bitmaps[ER]);
			__clear_bit(grp->index, &q->bitmaps[IR]);
			__clear_bit(grp->index, &q->bitmaps[EB]);
			__clear_bit(grp->index, &q->bitmaps[IB]);
			grp->S = roundedS;
			grp->F = roundedS + (2ULL << grp->slot_shift);
			s = qfq_calc_state(q, grp);
			__set_bit(grp->index, &q->bitmaps[s]);
		}
	}
}

static void qfq_qlen_notify(struct Qdisc *sch, unsigned long arg)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_class *cl = (struct qfq_class *)arg;

	qfq_deactivate_class(q, cl);
}

static int qfq_init_qdisc(struct Qdisc *sch, struct nlattr *opt,
			  struct netlink_ext_ack *extack)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_group *grp;
	int i, j, err;
	u32 max_cl_shift, maxbudg_shift, max_classes;

	err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
	if (err)
		return err;

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

	if (qdisc_dev(sch)->tx_queue_len + 1 > QFQ_MAX_AGG_CLASSES)
		max_classes = QFQ_MAX_AGG_CLASSES;
	else
		max_classes = qdisc_dev(sch)->tx_queue_len + 1;
	/* max_cl_shift = floor(log_2(max_classes)) */
	max_cl_shift = __fls(max_classes);
	q->max_agg_classes = 1<<max_cl_shift;

	/* maxbudg_shift = log2(max_len * max_classes_per_agg) */
	maxbudg_shift = QFQ_MTU_SHIFT + max_cl_shift;
	q->min_slot_shift = FRAC_BITS + maxbudg_shift - QFQ_MAX_INDEX;

	for (i = 0; i <= QFQ_MAX_INDEX; i++) {
		grp = &q->groups[i];
		grp->index = i;
		grp->slot_shift = q->min_slot_shift + i;
		for (j = 0; j < QFQ_MAX_SLOTS; j++)
			INIT_HLIST_HEAD(&grp->slots[j]);
	}

	INIT_HLIST_HEAD(&q->nonfull_aggs);

	return 0;
}

static void qfq_reset_qdisc(struct Qdisc *sch)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_class *cl;
	unsigned int i;

	for (i = 0; i < q->clhash.hashsize; i++) {
		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
			if (cl->qdisc->q.qlen > 0)
				qfq_deactivate_class(q, cl);

			qdisc_reset(cl->qdisc);
		}
	}
	sch->qstats.backlog = 0;
	sch->q.qlen = 0;
}

static void qfq_destroy_qdisc(struct Qdisc *sch)
{
	struct qfq_sched *q = qdisc_priv(sch);
	struct qfq_class *cl;
	struct hlist_node *next;
	unsigned int i;

	tcf_block_put(q->block);

	for (i = 0; i < q->clhash.hashsize; i++) {
		hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],
					  common.hnode) {
			qfq_destroy_class(sch, cl);
		}
	}
	qdisc_class_hash_destroy(&q->clhash);
}

static const struct Qdisc_class_ops qfq_class_ops = {
	.change		= qfq_change_class,
	.delete		= qfq_delete_class,
	.find		= qfq_search_class,
	.tcf_block	= qfq_tcf_block,
	.bind_tcf	= qfq_bind_tcf,
	.unbind_tcf	= qfq_unbind_tcf,
	.graft		= qfq_graft_class,
	.leaf		= qfq_class_leaf,
	.qlen_notify	= qfq_qlen_notify,
	.dump		= qfq_dump_class,
	.dump_stats	= qfq_dump_class_stats,
	.walk		= qfq_walk,
};

static struct Qdisc_ops qfq_qdisc_ops __read_mostly = {
	.cl_ops		= &qfq_class_ops,
	.id		= "qfq",
	.priv_size	= sizeof(struct qfq_sched),
	.enqueue	= qfq_enqueue,
	.dequeue	= qfq_dequeue,
	.peek		= qdisc_peek_dequeued,
	.init		= qfq_init_qdisc,
	.reset		= qfq_reset_qdisc,
	.destroy	= qfq_destroy_qdisc,
	.owner		= THIS_MODULE,
};

static int __init qfq_init(void)
{
	return register_qdisc(&qfq_qdisc_ops);
}

static void __exit qfq_exit(void)
{
	unregister_qdisc(&qfq_qdisc_ops);
}

module_init(qfq_init);
module_exit(qfq_exit);
MODULE_LICENSE("GPL");