summaryrefslogtreecommitdiffstats
path: root/kernel/trace/tracing_map.c
blob: c774e560f2f957127c7e41b825164a0d102b6fd0 (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
// SPDX-License-Identifier: GPL-2.0
/*
 * tracing_map - lock-free map for tracing
 *
 * Copyright (C) 2015 Tom Zanussi <tom.zanussi@linux.intel.com>
 *
 * tracing_map implementation inspired by lock-free map algorithms
 * originated by Dr. Cliff Click:
 *
 * http://www.azulsystems.com/blog/cliff/2007-03-26-non-blocking-hashtable
 * http://www.azulsystems.com/events/javaone_2007/2007_LockFreeHash.pdf
 */

#include <linux/vmalloc.h>
#include <linux/jhash.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include <linux/kmemleak.h>

#include "tracing_map.h"
#include "trace.h"

/*
 * NOTE: For a detailed description of the data structures used by
 * these functions (such as tracing_map_elt) please see the overview
 * of tracing_map data structures at the beginning of tracing_map.h.
 */

/**
 * tracing_map_update_sum - Add a value to a tracing_map_elt's sum field
 * @elt: The tracing_map_elt
 * @i: The index of the given sum associated with the tracing_map_elt
 * @n: The value to add to the sum
 *
 * Add n to sum i associated with the specified tracing_map_elt
 * instance.  The index i is the index returned by the call to
 * tracing_map_add_sum_field() when the tracing map was set up.
 */
void tracing_map_update_sum(struct tracing_map_elt *elt, unsigned int i, u64 n)
{
	atomic64_add(n, &elt->fields[i].sum);
}

/**
 * tracing_map_read_sum - Return the value of a tracing_map_elt's sum field
 * @elt: The tracing_map_elt
 * @i: The index of the given sum associated with the tracing_map_elt
 *
 * Retrieve the value of the sum i associated with the specified
 * tracing_map_elt instance.  The index i is the index returned by the
 * call to tracing_map_add_sum_field() when the tracing map was set
 * up.
 *
 * Return: The sum associated with field i for elt.
 */
u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i)
{
	return (u64)atomic64_read(&elt->fields[i].sum);
}

/**
 * tracing_map_set_var - Assign a tracing_map_elt's variable field
 * @elt: The tracing_map_elt
 * @i: The index of the given variable associated with the tracing_map_elt
 * @n: The value to assign
 *
 * Assign n to variable i associated with the specified tracing_map_elt
 * instance.  The index i is the index returned by the call to
 * tracing_map_add_var() when the tracing map was set up.
 */
void tracing_map_set_var(struct tracing_map_elt *elt, unsigned int i, u64 n)
{
	atomic64_set(&elt->vars[i], n);
	elt->var_set[i] = true;
}

/**
 * tracing_map_var_set - Return whether or not a variable has been set
 * @elt: The tracing_map_elt
 * @i: The index of the given variable associated with the tracing_map_elt
 *
 * Return true if the variable has been set, false otherwise.  The
 * index i is the index returned by the call to tracing_map_add_var()
 * when the tracing map was set up.
 */
bool tracing_map_var_set(struct tracing_map_elt *elt, unsigned int i)
{
	return elt->var_set[i];
}

/**
 * tracing_map_read_var - Return the value of a tracing_map_elt's variable field
 * @elt: The tracing_map_elt
 * @i: The index of the given variable associated with the tracing_map_elt
 *
 * Retrieve the value of the variable i associated with the specified
 * tracing_map_elt instance.  The index i is the index returned by the
 * call to tracing_map_add_var() when the tracing map was set
 * up.
 *
 * Return: The variable value associated with field i for elt.
 */
u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i)
{
	return (u64)atomic64_read(&elt->vars[i]);
}

/**
 * tracing_map_read_var_once - Return and reset a tracing_map_elt's variable field
 * @elt: The tracing_map_elt
 * @i: The index of the given variable associated with the tracing_map_elt
 *
 * Retrieve the value of the variable i associated with the specified
 * tracing_map_elt instance, and reset the variable to the 'not set'
 * state.  The index i is the index returned by the call to
 * tracing_map_add_var() when the tracing map was set up.  The reset
 * essentially makes the variable a read-once variable if it's only
 * accessed using this function.
 *
 * Return: The variable value associated with field i for elt.
 */
u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i)
{
	elt->var_set[i] = false;
	return (u64)atomic64_read(&elt->vars[i]);
}

int tracing_map_cmp_string(void *val_a, void *val_b)
{
	char *a = val_a;
	char *b = val_b;

	return strcmp(a, b);
}

int tracing_map_cmp_none(void *val_a, void *val_b)
{
	return 0;
}

static int tracing_map_cmp_atomic64(void *val_a, void *val_b)
{
	u64 a = atomic64_read((atomic64_t *)val_a);
	u64 b = atomic64_read((atomic64_t *)val_b);

	return (a > b) ? 1 : ((a < b) ? -1 : 0);
}

#define DEFINE_TRACING_MAP_CMP_FN(type)					\
static int tracing_map_cmp_##type(void *val_a, void *val_b)		\
{									\
	type a = (type)(*(u64 *)val_a);					\
	type b = (type)(*(u64 *)val_b);					\
									\
	return (a > b) ? 1 : ((a < b) ? -1 : 0);			\
}

DEFINE_TRACING_MAP_CMP_FN(s64);
DEFINE_TRACING_MAP_CMP_FN(u64);
DEFINE_TRACING_MAP_CMP_FN(s32);
DEFINE_TRACING_MAP_CMP_FN(u32);
DEFINE_TRACING_MAP_CMP_FN(s16);
DEFINE_TRACING_MAP_CMP_FN(u16);
DEFINE_TRACING_MAP_CMP_FN(s8);
DEFINE_TRACING_MAP_CMP_FN(u8);

tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size,
					 int field_is_signed)
{
	tracing_map_cmp_fn_t fn = tracing_map_cmp_none;

	switch (field_size) {
	case 8:
		if (field_is_signed)
			fn = tracing_map_cmp_s64;
		else
			fn = tracing_map_cmp_u64;
		break;
	case 4:
		if (field_is_signed)
			fn = tracing_map_cmp_s32;
		else
			fn = tracing_map_cmp_u32;
		break;
	case 2:
		if (field_is_signed)
			fn = tracing_map_cmp_s16;
		else
			fn = tracing_map_cmp_u16;
		break;
	case 1:
		if (field_is_signed)
			fn = tracing_map_cmp_s8;
		else
			fn = tracing_map_cmp_u8;
		break;
	}

	return fn;
}

static int tracing_map_add_field(struct tracing_map *map,
				 tracing_map_cmp_fn_t cmp_fn)
{
	int ret = -EINVAL;

	if (map->n_fields < TRACING_MAP_FIELDS_MAX) {
		ret = map->n_fields;
		map->fields[map->n_fields++].cmp_fn = cmp_fn;
	}

	return ret;
}

/**
 * tracing_map_add_sum_field - Add a field describing a tracing_map sum
 * @map: The tracing_map
 *
 * Add a sum field to the key and return the index identifying it in
 * the map and associated tracing_map_elts.  This is the index used
 * for instance to update a sum for a particular tracing_map_elt using
 * tracing_map_update_sum() or reading it via tracing_map_read_sum().
 *
 * Return: The index identifying the field in the map and associated
 * tracing_map_elts, or -EINVAL on error.
 */
int tracing_map_add_sum_field(struct tracing_map *map)
{
	return tracing_map_add_field(map, tracing_map_cmp_atomic64);
}

/**
 * tracing_map_add_var - Add a field describing a tracing_map var
 * @map: The tracing_map
 *
 * Add a var to the map and return the index identifying it in the map
 * and associated tracing_map_elts.  This is the index used for
 * instance to update a var for a particular tracing_map_elt using
 * tracing_map_update_var() or reading it via tracing_map_read_var().
 *
 * Return: The index identifying the var in the map and associated
 * tracing_map_elts, or -EINVAL on error.
 */
int tracing_map_add_var(struct tracing_map *map)
{
	int ret = -EINVAL;

	if (map->n_vars < TRACING_MAP_VARS_MAX)
		ret = map->n_vars++;

	return ret;
}

/**
 * tracing_map_add_key_field - Add a field describing a tracing_map key
 * @map: The tracing_map
 * @offset: The offset within the key
 * @cmp_fn: The comparison function that will be used to sort on the key
 *
 * Let the map know there is a key and that if it's used as a sort key
 * to use cmp_fn.
 *
 * A key can be a subset of a compound key; for that purpose, the
 * offset param is used to describe where within the compound key
 * the key referenced by this key field resides.
 *
 * Return: The index identifying the field in the map and associated
 * tracing_map_elts, or -EINVAL on error.
 */
int tracing_map_add_key_field(struct tracing_map *map,
			      unsigned int offset,
			      tracing_map_cmp_fn_t cmp_fn)

{
	int idx = tracing_map_add_field(map, cmp_fn);

	if (idx < 0)
		return idx;

	map->fields[idx].offset = offset;

	map->key_idx[map->n_keys++] = idx;

	return idx;
}

static void tracing_map_array_clear(struct tracing_map_array *a)
{
	unsigned int i;

	if (!a->pages)
		return;

	for (i = 0; i < a->n_pages; i++)
		memset(a->pages[i], 0, PAGE_SIZE);
}

static void tracing_map_array_free(struct tracing_map_array *a)
{
	unsigned int i;

	if (!a)
		return;

	if (!a->pages)
		goto free;

	for (i = 0; i < a->n_pages; i++) {
		if (!a->pages[i])
			break;
		kmemleak_free(a->pages[i]);
		free_page((unsigned long)a->pages[i]);
	}

	kfree(a->pages);

 free:
	kfree(a);
}

static struct tracing_map_array *tracing_map_array_alloc(unsigned int n_elts,
						  unsigned int entry_size)
{
	struct tracing_map_array *a;
	unsigned int i;

	a = kzalloc(sizeof(*a), GFP_KERNEL);
	if (!a)
		return NULL;

	a->entry_size_shift = fls(roundup_pow_of_two(entry_size) - 1);
	a->entries_per_page = PAGE_SIZE / (1 << a->entry_size_shift);
	a->n_pages = n_elts / a->entries_per_page;
	if (!a->n_pages)
		a->n_pages = 1;
	a->entry_shift = fls(a->entries_per_page) - 1;
	a->entry_mask = (1 << a->entry_shift) - 1;

	a->pages = kcalloc(a->n_pages, sizeof(void *), GFP_KERNEL);
	if (!a->pages)
		goto free;

	for (i = 0; i < a->n_pages; i++) {
		a->pages[i] = (void *)get_zeroed_page(GFP_KERNEL);
		if (!a->pages[i])
			goto free;
		kmemleak_alloc(a->pages[i], PAGE_SIZE, 1, GFP_KERNEL);
	}
 out:
	return a;
 free:
	tracing_map_array_free(a);
	a = NULL;

	goto out;
}

static void tracing_map_elt_clear(struct tracing_map_elt *elt)
{
	unsigned i;

	for (i = 0; i < elt->map->n_fields; i++)
		if (elt->fields[i].cmp_fn == tracing_map_cmp_atomic64)
			atomic64_set(&elt->fields[i].sum, 0);

	for (i = 0; i < elt->map->n_vars; i++) {
		atomic64_set(&elt->vars[i], 0);
		elt->var_set[i] = false;
	}

	if (elt->map->ops && elt->map->ops->elt_clear)
		elt->map->ops->elt_clear(elt);
}

static void tracing_map_elt_init_fields(struct tracing_map_elt *elt)
{
	unsigned int i;

	tracing_map_elt_clear(elt);

	for (i = 0; i < elt->map->n_fields; i++) {
		elt->fields[i].cmp_fn = elt->map->fields[i].cmp_fn;

		if (elt->fields[i].cmp_fn != tracing_map_cmp_atomic64)
			elt->fields[i].offset = elt->map->fields[i].offset;
	}
}

static void tracing_map_elt_free(struct tracing_map_elt *elt)
{
	if (!elt)
		return;

	if (elt->map->ops && elt->map->ops->elt_free)
		elt->map->ops->elt_free(elt);
	kfree(elt->fields);
	kfree(elt->vars);
	kfree(elt->var_set);
	kfree(elt->key);
	kfree(elt);
}

static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
{
	struct tracing_map_elt *elt;
	int err = 0;

	elt = kzalloc(sizeof(*elt), GFP_KERNEL);
	if (!elt)
		return ERR_PTR(-ENOMEM);

	elt->map = map;

	elt->key = kzalloc(map->key_size, GFP_KERNEL);
	if (!elt->key) {
		err = -ENOMEM;
		goto free;
	}

	elt->fields = kcalloc(map->n_fields, sizeof(*elt->fields), GFP_KERNEL);
	if (!elt->fields) {
		err = -ENOMEM;
		goto free;
	}

	elt->vars = kcalloc(map->n_vars, sizeof(*elt->vars), GFP_KERNEL);
	if (!elt->vars) {
		err = -ENOMEM;
		goto free;
	}

	elt->var_set = kcalloc(map->n_vars, sizeof(*elt->var_set), GFP_KERNEL);
	if (!elt->var_set) {
		err = -ENOMEM;
		goto free;
	}

	tracing_map_elt_init_fields(elt);

	if (map->ops && map->ops->elt_alloc) {
		err = map->ops->elt_alloc(elt);
		if (err)
			goto free;
	}
	return elt;
 free:
	tracing_map_elt_free(elt);

	return ERR_PTR(err);
}

static struct tracing_map_elt *get_free_elt(struct tracing_map *map)
{
	struct tracing_map_elt *elt = NULL;
	int idx;

	idx = atomic_inc_return(&map->next_elt);
	if (idx < map->max_elts) {
		elt = *(TRACING_MAP_ELT(map->elts, idx));
		if (map->ops && map->ops->elt_init)
			map->ops->elt_init(elt);
	}

	return elt;
}

static void tracing_map_free_elts(struct tracing_map *map)
{
	unsigned int i;

	if (!map->elts)
		return;

	for (i = 0; i < map->max_elts; i++) {
		tracing_map_elt_free(*(TRACING_MAP_ELT(map->elts, i)));
		*(TRACING_MAP_ELT(map->elts, i)) = NULL;
	}

	tracing_map_array_free(map->elts);
	map->elts = NULL;
}

static int tracing_map_alloc_elts(struct tracing_map *map)
{
	unsigned int i;

	map->elts = tracing_map_array_alloc(map->max_elts,
					    sizeof(struct tracing_map_elt *));
	if (!map->elts)
		return -ENOMEM;

	for (i = 0; i < map->max_elts; i++) {
		*(TRACING_MAP_ELT(map->elts, i)) = tracing_map_elt_alloc(map);
		if (IS_ERR(*(TRACING_MAP_ELT(map->elts, i)))) {
			*(TRACING_MAP_ELT(map->elts, i)) = NULL;
			tracing_map_free_elts(map);

			return -ENOMEM;
		}
	}

	return 0;
}

static inline bool keys_match(void *key, void *test_key, unsigned key_size)
{
	bool match = true;

	if (memcmp(key, test_key, key_size))
		match = false;

	return match;
}

static inline struct tracing_map_elt *
__tracing_map_insert(struct tracing_map *map, void *key, bool lookup_only)
{
	u32 idx, key_hash, test_key;
	int dup_try = 0;
	struct tracing_map_entry *entry;
	struct tracing_map_elt *val;

	key_hash = jhash(key, map->key_size, 0);
	if (key_hash == 0)
		key_hash = 1;
	idx = key_hash >> (32 - (map->map_bits + 1));

	while (1) {
		idx &= (map->map_size - 1);
		entry = TRACING_MAP_ENTRY(map->map, idx);
		test_key = entry->key;

		if (test_key && test_key == key_hash) {
			val = READ_ONCE(entry->val);
			if (val &&
			    keys_match(key, val->key, map->key_size)) {
				if (!lookup_only)
					atomic64_inc(&map->hits);
				return val;
			} else if (unlikely(!val)) {
				/*
				 * The key is present. But, val (pointer to elt
				 * struct) is still NULL. which means some other
				 * thread is in the process of inserting an
				 * element.
				 *
				 * On top of that, it's key_hash is same as the
				 * one being inserted right now. So, it's
				 * possible that the element has the same
				 * key as well.
				 */

				dup_try++;
				if (dup_try > map->map_size) {
					atomic64_inc(&map->drops);
					break;
				}
				continue;
			}
		}

		if (!test_key) {
			if (lookup_only)
				break;

			if (!cmpxchg(&entry->key, 0, key_hash)) {
				struct tracing_map_elt *elt;

				elt = get_free_elt(map);
				if (!elt) {
					atomic64_inc(&map->drops);
					entry->key = 0;
					break;
				}

				memcpy(elt->key, key, map->key_size);
				entry->val = elt;
				atomic64_inc(&map->hits);

				return entry->val;
			} else {
				/*
				 * cmpxchg() failed. Loop around once
				 * more to check what key was inserted.
				 */
				dup_try++;
				continue;
			}
		}

		idx++;
	}

	return NULL;
}

/**
 * tracing_map_insert - Insert key and/or retrieve val from a tracing_map
 * @map: The tracing_map to insert into
 * @key: The key to insert
 *
 * Inserts a key into a tracing_map and creates and returns a new
 * tracing_map_elt for it, or if the key has already been inserted by
 * a previous call, returns the tracing_map_elt already associated
 * with it.  When the map was created, the number of elements to be
 * allocated for the map was specified (internally maintained as
 * 'max_elts' in struct tracing_map), and that number of
 * tracing_map_elts was created by tracing_map_init().  This is the
 * pre-allocated pool of tracing_map_elts that tracing_map_insert()
 * will allocate from when adding new keys.  Once that pool is
 * exhausted, tracing_map_insert() is useless and will return NULL to
 * signal that state.  There are two user-visible tracing_map
 * variables, 'hits' and 'drops', which are updated by this function.
 * Every time an element is either successfully inserted or retrieved,
 * the 'hits' value is incremented.  Every time an element insertion
 * fails, the 'drops' value is incremented.
 *
 * This is a lock-free tracing map insertion function implementing a
 * modified form of Cliff Click's basic insertion algorithm.  It
 * requires the table size be a power of two.  To prevent any
 * possibility of an infinite loop we always make the internal table
 * size double the size of the requested table size (max_elts * 2).
 * Likewise, we never reuse a slot or resize or delete elements - when
 * we've reached max_elts entries, we simply return NULL once we've
 * run out of entries.  Readers can at any point in time traverse the
 * tracing map and safely access the key/val pairs.
 *
 * Return: the tracing_map_elt pointer val associated with the key.
 * If this was a newly inserted key, the val will be a newly allocated
 * and associated tracing_map_elt pointer val.  If the key wasn't
 * found and the pool of tracing_map_elts has been exhausted, NULL is
 * returned and no further insertions will succeed.
 */
struct tracing_map_elt *tracing_map_insert(struct tracing_map *map, void *key)
{
	return __tracing_map_insert(map, key, false);
}

/**
 * tracing_map_lookup - Retrieve val from a tracing_map
 * @map: The tracing_map to perform the lookup on
 * @key: The key to look up
 *
 * Looks up key in tracing_map and if found returns the matching
 * tracing_map_elt.  This is a lock-free lookup; see
 * tracing_map_insert() for details on tracing_map and how it works.
 * Every time an element is retrieved, the 'hits' value is
 * incremented.  There is one user-visible tracing_map variable,
 * 'hits', which is updated by this function.  Every time an element
 * is successfully retrieved, the 'hits' value is incremented.  The
 * 'drops' value is never updated by this function.
 *
 * Return: the tracing_map_elt pointer val associated with the key.
 * If the key wasn't found, NULL is returned.
 */
struct tracing_map_elt *tracing_map_lookup(struct tracing_map *map, void *key)
{
	return __tracing_map_insert(map, key, true);
}

/**
 * tracing_map_destroy - Destroy a tracing_map
 * @map: The tracing_map to destroy
 *
 * Frees a tracing_map along with its associated array of
 * tracing_map_elts.
 *
 * Callers should make sure there are no readers or writers actively
 * reading or inserting into the map before calling this.
 */
void tracing_map_destroy(struct tracing_map *map)
{
	if (!map)
		return;

	tracing_map_free_elts(map);

	tracing_map_array_free(map->map);
	kfree(map);
}

/**
 * tracing_map_clear - Clear a tracing_map
 * @map: The tracing_map to clear
 *
 * Resets the tracing map to a cleared or initial state.  The
 * tracing_map_elts are all cleared, and the array of struct
 * tracing_map_entry is reset to an initialized state.
 *
 * Callers should make sure there are no writers actively inserting
 * into the map before calling this.
 */
void tracing_map_clear(struct tracing_map *map)
{
	unsigned int i;

	atomic_set(&map->next_elt, -1);
	atomic64_set(&map->hits, 0);
	atomic64_set(&map->drops, 0);

	tracing_map_array_clear(map->map);

	for (i = 0; i < map->max_elts; i++)
		tracing_map_elt_clear(*(TRACING_MAP_ELT(map->elts, i)));
}

static void set_sort_key(struct tracing_map *map,
			 struct tracing_map_sort_key *sort_key)
{
	map->sort_key = *sort_key;
}

/**
 * tracing_map_create - Create a lock-free map and element pool
 * @map_bits: The size of the map (2 ** map_bits)
 * @key_size: The size of the key for the map in bytes
 * @ops: Optional client-defined tracing_map_ops instance
 * @private_data: Client data associated with the map
 *
 * Creates and sets up a map to contain 2 ** map_bits number of
 * elements (internally maintained as 'max_elts' in struct
 * tracing_map).  Before using, map fields should be added to the map
 * with tracing_map_add_sum_field() and tracing_map_add_key_field().
 * tracing_map_init() should then be called to allocate the array of
 * tracing_map_elts, in order to avoid allocating anything in the map
 * insertion path.  The user-specified map size reflects the maximum
 * number of elements that can be contained in the table requested by
 * the user - internally we double that in order to keep the table
 * sparse and keep collisions manageable.
 *
 * A tracing_map is a special-purpose map designed to aggregate or
 * 'sum' one or more values associated with a specific object of type
 * tracing_map_elt, which is attached by the map to a given key.
 *
 * tracing_map_create() sets up the map itself, and provides
 * operations for inserting tracing_map_elts, but doesn't allocate the
 * tracing_map_elts themselves, or provide a means for describing the
 * keys or sums associated with the tracing_map_elts.  All
 * tracing_map_elts for a given map have the same set of sums and
 * keys, which are defined by the client using the functions
 * tracing_map_add_key_field() and tracing_map_add_sum_field().  Once
 * the fields are defined, the pool of elements allocated for the map
 * can be created, which occurs when the client code calls
 * tracing_map_init().
 *
 * When tracing_map_init() returns, tracing_map_elt elements can be
 * inserted into the map using tracing_map_insert().  When called,
 * tracing_map_insert() grabs a free tracing_map_elt from the pool, or
 * finds an existing match in the map and in either case returns it.
 * The client can then use tracing_map_update_sum() and
 * tracing_map_read_sum() to update or read a given sum field for the
 * tracing_map_elt.
 *
 * The client can at any point retrieve and traverse the current set
 * of inserted tracing_map_elts in a tracing_map, via
 * tracing_map_sort_entries().  Sorting can be done on any field,
 * including keys.
 *
 * See tracing_map.h for a description of tracing_map_ops.
 *
 * Return: the tracing_map pointer if successful, ERR_PTR if not.
 */
struct tracing_map *tracing_map_create(unsigned int map_bits,
				       unsigned int key_size,
				       const struct tracing_map_ops *ops,
				       void *private_data)
{
	struct tracing_map *map;
	unsigned int i;

	if (map_bits < TRACING_MAP_BITS_MIN ||
	    map_bits > TRACING_MAP_BITS_MAX)
		return ERR_PTR(-EINVAL);

	map = kzalloc(sizeof(*map), GFP_KERNEL);
	if (!map)
		return ERR_PTR(-ENOMEM);

	map->map_bits = map_bits;
	map->max_elts = (1 << map_bits);
	atomic_set(&map->next_elt, -1);

	map->map_size = (1 << (map_bits + 1));
	map->ops = ops;

	map->private_data = private_data;

	map->map = tracing_map_array_alloc(map->map_size,
					   sizeof(struct tracing_map_entry));
	if (!map->map)
		goto free;

	map->key_size = key_size;
	for (i = 0; i < TRACING_MAP_KEYS_MAX; i++)
		map->key_idx[i] = -1;
 out:
	return map;
 free:
	tracing_map_destroy(map);
	map = ERR_PTR(-ENOMEM);

	goto out;
}

/**
 * tracing_map_init - Allocate and clear a map's tracing_map_elts
 * @map: The tracing_map to initialize
 *
 * Allocates a clears a pool of tracing_map_elts equal to the
 * user-specified size of 2 ** map_bits (internally maintained as
 * 'max_elts' in struct tracing_map).  Before using, the map fields
 * should be added to the map with tracing_map_add_sum_field() and
 * tracing_map_add_key_field().  tracing_map_init() should then be
 * called to allocate the array of tracing_map_elts, in order to avoid
 * allocating anything in the map insertion path.  The user-specified
 * map size reflects the max number of elements requested by the user
 * - internally we double that in order to keep the table sparse and
 * keep collisions manageable.
 *
 * See tracing_map.h for a description of tracing_map_ops.
 *
 * Return: the tracing_map pointer if successful, ERR_PTR if not.
 */
int tracing_map_init(struct tracing_map *map)
{
	int err;

	if (map->n_fields < 2)
		return -EINVAL; /* need at least 1 key and 1 val */

	err = tracing_map_alloc_elts(map);
	if (err)
		return err;

	tracing_map_clear(map);

	return err;
}

static int cmp_entries_dup(const void *A, const void *B)
{
	const struct tracing_map_sort_entry *a, *b;
	int ret = 0;

	a = *(const struct tracing_map_sort_entry **)A;
	b = *(const struct tracing_map_sort_entry **)B;

	if (memcmp(a->key, b->key, a->elt->map->key_size))
		ret = 1;

	return ret;
}

static int cmp_entries_sum(const void *A, const void *B)
{
	const struct tracing_map_elt *elt_a, *elt_b;
	const struct tracing_map_sort_entry *a, *b;
	struct tracing_map_sort_key *sort_key;
	struct tracing_map_field *field;
	tracing_map_cmp_fn_t cmp_fn;
	void *val_a, *val_b;
	int ret = 0;

	a = *(const struct tracing_map_sort_entry **)A;
	b = *(const struct tracing_map_sort_entry **)B;

	elt_a = a->elt;
	elt_b = b->elt;

	sort_key = &elt_a->map->sort_key;

	field = &elt_a->fields[sort_key->field_idx];
	cmp_fn = field->cmp_fn;

	val_a = &elt_a->fields[sort_key->field_idx].sum;
	val_b = &elt_b->fields[sort_key->field_idx].sum;

	ret = cmp_fn(val_a, val_b);
	if (sort_key->descending)
		ret = -ret;

	return ret;
}

static int cmp_entries_key(const void *A, const void *B)
{
	const struct tracing_map_elt *elt_a, *elt_b;
	const struct tracing_map_sort_entry *a, *b;
	struct tracing_map_sort_key *sort_key;
	struct tracing_map_field *field;
	tracing_map_cmp_fn_t cmp_fn;
	void *val_a, *val_b;
	int ret = 0;

	a = *(const struct tracing_map_sort_entry **)A;
	b = *(const struct tracing_map_sort_entry **)B;

	elt_a = a->elt;
	elt_b = b->elt;

	sort_key = &elt_a->map->sort_key;

	field = &elt_a->fields[sort_key->field_idx];

	cmp_fn = field->cmp_fn;

	val_a = elt_a->key + field->offset;
	val_b = elt_b->key + field->offset;

	ret = cmp_fn(val_a, val_b);
	if (sort_key->descending)
		ret = -ret;

	return ret;
}

static void destroy_sort_entry(struct tracing_map_sort_entry *entry)
{
	if (!entry)
		return;

	if (entry->elt_copied)
		tracing_map_elt_free(entry->elt);

	kfree(entry);
}

/**
 * tracing_map_destroy_sort_entries - Destroy an array of sort entries
 * @entries: The entries to destroy
 * @n_entries: The number of entries in the array
 *
 * Destroy the elements returned by a tracing_map_sort_entries() call.
 */
void tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries,
				      unsigned int n_entries)
{
	unsigned int i;

	for (i = 0; i < n_entries; i++)
		destroy_sort_entry(entries[i]);

	vfree(entries);
}

static struct tracing_map_sort_entry *
create_sort_entry(void *key, struct tracing_map_elt *elt)
{
	struct tracing_map_sort_entry *sort_entry;

	sort_entry = kzalloc(sizeof(*sort_entry), GFP_KERNEL);
	if (!sort_entry)
		return NULL;

	sort_entry->key = key;
	sort_entry->elt = elt;

	return sort_entry;
}

static void detect_dups(struct tracing_map_sort_entry **sort_entries,
		      int n_entries, unsigned int key_size)
{
	unsigned int total_dups = 0;
	int i;
	void *key;

	if (n_entries < 2)
		return;

	sort(sort_entries, n_entries, sizeof(struct tracing_map_sort_entry *),
	     (int (*)(const void *, const void *))cmp_entries_dup, NULL);

	key = sort_entries[0]->key;
	for (i = 1; i < n_entries; i++) {
		if (!memcmp(sort_entries[i]->key, key, key_size)) {
			total_dups++;
			continue;
		}
		key = sort_entries[i]->key;
	}

	WARN_ONCE(total_dups > 0,
		  "Duplicates detected: %d\n", total_dups);
}

static bool is_key(struct tracing_map *map, unsigned int field_idx)
{
	unsigned int i;

	for (i = 0; i < map->n_keys; i++)
		if (map->key_idx[i] == field_idx)
			return true;
	return false;
}

static void sort_secondary(struct tracing_map *map,
			   const struct tracing_map_sort_entry **entries,
			   unsigned int n_entries,
			   struct tracing_map_sort_key *primary_key,
			   struct tracing_map_sort_key *secondary_key)
{
	int (*primary_fn)(const void *, const void *);
	int (*secondary_fn)(const void *, const void *);
	unsigned i, start = 0, n_sub = 1;

	if (is_key(map, primary_key->field_idx))
		primary_fn = cmp_entries_key;
	else
		primary_fn = cmp_entries_sum;

	if (is_key(map, secondary_key->field_idx))
		secondary_fn = cmp_entries_key;
	else
		secondary_fn = cmp_entries_sum;

	for (i = 0; i < n_entries - 1; i++) {
		const struct tracing_map_sort_entry **a = &entries[i];
		const struct tracing_map_sort_entry **b = &entries[i + 1];

		if (primary_fn(a, b) == 0) {
			n_sub++;
			if (i < n_entries - 2)
				continue;
		}

		if (n_sub < 2) {
			start = i + 1;
			n_sub = 1;
			continue;
		}

		set_sort_key(map, secondary_key);
		sort(&entries[start], n_sub,
		     sizeof(struct tracing_map_sort_entry *),
		     (int (*)(const void *, const void *))secondary_fn, NULL);
		set_sort_key(map, primary_key);

		start = i + 1;
		n_sub = 1;
	}
}

/**
 * tracing_map_sort_entries - Sort the current set of tracing_map_elts in a map
 * @map: The tracing_map
 * @sort_keys: The sort key to use for sorting
 * @n_sort_keys: hitcount, always have at least one
 * @sort_entries: outval: pointer to allocated and sorted array of entries
 *
 * tracing_map_sort_entries() sorts the current set of entries in the
 * map and returns the list of tracing_map_sort_entries containing
 * them to the client in the sort_entries param.  The client can
 * access the struct tracing_map_elt element of interest directly as
 * the 'elt' field of a returned struct tracing_map_sort_entry object.
 *
 * The sort_key has only two fields: idx and descending.  'idx' refers
 * to the index of the field added via tracing_map_add_sum_field() or
 * tracing_map_add_key_field() when the tracing_map was initialized.
 * 'descending' is a flag that if set reverses the sort order, which
 * by default is ascending.
 *
 * The client should not hold on to the returned array but should use
 * it and call tracing_map_destroy_sort_entries() when done.
 *
 * Return: the number of sort_entries in the struct tracing_map_sort_entry
 * array, negative on error
 */
int tracing_map_sort_entries(struct tracing_map *map,
			     struct tracing_map_sort_key *sort_keys,
			     unsigned int n_sort_keys,
			     struct tracing_map_sort_entry ***sort_entries)
{
	int (*cmp_entries_fn)(const void *, const void *);
	struct tracing_map_sort_entry *sort_entry, **entries;
	int i, n_entries, ret;

	entries = vmalloc(array_size(sizeof(sort_entry), map->max_elts));
	if (!entries)
		return -ENOMEM;

	for (i = 0, n_entries = 0; i < map->map_size; i++) {
		struct tracing_map_entry *entry;

		entry = TRACING_MAP_ENTRY(map->map, i);

		if (!entry->key || !entry->val)
			continue;

		entries[n_entries] = create_sort_entry(entry->val->key,
						       entry->val);
		if (!entries[n_entries++]) {
			ret = -ENOMEM;
			goto free;
		}
	}

	if (n_entries == 0) {
		ret = 0;
		goto free;
	}

	if (n_entries == 1) {
		*sort_entries = entries;
		return 1;
	}

	detect_dups(entries, n_entries, map->key_size);

	if (is_key(map, sort_keys[0].field_idx))
		cmp_entries_fn = cmp_entries_key;
	else
		cmp_entries_fn = cmp_entries_sum;

	set_sort_key(map, &sort_keys[0]);

	sort(entries, n_entries, sizeof(struct tracing_map_sort_entry *),
	     (int (*)(const void *, const void *))cmp_entries_fn, NULL);

	if (n_sort_keys > 1)
		sort_secondary(map,
			       (const struct tracing_map_sort_entry **)entries,
			       n_entries,
			       &sort_keys[0],
			       &sort_keys[1]);

	*sort_entries = entries;

	return n_entries;
 free:
	tracing_map_destroy_sort_entries(entries, n_entries);

	return ret;
}