xref: /openbmc/linux/net/ceph/crush/mapper.c (revision 4800cd83)
1 
2 #ifdef __KERNEL__
3 # include <linux/string.h>
4 # include <linux/slab.h>
5 # include <linux/bug.h>
6 # include <linux/kernel.h>
7 # ifndef dprintk
8 #  define dprintk(args...)
9 # endif
10 #else
11 # include <string.h>
12 # include <stdio.h>
13 # include <stdlib.h>
14 # include <assert.h>
15 # define BUG_ON(x) assert(!(x))
16 # define dprintk(args...) /* printf(args) */
17 # define kmalloc(x, f) malloc(x)
18 # define kfree(x) free(x)
19 #endif
20 
21 #include <linux/crush/crush.h>
22 #include <linux/crush/hash.h>
23 
24 /*
25  * Implement the core CRUSH mapping algorithm.
26  */
27 
28 /**
29  * crush_find_rule - find a crush_rule id for a given ruleset, type, and size.
30  * @map: the crush_map
31  * @ruleset: the storage ruleset id (user defined)
32  * @type: storage ruleset type (user defined)
33  * @size: output set size
34  */
35 int crush_find_rule(struct crush_map *map, int ruleset, int type, int size)
36 {
37 	int i;
38 
39 	for (i = 0; i < map->max_rules; i++) {
40 		if (map->rules[i] &&
41 		    map->rules[i]->mask.ruleset == ruleset &&
42 		    map->rules[i]->mask.type == type &&
43 		    map->rules[i]->mask.min_size <= size &&
44 		    map->rules[i]->mask.max_size >= size)
45 			return i;
46 	}
47 	return -1;
48 }
49 
50 
51 /*
52  * bucket choose methods
53  *
54  * For each bucket algorithm, we have a "choose" method that, given a
55  * crush input @x and replica position (usually, position in output set) @r,
56  * will produce an item in the bucket.
57  */
58 
59 /*
60  * Choose based on a random permutation of the bucket.
61  *
62  * We used to use some prime number arithmetic to do this, but it
63  * wasn't very random, and had some other bad behaviors.  Instead, we
64  * calculate an actual random permutation of the bucket members.
65  * Since this is expensive, we optimize for the r=0 case, which
66  * captures the vast majority of calls.
67  */
68 static int bucket_perm_choose(struct crush_bucket *bucket,
69 			      int x, int r)
70 {
71 	unsigned pr = r % bucket->size;
72 	unsigned i, s;
73 
74 	/* start a new permutation if @x has changed */
75 	if (bucket->perm_x != x || bucket->perm_n == 0) {
76 		dprintk("bucket %d new x=%d\n", bucket->id, x);
77 		bucket->perm_x = x;
78 
79 		/* optimize common r=0 case */
80 		if (pr == 0) {
81 			s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
82 				bucket->size;
83 			bucket->perm[0] = s;
84 			bucket->perm_n = 0xffff;   /* magic value, see below */
85 			goto out;
86 		}
87 
88 		for (i = 0; i < bucket->size; i++)
89 			bucket->perm[i] = i;
90 		bucket->perm_n = 0;
91 	} else if (bucket->perm_n == 0xffff) {
92 		/* clean up after the r=0 case above */
93 		for (i = 1; i < bucket->size; i++)
94 			bucket->perm[i] = i;
95 		bucket->perm[bucket->perm[0]] = 0;
96 		bucket->perm_n = 1;
97 	}
98 
99 	/* calculate permutation up to pr */
100 	for (i = 0; i < bucket->perm_n; i++)
101 		dprintk(" perm_choose have %d: %d\n", i, bucket->perm[i]);
102 	while (bucket->perm_n <= pr) {
103 		unsigned p = bucket->perm_n;
104 		/* no point in swapping the final entry */
105 		if (p < bucket->size - 1) {
106 			i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
107 				(bucket->size - p);
108 			if (i) {
109 				unsigned t = bucket->perm[p + i];
110 				bucket->perm[p + i] = bucket->perm[p];
111 				bucket->perm[p] = t;
112 			}
113 			dprintk(" perm_choose swap %d with %d\n", p, p+i);
114 		}
115 		bucket->perm_n++;
116 	}
117 	for (i = 0; i < bucket->size; i++)
118 		dprintk(" perm_choose  %d: %d\n", i, bucket->perm[i]);
119 
120 	s = bucket->perm[pr];
121 out:
122 	dprintk(" perm_choose %d sz=%d x=%d r=%d (%d) s=%d\n", bucket->id,
123 		bucket->size, x, r, pr, s);
124 	return bucket->items[s];
125 }
126 
127 /* uniform */
128 static int bucket_uniform_choose(struct crush_bucket_uniform *bucket,
129 				 int x, int r)
130 {
131 	return bucket_perm_choose(&bucket->h, x, r);
132 }
133 
134 /* list */
135 static int bucket_list_choose(struct crush_bucket_list *bucket,
136 			      int x, int r)
137 {
138 	int i;
139 
140 	for (i = bucket->h.size-1; i >= 0; i--) {
141 		__u64 w = crush_hash32_4(bucket->h.hash,x, bucket->h.items[i],
142 					 r, bucket->h.id);
143 		w &= 0xffff;
144 		dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
145 			"sw %x rand %llx",
146 			i, x, r, bucket->h.items[i], bucket->item_weights[i],
147 			bucket->sum_weights[i], w);
148 		w *= bucket->sum_weights[i];
149 		w = w >> 16;
150 		/*dprintk(" scaled %llx\n", w);*/
151 		if (w < bucket->item_weights[i])
152 			return bucket->h.items[i];
153 	}
154 
155 	BUG_ON(1);
156 	return 0;
157 }
158 
159 
160 /* (binary) tree */
161 static int height(int n)
162 {
163 	int h = 0;
164 	while ((n & 1) == 0) {
165 		h++;
166 		n = n >> 1;
167 	}
168 	return h;
169 }
170 
171 static int left(int x)
172 {
173 	int h = height(x);
174 	return x - (1 << (h-1));
175 }
176 
177 static int right(int x)
178 {
179 	int h = height(x);
180 	return x + (1 << (h-1));
181 }
182 
183 static int terminal(int x)
184 {
185 	return x & 1;
186 }
187 
188 static int bucket_tree_choose(struct crush_bucket_tree *bucket,
189 			      int x, int r)
190 {
191 	int n, l;
192 	__u32 w;
193 	__u64 t;
194 
195 	/* start at root */
196 	n = bucket->num_nodes >> 1;
197 
198 	while (!terminal(n)) {
199 		/* pick point in [0, w) */
200 		w = bucket->node_weights[n];
201 		t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
202 					  bucket->h.id) * (__u64)w;
203 		t = t >> 32;
204 
205 		/* descend to the left or right? */
206 		l = left(n);
207 		if (t < bucket->node_weights[l])
208 			n = l;
209 		else
210 			n = right(n);
211 	}
212 
213 	return bucket->h.items[n >> 1];
214 }
215 
216 
217 /* straw */
218 
219 static int bucket_straw_choose(struct crush_bucket_straw *bucket,
220 			       int x, int r)
221 {
222 	int i;
223 	int high = 0;
224 	__u64 high_draw = 0;
225 	__u64 draw;
226 
227 	for (i = 0; i < bucket->h.size; i++) {
228 		draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
229 		draw &= 0xffff;
230 		draw *= bucket->straws[i];
231 		if (i == 0 || draw > high_draw) {
232 			high = i;
233 			high_draw = draw;
234 		}
235 	}
236 	return bucket->h.items[high];
237 }
238 
239 static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
240 {
241 	dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
242 	switch (in->alg) {
243 	case CRUSH_BUCKET_UNIFORM:
244 		return bucket_uniform_choose((struct crush_bucket_uniform *)in,
245 					  x, r);
246 	case CRUSH_BUCKET_LIST:
247 		return bucket_list_choose((struct crush_bucket_list *)in,
248 					  x, r);
249 	case CRUSH_BUCKET_TREE:
250 		return bucket_tree_choose((struct crush_bucket_tree *)in,
251 					  x, r);
252 	case CRUSH_BUCKET_STRAW:
253 		return bucket_straw_choose((struct crush_bucket_straw *)in,
254 					   x, r);
255 	default:
256 		BUG_ON(1);
257 		return in->items[0];
258 	}
259 }
260 
261 /*
262  * true if device is marked "out" (failed, fully offloaded)
263  * of the cluster
264  */
265 static int is_out(struct crush_map *map, __u32 *weight, int item, int x)
266 {
267 	if (weight[item] >= 0x10000)
268 		return 0;
269 	if (weight[item] == 0)
270 		return 1;
271 	if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
272 	    < weight[item])
273 		return 0;
274 	return 1;
275 }
276 
277 /**
278  * crush_choose - choose numrep distinct items of given type
279  * @map: the crush_map
280  * @bucket: the bucket we are choose an item from
281  * @x: crush input value
282  * @numrep: the number of items to choose
283  * @type: the type of item to choose
284  * @out: pointer to output vector
285  * @outpos: our position in that vector
286  * @firstn: true if choosing "first n" items, false if choosing "indep"
287  * @recurse_to_leaf: true if we want one device under each item of given type
288  * @out2: second output vector for leaf items (if @recurse_to_leaf)
289  */
290 static int crush_choose(struct crush_map *map,
291 			struct crush_bucket *bucket,
292 			__u32 *weight,
293 			int x, int numrep, int type,
294 			int *out, int outpos,
295 			int firstn, int recurse_to_leaf,
296 			int *out2)
297 {
298 	int rep;
299 	int ftotal, flocal;
300 	int retry_descent, retry_bucket, skip_rep;
301 	struct crush_bucket *in = bucket;
302 	int r;
303 	int i;
304 	int item = 0;
305 	int itemtype;
306 	int collide, reject;
307 	const int orig_tries = 5; /* attempts before we fall back to search */
308 
309 	dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
310 		bucket->id, x, outpos, numrep);
311 
312 	for (rep = outpos; rep < numrep; rep++) {
313 		/* keep trying until we get a non-out, non-colliding item */
314 		ftotal = 0;
315 		skip_rep = 0;
316 		do {
317 			retry_descent = 0;
318 			in = bucket;               /* initial bucket */
319 
320 			/* choose through intervening buckets */
321 			flocal = 0;
322 			do {
323 				collide = 0;
324 				retry_bucket = 0;
325 				r = rep;
326 				if (in->alg == CRUSH_BUCKET_UNIFORM) {
327 					/* be careful */
328 					if (firstn || numrep >= in->size)
329 						/* r' = r + f_total */
330 						r += ftotal;
331 					else if (in->size % numrep == 0)
332 						/* r'=r+(n+1)*f_local */
333 						r += (numrep+1) *
334 							(flocal+ftotal);
335 					else
336 						/* r' = r + n*f_local */
337 						r += numrep * (flocal+ftotal);
338 				} else {
339 					if (firstn)
340 						/* r' = r + f_total */
341 						r += ftotal;
342 					else
343 						/* r' = r + n*f_local */
344 						r += numrep * (flocal+ftotal);
345 				}
346 
347 				/* bucket choose */
348 				if (in->size == 0) {
349 					reject = 1;
350 					goto reject;
351 				}
352 				if (flocal >= (in->size>>1) &&
353 				    flocal > orig_tries)
354 					item = bucket_perm_choose(in, x, r);
355 				else
356 					item = crush_bucket_choose(in, x, r);
357 				BUG_ON(item >= map->max_devices);
358 
359 				/* desired type? */
360 				if (item < 0)
361 					itemtype = map->buckets[-1-item]->type;
362 				else
363 					itemtype = 0;
364 				dprintk("  item %d type %d\n", item, itemtype);
365 
366 				/* keep going? */
367 				if (itemtype != type) {
368 					BUG_ON(item >= 0 ||
369 					       (-1-item) >= map->max_buckets);
370 					in = map->buckets[-1-item];
371 					retry_bucket = 1;
372 					continue;
373 				}
374 
375 				/* collision? */
376 				for (i = 0; i < outpos; i++) {
377 					if (out[i] == item) {
378 						collide = 1;
379 						break;
380 					}
381 				}
382 
383 				reject = 0;
384 				if (recurse_to_leaf) {
385 					if (item < 0) {
386 						if (crush_choose(map,
387 							 map->buckets[-1-item],
388 							 weight,
389 							 x, outpos+1, 0,
390 							 out2, outpos,
391 							 firstn, 0,
392 							 NULL) <= outpos)
393 							/* didn't get leaf */
394 							reject = 1;
395 					} else {
396 						/* we already have a leaf! */
397 						out2[outpos] = item;
398 					}
399 				}
400 
401 				if (!reject) {
402 					/* out? */
403 					if (itemtype == 0)
404 						reject = is_out(map, weight,
405 								item, x);
406 					else
407 						reject = 0;
408 				}
409 
410 reject:
411 				if (reject || collide) {
412 					ftotal++;
413 					flocal++;
414 
415 					if (collide && flocal < 3)
416 						/* retry locally a few times */
417 						retry_bucket = 1;
418 					else if (flocal < in->size + orig_tries)
419 						/* exhaustive bucket search */
420 						retry_bucket = 1;
421 					else if (ftotal < 20)
422 						/* then retry descent */
423 						retry_descent = 1;
424 					else
425 						/* else give up */
426 						skip_rep = 1;
427 					dprintk("  reject %d  collide %d  "
428 						"ftotal %d  flocal %d\n",
429 						reject, collide, ftotal,
430 						flocal);
431 				}
432 			} while (retry_bucket);
433 		} while (retry_descent);
434 
435 		if (skip_rep) {
436 			dprintk("skip rep\n");
437 			continue;
438 		}
439 
440 		dprintk("CHOOSE got %d\n", item);
441 		out[outpos] = item;
442 		outpos++;
443 	}
444 
445 	dprintk("CHOOSE returns %d\n", outpos);
446 	return outpos;
447 }
448 
449 
450 /**
451  * crush_do_rule - calculate a mapping with the given input and rule
452  * @map: the crush_map
453  * @ruleno: the rule id
454  * @x: hash input
455  * @result: pointer to result vector
456  * @result_max: maximum result size
457  * @force: force initial replica choice; -1 for none
458  */
459 int crush_do_rule(struct crush_map *map,
460 		  int ruleno, int x, int *result, int result_max,
461 		  int force, __u32 *weight)
462 {
463 	int result_len;
464 	int force_context[CRUSH_MAX_DEPTH];
465 	int force_pos = -1;
466 	int a[CRUSH_MAX_SET];
467 	int b[CRUSH_MAX_SET];
468 	int c[CRUSH_MAX_SET];
469 	int recurse_to_leaf;
470 	int *w;
471 	int wsize = 0;
472 	int *o;
473 	int osize;
474 	int *tmp;
475 	struct crush_rule *rule;
476 	int step;
477 	int i, j;
478 	int numrep;
479 	int firstn;
480 	int rc = -1;
481 
482 	BUG_ON(ruleno >= map->max_rules);
483 
484 	rule = map->rules[ruleno];
485 	result_len = 0;
486 	w = a;
487 	o = b;
488 
489 	/*
490 	 * determine hierarchical context of force, if any.  note
491 	 * that this may or may not correspond to the specific types
492 	 * referenced by the crush rule.
493 	 */
494 	if (force >= 0) {
495 		if (force >= map->max_devices ||
496 		    map->device_parents[force] == 0) {
497 			/*dprintk("CRUSH: forcefed device dne\n");*/
498 			rc = -1;  /* force fed device dne */
499 			goto out;
500 		}
501 		if (!is_out(map, weight, force, x)) {
502 			while (1) {
503 				force_context[++force_pos] = force;
504 				if (force >= 0)
505 					force = map->device_parents[force];
506 				else
507 					force = map->bucket_parents[-1-force];
508 				if (force == 0)
509 					break;
510 			}
511 		}
512 	}
513 
514 	for (step = 0; step < rule->len; step++) {
515 		firstn = 0;
516 		switch (rule->steps[step].op) {
517 		case CRUSH_RULE_TAKE:
518 			w[0] = rule->steps[step].arg1;
519 			if (force_pos >= 0) {
520 				BUG_ON(force_context[force_pos] != w[0]);
521 				force_pos--;
522 			}
523 			wsize = 1;
524 			break;
525 
526 		case CRUSH_RULE_CHOOSE_LEAF_FIRSTN:
527 		case CRUSH_RULE_CHOOSE_FIRSTN:
528 			firstn = 1;
529 		case CRUSH_RULE_CHOOSE_LEAF_INDEP:
530 		case CRUSH_RULE_CHOOSE_INDEP:
531 			BUG_ON(wsize == 0);
532 
533 			recurse_to_leaf =
534 				rule->steps[step].op ==
535 				 CRUSH_RULE_CHOOSE_LEAF_FIRSTN ||
536 				rule->steps[step].op ==
537 				CRUSH_RULE_CHOOSE_LEAF_INDEP;
538 
539 			/* reset output */
540 			osize = 0;
541 
542 			for (i = 0; i < wsize; i++) {
543 				/*
544 				 * see CRUSH_N, CRUSH_N_MINUS macros.
545 				 * basically, numrep <= 0 means relative to
546 				 * the provided result_max
547 				 */
548 				numrep = rule->steps[step].arg1;
549 				if (numrep <= 0) {
550 					numrep += result_max;
551 					if (numrep <= 0)
552 						continue;
553 				}
554 				j = 0;
555 				if (osize == 0 && force_pos >= 0) {
556 					/* skip any intermediate types */
557 					while (force_pos &&
558 					       force_context[force_pos] < 0 &&
559 					       rule->steps[step].arg2 !=
560 					       map->buckets[-1 -
561 					       force_context[force_pos]]->type)
562 						force_pos--;
563 					o[osize] = force_context[force_pos];
564 					if (recurse_to_leaf)
565 						c[osize] = force_context[0];
566 					j++;
567 					force_pos--;
568 				}
569 				osize += crush_choose(map,
570 						      map->buckets[-1-w[i]],
571 						      weight,
572 						      x, numrep,
573 						      rule->steps[step].arg2,
574 						      o+osize, j,
575 						      firstn,
576 						      recurse_to_leaf, c+osize);
577 			}
578 
579 			if (recurse_to_leaf)
580 				/* copy final _leaf_ values to output set */
581 				memcpy(o, c, osize*sizeof(*o));
582 
583 			/* swap t and w arrays */
584 			tmp = o;
585 			o = w;
586 			w = tmp;
587 			wsize = osize;
588 			break;
589 
590 
591 		case CRUSH_RULE_EMIT:
592 			for (i = 0; i < wsize && result_len < result_max; i++) {
593 				result[result_len] = w[i];
594 				result_len++;
595 			}
596 			wsize = 0;
597 			break;
598 
599 		default:
600 			BUG_ON(1);
601 		}
602 	}
603 	rc = result_len;
604 
605 out:
606 	return rc;
607 }
608 
609 
610