aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/md/bcache/bset.c
blob: 8010eed06a51c8320786a1c49463c98c8aa70555 (plain) (blame)
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
/*
 * Code for working with individual keys, and sorted sets of keys with in a
 * btree node
 *
 * Copyright 2012 Google, Inc.
 */

#include "bcache.h"
#include "btree.h"
#include "debug.h"

#include <linux/random.h>
#include <linux/prefetch.h>

/* Keylists */

void bch_keylist_copy(struct keylist *dest, struct keylist *src)
{
	*dest = *src;

	if (src->list == src->d) {
		size_t n = (uint64_t *) src->top - src->d;
		dest->top = (struct bkey *) &dest->d[n];
		dest->list = dest->d;
	}
}

int bch_keylist_realloc(struct keylist *l, int nptrs, struct cache_set *c)
{
	unsigned oldsize = (uint64_t *) l->top - l->list;
	unsigned newsize = oldsize + 2 + nptrs;
	uint64_t *new;

	/* The journalling code doesn't handle the case where the keys to insert
	 * is bigger than an empty write: If we just return -ENOMEM here,
	 * bio_insert() and bio_invalidate() will insert the keys created so far
	 * and finish the rest when the keylist is empty.
	 */
	if (newsize * sizeof(uint64_t) > block_bytes(c) - sizeof(struct jset))
		return -ENOMEM;

	newsize = roundup_pow_of_two(newsize);

	if (newsize <= KEYLIST_INLINE ||
	    roundup_pow_of_two(oldsize) == newsize)
		return 0;

	new = krealloc(l->list == l->d ? NULL : l->list,
		       sizeof(uint64_t) * newsize, GFP_NOIO);

	if (!new)
		return -ENOMEM;

	if (l->list == l->d)
		memcpy(new, l->list, sizeof(uint64_t) * KEYLIST_INLINE);

	l->list = new;
	l->top = (struct bkey *) (&l->list[oldsize]);

	return 0;
}

struct bkey *bch_keylist_pop(struct keylist *l)
{
	struct bkey *k = l->bottom;

	if (k == l->top)
		return NULL;

	while (bkey_next(k) != l->top)
		k = bkey_next(k);

	return l->top = k;
}

/* Pointer validation */

bool __bch_ptr_invalid(struct cache_set *c, int level, const struct bkey *k)
{
	unsigned i;
	char buf[80];

	if (level && (!KEY_PTRS(k) || !KEY_SIZE(k) || KEY_DIRTY(k)))
		goto bad;

	if (!level && KEY_SIZE(k) > KEY_OFFSET(k))
		goto bad;

	if (!KEY_SIZE(k))
		return true;

	for (i = 0; i < KEY_PTRS(k); i++)
		if (ptr_available(c, k, i)) {
			struct cache *ca = PTR_CACHE(c, k, i);
			size_t bucket = PTR_BUCKET_NR(c, k, i);
			size_t r = bucket_remainder(c, PTR_OFFSET(k, i));

			if (KEY_SIZE(k) + r > c->sb.bucket_size ||
			    bucket <  ca->sb.first_bucket ||
			    bucket >= ca->sb.nbuckets)
				goto bad;
		}

	return false;
bad:
	bch_bkey_to_text(buf, sizeof(buf), k);
	cache_bug(c, "spotted bad key %s: %s", buf, bch_ptr_status(c, k));
	return true;
}

bool bch_ptr_bad(struct btree *b, const struct bkey *k)
{
	struct bucket *g;
	unsigned i, stale;

	if (!bkey_cmp(k, &ZERO_KEY) ||
	    !KEY_PTRS(k) ||
	    bch_ptr_invalid(b, k))
		return true;

	if (KEY_PTRS(k) && PTR_DEV(k, 0) == PTR_CHECK_DEV)
		return true;

	for (i = 0; i < KEY_PTRS(k); i++)
		if (ptr_available(b->c, k, i)) {
			g = PTR_BUCKET(b->c, k, i);
			stale = ptr_stale(b->c, k, i);

			btree_bug_on(stale > 96, b,
				     "key too stale: %i, need_gc %u",
				     stale, b->c->need_gc);

			btree_bug_on(stale && KEY_DIRTY(k) && KEY_SIZE(k),
				     b, "stale dirty pointer");

			if (stale)
				return true;

#ifdef CONFIG_BCACHE_EDEBUG
			if (!mutex_trylock(&b->c->bucket_lock))
				continue;

			if (b->level) {
				if (KEY_DIRTY(k) ||
				    g->prio != BTREE_PRIO ||
				    (b->c->gc_mark_valid &&
				     GC_MARK(g) != GC_MARK_METADATA))
					goto bug;

			} else {
				if (g->prio == BTREE_PRIO)
					goto bug;

				if (KEY_DIRTY(k) &&
				    b->c->gc_mark_valid &&
				    GC_MARK(g) != GC_MARK_DIRTY)
					goto bug;
			}
			mutex_unlock(&b->c->bucket_lock);
#endif
		}

	return false;
#ifdef CONFIG_BCACHE_EDEBUG
bug:
	mutex_unlock(&b->c->bucket_lock);

	{
		char buf[80];

		bch_bkey_to_text(buf, sizeof(buf), k);
		btree_bug(b,
"inconsistent pointer %s: bucket %zu pin %i prio %i gen %i last_gc %i mark %llu gc_gen %i",
			  buf, PTR_BUCKET_NR(b->c, k, i), atomic_read(&g->pin),
			  g->prio, g->gen, g->last_gc, GC_MARK(g), g->gc_gen);
	}
	return true;
#endif
}

/* Key/pointer manipulation */

void bch_bkey_copy_single_ptr(struct bkey *dest, const struct bkey *src,
			      unsigned i)
{
	BUG_ON(i > KEY_PTRS(src));

	/* Only copy the header, key, and one pointer. */
	memcpy(dest, src, 2 * sizeof(uint64_t));
	dest->ptr[0] = src->ptr[i];
	SET_KEY_PTRS(dest, 1);
	/* We didn't copy the checksum so clear that bit. */
	SET_KEY_CSUM(dest, 0);
}

bool __bch_cut_front(const struct bkey *where, struct bkey *k)
{
	unsigned i, len = 0;

	if (bkey_cmp(where, &START_KEY(k)) <= 0)
		return false;

	if (bkey_cmp(where, k) < 0)
		len = KEY_OFFSET(k) - KEY_OFFSET(where);
	else
		bkey_copy_key(k, where);

	for (i = 0; i < KEY_PTRS(k); i++)
		SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + KEY_SIZE(k) - len);

	BUG_ON(len > KEY_SIZE(k));
	SET_KEY_SIZE(k, len);
	return true;
}

bool __bch_cut_back(const struct bkey *where, struct bkey *k)
{
	unsigned len = 0;

	if (bkey_cmp(where, k) >= 0)
		return false;

	BUG_ON(KEY_INODE(where) != KEY_INODE(k));

	if (bkey_cmp(where, &START_KEY(k)) > 0)
		len = KEY_OFFSET(where) - KEY_START(k);

	bkey_copy_key(k, where);

	BUG_ON(len > KEY_SIZE(k));
	SET_KEY_SIZE(k, len);
	return true;
}

static uint64_t merge_chksums(struct bkey *l, struct bkey *r)
{
	return (l->ptr[KEY_PTRS(l)] + r->ptr[KEY_PTRS(r)]) &
		~((uint64_t)1 << 63);
}

/* Tries to merge l and r: l should be lower than r
 * Returns true if we were able to merge. If we did merge, l will be the merged
 * key, r will be untouched.
 */
bool bch_bkey_try_merge(struct btree *b, struct bkey *l, struct bkey *r)
{
	unsigned i;

	if (key_merging_disabled(b->c))
		return false;

	if (KEY_PTRS(l) != KEY_PTRS(r) ||
	    KEY_DIRTY(l) != KEY_DIRTY(r) ||
	    bkey_cmp(l, &START_KEY(r)))
		return false;

	for (i = 0; i < KEY_PTRS(l); i++)
		if (l->ptr[i] + PTR(0, KEY_SIZE(l), 0) != r->ptr[i] ||
		    PTR_BUCKET_NR(b->c, l, i) != PTR_BUCKET_NR(b->c, r, i))
			return false;

	/* Keys with no pointers aren't restricted to one bucket and could
	 * overflow KEY_SIZE
	 */
	if (KEY_SIZE(l) + KEY_SIZE(r) > USHRT_MAX) {
		SET_KEY_OFFSET(l, KEY_OFFSET(l) + USHRT_MAX - KEY_SIZE(l));
		SET_KEY_SIZE(l, USHRT_MAX);

		bch_cut_front(l, r);
		return false;
	}

	if (KEY_CSUM(l)) {
		if (KEY_CSUM(r))
			l->ptr[KEY_PTRS(l)] = merge_chksums(l, r);
		else
			SET_KEY_CSUM(l, 0);
	}

	SET_KEY_OFFSET(l, KEY_OFFSET(l) + KEY_SIZE(r));
	SET_KEY_SIZE(l, KEY_SIZE(l) + KEY_SIZE(r));

	return true;
}

/* Binary tree stuff for auxiliary search trees */

static unsigned inorder_next(unsigned j, unsigned size)
{
	if (j * 2 + 1 < size) {
		j = j * 2 + 1;

		while (j * 2 < size)
			j *= 2;
	} else
		j >>= ffz(j) + 1;

	return j;
}

static unsigned inorder_prev(unsigned j, unsigned size)
{
	if (j * 2 < size) {
		j = j * 2;

		while (j * 2 + 1 < size)
			j = j * 2 + 1;
	} else
		j >>= ffs(j);

	return j;
}

/* I have no idea why this code works... and I'm the one who wrote it
 *
 * However, I do know what it does:
 * Given a binary tree constructed in an array (i.e. how you normally implement
 * a heap), it converts a node in the tree - referenced by array index - to the
 * index it would have if you did an inorder traversal.
 *
 * Also tested for every j, size up to size somewhere around 6 million.
 *
 * The binary tree starts at array index 1, not 0
 * extra is a function of size:
 *   extra = (size - rounddown_pow_of_two(size - 1)) << 1;
 */
static unsigned __to_inorder(unsigned j, unsigned size, unsigned extra)
{
	unsigned b = fls(j);
	unsigned shift = fls(size - 1) - b;

	j  ^= 1U << (b - 1);
	j <<= 1;
	j  |= 1;
	j <<= shift;

	if (j > extra)
		j -= (j - extra) >> 1;

	return j;
}

static unsigned to_inorder(unsigned j, struct bset_tree *t)
{
	return __to_inorder(j, t->size, t->extra);
}

static unsigned __inorder_to_tree(unsigned j, unsigned size, unsigned extra)
{
	unsigned shift;

	if (j > extra)
		j += j - extra;

	shift = ffs(j);

	j >>= shift;
	j  |= roundup_pow_of_two(size) >> shift;

	return j;
}

static unsigned inorder_to_tree(unsigned j, struct bset_tree *t)
{
	return __inorder_to_tree(j, t->size, t->extra);
}

#if 0
void inorder_test(void)
{
	unsigned long done = 0;
	ktime_t start = ktime_get();

	for (unsigned size = 2;
	     size < 65536000;
	     size++) {
		unsigned extra = (size - rounddown_pow_of_two(size - 1)) << 1;
		unsigned i = 1, j = rounddown_pow_of_two(size - 1);

		if (!(size % 4096))
			printk(KERN_NOTICE "loop %u, %llu per us\n", size,
			       done / ktime_us_delta(ktime_get(), start));

		while (1) {
			if (__inorder_to_tree(i, size, extra) != j)
				panic("size %10u j %10u i %10u", size, j, i);

			if (__to_inorder(j, size, extra) != i)
				panic("size %10u j %10u i %10u", size, j, i);

			if (j == rounddown_pow_of_two(size) - 1)
				break;

			BUG_ON(inorder_prev(inorder_next(j, size), size) != j);

			j = inorder_next(j, size);
			i++;
		}

		done += size - 1;
	}
}
#endif

/*
 * Cacheline/offset <-> bkey pointer arithmetic:
 *
 * t->tree is a binary search tree in an array; each node corresponds to a key
 * in one cacheline in t->set (BSET_CACHELINE bytes).
 *
 * This means we don't have to store the full index of the key that a node in
 * the binary tree points to; to_inorder() gives us the cacheline, and then
 * bkey_float->m gives us the offset within that cacheline, in units of 8 bytes.
 *
 * cacheline_to_bkey() and friends abstract out all the pointer arithmetic to
 * make this work.
 *
 * To construct the bfloat for an arbitrary key we need to know what the key
 * immediately preceding it is: we have to check if the two keys differ in the
 * bits we're going to store in bkey_float->mantissa. t->prev[j] stores the size
 * of the previous key so we can walk backwards to it from t->tree[j]'s key.
 */

static struct bkey *cacheline_to_bkey(struct bset_tree *t, unsigned cacheline,
				      unsigned offset)
{
	return ((void *) t->data) + cacheline * BSET_CACHELINE + offset * 8;
}

static unsigned bkey_to_cacheline(struct bset_tree *t, struct bkey *k)
{
	return ((void *) k - (void *) t->data) / BSET_CACHELINE;
}

static unsigned bkey_to_cacheline_offset(struct bkey *k)
{
	return ((size_t) k & (BSET_CACHELINE - 1)) / sizeof(uint64_t);
}

static struct bkey *tree_to_bkey(struct bset_tree *t, unsigned j)
{
	return cacheline_to_bkey(t, to_inorder(j, t), t->tree[j].m);
}

static struct bkey *tree_to_prev_bkey(struct bset_tree *t, unsigned j)
{
	return (void *) (((uint64_t *) tree_to_bkey(t, j)) - t->prev[j]);
}

/*
 * For the write set - the one we're currently inserting keys into - we don't
 * maintain a full search tree, we just keep a simple lookup table in t->prev.
 */
static struct bkey *table_to_bkey(struct bset_tree *t, unsigned cacheline)
{
	return cacheline_to_bkey(t, cacheline, t->prev[cacheline]);
}

static inline uint64_t shrd128(uint64_t high, uint64_t low, uint8_t shift)
{
#ifdef CONFIG_X86_64
	asm("shrd %[shift],%[high],%[low]"
	    : [low] "+Rm" (low)
	    : [high] "R" (high),
	    [shift] "ci" (shift)
	    : "cc");
#else
	low >>= shift;
	low  |= (high << 1) << (63U - shift);
#endif
	return low;
}

static inline unsigned bfloat_mantissa(const struct bkey *k,
				       struct bkey_float *f)
{
	const uint64_t *p = &k->low - (f->exponent >> 6);
	return shrd128(p[-1], p[0], f->exponent & 63) & BKEY_MANTISSA_MASK;
}

static void make_bfloat(struct bset_tree *t, unsigned j)
{
	struct bkey_float *f = &t->tree[j];
	struct bkey *m = tree_to_bkey(t, j);
	struct bkey *p = tree_to_prev_bkey(t, j);

	struct bkey *l = is_power_of_2(j)
		? t->data->start
		: tree_to_prev_bkey(t, j >> ffs(j));

	struct bkey *r = is_power_of_2(j + 1)
		? node(t->data, t->data->keys - bkey_u64s(&t->end))
		: tree_to_bkey(t, j >> (ffz(j) + 1));

	BUG_ON(m < l || m > r);
	BUG_ON(bkey_next(p) != m);

	if (KEY_INODE(l) != KEY_INODE(r))
		f->exponent = fls64(KEY_INODE(r) ^ KEY_INODE(l)) + 64;
	else
		f->exponent = fls64(r->low ^ l->low);

	f->exponent = max_t(int, f->exponent - BKEY_MANTISSA_BITS, 0);

	/*
	 * Setting f->exponent = 127 flags this node as failed, and causes the
	 * lookup code to fall back to comparing against the original key.
	 */

	if (bfloat_mantissa(m, f) != bfloat_mantissa(p, f))
		f->mantissa = bfloat_mantissa(m, f) - 1;
	else
		f->exponent = 127;
}

static void bset_alloc_tree(struct btree *b, struct bset_tree *t)
{
	if (t != b->sets) {
		unsigned j = roundup(t[-1].size,
				     64 / sizeof(struct bkey_float));

		t->tree = t[-1].tree + j;
		t->prev = t[-1].prev + j;
	}

	while (t < b->sets + MAX_BSETS)
		t++->size = 0;
}

static void bset_build_unwritten_tree(struct btree *b)
{
	struct bset_tree *t = b->sets + b->nsets;

	bset_alloc_tree(b, t);

	if (t->tree != b->sets->tree + bset_tree_space(b)) {
		t->prev[0] = bkey_to_cacheline_offset(t->data->start);
		t->size = 1;
	}
}

static void bset_build_written_tree(struct btree *b)
{
	struct bset_tree *t = b->sets + b->nsets;
	struct bkey *k = t->data->start;
	unsigned j, cacheline = 1;

	bset_alloc_tree(b, t);

	t->size = min_t(unsigned,
			bkey_to_cacheline(t, end(t->data)),
			b->sets->tree + bset_tree_space(b) - t->tree);

	if (t->size < 2) {
		t->size = 0;
		return;
	}

	t->extra = (t->size - rounddown_pow_of_two(t->size - 1)) << 1;

	/* First we figure out where the first key in each cacheline is */
	for (j = inorder_next(0, t->size);
	     j;
	     j = inorder_next(j, t->size)) {
		while (bkey_to_cacheline(t, k) != cacheline)
			k = bkey_next(k);

		t->prev[j] = bkey_u64s(k);
		k = bkey_next(k);
		cacheline++;
		t->tree[j].m = bkey_to_cacheline_offset(k);
	}

	while (bkey_next(k) != end(t->data))
		k = bkey_next(k);

	t->end = *k;

	/* Then we build the tree */
	for (j = inorder_next(0, t->size);
	     j;
	     j = inorder_next(j, t->size))
		make_bfloat(t, j);
}

void bch_bset_fix_invalidated_key(struct btree *b, struct bkey *k)
{
	struct bset_tree *t;
	unsigned inorder, j = 1;

	for (t = b->sets; t <= &b->sets[b->nsets]; t++)
		if (k < end(t->data))
			goto found_set;

	BUG();
found_set:
	if (!t->size || !bset_written(b, t))
		return;

	inorder = bkey_to_cacheline(t, k);

	if (k == t->data->start)
		goto fix_left;

	if (bkey_next(k) == end(t->data)) {
		t->end = *k;
		goto fix_right;
	}

	j = inorder_to_tree(inorder, t);

	if (j &&
	    j < t->size &&
	    k == tree_to_bkey(t, j))
fix_left:	do {
			make_bfloat(t, j);
			j = j * 2;
		} while (j < t->size);

	j = inorder_to_tree(inorder + 1, t);

	if (j &&
	    j < t->size &&
	    k == tree_to_prev_bkey(t, j))
fix_right:	do {
			make_bfloat(t, j);
			j = j * 2 + 1;
		} while (j < t->size);
}

void bch_bset_fix_lookup_table(struct btree *b, struct bkey *k)
{
	struct bset_tree *t = &b->sets[b->nsets];
	unsigned shift = bkey_u64s(k);
	unsigned j = bkey_to_cacheline(t, k);

	/* We're getting called from btree_split() or btree_gc, just bail out */
	if (!t->size)
		return;

	/* k is the key we just inserted; we need to find the entry in the
	 * lookup table for the first key that is strictly greater than k:
	 * it's either k's cacheline or the next one
	 */
	if (j < t->size &&
	    table_to_bkey(t, j) <= k)
		j++;

	/* Adjust all the lookup table entries, and find a new key for any that
	 * have gotten too big
	 */
	for (; j < t->size; j++) {
		t->prev[j] += shift;

		if (t->prev[j] > 7) {
			k = table_to_bkey(t, j - 1);

			while (k < cacheline_to_bkey(t, j, 0))
				k = bkey_next(k);

			t->prev[j] = bkey_to_cacheline_offset(k);
		}
	}

	if (t->size == b->sets->tree + bset_tree_space(b) - t->tree)
		return;

	/* Possibly add a new entry to the end of the lookup table */

	for (k = table_to_bkey(t, t->size - 1);
	     k != end(t->data);
	     k = bkey_next(k))
		if (t->size == bkey_to_cacheline(t, k)) {
			t->prev[t->size] = bkey_to_cacheline_offset(k);
			t->size++;
		}
}

void bch_bset_init_next(struct btree *b)
{
	struct bset *i = write_block(b);

	if (i != b->sets[0].data) {
		b->sets[++b->nsets].data = i;
		i->seq = b->sets[0].data->seq;
	} else
		get_random_bytes(&i->seq, sizeof(uint64_t));

	i->magic	= bset_magic(b->c);
	i->version	= 0;
	i->keys		= 0;

	bset_build_unwritten_tree(b);
}

struct bset_search_iter {
	struct bkey *l, *r;
};

static struct bset_search_iter bset_search_write_set(struct btree *b,
						     struct bset_tree *t,
						     const struct bkey *search)
{
	unsigned li = 0, ri = t->size;

	BUG_ON(!b->nsets &&
	       t->size < bkey_to_cacheline(t, end(t->data)));

	while (li + 1 != ri) {
		unsigned m = (li + ri) >> 1;

		if (bkey_cmp(table_to_bkey(t, m), search) > 0)
			ri = m;
		else
			li = m;
	}

	return (struct bset_search_iter) {
		table_to_bkey(t, li),
		ri < t->size ? table_to_bkey(t, ri) : end(t->data)
	};
}

static struct bset_search_iter bset_search_tree(struct btree *b,
						struct bset_tree *t,
						const struct bkey *search)
{
	struct bkey *l, *r;
	struct bkey_float *f;
	unsigned inorder, j, n = 1;

	do {
		unsigned p = n << 4;
		p &= ((int) (p - t->size)) >> 31;

		prefetch(&t->tree[p]);

		j = n;
		f = &t->tree[j];

		/*
		 * n = (f->mantissa > bfloat_mantissa())
		 *	? j * 2
		 *	: j * 2 + 1;
		 *
		 * We need to subtract 1 from f->mantissa for the sign bit trick
		 * to work  - that's done in make_bfloat()
		 */
		if (likely(f->exponent != 127))
			n = j * 2 + (((unsigned)
				      (f->mantissa -
				       bfloat_mantissa(search, f))) >> 31);
		else
			n = (bkey_cmp(tree_to_bkey(t, j), search) > 0)
				? j * 2
				: j * 2 + 1;
	} while (n < t->size);

	inorder = to_inorder(j, t);

	/*
	 * n would have been the node we recursed to - the low bit tells us if
	 * we recursed left or recursed right.
	 */
	if (n & 1) {
		l = cacheline_to_bkey(t, inorder, f->m);

		if (++inorder != t->size) {
			f = &t->tree[inorder_next(j, t->size)];
			r = cacheline_to_bkey(t, inorder, f->m);
		} else
			r = end(t->data);
	} else {
		r = cacheline_to_bkey(t, inorder, f->m);

		if (--inorder) {
			f = &t->tree[inorder_prev(j, t->size)];
			l = cacheline_to_bkey(t, inorder, f->m);
		} else
			l = t->data->start;
	}

	return (struct bset_search_iter) {l, r};
}

struct bkey *__bch_bset_search(struct btree *b, struct bset_tree *t,
			       const struct bkey *search)
{
	struct bset_search_iter i;

	/*
	 * First, we search for a cacheline, then lastly we do a linear search
	 * within that cacheline.
	 *
	 * To search for the cacheline, there's three different possibilities:
	 *  * The set is too small to have a search tree, so we just do a linear
	 *    search over the whole set.
	 *  * The set is the one we're currently inserting into; keeping a full
	 *    auxiliary search tree up to date would be too expensive, so we
	 *    use a much simpler lookup table to do a binary search -
	 *    bset_search_write_set().
	 *  * Or we use the auxiliary search tree we constructed earlier -
	 *    bset_search_tree()
	 */

	if (unlikely(!t->size)) {
		i.l = t->data->start;
		i.r = end(t->data);
	} else if (bset_written(b, t)) {
		/*
		 * Each node in the auxiliary search tree covers a certain range
		 * of bits, and keys above and below the set it covers might
		 * differ outside those bits - so we have to special case the
		 * start and end - handle that here:
		 */

		if (unlikely(bkey_cmp(search, &t->end) >= 0))
			return end(t->data);

		if (unlikely(bkey_cmp(search, t->data->start) < 0))
			return t->data->start;

		i = bset_search_tree(b, t, search);
	} else
		i = bset_search_write_set(b, t, search);

#ifdef CONFIG_BCACHE_EDEBUG
	BUG_ON(bset_written(b, t) &&
	       i.l != t->data->start &&
	       bkey_cmp(tree_to_prev_bkey(t,
		  inorder_to_tree(bkey_to_cacheline(t, i.l), t)),
			search) > 0);

	BUG_ON(i.r != end(t->data) &&
	       bkey_cmp(i.r, search) <= 0);
#endif

	while (likely(i.l != i.r) &&
	       bkey_cmp(i.l, search) <= 0)
		i.l = bkey_next(i.l);

	return i.l;
}

/* Btree iterator */

static inline bool btree_iter_cmp(struct btree_iter_set l,
				  struct btree_iter_set r)
{
	int64_t c = bkey_cmp(&START_KEY(l.k), &START_KEY(r.k));

	return c ? c > 0 : l.k < r.k;
}

static inline bool btree_iter_end(struct btree_iter *iter)
{
	return !iter->used;
}

void bch_btree_iter_push(struct btree_iter *iter, struct bkey *k,
			 struct bkey *end)
{
	if (k != end)
		BUG_ON(!heap_add(iter,
				 ((struct btree_iter_set) { k, end }),
				 btree_iter_cmp));
}

struct bkey *__bch_btree_iter_init(struct btree *b, struct btree_iter *iter,
			       struct bkey *search, struct bset_tree *start)
{
	struct bkey *ret = NULL;
	iter->size = ARRAY_SIZE(iter->data);
	iter->used = 0;

	for (; start <= &b->sets[b->nsets]; start++) {
		ret = bch_bset_search(b, start, search);
		bch_btree_iter_push(iter, ret, end(start->data));
	}

	return ret;
}

struct bkey *bch_btree_iter_next(struct btree_iter *iter)
{
	struct btree_iter_set unused;
	struct bkey *ret = NULL;

	if (!btree_iter_end(iter)) {
		ret = iter->data->k;
		iter->data->k = bkey_next(iter->data->k);

		if (iter->data->k > iter->data->end) {
			WARN_ONCE(1, "bset was corrupt!\n");
			iter->data->k = iter->data->end;
		}

		if (iter->data->k == iter->data->end)
			heap_pop(iter, unused, btree_iter_cmp);
		else
			heap_sift(iter, 0, btree_iter_cmp);
	}

	return ret;
}

struct bkey *bch_btree_iter_next_filter(struct btree_iter *iter,
					struct btree *b, ptr_filter_fn fn)
{
	struct bkey *ret;

	do {
		ret = bch_btree_iter_next(iter);
	} while (ret && fn(b, ret));

	return ret;
}

struct bkey *bch_next_recurse_key(struct btree *b, struct bkey *search)
{
	struct btree_iter iter;

	bch_btree_iter_init(b, &iter, search);
	return bch_btree_iter_next_filter(&iter, b, bch_ptr_bad);
}

/* Mergesort */

static void btree_sort_fixup(struct btree_iter *iter)
{
	while (iter->used > 1) {
		struct btree_iter_set *top = iter->data, *i = top + 1;
		struct bkey *k;

		if (iter->used > 2 &&
		    btree_iter_cmp(i[0], i[1]))
			i++;

		for (k = i->k;
		     k != i->end && bkey_cmp(top->k, &START_KEY(k)) > 0;
		     k = bkey_next(k))
			if (top->k > i->k)
				__bch_cut_front(top->k, k);
			else if (KEY_SIZE(k))
				bch_cut_back(&START_KEY(k), top->k);

		if (top->k < i->k || k == i->k)
			break;

		heap_sift(iter, i - top, btree_iter_cmp);
	}
}

static void btree_mergesort(struct btree *b, struct bset *out,
			    struct btree_iter *iter,
			    bool fixup, bool remove_stale)
{
	struct bkey *k, *last = NULL;
	bool (*bad)(struct btree *, const struct bkey *) = remove_stale
		? bch_ptr_bad
		: bch_ptr_invalid;

	while (!btree_iter_end(iter)) {
		if (fixup && !b->level)
			btree_sort_fixup(iter);

		k = bch_btree_iter_next(iter);
		if (bad(b, k))
			continue;

		if (!last) {
			last = out->start;
			bkey_copy(last, k);
		} else if (b->level ||
			   !bch_bkey_try_merge(b, last, k)) {
			last = bkey_next(last);
			bkey_copy(last, k);
		}
	}

	out->keys = last ? (uint64_t *) bkey_next(last) - out->d : 0;

	pr_debug("sorted %i keys", out->keys);
	bch_check_key_order(b, out);
}

static void __btree_sort(struct btree *b, struct btree_iter *iter,
			 unsigned start, unsigned order, bool fixup)
{
	uint64_t start_time;
	bool remove_stale = !b->written;
	struct bset *out = (void *) __get_free_pages(__GFP_NOWARN|GFP_NOIO,
						     order);
	if (!out) {
		mutex_lock(&b->c->sort_lock);
		out = b->c->sort;
		order = ilog2(bucket_pages(b->c));
	}

	start_time = local_clock();

	btree_mergesort(b, out, iter, fixup, remove_stale);
	b->nsets = start;

	if (!fixup && !start && b->written)
		bch_btree_verify(b, out);

	if (!start && order == b->page_order) {
		/*
		 * Our temporary buffer is the same size as the btree node's
		 * buffer, we can just swap buffers instead of doing a big
		 * memcpy()
		 */

		out->magic	= bset_magic(b->c);
		out->seq	= b->sets[0].data->seq;
		out->version	= b->sets[0].data->version;
		swap(out, b->sets[0].data);

		if (b->c->sort == b->sets[0].data)
			b->c->sort = out;
	} else {
		b->sets[start].data->keys = out->keys;
		memcpy(b->sets[start].data->start, out->start,
		       (void *) end(out) - (void *) out->start);
	}

	if (out == b->c->sort)
		mutex_unlock(&b->c->sort_lock);
	else
		free_pages((unsigned long) out, order);

	if (b->written)
		bset_build_written_tree(b);

	if (!start) {
		spin_lock(&b->c->sort_time_lock);
		bch_time_stats_update(&b->c->sort_time, start_time);
		spin_unlock(&b->c->sort_time_lock);
	}
}

void bch_btree_sort_partial(struct btree *b, unsigned start)
{
	size_t oldsize = 0, order = b->page_order, keys = 0;
	struct btree_iter iter;
	__bch_btree_iter_init(b, &iter, NULL, &b->sets[start]);

	BUG_ON(b->sets[b->nsets].data == write_block(b) &&
	       (b->sets[b->nsets].size || b->nsets));

	if (b->written)
		oldsize = bch_count_data(b);

	if (start) {
		unsigned i;

		for (i = start; i <= b->nsets; i++)
			keys += b->sets[i].data->keys;

		order = roundup_pow_of_two(__set_bytes(b->sets->data,
						       keys)) / PAGE_SIZE;
		if (order)
			order = ilog2(order);
	}

	__btree_sort(b, &iter, start, order, false);

	EBUG_ON(b->written && bch_count_data(b) != oldsize);
}

void bch_btree_sort_and_fix_extents(struct btree *b, struct btree_iter *iter)
{
	BUG_ON(!b->written);
	__btree_sort(b, iter, 0, b->page_order, true);
}

void bch_btree_sort_into(struct btree *b, struct btree *new)
{
	uint64_t start_time = local_clock();

	struct btree_iter iter;
	bch_btree_iter_init(b, &iter, NULL);

	btree_mergesort(b, new->sets->data, &iter, false, true);

	spin_lock(&b->c->sort_time_lock);
	bch_time_stats_update(&b->c->sort_time, start_time);
	spin_unlock(&b->c->sort_time_lock);

	bkey_copy_key(&new->key, &b->key);
	new->sets->size = 0;
}

#define SORT_CRIT	(4096 / sizeof(uint64_t))

void bch_btree_sort_lazy(struct btree *b)
{
	unsigned crit = SORT_CRIT;
	int i;

	/* Don't sort if nothing to do */
	if (!b->nsets)
		goto out;

	/* If not a leaf node, always sort */
	if (b->level) {
		bch_btree_sort(b);
		return;
	}

	for (i = b->nsets - 1; i >= 0; --i) {
		crit *= b->c->sort_crit_factor;

		if (b->sets[i].data->keys < crit) {
			bch_btree_sort_partial(b, i);
			return;
		}
	}

	/* Sort if we'd overflow */
	if (b->nsets + 1 == MAX_BSETS) {
		bch_btree_sort(b);
		return;
	}

out:
	bset_build_written_tree(b);
}

/* Sysfs stuff */

struct bset_stats {
	size_t nodes;
	size_t sets_written, sets_unwritten;
	size_t bytes_written, bytes_unwritten;
	size_t floats, failed;
};

static int bch_btree_bset_stats(struct btree *b, struct btree_op *op,
			    struct bset_stats *stats)
{
	struct bkey *k;
	unsigned i;

	stats->nodes++;

	for (i = 0; i <= b->nsets; i++) {
		struct bset_tree *t = &b->sets[i];
		size_t bytes = t->data->keys * sizeof(uint64_t);
		size_t j;

		if (bset_written(b, t)) {
			stats->sets_written++;
			stats->bytes_written += bytes;

			stats->floats += t->size - 1;

			for (j = 1; j < t->size; j++)
				if (t->tree[j].exponent == 127)
					stats->failed++;
		} else {
			stats->sets_unwritten++;
			stats->bytes_unwritten += bytes;
		}
	}

	if (b->level) {
		struct btree_iter iter;

		for_each_key_filter(b, k, &iter, bch_ptr_bad) {
			int ret = btree(bset_stats, k, b, op, stats);
			if (ret)
				return ret;
		}
	}

	return 0;
}

int bch_bset_print_stats(struct cache_set *c, char *buf)
{
	struct btree_op op;
	struct bset_stats t;
	int ret;

	bch_btree_op_init_stack(&op);
	memset(&t, 0, sizeof(struct bset_stats));

	ret = btree_root(bset_stats, c, &op, &t);
	if (ret)
		return ret;

	return snprintf(buf, PAGE_SIZE,
			"btree nodes:		%zu\n"
			"written sets:		%zu\n"
			"unwritten sets:		%zu\n"
			"written key bytes:	%zu\n"
			"unwritten key bytes:	%zu\n"
			"floats:			%zu\n"
			"failed:			%zu\n",
			t.nodes,
			t.sets_written, t.sets_unwritten,
			t.bytes_written, t.bytes_unwritten,
			t.floats, t.failed);
}