xref: /openbmc/linux/net/ceph/crush/mapper.c (revision d9d58f04)
1 /*
2  * Ceph - scalable distributed file system
3  *
4  * Copyright (C) 2015 Intel Corporation All Rights Reserved
5  *
6  * This is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License version 2.1, as published by the Free Software
9  * Foundation.  See file COPYING.
10  *
11  */
12 
13 #ifdef __KERNEL__
14 # include <linux/string.h>
15 # include <linux/slab.h>
16 # include <linux/bug.h>
17 # include <linux/kernel.h>
18 # include <linux/crush/crush.h>
19 # include <linux/crush/hash.h>
20 # include <linux/crush/mapper.h>
21 #else
22 # include "crush_compat.h"
23 # include "crush.h"
24 # include "hash.h"
25 # include "mapper.h"
26 #endif
27 #include "crush_ln_table.h"
28 
29 #define dprintk(args...) /* printf(args) */
30 
31 /*
32  * Implement the core CRUSH mapping algorithm.
33  */
34 
35 /**
36  * crush_find_rule - find a crush_rule id for a given ruleset, type, and size.
37  * @map: the crush_map
38  * @ruleset: the storage ruleset id (user defined)
39  * @type: storage ruleset type (user defined)
40  * @size: output set size
41  */
crush_find_rule(const struct crush_map * map,int ruleset,int type,int size)42 int crush_find_rule(const struct crush_map *map, int ruleset, int type, int size)
43 {
44 	__u32 i;
45 
46 	for (i = 0; i < map->max_rules; i++) {
47 		if (map->rules[i] &&
48 		    map->rules[i]->mask.ruleset == ruleset &&
49 		    map->rules[i]->mask.type == type &&
50 		    map->rules[i]->mask.min_size <= size &&
51 		    map->rules[i]->mask.max_size >= size)
52 			return i;
53 	}
54 	return -1;
55 }
56 
57 /*
58  * bucket choose methods
59  *
60  * For each bucket algorithm, we have a "choose" method that, given a
61  * crush input @x and replica position (usually, position in output set) @r,
62  * will produce an item in the bucket.
63  */
64 
65 /*
66  * Choose based on a random permutation of the bucket.
67  *
68  * We used to use some prime number arithmetic to do this, but it
69  * wasn't very random, and had some other bad behaviors.  Instead, we
70  * calculate an actual random permutation of the bucket members.
71  * Since this is expensive, we optimize for the r=0 case, which
72  * captures the vast majority of calls.
73  */
bucket_perm_choose(const struct crush_bucket * bucket,struct crush_work_bucket * work,int x,int r)74 static int bucket_perm_choose(const struct crush_bucket *bucket,
75 			      struct crush_work_bucket *work,
76 			      int x, int r)
77 {
78 	unsigned int pr = r % bucket->size;
79 	unsigned int i, s;
80 
81 	/* start a new permutation if @x has changed */
82 	if (work->perm_x != (__u32)x || work->perm_n == 0) {
83 		dprintk("bucket %d new x=%d\n", bucket->id, x);
84 		work->perm_x = x;
85 
86 		/* optimize common r=0 case */
87 		if (pr == 0) {
88 			s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
89 				bucket->size;
90 			work->perm[0] = s;
91 			work->perm_n = 0xffff;   /* magic value, see below */
92 			goto out;
93 		}
94 
95 		for (i = 0; i < bucket->size; i++)
96 			work->perm[i] = i;
97 		work->perm_n = 0;
98 	} else if (work->perm_n == 0xffff) {
99 		/* clean up after the r=0 case above */
100 		for (i = 1; i < bucket->size; i++)
101 			work->perm[i] = i;
102 		work->perm[work->perm[0]] = 0;
103 		work->perm_n = 1;
104 	}
105 
106 	/* calculate permutation up to pr */
107 	for (i = 0; i < work->perm_n; i++)
108 		dprintk(" perm_choose have %d: %d\n", i, work->perm[i]);
109 	while (work->perm_n <= pr) {
110 		unsigned int p = work->perm_n;
111 		/* no point in swapping the final entry */
112 		if (p < bucket->size - 1) {
113 			i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
114 				(bucket->size - p);
115 			if (i) {
116 				unsigned int t = work->perm[p + i];
117 				work->perm[p + i] = work->perm[p];
118 				work->perm[p] = t;
119 			}
120 			dprintk(" perm_choose swap %d with %d\n", p, p+i);
121 		}
122 		work->perm_n++;
123 	}
124 	for (i = 0; i < bucket->size; i++)
125 		dprintk(" perm_choose  %d: %d\n", i, work->perm[i]);
126 
127 	s = work->perm[pr];
128 out:
129 	dprintk(" perm_choose %d sz=%d x=%d r=%d (%d) s=%d\n", bucket->id,
130 		bucket->size, x, r, pr, s);
131 	return bucket->items[s];
132 }
133 
134 /* uniform */
bucket_uniform_choose(const struct crush_bucket_uniform * bucket,struct crush_work_bucket * work,int x,int r)135 static int bucket_uniform_choose(const struct crush_bucket_uniform *bucket,
136 				 struct crush_work_bucket *work, int x, int r)
137 {
138 	return bucket_perm_choose(&bucket->h, work, x, r);
139 }
140 
141 /* list */
bucket_list_choose(const struct crush_bucket_list * bucket,int x,int r)142 static int bucket_list_choose(const struct crush_bucket_list *bucket,
143 			      int x, int r)
144 {
145 	int i;
146 
147 	for (i = bucket->h.size-1; i >= 0; i--) {
148 		__u64 w = crush_hash32_4(bucket->h.hash, x, bucket->h.items[i],
149 					 r, bucket->h.id);
150 		w &= 0xffff;
151 		dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
152 			"sw %x rand %llx",
153 			i, x, r, bucket->h.items[i], bucket->item_weights[i],
154 			bucket->sum_weights[i], w);
155 		w *= bucket->sum_weights[i];
156 		w = w >> 16;
157 		/*dprintk(" scaled %llx\n", w);*/
158 		if (w < bucket->item_weights[i]) {
159 			return bucket->h.items[i];
160 		}
161 	}
162 
163 	dprintk("bad list sums for bucket %d\n", bucket->h.id);
164 	return bucket->h.items[0];
165 }
166 
167 
168 /* (binary) tree */
height(int n)169 static int height(int n)
170 {
171 	int h = 0;
172 	while ((n & 1) == 0) {
173 		h++;
174 		n = n >> 1;
175 	}
176 	return h;
177 }
178 
left(int x)179 static int left(int x)
180 {
181 	int h = height(x);
182 	return x - (1 << (h-1));
183 }
184 
right(int x)185 static int right(int x)
186 {
187 	int h = height(x);
188 	return x + (1 << (h-1));
189 }
190 
terminal(int x)191 static int terminal(int x)
192 {
193 	return x & 1;
194 }
195 
bucket_tree_choose(const struct crush_bucket_tree * bucket,int x,int r)196 static int bucket_tree_choose(const struct crush_bucket_tree *bucket,
197 			      int x, int r)
198 {
199 	int n;
200 	__u32 w;
201 	__u64 t;
202 
203 	/* start at root */
204 	n = bucket->num_nodes >> 1;
205 
206 	while (!terminal(n)) {
207 		int l;
208 		/* pick point in [0, w) */
209 		w = bucket->node_weights[n];
210 		t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
211 					  bucket->h.id) * (__u64)w;
212 		t = t >> 32;
213 
214 		/* descend to the left or right? */
215 		l = left(n);
216 		if (t < bucket->node_weights[l])
217 			n = l;
218 		else
219 			n = right(n);
220 	}
221 
222 	return bucket->h.items[n >> 1];
223 }
224 
225 
226 /* straw */
227 
bucket_straw_choose(const struct crush_bucket_straw * bucket,int x,int r)228 static int bucket_straw_choose(const struct crush_bucket_straw *bucket,
229 			       int x, int r)
230 {
231 	__u32 i;
232 	int high = 0;
233 	__u64 high_draw = 0;
234 	__u64 draw;
235 
236 	for (i = 0; i < bucket->h.size; i++) {
237 		draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
238 		draw &= 0xffff;
239 		draw *= bucket->straws[i];
240 		if (i == 0 || draw > high_draw) {
241 			high = i;
242 			high_draw = draw;
243 		}
244 	}
245 	return bucket->h.items[high];
246 }
247 
248 /* compute 2^44*log2(input+1) */
crush_ln(unsigned int xin)249 static __u64 crush_ln(unsigned int xin)
250 {
251 	unsigned int x = xin;
252 	int iexpon, index1, index2;
253 	__u64 RH, LH, LL, xl64, result;
254 
255 	x++;
256 
257 	/* normalize input */
258 	iexpon = 15;
259 
260 	/*
261 	 * figure out number of bits we need to shift and
262 	 * do it in one step instead of iteratively
263 	 */
264 	if (!(x & 0x18000)) {
265 		int bits = __builtin_clz(x & 0x1FFFF) - 16;
266 		x <<= bits;
267 		iexpon = 15 - bits;
268 	}
269 
270 	index1 = (x >> 8) << 1;
271 	/* RH ~ 2^56/index1 */
272 	RH = __RH_LH_tbl[index1 - 256];
273 	/* LH ~ 2^48 * log2(index1/256) */
274 	LH = __RH_LH_tbl[index1 + 1 - 256];
275 
276 	/* RH*x ~ 2^48 * (2^15 + xf), xf<2^8 */
277 	xl64 = (__s64)x * RH;
278 	xl64 >>= 48;
279 
280 	result = iexpon;
281 	result <<= (12 + 32);
282 
283 	index2 = xl64 & 0xff;
284 	/* LL ~ 2^48*log2(1.0+index2/2^15) */
285 	LL = __LL_tbl[index2];
286 
287 	LH = LH + LL;
288 
289 	LH >>= (48 - 12 - 32);
290 	result += LH;
291 
292 	return result;
293 }
294 
295 
296 /*
297  * straw2
298  *
299  * for reference, see:
300  *
301  * https://en.wikipedia.org/wiki/Exponential_distribution#Distribution_of_the_minimum_of_exponential_random_variables
302  *
303  */
304 
get_choose_arg_weights(const struct crush_bucket_straw2 * bucket,const struct crush_choose_arg * arg,int position)305 static __u32 *get_choose_arg_weights(const struct crush_bucket_straw2 *bucket,
306 				     const struct crush_choose_arg *arg,
307 				     int position)
308 {
309 	if (!arg || !arg->weight_set)
310 		return bucket->item_weights;
311 
312 	if (position >= arg->weight_set_size)
313 		position = arg->weight_set_size - 1;
314 	return arg->weight_set[position].weights;
315 }
316 
get_choose_arg_ids(const struct crush_bucket_straw2 * bucket,const struct crush_choose_arg * arg)317 static __s32 *get_choose_arg_ids(const struct crush_bucket_straw2 *bucket,
318 				 const struct crush_choose_arg *arg)
319 {
320 	if (!arg || !arg->ids)
321 		return bucket->h.items;
322 
323 	return arg->ids;
324 }
325 
bucket_straw2_choose(const struct crush_bucket_straw2 * bucket,int x,int r,const struct crush_choose_arg * arg,int position)326 static int bucket_straw2_choose(const struct crush_bucket_straw2 *bucket,
327 				int x, int r,
328 				const struct crush_choose_arg *arg,
329 				int position)
330 {
331 	unsigned int i, high = 0;
332 	unsigned int u;
333 	__s64 ln, draw, high_draw = 0;
334 	__u32 *weights = get_choose_arg_weights(bucket, arg, position);
335 	__s32 *ids = get_choose_arg_ids(bucket, arg);
336 
337 	for (i = 0; i < bucket->h.size; i++) {
338 		dprintk("weight 0x%x item %d\n", weights[i], ids[i]);
339 		if (weights[i]) {
340 			u = crush_hash32_3(bucket->h.hash, x, ids[i], r);
341 			u &= 0xffff;
342 
343 			/*
344 			 * for some reason slightly less than 0x10000 produces
345 			 * a slightly more accurate distribution... probably a
346 			 * rounding effect.
347 			 *
348 			 * the natural log lookup table maps [0,0xffff]
349 			 * (corresponding to real numbers [1/0x10000, 1] to
350 			 * [0, 0xffffffffffff] (corresponding to real numbers
351 			 * [-11.090355,0]).
352 			 */
353 			ln = crush_ln(u) - 0x1000000000000ll;
354 
355 			/*
356 			 * divide by 16.16 fixed-point weight.  note
357 			 * that the ln value is negative, so a larger
358 			 * weight means a larger (less negative) value
359 			 * for draw.
360 			 */
361 			draw = div64_s64(ln, weights[i]);
362 		} else {
363 			draw = S64_MIN;
364 		}
365 
366 		if (i == 0 || draw > high_draw) {
367 			high = i;
368 			high_draw = draw;
369 		}
370 	}
371 
372 	return bucket->h.items[high];
373 }
374 
375 
crush_bucket_choose(const struct crush_bucket * in,struct crush_work_bucket * work,int x,int r,const struct crush_choose_arg * arg,int position)376 static int crush_bucket_choose(const struct crush_bucket *in,
377 			       struct crush_work_bucket *work,
378 			       int x, int r,
379 			       const struct crush_choose_arg *arg,
380 			       int position)
381 {
382 	dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
383 	BUG_ON(in->size == 0);
384 	switch (in->alg) {
385 	case CRUSH_BUCKET_UNIFORM:
386 		return bucket_uniform_choose(
387 			(const struct crush_bucket_uniform *)in,
388 			work, x, r);
389 	case CRUSH_BUCKET_LIST:
390 		return bucket_list_choose((const struct crush_bucket_list *)in,
391 					  x, r);
392 	case CRUSH_BUCKET_TREE:
393 		return bucket_tree_choose((const struct crush_bucket_tree *)in,
394 					  x, r);
395 	case CRUSH_BUCKET_STRAW:
396 		return bucket_straw_choose(
397 			(const struct crush_bucket_straw *)in,
398 			x, r);
399 	case CRUSH_BUCKET_STRAW2:
400 		return bucket_straw2_choose(
401 			(const struct crush_bucket_straw2 *)in,
402 			x, r, arg, position);
403 	default:
404 		dprintk("unknown bucket %d alg %d\n", in->id, in->alg);
405 		return in->items[0];
406 	}
407 }
408 
409 /*
410  * true if device is marked "out" (failed, fully offloaded)
411  * of the cluster
412  */
is_out(const struct crush_map * map,const __u32 * weight,int weight_max,int item,int x)413 static int is_out(const struct crush_map *map,
414 		  const __u32 *weight, int weight_max,
415 		  int item, int x)
416 {
417 	if (item >= weight_max)
418 		return 1;
419 	if (weight[item] >= 0x10000)
420 		return 0;
421 	if (weight[item] == 0)
422 		return 1;
423 	if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
424 	    < weight[item])
425 		return 0;
426 	return 1;
427 }
428 
429 /**
430  * crush_choose_firstn - choose numrep distinct items of given type
431  * @map: the crush_map
432  * @bucket: the bucket we are choose an item from
433  * @x: crush input value
434  * @numrep: the number of items to choose
435  * @type: the type of item to choose
436  * @out: pointer to output vector
437  * @outpos: our position in that vector
438  * @out_size: size of the out vector
439  * @tries: number of attempts to make
440  * @recurse_tries: number of attempts to have recursive chooseleaf make
441  * @local_retries: localized retries
442  * @local_fallback_retries: localized fallback retries
443  * @recurse_to_leaf: true if we want one device under each item of given type (chooseleaf instead of choose)
444  * @stable: stable mode starts rep=0 in the recursive call for all replicas
445  * @vary_r: pass r to recursive calls
446  * @out2: second output vector for leaf items (if @recurse_to_leaf)
447  * @parent_r: r value passed from the parent
448  */
crush_choose_firstn(const struct crush_map * map,struct crush_work * work,const 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,const struct crush_choose_arg * choose_args)449 static int crush_choose_firstn(const struct crush_map *map,
450 			       struct crush_work *work,
451 			       const struct crush_bucket *bucket,
452 			       const __u32 *weight, int weight_max,
453 			       int x, int numrep, int type,
454 			       int *out, int outpos,
455 			       int out_size,
456 			       unsigned int tries,
457 			       unsigned int recurse_tries,
458 			       unsigned int local_retries,
459 			       unsigned int local_fallback_retries,
460 			       int recurse_to_leaf,
461 			       unsigned int vary_r,
462 			       unsigned int stable,
463 			       int *out2,
464 			       int parent_r,
465 			       const struct crush_choose_arg *choose_args)
466 {
467 	int rep;
468 	unsigned int ftotal, flocal;
469 	int retry_descent, retry_bucket, skip_rep;
470 	const struct crush_bucket *in = bucket;
471 	int r;
472 	int i;
473 	int item = 0;
474 	int itemtype;
475 	int collide, reject;
476 	int count = out_size;
477 
478 	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",
479 		recurse_to_leaf ? "_LEAF" : "",
480 		bucket->id, x, outpos, numrep,
481 		tries, recurse_tries, local_retries, local_fallback_retries,
482 		parent_r, stable);
483 
484 	for (rep = stable ? 0 : outpos; rep < numrep && count > 0 ; rep++) {
485 		/* keep trying until we get a non-out, non-colliding item */
486 		ftotal = 0;
487 		skip_rep = 0;
488 		do {
489 			retry_descent = 0;
490 			in = bucket;               /* initial bucket */
491 
492 			/* choose through intervening buckets */
493 			flocal = 0;
494 			do {
495 				collide = 0;
496 				retry_bucket = 0;
497 				r = rep + parent_r;
498 				/* r' = r + f_total */
499 				r += ftotal;
500 
501 				/* bucket choose */
502 				if (in->size == 0) {
503 					reject = 1;
504 					goto reject;
505 				}
506 				if (local_fallback_retries > 0 &&
507 				    flocal >= (in->size>>1) &&
508 				    flocal > local_fallback_retries)
509 					item = bucket_perm_choose(
510 						in, work->work[-1-in->id],
511 						x, r);
512 				else
513 					item = crush_bucket_choose(
514 						in, work->work[-1-in->id],
515 						x, r,
516 						(choose_args ?
517 						 &choose_args[-1-in->id] : NULL),
518 						outpos);
519 				if (item >= map->max_devices) {
520 					dprintk("   bad item %d\n", item);
521 					skip_rep = 1;
522 					break;
523 				}
524 
525 				/* desired type? */
526 				if (item < 0)
527 					itemtype = map->buckets[-1-item]->type;
528 				else
529 					itemtype = 0;
530 				dprintk("  item %d type %d\n", item, itemtype);
531 
532 				/* keep going? */
533 				if (itemtype != type) {
534 					if (item >= 0 ||
535 					    (-1-item) >= map->max_buckets) {
536 						dprintk("   bad item type %d\n", type);
537 						skip_rep = 1;
538 						break;
539 					}
540 					in = map->buckets[-1-item];
541 					retry_bucket = 1;
542 					continue;
543 				}
544 
545 				/* collision? */
546 				for (i = 0; i < outpos; i++) {
547 					if (out[i] == item) {
548 						collide = 1;
549 						break;
550 					}
551 				}
552 
553 				reject = 0;
554 				if (!collide && recurse_to_leaf) {
555 					if (item < 0) {
556 						int sub_r;
557 						if (vary_r)
558 							sub_r = r >> (vary_r-1);
559 						else
560 							sub_r = 0;
561 						if (crush_choose_firstn(
562 							    map,
563 							    work,
564 							    map->buckets[-1-item],
565 							    weight, weight_max,
566 							    x, stable ? 1 : outpos+1, 0,
567 							    out2, outpos, count,
568 							    recurse_tries, 0,
569 							    local_retries,
570 							    local_fallback_retries,
571 							    0,
572 							    vary_r,
573 							    stable,
574 							    NULL,
575 							    sub_r,
576 							    choose_args) <= outpos)
577 							/* didn't get leaf */
578 							reject = 1;
579 					} else {
580 						/* we already have a leaf! */
581 						out2[outpos] = item;
582 					}
583 				}
584 
585 				if (!reject && !collide) {
586 					/* out? */
587 					if (itemtype == 0)
588 						reject = is_out(map, weight,
589 								weight_max,
590 								item, x);
591 				}
592 
593 reject:
594 				if (reject || collide) {
595 					ftotal++;
596 					flocal++;
597 
598 					if (collide && flocal <= local_retries)
599 						/* retry locally a few times */
600 						retry_bucket = 1;
601 					else if (local_fallback_retries > 0 &&
602 						 flocal <= in->size + local_fallback_retries)
603 						/* exhaustive bucket search */
604 						retry_bucket = 1;
605 					else if (ftotal < tries)
606 						/* then retry descent */
607 						retry_descent = 1;
608 					else
609 						/* else give up */
610 						skip_rep = 1;
611 					dprintk("  reject %d  collide %d  "
612 						"ftotal %u  flocal %u\n",
613 						reject, collide, ftotal,
614 						flocal);
615 				}
616 			} while (retry_bucket);
617 		} while (retry_descent);
618 
619 		if (skip_rep) {
620 			dprintk("skip rep\n");
621 			continue;
622 		}
623 
624 		dprintk("CHOOSE got %d\n", item);
625 		out[outpos] = item;
626 		outpos++;
627 		count--;
628 #ifndef __KERNEL__
629 		if (map->choose_tries && ftotal <= map->choose_total_tries)
630 			map->choose_tries[ftotal]++;
631 #endif
632 	}
633 
634 	dprintk("CHOOSE returns %d\n", outpos);
635 	return outpos;
636 }
637 
638 
639 /**
640  * crush_choose_indep: alternative breadth-first positionally stable mapping
641  *
642  */
crush_choose_indep(const struct crush_map * map,struct crush_work * work,const 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,const struct crush_choose_arg * choose_args)643 static void crush_choose_indep(const struct crush_map *map,
644 			       struct crush_work *work,
645 			       const struct crush_bucket *bucket,
646 			       const __u32 *weight, int weight_max,
647 			       int x, int left, int numrep, int type,
648 			       int *out, int outpos,
649 			       unsigned int tries,
650 			       unsigned int recurse_tries,
651 			       int recurse_to_leaf,
652 			       int *out2,
653 			       int parent_r,
654 			       const struct crush_choose_arg *choose_args)
655 {
656 	const struct crush_bucket *in = bucket;
657 	int endpos = outpos + left;
658 	int rep;
659 	unsigned int ftotal;
660 	int r;
661 	int i;
662 	int item = 0;
663 	int itemtype;
664 	int collide;
665 
666 	dprintk("CHOOSE%s INDEP bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
667 		bucket->id, x, outpos, numrep);
668 
669 	/* initially my result is undefined */
670 	for (rep = outpos; rep < endpos; rep++) {
671 		out[rep] = CRUSH_ITEM_UNDEF;
672 		if (out2)
673 			out2[rep] = CRUSH_ITEM_UNDEF;
674 	}
675 
676 	for (ftotal = 0; left > 0 && ftotal < tries; ftotal++) {
677 #ifdef DEBUG_INDEP
678 		if (out2 && ftotal) {
679 			dprintk("%u %d a: ", ftotal, left);
680 			for (rep = outpos; rep < endpos; rep++) {
681 				dprintk(" %d", out[rep]);
682 			}
683 			dprintk("\n");
684 			dprintk("%u %d b: ", ftotal, left);
685 			for (rep = outpos; rep < endpos; rep++) {
686 				dprintk(" %d", out2[rep]);
687 			}
688 			dprintk("\n");
689 		}
690 #endif
691 		for (rep = outpos; rep < endpos; rep++) {
692 			if (out[rep] != CRUSH_ITEM_UNDEF)
693 				continue;
694 
695 			in = bucket;  /* initial bucket */
696 
697 			/* choose through intervening buckets */
698 			for (;;) {
699 				/* note: we base the choice on the position
700 				 * even in the nested call.  that means that
701 				 * if the first layer chooses the same bucket
702 				 * in a different position, we will tend to
703 				 * choose a different item in that bucket.
704 				 * this will involve more devices in data
705 				 * movement and tend to distribute the load.
706 				 */
707 				r = rep + parent_r;
708 
709 				/* be careful */
710 				if (in->alg == CRUSH_BUCKET_UNIFORM &&
711 				    in->size % numrep == 0)
712 					/* r'=r+(n+1)*f_total */
713 					r += (numrep+1) * ftotal;
714 				else
715 					/* r' = r + n*f_total */
716 					r += numrep * ftotal;
717 
718 				/* bucket choose */
719 				if (in->size == 0) {
720 					dprintk("   empty bucket\n");
721 					break;
722 				}
723 
724 				item = crush_bucket_choose(
725 					in, work->work[-1-in->id],
726 					x, r,
727 					(choose_args ?
728 					 &choose_args[-1-in->id] : NULL),
729 					outpos);
730 				if (item >= map->max_devices) {
731 					dprintk("   bad item %d\n", item);
732 					out[rep] = CRUSH_ITEM_NONE;
733 					if (out2)
734 						out2[rep] = CRUSH_ITEM_NONE;
735 					left--;
736 					break;
737 				}
738 
739 				/* desired type? */
740 				if (item < 0)
741 					itemtype = map->buckets[-1-item]->type;
742 				else
743 					itemtype = 0;
744 				dprintk("  item %d type %d\n", item, itemtype);
745 
746 				/* keep going? */
747 				if (itemtype != type) {
748 					if (item >= 0 ||
749 					    (-1-item) >= map->max_buckets) {
750 						dprintk("   bad item type %d\n", type);
751 						out[rep] = CRUSH_ITEM_NONE;
752 						if (out2)
753 							out2[rep] =
754 								CRUSH_ITEM_NONE;
755 						left--;
756 						break;
757 					}
758 					in = map->buckets[-1-item];
759 					continue;
760 				}
761 
762 				/* collision? */
763 				collide = 0;
764 				for (i = outpos; i < endpos; i++) {
765 					if (out[i] == item) {
766 						collide = 1;
767 						break;
768 					}
769 				}
770 				if (collide)
771 					break;
772 
773 				if (recurse_to_leaf) {
774 					if (item < 0) {
775 						crush_choose_indep(
776 							map,
777 							work,
778 							map->buckets[-1-item],
779 							weight, weight_max,
780 							x, 1, numrep, 0,
781 							out2, rep,
782 							recurse_tries, 0,
783 							0, NULL, r,
784 							choose_args);
785 						if (out2[rep] == CRUSH_ITEM_NONE) {
786 							/* placed nothing; no leaf */
787 							break;
788 						}
789 					} else {
790 						/* we already have a leaf! */
791 						out2[rep] = item;
792 					}
793 				}
794 
795 				/* out? */
796 				if (itemtype == 0 &&
797 				    is_out(map, weight, weight_max, item, x))
798 					break;
799 
800 				/* yay! */
801 				out[rep] = item;
802 				left--;
803 				break;
804 			}
805 		}
806 	}
807 	for (rep = outpos; rep < endpos; rep++) {
808 		if (out[rep] == CRUSH_ITEM_UNDEF) {
809 			out[rep] = CRUSH_ITEM_NONE;
810 		}
811 		if (out2 && out2[rep] == CRUSH_ITEM_UNDEF) {
812 			out2[rep] = CRUSH_ITEM_NONE;
813 		}
814 	}
815 #ifndef __KERNEL__
816 	if (map->choose_tries && ftotal <= map->choose_total_tries)
817 		map->choose_tries[ftotal]++;
818 #endif
819 #ifdef DEBUG_INDEP
820 	if (out2) {
821 		dprintk("%u %d a: ", ftotal, left);
822 		for (rep = outpos; rep < endpos; rep++) {
823 			dprintk(" %d", out[rep]);
824 		}
825 		dprintk("\n");
826 		dprintk("%u %d b: ", ftotal, left);
827 		for (rep = outpos; rep < endpos; rep++) {
828 			dprintk(" %d", out2[rep]);
829 		}
830 		dprintk("\n");
831 	}
832 #endif
833 }
834 
835 
836 /*
837  * This takes a chunk of memory and sets it up to be a shiny new
838  * working area for a CRUSH placement computation. It must be called
839  * on any newly allocated memory before passing it in to
840  * crush_do_rule. It may be used repeatedly after that, so long as the
841  * map has not changed. If the map /has/ changed, you must make sure
842  * the working size is no smaller than what was allocated and re-run
843  * crush_init_workspace.
844  *
845  * If you do retain the working space between calls to crush, make it
846  * thread-local.
847  */
crush_init_workspace(const struct crush_map * map,void * v)848 void crush_init_workspace(const struct crush_map *map, void *v)
849 {
850 	struct crush_work *w = v;
851 	__s32 b;
852 
853 	/*
854 	 * We work by moving through the available space and setting
855 	 * values and pointers as we go.
856 	 *
857 	 * It's a bit like Forth's use of the 'allot' word since we
858 	 * set the pointer first and then reserve the space for it to
859 	 * point to by incrementing the point.
860 	 */
861 	v += sizeof(struct crush_work);
862 	w->work = v;
863 	v += map->max_buckets * sizeof(struct crush_work_bucket *);
864 	for (b = 0; b < map->max_buckets; ++b) {
865 		if (!map->buckets[b])
866 			continue;
867 
868 		w->work[b] = v;
869 		switch (map->buckets[b]->alg) {
870 		default:
871 			v += sizeof(struct crush_work_bucket);
872 			break;
873 		}
874 		w->work[b]->perm_x = 0;
875 		w->work[b]->perm_n = 0;
876 		w->work[b]->perm = v;
877 		v += map->buckets[b]->size * sizeof(__u32);
878 	}
879 	BUG_ON(v - (void *)w != map->working_size);
880 }
881 
882 /**
883  * crush_do_rule - calculate a mapping with the given input and rule
884  * @map: the crush_map
885  * @ruleno: the rule id
886  * @x: hash input
887  * @result: pointer to result vector
888  * @result_max: maximum result size
889  * @weight: weight vector (for map leaves)
890  * @weight_max: size of weight vector
891  * @cwin: pointer to at least crush_work_size() bytes of memory
892  * @choose_args: weights and ids for each known bucket
893  */
crush_do_rule(const struct crush_map * map,int ruleno,int x,int * result,int result_max,const __u32 * weight,int weight_max,void * cwin,const struct crush_choose_arg * choose_args)894 int crush_do_rule(const struct crush_map *map,
895 		  int ruleno, int x, int *result, int result_max,
896 		  const __u32 *weight, int weight_max,
897 		  void *cwin, const struct crush_choose_arg *choose_args)
898 {
899 	int result_len;
900 	struct crush_work *cw = cwin;
901 	int *a = cwin + map->working_size;
902 	int *b = a + result_max;
903 	int *c = b + result_max;
904 	int *w = a;
905 	int *o = b;
906 	int recurse_to_leaf;
907 	int wsize = 0;
908 	int osize;
909 	const struct crush_rule *rule;
910 	__u32 step;
911 	int i, j;
912 	int numrep;
913 	int out_size;
914 	/*
915 	 * the original choose_total_tries value was off by one (it
916 	 * counted "retries" and not "tries").  add one.
917 	 */
918 	int choose_tries = map->choose_total_tries + 1;
919 	int choose_leaf_tries = 0;
920 	/*
921 	 * the local tries values were counted as "retries", though,
922 	 * and need no adjustment
923 	 */
924 	int choose_local_retries = map->choose_local_tries;
925 	int choose_local_fallback_retries = map->choose_local_fallback_tries;
926 
927 	int vary_r = map->chooseleaf_vary_r;
928 	int stable = map->chooseleaf_stable;
929 
930 	if ((__u32)ruleno >= map->max_rules) {
931 		dprintk(" bad ruleno %d\n", ruleno);
932 		return 0;
933 	}
934 
935 	rule = map->rules[ruleno];
936 	result_len = 0;
937 
938 	for (step = 0; step < rule->len; step++) {
939 		int firstn = 0;
940 		const struct crush_rule_step *curstep = &rule->steps[step];
941 
942 		switch (curstep->op) {
943 		case CRUSH_RULE_TAKE:
944 			if ((curstep->arg1 >= 0 &&
945 			     curstep->arg1 < map->max_devices) ||
946 			    (-1-curstep->arg1 >= 0 &&
947 			     -1-curstep->arg1 < map->max_buckets &&
948 			     map->buckets[-1-curstep->arg1])) {
949 				w[0] = curstep->arg1;
950 				wsize = 1;
951 			} else {
952 				dprintk(" bad take value %d\n", curstep->arg1);
953 			}
954 			break;
955 
956 		case CRUSH_RULE_SET_CHOOSE_TRIES:
957 			if (curstep->arg1 > 0)
958 				choose_tries = curstep->arg1;
959 			break;
960 
961 		case CRUSH_RULE_SET_CHOOSELEAF_TRIES:
962 			if (curstep->arg1 > 0)
963 				choose_leaf_tries = curstep->arg1;
964 			break;
965 
966 		case CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES:
967 			if (curstep->arg1 >= 0)
968 				choose_local_retries = curstep->arg1;
969 			break;
970 
971 		case CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES:
972 			if (curstep->arg1 >= 0)
973 				choose_local_fallback_retries = curstep->arg1;
974 			break;
975 
976 		case CRUSH_RULE_SET_CHOOSELEAF_VARY_R:
977 			if (curstep->arg1 >= 0)
978 				vary_r = curstep->arg1;
979 			break;
980 
981 		case CRUSH_RULE_SET_CHOOSELEAF_STABLE:
982 			if (curstep->arg1 >= 0)
983 				stable = curstep->arg1;
984 			break;
985 
986 		case CRUSH_RULE_CHOOSELEAF_FIRSTN:
987 		case CRUSH_RULE_CHOOSE_FIRSTN:
988 			firstn = 1;
989 			fallthrough;
990 		case CRUSH_RULE_CHOOSELEAF_INDEP:
991 		case CRUSH_RULE_CHOOSE_INDEP:
992 			if (wsize == 0)
993 				break;
994 
995 			recurse_to_leaf =
996 				curstep->op ==
997 				 CRUSH_RULE_CHOOSELEAF_FIRSTN ||
998 				curstep->op ==
999 				CRUSH_RULE_CHOOSELEAF_INDEP;
1000 
1001 			/* reset output */
1002 			osize = 0;
1003 
1004 			for (i = 0; i < wsize; i++) {
1005 				int bno;
1006 				numrep = curstep->arg1;
1007 				if (numrep <= 0) {
1008 					numrep += result_max;
1009 					if (numrep <= 0)
1010 						continue;
1011 				}
1012 				j = 0;
1013 				/* make sure bucket id is valid */
1014 				bno = -1 - w[i];
1015 				if (bno < 0 || bno >= map->max_buckets) {
1016 					/* w[i] is probably CRUSH_ITEM_NONE */
1017 					dprintk("  bad w[i] %d\n", w[i]);
1018 					continue;
1019 				}
1020 				if (firstn) {
1021 					int recurse_tries;
1022 					if (choose_leaf_tries)
1023 						recurse_tries =
1024 							choose_leaf_tries;
1025 					else if (map->chooseleaf_descend_once)
1026 						recurse_tries = 1;
1027 					else
1028 						recurse_tries = choose_tries;
1029 					osize += crush_choose_firstn(
1030 						map,
1031 						cw,
1032 						map->buckets[bno],
1033 						weight, weight_max,
1034 						x, numrep,
1035 						curstep->arg2,
1036 						o+osize, j,
1037 						result_max-osize,
1038 						choose_tries,
1039 						recurse_tries,
1040 						choose_local_retries,
1041 						choose_local_fallback_retries,
1042 						recurse_to_leaf,
1043 						vary_r,
1044 						stable,
1045 						c+osize,
1046 						0,
1047 						choose_args);
1048 				} else {
1049 					out_size = ((numrep < (result_max-osize)) ?
1050 						    numrep : (result_max-osize));
1051 					crush_choose_indep(
1052 						map,
1053 						cw,
1054 						map->buckets[bno],
1055 						weight, weight_max,
1056 						x, out_size, numrep,
1057 						curstep->arg2,
1058 						o+osize, j,
1059 						choose_tries,
1060 						choose_leaf_tries ?
1061 						   choose_leaf_tries : 1,
1062 						recurse_to_leaf,
1063 						c+osize,
1064 						0,
1065 						choose_args);
1066 					osize += out_size;
1067 				}
1068 			}
1069 
1070 			if (recurse_to_leaf)
1071 				/* copy final _leaf_ values to output set */
1072 				memcpy(o, c, osize*sizeof(*o));
1073 
1074 			/* swap o and w arrays */
1075 			swap(o, w);
1076 			wsize = osize;
1077 			break;
1078 
1079 
1080 		case CRUSH_RULE_EMIT:
1081 			for (i = 0; i < wsize && result_len < result_max; i++) {
1082 				result[result_len] = w[i];
1083 				result_len++;
1084 			}
1085 			wsize = 0;
1086 			break;
1087 
1088 		default:
1089 			dprintk(" unknown op %d at step %d\n",
1090 				curstep->op, step);
1091 			break;
1092 		}
1093 	}
1094 
1095 	return result_len;
1096 }
1097