net/ceph/crush/mapper.c

   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 #else
  21 # include "crush_compat.h"
  22 # include "crush.h"
  23 # include "hash.h"
  24 #endif
  25 #include "crush_ln_table.h"
  26
  27 #define dprintk(args...) /* printf(args) */
  28
  29 /*
  30  * Implement the core CRUSH mapping algorithm.
  31  */
  32
  33 /**
  34  * crush_find_rule - find a crush_rule id for a given ruleset, type, and size.
  35  * @map: the crush_map
  36  * @ruleset: the storage ruleset id (user defined)
  37  * @type: storage ruleset type (user defined)
  38  * @size: output set size
  39  */
  40 int crush_find_rule(const struct crush_map *map, int ruleset, int type, int size)
  41 {
  42         __u32 i;
  43
  44         for (i = 0; i < map->max_rules; i++) {
  45                 if (map->rules[i] &&
  46                     map->rules[i]->mask.ruleset == ruleset &&
  47                     map->rules[i]->mask.type == type &&
  48                     map->rules[i]->mask.min_size <= size &&
  49                     map->rules[i]->mask.max_size >= size)
  50                         return i;
  51         }
  52         return -1;
  53 }
  54
  55
  56 /*
  57  * bucket choose methods
  58  *
  59  * For each bucket algorithm, we have a "choose" method that, given a
  60  * crush input @x and replica position (usually, position in output set) @r,
  61  * will produce an item in the bucket.
  62  */
  63
  64 /*
  65  * Choose based on a random permutation of the bucket.
  66  *
  67  * We used to use some prime number arithmetic to do this, but it
  68  * wasn't very random, and had some other bad behaviors.  Instead, we
  69  * calculate an actual random permutation of the bucket members.
  70  * Since this is expensive, we optimize for the r=0 case, which
  71  * captures the vast majority of calls.
  72  */
  73 static int bucket_perm_choose(struct crush_bucket *bucket,
  74                               int x, int r)
  75 {
  76         unsigned int pr = r % bucket->size;
  77         unsigned int i, s;
  78
  79         /* start a new permutation if @x has changed */
  80         if (bucket->perm_x != (__u32)x || bucket->perm_n == 0) {
  81                 dprintk("bucket %d new x=%d\n", bucket->id, x);
  82                 bucket->perm_x = x;
  83
  84                 /* optimize common r=0 case */
  85                 if (pr == 0) {
  86                         s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
  87                                 bucket->size;
  88                         bucket->perm[0] = s;
  89                         bucket->perm_n = 0xffff;   /* magic value, see below */
  90                         goto out;
  91                 }
  92
  93                 for (i = 0; i < bucket->size; i++)
  94                         bucket->perm[i] = i;
  95                 bucket->perm_n = 0;
  96         } else if (bucket->perm_n == 0xffff) {
  97                 /* clean up after the r=0 case above */
  98                 for (i = 1; i < bucket->size; i++)
  99                         bucket->perm[i] = i;
 100                 bucket->perm[bucket->perm[0]] = 0;
 101                 bucket->perm_n = 1;
 102         }
 103
 104         /* calculate permutation up to pr */
 105         for (i = 0; i < bucket->perm_n; i++)
 106                 dprintk(" perm_choose have %d: %d\n", i, bucket->perm[i]);
 107         while (bucket->perm_n <= pr) {
 108                 unsigned int p = bucket->perm_n;
 109                 /* no point in swapping the final entry */
 110                 if (p < bucket->size - 1) {
 111                         i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
 112                                 (bucket->size - p);
 113                         if (i) {
 114                                 unsigned int t = bucket->perm[p + i];
 115                                 bucket->perm[p + i] = bucket->perm[p];
 116                                 bucket->perm[p] = t;
 117                         }
 118                         dprintk(" perm_choose swap %d with %d\n", p, p+i);
 119                 }
 120                 bucket->perm_n++;
 121         }
 122         for (i = 0; i < bucket->size; i++)
 123                 dprintk(" perm_choose  %d: %d\n", i, bucket->perm[i]);
 124
 125         s = bucket->perm[pr];
 126 out:
 127         dprintk(" perm_choose %d sz=%d x=%d r=%d (%d) s=%d\n", bucket->id,
 128                 bucket->size, x, r, pr, s);
 129         return bucket->items[s];
 130 }
 131
 132 /* uniform */
 133 static int bucket_uniform_choose(struct crush_bucket_uniform *bucket,
 134                                  int x, int r)
 135 {
 136         return bucket_perm_choose(&bucket->h, x, r);
 137 }
 138
 139 /* list */
 140 static int bucket_list_choose(struct crush_bucket_list *bucket,
 141                               int x, int r)
 142 {
 143         int i;
 144
 145         for (i = bucket->h.size-1; i >= 0; i--) {
 146                 __u64 w = crush_hash32_4(bucket->h.hash, x, bucket->h.items[i],
 147                                          r, bucket->h.id);
 148                 w &= 0xffff;
 149                 dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
 150                         "sw %x rand %llx",
 151                         i, x, r, bucket->h.items[i], bucket->item_weights[i],
 152                         bucket->sum_weights[i], w);
 153                 w *= bucket->sum_weights[i];
 154                 w = w >> 16;
 155                 /*dprintk(" scaled %llx\n", w);*/
 156                 if (w < bucket->item_weights[i])
 157                         return bucket->h.items[i];
 158         }
 159
 160         dprintk("bad list sums for bucket %d\n", bucket->h.id);
 161         return bucket->h.items[0];
 162 }
 163
 164
 165 /* (binary) tree */
 166 static int height(int n)
 167 {
 168         int h = 0;
 169         while ((n & 1) == 0) {
 170                 h++;
 171                 n = n >> 1;
 172         }
 173         return h;
 174 }
 175
 176 static int left(int x)
 177 {
 178         int h = height(x);
 179         return x - (1 << (h-1));
 180 }
 181
 182 static int right(int x)
 183 {
 184         int h = height(x);
 185         return x + (1 << (h-1));
 186 }
 187
 188 static int terminal(int x)
 189 {
 190         return x & 1;
 191 }
 192
 193 static int bucket_tree_choose(struct crush_bucket_tree *bucket,
 194                               int x, int r)
 195 {
 196         int n;
 197         __u32 w;
 198         __u64 t;
 199
 200         /* start at root */
 201         n = bucket->num_nodes >> 1;
 202
 203         while (!terminal(n)) {
 204                 int l;
 205                 /* pick point in [0, w) */
 206                 w = bucket->node_weights[n];
 207                 t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
 208                                           bucket->h.id) * (__u64)w;
 209                 t = t >> 32;
 210
 211                 /* descend to the left or right? */
 212                 l = left(n);
 213                 if (t < bucket->node_weights[l])
 214                         n = l;
 215                 else
 216                         n = right(n);
 217         }
 218
 219         return bucket->h.items[n >> 1];
 220 }
 221
 222
 223 /* straw */
 224
 225 static int bucket_straw_choose(struct crush_bucket_straw *bucket,
 226                                int x, int r)
 227 {
 228         __u32 i;
 229         int high = 0;
 230         __u64 high_draw = 0;
 231         __u64 draw;
 232
 233         for (i = 0; i < bucket->h.size; i++) {
 234                 draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
 235                 draw &= 0xffff;
 236                 draw *= bucket->straws[i];
 237                 if (i == 0 || draw > high_draw) {
 238                         high = i;
 239                         high_draw = draw;
 240                 }
 241         }
 242         return bucket->h.items[high];
 243 }
 244
 245 /* compute 2^44*log2(input+1) */
 246 static __u64 crush_ln(unsigned int xin)
 247 {
 248         unsigned int x = xin, x1;
 249         int iexpon, index1, index2;
 250         __u64 RH, LH, LL, xl64, result;
 251
 252         x++;
 253
 254         /* normalize input */
 255         iexpon = 15;
 256         while (!(x & 0x18000)) {
 257                 x <<= 1;
 258                 iexpon--;
 259         }
 260
 261         index1 = (x >> 8) << 1;
 262         /* RH ~ 2^56/index1 */
 263         RH = __RH_LH_tbl[index1 - 256];
 264         /* LH ~ 2^48 * log2(index1/256) */
 265         LH = __RH_LH_tbl[index1 + 1 - 256];
 266
 267         /* RH*x ~ 2^48 * (2^15 + xf), xf<2^8 */
 268         xl64 = (__s64)x * RH;
 269         xl64 >>= 48;
 270         x1 = xl64;
 271
 272         result = iexpon;
 273         result <<= (12 + 32);
 274
 275         index2 = x1 & 0xff;
 276         /* LL ~ 2^48*log2(1.0+index2/2^15) */
 277         LL = __LL_tbl[index2];
 278
 279         LH = LH + LL;
 280
 281         LH >>= (48 - 12 - 32);
 282         result += LH;
 283
 284         return result;
 285 }
 286
 287
 288 /*
 289  * straw2
 290  *
 291  * for reference, see:
 292  *
 293  * http://en.wikipedia.org/wiki/Exponential_distribution#Distribution_of_the_minimum_of_exponential_random_variables
 294  *
 295  */
 296
 297 static int bucket_straw2_choose(struct crush_bucket_straw2 *bucket,
 298                                 int x, int r)
 299 {
 300         unsigned int i, high = 0;
 301         unsigned int u;
 302         unsigned int w;
 303         __s64 ln, draw, high_draw = 0;
 304
 305         for (i = 0; i < bucket->h.size; i++) {
 306                 w = bucket->item_weights[i];
 307                 if (w) {
 308                         u = crush_hash32_3(bucket->h.hash, x,
 309                                            bucket->h.items[i], r);
 310                         u &= 0xffff;
 311
 312                         /*
 313                          * for some reason slightly less than 0x10000 produces
 314                          * a slightly more accurate distribution... probably a
 315                          * rounding effect.
 316                          *
 317                          * the natural log lookup table maps [0,0xffff]
 318                          * (corresponding to real numbers [1/0x10000, 1] to
 319                          * [0, 0xffffffffffff] (corresponding to real numbers
 320                          * [-11.090355,0]).
 321                          */
 322                         ln = crush_ln(u) - 0x1000000000000ll;
 323
 324                         /*
 325                          * divide by 16.16 fixed-point weight.  note
 326                          * that the ln value is negative, so a larger
 327                          * weight means a larger (less negative) value
 328                          * for draw.
 329                          */
 330                         draw = div64_s64(ln, w);
 331                 } else {
 332                         draw = S64_MIN;
 333                 }
 334
 335                 if (i == 0 || draw > high_draw) {
 336                         high = i;
 337                         high_draw = draw;
 338                 }
 339         }
 340         return bucket->h.items[high];
 341 }
 342
 343
 344 static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
 345 {
 346         dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
 347         BUG_ON(in->size == 0);
 348         switch (in->alg) {
 349         case CRUSH_BUCKET_UNIFORM:
 350                 return bucket_uniform_choose((struct crush_bucket_uniform *)in,
 351                                           x, r);
 352         case CRUSH_BUCKET_LIST:
 353                 return bucket_list_choose((struct crush_bucket_list *)in,
 354                                           x, r);
 355         case CRUSH_BUCKET_TREE:
 356                 return bucket_tree_choose((struct crush_bucket_tree *)in,
 357                                           x, r);
 358         case CRUSH_BUCKET_STRAW:
 359                 return bucket_straw_choose((struct crush_bucket_straw *)in,
 360                                            x, r);
 361         case CRUSH_BUCKET_STRAW2:
 362                 return bucket_straw2_choose((struct crush_bucket_straw2 *)in,
 363                                             x, r);
 364         default:
 365                 dprintk("unknown bucket %d alg %d\n", in->id, in->alg);
 366                 return in->items[0];
 367         }
 368 }
 369
 370
 371 /*
 372  * true if device is marked "out" (failed, fully offloaded)
 373  * of the cluster
 374  */
 375 static int is_out(const struct crush_map *map,
 376                   const __u32 *weight, int weight_max,
 377                   int item, int x)
 378 {
 379         if (item >= weight_max)
 380                 return 1;
 381         if (weight[item] >= 0x10000)
 382                 return 0;
 383         if (weight[item] == 0)
 384                 return 1;
 385         if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
 386             < weight[item])
 387                 return 0;
 388         return 1;
 389 }
 390
 391 /**
 392  * crush_choose_firstn - choose numrep distinct items of given type
 393  * @map: the crush_map
 394  * @bucket: the bucket we are choose an item from
 395  * @x: crush input value
 396  * @numrep: the number of items to choose
 397  * @type: the type of item to choose
 398  * @out: pointer to output vector
 399  * @outpos: our position in that vector
 400  * @out_size: size of the out vector
 401  * @tries: number of attempts to make
 402  * @recurse_tries: number of attempts to have recursive chooseleaf make
 403  * @local_retries: localized retries
 404  * @local_fallback_retries: localized fallback retries
 405  * @recurse_to_leaf: true if we want one device under each item of given type (chooseleaf instead of choose)
 406  * @stable: stable mode starts rep=0 in the recursive call for all replicas
 407  * @vary_r: pass r to recursive calls
 408  * @out2: second output vector for leaf items (if @recurse_to_leaf)
 409  * @parent_r: r value passed from the parent
 410  */
 411 static int crush_choose_firstn(const struct crush_map *map,
 412                                struct crush_bucket *bucket,
 413                                const __u32 *weight, int weight_max,
 414                                int x, int numrep, int type,
 415                                int *out, int outpos,
 416                                int out_size,
 417                                unsigned int tries,
 418                                unsigned int recurse_tries,
 419                                unsigned int local_retries,
 420                                unsigned int local_fallback_retries,
 421                                int recurse_to_leaf,
 422                                unsigned int vary_r,
 423                                unsigned int stable,
 424                                int *out2,
 425                                int parent_r)
 426 {
 427         int rep;
 428         unsigned int ftotal, flocal;
 429         int retry_descent, retry_bucket, skip_rep;
 430         struct crush_bucket *in = bucket;
 431         int r;
 432         int i;
 433         int item = 0;
 434         int itemtype;
 435         int collide, reject;
 436         int count = out_size;
 437
 438         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",
 439                 recurse_to_leaf ? "_LEAF" : "",
 440                 bucket->id, x, outpos, numrep,
 441                 tries, recurse_tries, local_retries, local_fallback_retries,
 442                 parent_r, stable);
 443
 444         for (rep = stable ? 0 : outpos; rep < numrep && count > 0 ; rep++) {
 445                 /* keep trying until we get a non-out, non-colliding item */
 446                 ftotal = 0;
 447                 skip_rep = 0;
 448                 do {
 449                         retry_descent = 0;
 450                         in = bucket;               /* initial bucket */
 451
 452                         /* choose through intervening buckets */
 453                         flocal = 0;
 454                         do {
 455                                 collide = 0;
 456                                 retry_bucket = 0;
 457                                 r = rep + parent_r;
 458                                 /* r' = r + f_total */
 459                                 r += ftotal;
 460
 461                                 /* bucket choose */
 462                                 if (in->size == 0) {
 463                                         reject = 1;
 464                                         goto reject;
 465                                 }
 466                                 if (local_fallback_retries > 0 &&
 467                                     flocal >= (in->size>>1) &&
 468                                     flocal > local_fallback_retries)
 469                                         item = bucket_perm_choose(in, x, r);
 470                                 else
 471                                         item = crush_bucket_choose(in, x, r);
 472                                 if (item >= map->max_devices) {
 473                                         dprintk("   bad item %d\n", item);
 474                                         skip_rep = 1;
 475                                         break;
 476                                 }
 477
 478                                 /* desired type? */
 479                                 if (item < 0)
 480                                         itemtype = map->buckets[-1-item]->type;
 481                                 else
 482                                         itemtype = 0;
 483                                 dprintk("  item %d type %d\n", item, itemtype);
 484
 485                                 /* keep going? */
 486                                 if (itemtype != type) {
 487                                         if (item >= 0 ||
 488                                             (-1-item) >= map->max_buckets) {
 489                                                 dprintk("   bad item type %d\n", type);
 490                                                 skip_rep = 1;
 491                                                 break;
 492                                         }
 493                                         in = map->buckets[-1-item];
 494                                         retry_bucket = 1;
 495                                         continue;
 496                                 }
 497
 498                                 /* collision? */
 499                                 for (i = 0; i < outpos; i++) {
 500                                         if (out[i] == item) {
 501                                                 collide = 1;
 502                                                 break;
 503                                         }
 504                                 }
 505
 506                                 reject = 0;
 507                                 if (!collide && recurse_to_leaf) {
 508                                         if (item < 0) {
 509                                                 int sub_r;
 510                                                 if (vary_r)
 511                                                         sub_r = r >> (vary_r-1);
 512                                                 else
 513                                                         sub_r = 0;
 514                                                 if (crush_choose_firstn(map,
 515                                                          map->buckets[-1-item],
 516                                                          weight, weight_max,
 517                                                          x, stable ? 1 : outpos+1, 0,
 518                                                          out2, outpos, count,
 519                                                          recurse_tries, 0,
 520                                                          local_retries,
 521                                                          local_fallback_retries,
 522                                                          0,
 523                                                          vary_r,
 524                                                          stable,
 525                                                          NULL,
 526                                                          sub_r) <= outpos)
 527                                                         /* didn't get leaf */
 528                                                         reject = 1;
 529                                         } else {
 530                                                 /* we already have a leaf! */
 531                                                 out2[outpos] = item;
 532                                         }
 533                                 }
 534
 535                                 if (!reject) {
 536                                         /* out? */
 537                                         if (itemtype == 0)
 538                                                 reject = is_out(map, weight,
 539                                                                 weight_max,
 540                                                                 item, x);
 541                                         else
 542                                                 reject = 0;
 543                                 }
 544
 545 reject:
 546                                 if (reject || collide) {
 547                                         ftotal++;
 548                                         flocal++;
 549
 550                                         if (collide && flocal <= local_retries)
 551                                                 /* retry locally a few times */
 552                                                 retry_bucket = 1;
 553                                         else if (local_fallback_retries > 0 &&
 554                                                  flocal <= in->size + local_fallback_retries)
 555                                                 /* exhaustive bucket search */
 556                                                 retry_bucket = 1;
 557                                         else if (ftotal < tries)
 558                                                 /* then retry descent */
 559                                                 retry_descent = 1;
 560                                         else
 561                                                 /* else give up */
 562                                                 skip_rep = 1;
 563                                         dprintk("  reject %d  collide %d  "
 564                                                 "ftotal %u  flocal %u\n",
 565                                                 reject, collide, ftotal,
 566                                                 flocal);
 567                                 }
 568                         } while (retry_bucket);
 569                 } while (retry_descent);
 570
 571                 if (skip_rep) {
 572                         dprintk("skip rep\n");
 573                         continue;
 574                 }
 575
 576                 dprintk("CHOOSE got %d\n", item);
 577                 out[outpos] = item;
 578                 outpos++;
 579                 count--;
 580 #ifndef __KERNEL__
 581                 if (map->choose_tries && ftotal <= map->choose_total_tries)
 582                         map->choose_tries[ftotal]++;
 583 #endif
 584         }
 585
 586         dprintk("CHOOSE returns %d\n", outpos);
 587         return outpos;
 588 }
 589
 590
 591 /**
 592  * crush_choose_indep: alternative breadth-first positionally stable mapping
 593  *
 594  */
 595 static void crush_choose_indep(const struct crush_map *map,
 596                                struct crush_bucket *bucket,
 597                                const __u32 *weight, int weight_max,
 598                                int x, int left, int numrep, int type,
 599                                int *out, int outpos,
 600                                unsigned int tries,
 601                                unsigned int recurse_tries,
 602                                int recurse_to_leaf,
 603                                int *out2,
 604                                int parent_r)
 605 {
 606         struct crush_bucket *in = bucket;
 607         int endpos = outpos + left;
 608         int rep;
 609         unsigned int ftotal;
 610         int r;
 611         int i;
 612         int item = 0;
 613         int itemtype;
 614         int collide;
 615
 616         dprintk("CHOOSE%s INDEP bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
 617                 bucket->id, x, outpos, numrep);
 618
 619         /* initially my result is undefined */
 620         for (rep = outpos; rep < endpos; rep++) {
 621                 out[rep] = CRUSH_ITEM_UNDEF;
 622                 if (out2)
 623                         out2[rep] = CRUSH_ITEM_UNDEF;
 624         }
 625
 626         for (ftotal = 0; left > 0 && ftotal < tries; ftotal++) {
 627 #ifdef DEBUG_INDEP
 628                 if (out2 && ftotal) {
 629                         dprintk("%u %d a: ", ftotal, left);
 630                         for (rep = outpos; rep < endpos; rep++) {
 631                                 dprintk(" %d", out[rep]);
 632                         }
 633                         dprintk("\n");
 634                         dprintk("%u %d b: ", ftotal, left);
 635                         for (rep = outpos; rep < endpos; rep++) {
 636                                 dprintk(" %d", out2[rep]);
 637                         }
 638                         dprintk("\n");
 639                 }
 640 #endif
 641                 for (rep = outpos; rep < endpos; rep++) {
 642                         if (out[rep] != CRUSH_ITEM_UNDEF)
 643                                 continue;
 644
 645                         in = bucket;  /* initial bucket */
 646
 647                         /* choose through intervening buckets */
 648                         for (;;) {
 649                                 /* note: we base the choice on the position
 650                                  * even in the nested call.  that means that
 651                                  * if the first layer chooses the same bucket
 652                                  * in a different position, we will tend to
 653                                  * choose a different item in that bucket.
 654                                  * this will involve more devices in data
 655                                  * movement and tend to distribute the load.
 656                                  */
 657                                 r = rep + parent_r;
 658
 659                                 /* be careful */
 660                                 if (in->alg == CRUSH_BUCKET_UNIFORM &&
 661                                     in->size % numrep == 0)
 662                                         /* r'=r+(n+1)*f_total */
 663                                         r += (numrep+1) * ftotal;
 664                                 else
 665                                         /* r' = r + n*f_total */
 666                                         r += numrep * ftotal;
 667
 668                                 /* bucket choose */
 669                                 if (in->size == 0) {
 670                                         dprintk("   empty bucket\n");
 671                                         break;
 672                                 }
 673
 674                                 item = crush_bucket_choose(in, x, r);
 675                                 if (item >= map->max_devices) {
 676                                         dprintk("   bad item %d\n", item);
 677                                         out[rep] = CRUSH_ITEM_NONE;
 678                                         if (out2)
 679                                                 out2[rep] = CRUSH_ITEM_NONE;
 680                                         left--;
 681                                         break;
 682                                 }
 683
 684                                 /* desired type? */
 685                                 if (item < 0)
 686                                         itemtype = map->buckets[-1-item]->type;
 687                                 else
 688                                         itemtype = 0;
 689                                 dprintk("  item %d type %d\n", item, itemtype);
 690
 691                                 /* keep going? */
 692                                 if (itemtype != type) {
 693                                         if (item >= 0 ||
 694                                             (-1-item) >= map->max_buckets) {
 695                                                 dprintk("   bad item type %d\n", type);
 696                                                 out[rep] = CRUSH_ITEM_NONE;
 697                                                 if (out2)
 698                                                         out2[rep] =
 699                                                                 CRUSH_ITEM_NONE;
 700                                                 left--;
 701                                                 break;
 702                                         }
 703                                         in = map->buckets[-1-item];
 704                                         continue;
 705                                 }
 706
 707                                 /* collision? */
 708                                 collide = 0;
 709                                 for (i = outpos; i < endpos; i++) {
 710                                         if (out[i] == item) {
 711                                                 collide = 1;
 712                                                 break;
 713                                         }
 714                                 }
 715                                 if (collide)
 716                                         break;
 717
 718                                 if (recurse_to_leaf) {
 719                                         if (item < 0) {
 720                                                 crush_choose_indep(map,
 721                                                    map->buckets[-1-item],
 722                                                    weight, weight_max,
 723                                                    x, 1, numrep, 0,
 724                                                    out2, rep,
 725                                                    recurse_tries, 0,
 726                                                    0, NULL, r);
 727                                                 if (out2[rep] == CRUSH_ITEM_NONE) {
 728                                                         /* placed nothing; no leaf */
 729                                                         break;
 730                                                 }
 731                                         } else {
 732                                                 /* we already have a leaf! */
 733                                                 out2[rep] = item;
 734                                         }
 735                                 }
 736
 737                                 /* out? */
 738                                 if (itemtype == 0 &&
 739                                     is_out(map, weight, weight_max, item, x))
 740                                         break;
 741
 742                                 /* yay! */
 743                                 out[rep] = item;
 744                                 left--;
 745                                 break;
 746                         }
 747                 }
 748         }
 749         for (rep = outpos; rep < endpos; rep++) {
 750                 if (out[rep] == CRUSH_ITEM_UNDEF) {
 751                         out[rep] = CRUSH_ITEM_NONE;
 752                 }
 753                 if (out2 && out2[rep] == CRUSH_ITEM_UNDEF) {
 754                         out2[rep] = CRUSH_ITEM_NONE;
 755                 }
 756         }
 757 #ifndef __KERNEL__
 758         if (map->choose_tries && ftotal <= map->choose_total_tries)
 759                 map->choose_tries[ftotal]++;
 760 #endif
 761 #ifdef DEBUG_INDEP
 762         if (out2) {
 763                 dprintk("%u %d a: ", ftotal, left);
 764                 for (rep = outpos; rep < endpos; rep++) {
 765                         dprintk(" %d", out[rep]);
 766                 }
 767                 dprintk("\n");
 768                 dprintk("%u %d b: ", ftotal, left);
 769                 for (rep = outpos; rep < endpos; rep++) {
 770                         dprintk(" %d", out2[rep]);
 771                 }
 772                 dprintk("\n");
 773         }
 774 #endif
 775 }
 776
 777 /**
 778  * crush_do_rule - calculate a mapping with the given input and rule
 779  * @map: the crush_map
 780  * @ruleno: the rule id
 781  * @x: hash input
 782  * @result: pointer to result vector
 783  * @result_max: maximum result size
 784  * @weight: weight vector (for map leaves)
 785  * @weight_max: size of weight vector
 786  * @scratch: scratch vector for private use; must be >= 3 * result_max
 787  */
 788 int crush_do_rule(const struct crush_map *map,
 789                   int ruleno, int x, int *result, int result_max,
 790                   const __u32 *weight, int weight_max,
 791                   int *scratch)
 792 {
 793         int result_len;
 794         int *a = scratch;
 795         int *b = scratch + result_max;
 796         int *c = scratch + result_max*2;
 797         int recurse_to_leaf;
 798         int *w;
 799         int wsize = 0;
 800         int *o;
 801         int osize;
 802         int *tmp;
 803         struct crush_rule *rule;
 804         __u32 step;
 805         int i, j;
 806         int numrep;
 807         int out_size;
 808         /*
 809          * the original choose_total_tries value was off by one (it
 810          * counted "retries" and not "tries").  add one.
 811          */
 812         int choose_tries = map->choose_total_tries + 1;
 813         int choose_leaf_tries = 0;
 814         /*
 815          * the local tries values were counted as "retries", though,
 816          * and need no adjustment
 817          */
 818         int choose_local_retries = map->choose_local_tries;
 819         int choose_local_fallback_retries = map->choose_local_fallback_tries;
 820
 821         int vary_r = map->chooseleaf_vary_r;
 822         int stable = map->chooseleaf_stable;
 823
 824         if ((__u32)ruleno >= map->max_rules) {
 825                 dprintk(" bad ruleno %d\n", ruleno);
 826                 return 0;
 827         }
 828
 829         rule = map->rules[ruleno];
 830         result_len = 0;
 831         w = a;
 832         o = b;
 833
 834         for (step = 0; step < rule->len; step++) {
 835                 int firstn = 0;
 836                 struct crush_rule_step *curstep = &rule->steps[step];
 837
 838                 switch (curstep->op) {
 839                 case CRUSH_RULE_TAKE:
 840                         if ((curstep->arg1 >= 0 &&
 841                              curstep->arg1 < map->max_devices) ||
 842                             (-1-curstep->arg1 >= 0 &&
 843                              -1-curstep->arg1 < map->max_buckets &&
 844                              map->buckets[-1-curstep->arg1])) {
 845                                 w[0] = curstep->arg1;
 846                                 wsize = 1;
 847                         } else {
 848                                 dprintk(" bad take value %d\n", curstep->arg1);
 849                         }
 850                         break;
 851
 852                 case CRUSH_RULE_SET_CHOOSE_TRIES:
 853                         if (curstep->arg1 > 0)
 854                                 choose_tries = curstep->arg1;
 855                         break;
 856
 857                 case CRUSH_RULE_SET_CHOOSELEAF_TRIES:
 858                         if (curstep->arg1 > 0)
 859                                 choose_leaf_tries = curstep->arg1;
 860                         break;
 861
 862                 case CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES:
 863                         if (curstep->arg1 >= 0)
 864                                 choose_local_retries = curstep->arg1;
 865                         break;
 866
 867                 case CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES:
 868                         if (curstep->arg1 >= 0)
 869                                 choose_local_fallback_retries = curstep->arg1;
 870                         break;
 871
 872                 case CRUSH_RULE_SET_CHOOSELEAF_VARY_R:
 873                         if (curstep->arg1 >= 0)
 874                                 vary_r = curstep->arg1;
 875                         break;
 876
 877                 case CRUSH_RULE_SET_CHOOSELEAF_STABLE:
 878                         if (curstep->arg1 >= 0)
 879                                 stable = curstep->arg1;
 880                         break;
 881
 882                 case CRUSH_RULE_CHOOSELEAF_FIRSTN:
 883                 case CRUSH_RULE_CHOOSE_FIRSTN:
 884                         firstn = 1;
 885                         /* fall through */
 886                 case CRUSH_RULE_CHOOSELEAF_INDEP:
 887                 case CRUSH_RULE_CHOOSE_INDEP:
 888                         if (wsize == 0)
 889                                 break;
 890
 891                         recurse_to_leaf =
 892                                 curstep->op ==
 893                                  CRUSH_RULE_CHOOSELEAF_FIRSTN ||
 894                                 curstep->op ==
 895                                 CRUSH_RULE_CHOOSELEAF_INDEP;
 896
 897                         /* reset output */
 898                         osize = 0;
 899
 900                         for (i = 0; i < wsize; i++) {
 901                                 int bno;
 902                                 /*
 903                                  * see CRUSH_N, CRUSH_N_MINUS macros.
 904                                  * basically, numrep <= 0 means relative to
 905                                  * the provided result_max
 906                                  */
 907                                 numrep = curstep->arg1;
 908                                 if (numrep <= 0) {
 909                                         numrep += result_max;
 910                                         if (numrep <= 0)
 911                                                 continue;
 912                                 }
 913                                 j = 0;
 914                                 /* make sure bucket id is valid */
 915                                 bno = -1 - w[i];
 916                                 if (bno < 0 || bno >= map->max_buckets) {
 917                                         /* w[i] is probably CRUSH_ITEM_NONE */
 918                                         dprintk("  bad w[i] %d\n", w[i]);
 919                                         continue;
 920                                 }
 921                                 if (firstn) {
 922                                         int recurse_tries;
 923                                         if (choose_leaf_tries)
 924                                                 recurse_tries =
 925                                                         choose_leaf_tries;
 926                                         else if (map->chooseleaf_descend_once)
 927                                                 recurse_tries = 1;
 928                                         else
 929                                                 recurse_tries = choose_tries;
 930                                         osize += crush_choose_firstn(
 931                                                 map,
 932                                                 map->buckets[bno],
 933                                                 weight, weight_max,
 934                                                 x, numrep,
 935                                                 curstep->arg2,
 936                                                 o+osize, j,
 937                                                 result_max-osize,
 938                                                 choose_tries,
 939                                                 recurse_tries,
 940                                                 choose_local_retries,
 941                                                 choose_local_fallback_retries,
 942                                                 recurse_to_leaf,
 943                                                 vary_r,
 944                                                 stable,
 945                                                 c+osize,
 946                                                 0);
 947                                 } else {
 948                                         out_size = ((numrep < (result_max-osize)) ?
 949                                                     numrep : (result_max-osize));
 950                                         crush_choose_indep(
 951                                                 map,
 952                                                 map->buckets[bno],
 953                                                 weight, weight_max,
 954                                                 x, out_size, numrep,
 955                                                 curstep->arg2,
 956                                                 o+osize, j,
 957                                                 choose_tries,
 958                                                 choose_leaf_tries ?
 959                                                    choose_leaf_tries : 1,
 960                                                 recurse_to_leaf,
 961                                                 c+osize,
 962                                                 0);
 963                                         osize += out_size;
 964                                 }
 965                         }
 966
 967                         if (recurse_to_leaf)
 968                                 /* copy final _leaf_ values to output set */
 969                                 memcpy(o, c, osize*sizeof(*o));
 970
 971                         /* swap o and w arrays */
 972                         tmp = o;
 973                         o = w;
 974                         w = tmp;
 975                         wsize = osize;
 976                         break;
 977
 978
 979                 case CRUSH_RULE_EMIT:
 980                         for (i = 0; i < wsize && result_len < result_max; i++) {
 981                                 result[result_len] = w[i];
 982                                 result_len++;
 983                         }
 984                         wsize = 0;
 985                         break;
 986
 987                 default:
 988                         dprintk(" unknown op %d at step %d\n",
 989                                 curstep->op, step);
 990                         break;
 991                 }
 992         }
 993         return result_len;
 994 }