aboutsummaryrefslogtreecommitdiffstats
path: root/net/ceph/crush/mapper.c
blob: 42599e31dcad8a6ceb1f3b29d9171f6a249e56a3 (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

#ifdef __KERNEL__
# include <linux/string.h>
# include <linux/slab.h>
# include <linux/bug.h>
# include <linux/kernel.h>
# ifndef dprintk
#  define dprintk(args...)
# endif
#else
# include <string.h>
# include <stdio.h>
# include <stdlib.h>
# include <assert.h>
# define BUG_ON(x) assert(!(x))
# define dprintk(args...) /* printf(args) */
# define kmalloc(x, f) malloc(x)
# define kfree(x) free(x)
#endif

#include <linux/crush/crush.h>
#include <linux/crush/hash.h>

/*
 * 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(struct crush_map *map, int ruleset, int type, int size)
{
	int 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 pr = r % bucket->size;
	unsigned i, s;

	/* start a new permutation if @x has changed */
	if (bucket->perm_x != 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 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 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];
	}

	BUG_ON(1);
	return 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, l;
	__u32 w;
	__u64 t;

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

	while (!terminal(n)) {
		/* 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)
{
	int 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];
}

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);
	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);
	default:
		BUG_ON(1);
		return in->items[0];
	}
}

/*
 * true if device is marked "out" (failed, fully offloaded)
 * of the cluster
 */
static int is_out(struct crush_map *map, __u32 *weight, int item, int x)
{
	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 - 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
 * @firstn: true if choosing "first n" items, false if choosing "indep"
 * @recurse_to_leaf: true if we want one device under each item of given type
 * @out2: second output vector for leaf items (if @recurse_to_leaf)
 */
static int crush_choose(struct crush_map *map,
			struct crush_bucket *bucket,
			__u32 *weight,
			int x, int numrep, int type,
			int *out, int outpos,
			int firstn, int recurse_to_leaf,
			int *out2)
{
	int rep;
	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;
	const int orig_tries = 5; /* attempts before we fall back to search */

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

	for (rep = outpos; rep < numrep; 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;
				if (in->alg == CRUSH_BUCKET_UNIFORM) {
					/* be careful */
					if (firstn || numrep >= in->size)
						/* r' = r + f_total */
						r += ftotal;
					else if (in->size % numrep == 0)
						/* r'=r+(n+1)*f_local */
						r += (numrep+1) *
							(flocal+ftotal);
					else
						/* r' = r + n*f_local */
						r += numrep * (flocal+ftotal);
				} else {
					if (firstn)
						/* r' = r + f_total */
						r += ftotal;
					else
						/* r' = r + n*f_local */
						r += numrep * (flocal+ftotal);
				}

				/* bucket choose */
				if (in->size == 0) {
					reject = 1;
					goto reject;
				}
				if (flocal >= (in->size>>1) &&
				    flocal > orig_tries)
					item = bucket_perm_choose(in, x, r);
				else
					item = crush_bucket_choose(in, x, r);
				BUG_ON(item >= map->max_devices);

				/* 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) {
					BUG_ON(item >= 0 ||
					       (-1-item) >= map->max_buckets);
					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 (recurse_to_leaf) {
					if (item < 0) {
						if (crush_choose(map,
							 map->buckets[-1-item],
							 weight,
							 x, outpos+1, 0,
							 out2, outpos,
							 firstn, 0,
							 NULL) <= 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,
								item, x);
					else
						reject = 0;
				}

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

					if (collide && flocal < 3)
						/* retry locally a few times */
						retry_bucket = 1;
					else if (flocal < in->size + orig_tries)
						/* exhaustive bucket search */
						retry_bucket = 1;
					else if (ftotal < 20)
						/* then retry descent */
						retry_descent = 1;
					else
						/* else give up */
						skip_rep = 1;
					dprintk("  reject %d  collide %d  "
						"ftotal %d  flocal %d\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++;
	}

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


/**
 * 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
 * @force: force initial replica choice; -1 for none
 */
int crush_do_rule(struct crush_map *map,
		  int ruleno, int x, int *result, int result_max,
		  int force, __u32 *weight)
{
	int result_len;
	int force_context[CRUSH_MAX_DEPTH];
	int force_pos = -1;
	int a[CRUSH_MAX_SET];
	int b[CRUSH_MAX_SET];
	int c[CRUSH_MAX_SET];
	int recurse_to_leaf;
	int *w;
	int wsize = 0;
	int *o;
	int osize;
	int *tmp;
	struct crush_rule *rule;
	int step;
	int i, j;
	int numrep;
	int firstn;
	int rc = -1;

	BUG_ON(ruleno >= map->max_rules);

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

	/*
	 * determine hierarchical context of force, if any.  note
	 * that this may or may not correspond to the specific types
	 * referenced by the crush rule.
	 */
	if (force >= 0) {
		if (force >= map->max_devices ||
		    map->device_parents[force] == 0) {
			/*dprintk("CRUSH: forcefed device dne\n");*/
			rc = -1;  /* force fed device dne */
			goto out;
		}
		if (!is_out(map, weight, force, x)) {
			while (1) {
				force_context[++force_pos] = force;
				if (force >= 0)
					force = map->device_parents[force];
				else
					force = map->bucket_parents[-1-force];
				if (force == 0)
					break;
			}
		}
	}

	for (step = 0; step < rule->len; step++) {
		firstn = 0;
		switch (rule->steps[step].op) {
		case CRUSH_RULE_TAKE:
			w[0] = rule->steps[step].arg1;
			if (force_pos >= 0) {
				BUG_ON(force_context[force_pos] != w[0]);
				force_pos--;
			}
			wsize = 1;
			break;

		case CRUSH_RULE_CHOOSE_LEAF_FIRSTN:
		case CRUSH_RULE_CHOOSE_FIRSTN:
			firstn = 1;
		case CRUSH_RULE_CHOOSE_LEAF_INDEP:
		case CRUSH_RULE_CHOOSE_INDEP:
			BUG_ON(wsize == 0);

			recurse_to_leaf =
				rule->steps[step].op ==
				 CRUSH_RULE_CHOOSE_LEAF_FIRSTN ||
				rule->steps[step].op ==
				CRUSH_RULE_CHOOSE_LEAF_INDEP;

			/* reset output */
			osize = 0;

			for (i = 0; i < wsize; i++) {
				/*
				 * see CRUSH_N, CRUSH_N_MINUS macros.
				 * basically, numrep <= 0 means relative to
				 * the provided result_max
				 */
				numrep = rule->steps[step].arg1;
				if (numrep <= 0) {
					numrep += result_max;
					if (numrep <= 0)
						continue;
				}
				j = 0;
				if (osize == 0 && force_pos >= 0) {
					/* skip any intermediate types */
					while (force_pos &&
					       force_context[force_pos] < 0 &&
					       rule->steps[step].arg2 !=
					       map->buckets[-1 -
					       force_context[force_pos]]->type)
						force_pos--;
					o[osize] = force_context[force_pos];
					if (recurse_to_leaf)
						c[osize] = force_context[0];
					j++;
					force_pos--;
				}
				osize += crush_choose(map,
						      map->buckets[-1-w[i]],
						      weight,
						      x, numrep,
						      rule->steps[step].arg2,
						      o+osize, j,
						      firstn,
						      recurse_to_leaf, c+osize);
			}

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

			/* swap t 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:
			BUG_ON(1);
		}
	}
	rc = result_len;

out:
	return rc;
}