summaryrefslogtreecommitdiff
path: root/net/ceph/crush/mapper.c
blob: 5fcfb98f309efb5018f84628902cd1711fc36705 (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
/*
 * Ceph - scalable distributed file system
 *
 * Copyright (C) 2015 Intel Corporation All Rights Reserved
 *
 * This is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 2.1, as published by the Free Software
 * Foundation.  See file COPYING.
 *
 */

#ifdef __KERNEL__
# include <linux/string.h>
# include <linux/slab.h>
# include <linux/bug.h>
# include <linux/kernel.h>
# include <linux/crush/crush.h>
# include <linux/crush/hash.h>
#else
# include "crush_compat.h"
# include "crush.h"
# include "hash.h"
#endif
#include "crush_ln_table.h"

#define dprintk(args...) /* printf(args) */

/*
 * Implement the core CRUSH mapping algorithm.
 */

/**
 * crush_find_rule - find a crush_rule id for a given ruleset, type, and size.
 * @map: the crush_map
 * @ruleset: the storage ruleset id (user defined)
 * @type: storage ruleset type (user defined)
 * @size: output set size
 */
int crush_find_rule(const struct crush_map *map, int ruleset, int type, int size)
{
	__u32 i;

	for (i = 0; i < map->max_rules; i++) {
		if (map->rules[i] &&
		    map->rules[i]->mask.ruleset == ruleset &&
		    map->rules[i]->mask.type == type &&
		    map->rules[i]->mask.min_size <= size &&
		    map->rules[i]->mask.max_size >= size)
			return i;
	}
	return -1;
}


/*
 * bucket choose methods
 *
 * For each bucket algorithm, we have a "choose" method that, given a
 * crush input @x and replica position (usually, position in output set) @r,
 * will produce an item in the bucket.
 */

/*
 * Choose based on a random permutation of the bucket.
 *
 * We used to use some prime number arithmetic to do this, but it
 * wasn't very random, and had some other bad behaviors.  Instead, we
 * calculate an actual random permutation of the bucket members.
 * Since this is expensive, we optimize for the r=0 case, which
 * captures the vast majority of calls.
 */
static int bucket_perm_choose(struct crush_bucket *bucket,
			      int x, int r)
{
	unsigned int pr = r % bucket->size;
	unsigned int i, s;

	/* start a new permutation if @x has changed */
	if (bucket->perm_x != (__u32)x || bucket->perm_n == 0) {
		dprintk("bucket %d new x=%d\n", bucket->id, x);
		bucket->perm_x = x;

		/* optimize common r=0 case */
		if (pr == 0) {
			s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
				bucket->size;
			bucket->perm[0] = s;
			bucket->perm_n = 0xffff;   /* magic value, see below */
			goto out;
		}

		for (i = 0; i < bucket->size; i++)
			bucket->perm[i] = i;
		bucket->perm_n = 0;
	} else if (bucket->perm_n == 0xffff) {
		/* clean up after the r=0 case above */
		for (i = 1; i < bucket->size; i++)
			bucket->perm[i] = i;
		bucket->perm[bucket->perm[0]] = 0;
		bucket->perm_n = 1;
	}

	/* calculate permutation up to pr */
	for (i = 0; i < bucket->perm_n; i++)
		dprintk(" perm_choose have %d: %d\n", i, bucket->perm[i]);
	while (bucket->perm_n <= pr) {
		unsigned int p = bucket->perm_n;
		/* no point in swapping the final entry */
		if (p < bucket->size - 1) {
			i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
				(bucket->size - p);
			if (i) {
				unsigned int t = bucket->perm[p + i];
				bucket->perm[p + i] = bucket->perm[p];
				bucket->perm[p] = t;
			}
			dprintk(" perm_choose swap %d with %d\n", p, p+i);
		}
		bucket->perm_n++;
	}
	for (i = 0; i < bucket->size; i++)
		dprintk(" perm_choose  %d: %d\n", i, bucket->perm[i]);

	s = bucket->perm[pr];
out:
	dprintk(" perm_choose %d sz=%d x=%d r=%d (%d) s=%d\n", bucket->id,
		bucket->size, x, r, pr, s);
	return bucket->items[s];
}

/* uniform */
static int bucket_uniform_choose(struct crush_bucket_uniform *bucket,
				 int x, int r)
{
	return bucket_perm_choose(&bucket->h, x, r);
}

/* list */
static int bucket_list_choose(struct crush_bucket_list *bucket,
			      int x, int r)
{
	int i;

	for (i = bucket->h.size-1; i >= 0; i--) {
		__u64 w = crush_hash32_4(bucket->h.hash, x, bucket->h.items[i],
					 r, bucket->h.id);
		w &= 0xffff;
		dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
			"sw %x rand %llx",
			i, x, r, bucket->h.items[i], bucket->item_weights[i],
			bucket->sum_weights[i], w);
		w *= bucket->sum_weights[i];
		w = w >> 16;
		/*dprintk(" scaled %llx\n", w);*/
		if (w < bucket->item_weights[i])
			return bucket->h.items[i];
	}

	dprintk("bad list sums for bucket %d\n", bucket->h.id);
	return bucket->h.items[0];
}


/* (binary) tree */
static int height(int n)
{
	int h = 0;
	while ((n & 1) == 0) {
		h++;
		n = n >> 1;
	}
	return h;
}

static int left(int x)
{
	int h = height(x);
	return x - (1 << (h-1));
}

static int right(int x)
{
	int h = height(x);
	return x + (1 << (h-1));
}

static int terminal(int x)
{
	return x & 1;
}

static int bucket_tree_choose(struct crush_bucket_tree *bucket,
			      int x, int r)
{
	int n;
	__u32 w;
	__u64 t;

	/* start at root */
	n = bucket->num_nodes >> 1;

	while (!terminal(n)) {
		int l;
		/* pick point in [0, w) */
		w = bucket->node_weights[n];
		t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
					  bucket->h.id) * (__u64)w;
		t = t >> 32;

		/* descend to the left or right? */
		l = left(n);
		if (t < bucket->node_weights[l])
			n = l;
		else
			n = right(n);
	}

	return bucket->h.items[n >> 1];
}


/* straw */

static int bucket_straw_choose(struct crush_bucket_straw *bucket,
			       int x, int r)
{
	__u32 i;
	int high = 0;
	__u64 high_draw = 0;
	__u64 draw;

	for (i = 0; i < bucket->h.size; i++) {
		draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
		draw &= 0xffff;
		draw *= bucket->straws[i];
		if (i == 0 || draw > high_draw) {
			high = i;
			high_draw = draw;
		}
	}
	return bucket->h.items[high];
}

/* compute 2^44*log2(input+1) */
static __u64 crush_ln(unsigned int xin)
{
	unsigned int x = xin, x1;
	int iexpon, index1, index2;
	__u64 RH, LH, LL, xl64, result;

	x++;

	/* normalize input */
	iexpon = 15;
	while (!(x & 0x18000)) {
		x <<= 1;
		iexpon--;
	}

	index1 = (x >> 8) << 1;
	/* RH ~ 2^56/index1 */
	RH = __RH_LH_tbl[index1 - 256];
	/* LH ~ 2^48 * log2(index1/256) */
	LH = __RH_LH_tbl[index1 + 1 - 256];

	/* RH*x ~ 2^48 * (2^15 + xf), xf<2^8 */
	xl64 = (__s64)x * RH;
	xl64 >>= 48;
	x1 = xl64;

	result = iexpon;
	result <<= (12 + 32);

	index2 = x1 & 0xff;
	/* LL ~ 2^48*log2(1.0+index2/2^15) */
	LL = __LL_tbl[index2];

	LH = LH + LL;

	LH >>= (48 - 12 - 32);
	result += LH;

	return result;
}


/*
 * straw2
 *
 * for reference, see:
 *
 * http://en.wikipedia.org/wiki/Exponential_distribution#Distribution_of_the_minimum_of_exponential_random_variables
 *
 */

static int bucket_straw2_choose(struct crush_bucket_straw2 *bucket,
				int x, int r)
{
	unsigned int i, high = 0;
	unsigned int u;
	unsigned int w;
	__s64 ln, draw, high_draw = 0;

	for (i = 0; i < bucket->h.size; i++) {
		w = bucket->item_weights[i];
		if (w) {
			u = crush_hash32_3(bucket->h.hash, x,
					   bucket->h.items[i], r);
			u &= 0xffff;

			/*
			 * for some reason slightly less than 0x10000 produces
			 * a slightly more accurate distribution... probably a
			 * rounding effect.
			 *
			 * the natural log lookup table maps [0,0xffff]
			 * (corresponding to real numbers [1/0x10000, 1] to
			 * [0, 0xffffffffffff] (corresponding to real numbers
			 * [-11.090355,0]).
			 */
			ln = crush_ln(u) - 0x1000000000000ll;

			/*
			 * divide by 16.16 fixed-point weight.  note
			 * that the ln value is negative, so a larger
			 * weight means a larger (less negative) value
			 * for draw.
			 */
			draw = div64_s64(ln, w);
		} else {
			draw = S64_MIN;
		}

		if (i == 0 || draw > high_draw) {
			high = i;
			high_draw = draw;
		}
	}
	return bucket->h.items[high];
}


static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
{
	dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
	BUG_ON(in->size == 0);
	switch (in->alg) {
	case CRUSH_BUCKET_UNIFORM:
		return bucket_uniform_choose((struct crush_bucket_uniform *)in,
					  x, r);
	case CRUSH_BUCKET_LIST:
		return bucket_list_choose((struct crush_bucket_list *)in,
					  x, r);
	case CRUSH_BUCKET_TREE:
		return bucket_tree_choose((struct crush_bucket_tree *)in,
					  x, r);
	case CRUSH_BUCKET_STRAW:
		return bucket_straw_choose((struct crush_bucket_straw *)in,
					   x, r);
	case CRUSH_BUCKET_STRAW2:
		return bucket_straw2_choose((struct crush_bucket_straw2 *)in,
					    x, r);
	default:
		dprintk("unknown bucket %d alg %d\n", in->id, in->alg);
		return in->items[0];
	}
}


/*
 * true if device is marked "out" (failed, fully offloaded)
 * of the cluster
 */
static int is_out(const struct crush_map *map,
		  const __u32 *weight, int weight_max,
		  int item, int x)
{
	if (item >= weight_max)
		return 1;
	if (weight[item] >= 0x10000)
		return 0;
	if (weight[item] == 0)
		return 1;
	if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
	    < weight[item])
		return 0;
	return 1;
}

/**
 * crush_choose_firstn - choose numrep distinct items of given type
 * @map: the crush_map
 * @bucket: the bucket we are choose an item from
 * @x: crush input value
 * @numrep: the number of items to choose
 * @type: the type of item to choose
 * @out: pointer to output vector
 * @outpos: our position in that vector
 * @out_size: size of the out vector
 * @tries: number of attempts to make
 * @recurse_tries: number of attempts to have recursive chooseleaf make
 * @local_retries: localized retries
 * @local_fallback_retries: localized fallback retries
 * @recurse_to_leaf: true if we want one device under each item of given type (chooseleaf instead of choose)
 * @stable: stable mode starts rep=0 in the recursive call for all replicas
 * @vary_r: pass r to recursive calls
 * @out2: second output vector for leaf items (if @recurse_to_leaf)
 * @parent_r: r value passed from the parent
 */
static int crush_choose_firstn(const struct crush_map *map,
			       struct crush_bucket *bucket,
			       const __u32 *weight, int weight_max,
			       int x, int numrep, int type,
			       int *out, int outpos,
			       int out_size,
			       unsigned int tries,
			       unsigned int recurse_tries,
			       unsigned int local_retries,
			       unsigned int local_fallback_retries,
			       int recurse_to_leaf,
			       unsigned int vary_r,
			       unsigned int stable,
			       int *out2,
			       int parent_r)
{
	int rep;
	unsigned int ftotal, flocal;
	int retry_descent, retry_bucket, skip_rep;
	struct crush_bucket *in = bucket;
	int r;
	int i;
	int item = 0;
	int itemtype;
	int collide, reject;
	int count = out_size;

	dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d tries %d recurse_tries %d local_retries %d local_fallback_retries %d parent_r %d stable %d\n",
		recurse_to_leaf ? "_LEAF" : "",
		bucket->id, x, outpos, numrep,
		tries, recurse_tries, local_retries, local_fallback_retries,
		parent_r, stable);

	for (rep = stable ? 0 : outpos; rep < numrep && count > 0 ; rep++) {
		/* keep trying until we get a non-out, non-colliding item */
		ftotal = 0;
		skip_rep = 0;
		do {
			retry_descent = 0;
			in = bucket;               /* initial bucket */

			/* choose through intervening buckets */
			flocal = 0;
			do {
				collide = 0;
				retry_bucket = 0;
				r = rep + parent_r;
				/* r' = r + f_total */
				r += ftotal;

				/* bucket choose */
				if (in->size == 0) {
					reject = 1;
					goto reject;
				}
				if (local_fallback_retries > 0 &&
				    flocal >= (in->size>>1) &&
				    flocal > local_fallback_retries)
					item = bucket_perm_choose(in, x, r);
				else
					item = crush_bucket_choose(in, x, r);
				if (item >= map->max_devices) {
					dprintk("   bad item %d\n", item);
					skip_rep = 1;
					break;
				}

				/* desired type? */
				if (item < 0)
					itemtype = map->buckets[-1-item]->type;
				else
					itemtype = 0;
				dprintk("  item %d type %d\n", item, itemtype);

				/* keep going? */
				if (itemtype != type) {
					if (item >= 0 ||
					    (-1-item) >= map->max_buckets) {
						dprintk("   bad item type %d\n", type);
						skip_rep = 1;
						break;
					}
					in = map->buckets[-1-item];
					retry_bucket = 1;
					continue;
				}

				/* collision? */
				for (i = 0; i < outpos; i++) {
					if (out[i] == item) {
						collide = 1;
						break;
					}
				}

				reject = 0;
				if (!collide && recurse_to_leaf) {
					if (item < 0) {
						int sub_r;
						if (vary_r)
							sub_r = r >> (vary_r-1);
						else
							sub_r = 0;
						if (crush_choose_firstn(map,
							 map->buckets[-1-item],
							 weight, weight_max,
							 x, stable ? 1 : outpos+1, 0,
							 out2, outpos, count,
							 recurse_tries, 0,
							 local_retries,
							 local_fallback_retries,
							 0,
							 vary_r,
							 stable,
							 NULL,
							 sub_r) <= outpos)
							/* didn't get leaf */
							reject = 1;
					} else {
						/* we already have a leaf! */
						out2[outpos] = item;
					}
				}

				if (!reject) {
					/* out? */
					if (itemtype == 0)
						reject = is_out(map, weight,
								weight_max,
								item, x);
					else
						reject = 0;
				}

reject:
				if (reject || collide) {
					ftotal++;
					flocal++;

					if (collide && flocal <= local_retries)
						/* retry locally a few times */
						retry_bucket = 1;
					else if (local_fallback_retries > 0 &&
						 flocal <= in->size + local_fallback_retries)
						/* exhaustive bucket search */
						retry_bucket = 1;
					else if (ftotal < tries)
						/* then retry descent */
						retry_descent = 1;
					else
						/* else give up */
						skip_rep = 1;
					dprintk("  reject %d  collide %d  "
						"ftotal %u  flocal %u\n",
						reject, collide, ftotal,
						flocal);
				}
			} while (retry_bucket);
		} while (retry_descent);

		if (skip_rep) {
			dprintk("skip rep\n");
			continue;
		}

		dprintk("CHOOSE got %d\n", item);
		out[outpos] = item;
		outpos++;
		count--;
#ifndef __KERNEL__
		if (map->choose_tries && ftotal <= map->choose_total_tries)
			map->choose_tries[ftotal]++;
#endif
	}

	dprintk("CHOOSE returns %d\n", outpos);
	return outpos;
}


/**
 * crush_choose_indep: alternative breadth-first positionally stable mapping
 *
 */
static void crush_choose_indep(const struct crush_map *map,
			       struct crush_bucket *bucket,
			       const __u32 *weight, int weight_max,
			       int x, int left, int numrep, int type,
			       int *out, int outpos,
			       unsigned int tries,
			       unsigned int recurse_tries,
			       int recurse_to_leaf,
			       int *out2,
			       int parent_r)
{
	struct crush_bucket *in = bucket;
	int endpos = outpos + left;
	int rep;
	unsigned int ftotal;
	int r;
	int i;
	int item = 0;
	int itemtype;
	int collide;

	dprintk("CHOOSE%s INDEP bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
		bucket->id, x, outpos, numrep);

	/* initially my result is undefined */
	for (rep = outpos; rep < endpos; rep++) {
		out[rep] = CRUSH_ITEM_UNDEF;
		if (out2)
			out2[rep] = CRUSH_ITEM_UNDEF;
	}

	for (ftotal = 0; left > 0 && ftotal < tries; ftotal++) {
#ifdef DEBUG_INDEP
		if (out2 && ftotal) {
			dprintk("%u %d a: ", ftotal, left);
			for (rep = outpos; rep < endpos; rep++) {
				dprintk(" %d", out[rep]);
			}
			dprintk("\n");
			dprintk("%u %d b: ", ftotal, left);
			for (rep = outpos; rep < endpos; rep++) {
				dprintk(" %d", out2[rep]);
			}
			dprintk("\n");
		}
#endif
		for (rep = outpos; rep < endpos; rep++) {
			if (out[rep] != CRUSH_ITEM_UNDEF)
				continue;

			in = bucket;  /* initial bucket */

			/* choose through intervening buckets */
			for (;;) {
				/* note: we base the choice on the position
				 * even in the nested call.  that means that
				 * if the first layer chooses the same bucket
				 * in a different position, we will tend to
				 * choose a different item in that bucket.
				 * this will involve more devices in data
				 * movement and tend to distribute the load.
				 */
				r = rep + parent_r;

				/* be careful */
				if (in->alg == CRUSH_BUCKET_UNIFORM &&
				    in->size % numrep == 0)
					/* r'=r+(n+1)*f_total */
					r += (numrep+1) * ftotal;
				else
					/* r' = r + n*f_total */
					r += numrep * ftotal;

				/* bucket choose */
				if (in->size == 0) {
					dprintk("   empty bucket\n");
					break;
				}

				item = crush_bucket_choose(in, x, r);
				if (item >= map->max_devices) {
					dprintk("   bad item %d\n", item);
					out[rep] = CRUSH_ITEM_NONE;
					if (out2)
						out2[rep] = CRUSH_ITEM_NONE;
					left--;
					break;
				}

				/* desired type? */
				if (item < 0)
					itemtype = map->buckets[-1-item]->type;
				else
					itemtype = 0;
				dprintk("  item %d type %d\n", item, itemtype);

				/* keep going? */
				if (itemtype != type) {
					if (item >= 0 ||
					    (-1-item) >= map->max_buckets) {
						dprintk("   bad item type %d\n", type);
						out[rep] = CRUSH_ITEM_NONE;
						if (out2)
							out2[rep] =
								CRUSH_ITEM_NONE;
						left--;
						break;
					}
					in = map->buckets[-1-item];
					continue;
				}

				/* collision? */
				collide = 0;
				for (i = outpos; i < endpos; i++) {
					if (out[i] == item) {
						collide = 1;
						break;
					}
				}
				if (collide)
					break;

				if (recurse_to_leaf) {
					if (item < 0) {
						crush_choose_indep(map,
						   map->buckets[-1-item],
						   weight, weight_max,
						   x, 1, numrep, 0,
						   out2, rep,
						   recurse_tries, 0,
						   0, NULL, r);
						if (out2[rep] == CRUSH_ITEM_NONE) {
							/* placed nothing; no leaf */
							break;
						}
					} else {
						/* we already have a leaf! */
						out2[rep] = item;
					}
				}

				/* out? */
				if (itemtype == 0 &&
				    is_out(map, weight, weight_max, item, x))
					break;

				/* yay! */
				out[rep] = item;
				left--;
				break;
			}
		}
	}
	for (rep = outpos; rep < endpos; rep++) {
		if (out[rep] == CRUSH_ITEM_UNDEF) {
			out[rep] = CRUSH_ITEM_NONE;
		}
		if (out2 && out2[rep] == CRUSH_ITEM_UNDEF) {
			out2[rep] = CRUSH_ITEM_NONE;
		}
	}
#ifndef __KERNEL__
	if (map->choose_tries && ftotal <= map->choose_total_tries)
		map->choose_tries[ftotal]++;
#endif
#ifdef DEBUG_INDEP
	if (out2) {
		dprintk("%u %d a: ", ftotal, left);
		for (rep = outpos; rep < endpos; rep++) {
			dprintk(" %d", out[rep]);
		}
		dprintk("\n");
		dprintk("%u %d b: ", ftotal, left);
		for (rep = outpos; rep < endpos; rep++) {
			dprintk(" %d", out2[rep]);
		}
		dprintk("\n");
	}
#endif
}

/**
 * crush_do_rule - calculate a mapping with the given input and rule
 * @map: the crush_map
 * @ruleno: the rule id
 * @x: hash input
 * @result: pointer to result vector
 * @result_max: maximum result size
 * @weight: weight vector (for map leaves)
 * @weight_max: size of weight vector
 * @scratch: scratch vector for private use; must be >= 3 * result_max
 */
int crush_do_rule(const struct crush_map *map,
		  int ruleno, int x, int *result, int result_max,
		  const __u32 *weight, int weight_max,
		  int *scratch)
{
	int result_len;
	int *a = scratch;
	int *b = scratch + result_max;
	int *c = scratch + result_max*2;
	int recurse_to_leaf;
	int *w;
	int wsize = 0;
	int *o;
	int osize;
	int *tmp;
	struct crush_rule *rule;
	__u32 step;
	int i, j;
	int numrep;
	int out_size;
	/*
	 * the original choose_total_tries value was off by one (it
	 * counted "retries" and not "tries").  add one.
	 */
	int choose_tries = map->choose_total_tries + 1;
	int choose_leaf_tries = 0;
	/*
	 * the local tries values were counted as "retries", though,
	 * and need no adjustment
	 */
	int choose_local_retries = map->choose_local_tries;
	int choose_local_fallback_retries = map->choose_local_fallback_tries;

	int vary_r = map->chooseleaf_vary_r;
	int stable = map->chooseleaf_stable;

	if ((__u32)ruleno >= map->max_rules) {
		dprintk(" bad ruleno %d\n", ruleno);
		return 0;
	}

	rule = map->rules[ruleno];
	result_len = 0;
	w = a;
	o = b;

	for (step = 0; step < rule->len; step++) {
		int firstn = 0;
		struct crush_rule_step *curstep = &rule->steps[step];

		switch (curstep->op) {
		case CRUSH_RULE_TAKE:
			if ((curstep->arg1 >= 0 &&
			     curstep->arg1 < map->max_devices) ||
			    (-1-curstep->arg1 >= 0 &&
			     -1-curstep->arg1 < map->max_buckets &&
			     map->buckets[-1-curstep->arg1])) {
				w[0] = curstep->arg1;
				wsize = 1;
			} else {
				dprintk(" bad take value %d\n", curstep->arg1);
			}
			break;

		case CRUSH_RULE_SET_CHOOSE_TRIES:
			if (curstep->arg1 > 0)
				choose_tries = curstep->arg1;
			break;

		case CRUSH_RULE_SET_CHOOSELEAF_TRIES:
			if (curstep->arg1 > 0)
				choose_leaf_tries = curstep->arg1;
			break;

		case CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES:
			if (curstep->arg1 >= 0)
				choose_local_retries = curstep->arg1;
			break;

		case CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES:
			if (curstep->arg1 >= 0)
				choose_local_fallback_retries = curstep->arg1;
			break;

		case CRUSH_RULE_SET_CHOOSELEAF_VARY_R:
			if (curstep->arg1 >= 0)
				vary_r = curstep->arg1;
			break;

		case CRUSH_RULE_SET_CHOOSELEAF_STABLE:
			if (curstep->arg1 >= 0)
				stable = curstep->arg1;
			break;

		case CRUSH_RULE_CHOOSELEAF_FIRSTN:
		case CRUSH_RULE_CHOOSE_FIRSTN:
			firstn = 1;
			/* fall through */
		case CRUSH_RULE_CHOOSELEAF_INDEP:
		case CRUSH_RULE_CHOOSE_INDEP:
			if (wsize == 0)
				break;

			recurse_to_leaf =
				curstep->op ==
				 CRUSH_RULE_CHOOSELEAF_FIRSTN ||
				curstep->op ==
				CRUSH_RULE_CHOOSELEAF_INDEP;

			/* reset output */
			osize = 0;

			for (i = 0; i < wsize; i++) {
				int bno;
				/*
				 * see CRUSH_N, CRUSH_N_MINUS macros.
				 * basically, numrep <= 0 means relative to
				 * the provided result_max
				 */
				numrep = curstep->arg1;
				if (numrep <= 0) {
					numrep += result_max;
					if (numrep <= 0)
						continue;
				}
				j = 0;
				/* make sure bucket id is valid */
				bno = -1 - w[i];
				if (bno < 0 || bno >= map->max_buckets) {
					/* w[i] is probably CRUSH_ITEM_NONE */
					dprintk("  bad w[i] %d\n", w[i]);
					continue;
				}
				if (firstn) {
					int recurse_tries;
					if (choose_leaf_tries)
						recurse_tries =
							choose_leaf_tries;
					else if (map->chooseleaf_descend_once)
						recurse_tries = 1;
					else
						recurse_tries = choose_tries;
					osize += crush_choose_firstn(
						map,
						map->buckets[bno],
						weight, weight_max,
						x, numrep,
						curstep->arg2,
						o+osize, j,
						result_max-osize,
						choose_tries,
						recurse_tries,
						choose_local_retries,
						choose_local_fallback_retries,
						recurse_to_leaf,
						vary_r,
						stable,
						c+osize,
						0);
				} else {
					out_size = ((numrep < (result_max-osize)) ?
						    numrep : (result_max-osize));
					crush_choose_indep(
						map,
						map->buckets[bno],
						weight, weight_max,
						x, out_size, numrep,
						curstep->arg2,
						o+osize, j,
						choose_tries,
						choose_leaf_tries ?
						   choose_leaf_tries : 1,
						recurse_to_leaf,
						c+osize,
						0);
					osize += out_size;
				}
			}

			if (recurse_to_leaf)
				/* copy final _leaf_ values to output set */
				memcpy(o, c, osize*sizeof(*o));

			/* swap o and w arrays */
			tmp = o;
			o = w;
			w = tmp;
			wsize = osize;
			break;


		case CRUSH_RULE_EMIT:
			for (i = 0; i < wsize && result_len < result_max; i++) {
				result[result_len] = w[i];
				result_len++;
			}
			wsize = 0;
			break;

		default:
			dprintk(" unknown op %d at step %d\n",
				curstep->op, step);
			break;
		}
	}
	return result_len;
}