net/ceph/crush/mapper.c

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