kernel/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 "crush_ln_table.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 // compute 2^44*log2(input+1)
 242 uint64_t crush_ln(unsigned xin)
 243 {
 244     unsigned x=xin, x1;
 245     int iexpon, index1, index2;
 246     uint64_t RH, LH, LL, xl64, result;
 247
 248     x++;
 249
 250     // normalize input
 251     iexpon = 15;
 252     while(!(x&0x18000)) { x<<=1; iexpon--; }
 253
 254     index1 = (x>>8)<<1;
 255     // RH ~ 2^56/index1
 256     RH = __RH_LH_tbl[index1 - 256];
 257     // LH ~ 2^48 * log2(index1/256)
 258     LH = __RH_LH_tbl[index1 + 1 - 256];
 259
 260     // RH*x ~ 2^48 * (2^15 + xf), xf<2^8
 261     xl64 = (int64_t)x * RH;
 262     xl64 >>= 48;
 263     x1 = xl64;
 264
 265     result = iexpon;
 266     result <<= (12 + 32);
 267
 268     index2 = x1 & 0xff;
 269     // LL ~ 2^48*log2(1.0+index2/2^15)
 270     LL = __LL_tbl[index2];
 271
 272     LH = LH + LL;
 273
 274     LH >>= (48-12 - 32);
 275     result += LH;
 276
 277     return result;
 278 }
 279
 280
 281 /*
 282  * straw2
 283  *
 284  * for reference, see:
 285  *
 286  * http://en.wikipedia.org/wiki/Exponential_distribution#Distribution_of_the_minimum_of_exponential_random_variables
 287  *
 288  */
 289
 290 static int bucket_straw2_choose(struct crush_bucket_straw2 *bucket,
 291                                 int x, int r)
 292 {
 293         unsigned i, high = 0;
 294         unsigned u;
 295         unsigned w;
 296         __s64 ln, draw, high_draw = 0;
 297
 298         for (i = 0; i < bucket->h.size; i++) {
 299                 w = bucket->item_weights[i];
 300                 if (w) {
 301                         u = crush_hash32_3(bucket->h.hash, x,
 302                                            bucket->h.items[i], r);
 303                         u &= 0xffff;
 304
 305                         /*
 306                          * for some reason slightly less than 0x10000 produces
 307                          * a slightly more accurate distribution... probably a
 308                          * rounding effect.
 309                          *
 310                          * the natural log lookup table maps [0,0xffff]
 311                          * (corresponding to real numbers [1/0x10000, 1] to
 312                          * [0, 0xffffffffffff] (corresponding to real numbers
 313                          * [-11.090355,0]).
 314                          */
 315                         ln = crush_ln(u) - 0x1000000000000ll;
 316
 317                         /*
 318                          * divide by 16.16 fixed-point weight.  note
 319                          * that the ln value is negative, so a larger
 320                          * weight means a larger (less negative) value
 321                          * for draw.
 322                          */
 323                         draw = div64_s64(ln, w);
 324                 } else {
 325                         draw = S64_MIN;
 326                 }
 327
 328                 if (i == 0 || draw > high_draw) {
 329                         high = i;
 330                         high_draw = draw;
 331                 }
 332         }
 333         return bucket->h.items[high];
 334 }
 335
 336
 337 static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
 338 {
 339         dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
 340         BUG_ON(in->size == 0);
 341         switch (in->alg) {
 342         case CRUSH_BUCKET_UNIFORM:
 343                 return bucket_uniform_choose((struct crush_bucket_uniform *)in,
 344                                           x, r);
 345         case CRUSH_BUCKET_LIST:
 346                 return bucket_list_choose((struct crush_bucket_list *)in,
 347                                           x, r);
 348         case CRUSH_BUCKET_TREE:
 349                 return bucket_tree_choose((struct crush_bucket_tree *)in,
 350                                           x, r);
 351         case CRUSH_BUCKET_STRAW:
 352                 return bucket_straw_choose((struct crush_bucket_straw *)in,
 353                                            x, r);
 354         case CRUSH_BUCKET_STRAW2:
 355                 return bucket_straw2_choose((struct crush_bucket_straw2 *)in,
 356                                             x, r);
 357         default:
 358                 dprintk("unknown bucket %d alg %d\n", in->id, in->alg);
 359                 return in->items[0];
 360         }
 361 }
 362
 363
 364 /*
 365  * true if device is marked "out" (failed, fully offloaded)
 366  * of the cluster
 367  */
 368 static int is_out(const struct crush_map *map,
 369                   const __u32 *weight, int weight_max,
 370                   int item, int x)
 371 {
 372         if (item >= weight_max)
 373                 return 1;
 374         if (weight[item] >= 0x10000)
 375                 return 0;
 376         if (weight[item] == 0)
 377                 return 1;
 378         if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
 379             < weight[item])
 380                 return 0;
 381         return 1;
 382 }
 383
 384 /**
 385  * crush_choose_firstn - choose numrep distinct items of given type
 386  * @map: the crush_map
 387  * @bucket: the bucket we are choose an item from
 388  * @x: crush input value
 389  * @numrep: the number of items to choose
 390  * @type: the type of item to choose
 391  * @out: pointer to output vector
 392  * @outpos: our position in that vector
 393  * @out_size: size of the out vector
 394  * @tries: number of attempts to make
 395  * @recurse_tries: number of attempts to have recursive chooseleaf make
 396  * @local_retries: localized retries
 397  * @local_fallback_retries: localized fallback retries
 398  * @recurse_to_leaf: true if we want one device under each item of given type (chooseleaf instead of choose)
 399  * @vary_r: pass r to recursive calls
 400  * @out2: second output vector for leaf items (if @recurse_to_leaf)
 401  * @parent_r: r value passed from the parent
 402  */
 403 static int crush_choose_firstn(const struct crush_map *map,
 404                                struct crush_bucket *bucket,
 405                                const __u32 *weight, int weight_max,
 406                                int x, int numrep, int type,
 407                                int *out, int outpos,
 408                                int out_size,
 409                                unsigned int tries,
 410                                unsigned int recurse_tries,
 411                                unsigned int local_retries,
 412                                unsigned int local_fallback_retries,
 413                                int recurse_to_leaf,
 414                                unsigned int vary_r,
 415                                int *out2,
 416                                int parent_r)
 417 {
 418         int rep;
 419         unsigned int ftotal, flocal;
 420         int retry_descent, retry_bucket, skip_rep;
 421         struct crush_bucket *in = bucket;
 422         int r;
 423         int i;
 424         int item = 0;
 425         int itemtype;
 426         int collide, reject;
 427         int count = out_size;
 428
 429         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",
 430                 recurse_to_leaf ? "_LEAF" : "",
 431                 bucket->id, x, outpos, numrep,
 432                 tries, recurse_tries, local_retries, local_fallback_retries,
 433                 parent_r);
 434
 435         for (rep = outpos; rep < numrep && count > 0 ; rep++) {
 436                 /* keep trying until we get a non-out, non-colliding item */
 437                 ftotal = 0;
 438                 skip_rep = 0;
 439                 do {
 440                         retry_descent = 0;
 441                         in = bucket;               /* initial bucket */
 442
 443                         /* choose through intervening buckets */
 444                         flocal = 0;
 445                         do {
 446                                 collide = 0;
 447                                 retry_bucket = 0;
 448                                 r = rep + parent_r;
 449                                 /* r' = r + f_total */
 450                                 r += ftotal;
 451
 452                                 /* bucket choose */
 453                                 if (in->size == 0) {
 454                                         reject = 1;
 455                                         goto reject;
 456                                 }
 457                                 if (local_fallback_retries > 0 &&
 458                                     flocal >= (in->size>>1) &&
 459                                     flocal > local_fallback_retries)
 460                                         item = bucket_perm_choose(in, x, r);
 461                                 else
 462                                         item = crush_bucket_choose(in, x, r);
 463                                 if (item >= map->max_devices) {
 464                                         dprintk("   bad item %d\n", item);
 465                                         skip_rep = 1;
 466                                         break;
 467                                 }
 468
 469                                 /* desired type? */
 470                                 if (item < 0)
 471                                         itemtype = map->buckets[-1-item]->type;
 472                                 else
 473                                         itemtype = 0;
 474                                 dprintk("  item %d type %d\n", item, itemtype);
 475
 476                                 /* keep going? */
 477                                 if (itemtype != type) {
 478                                         if (item >= 0 ||
 479                                             (-1-item) >= map->max_buckets) {
 480                                                 dprintk("   bad item type %d\n", type);
 481                                                 skip_rep = 1;
 482                                                 break;
 483                                         }
 484                                         in = map->buckets[-1-item];
 485                                         retry_bucket = 1;
 486                                         continue;
 487                                 }
 488
 489                                 /* collision? */
 490                                 for (i = 0; i < outpos; i++) {
 491                                         if (out[i] == item) {
 492                                                 collide = 1;
 493                                                 break;
 494                                         }
 495                                 }
 496
 497                                 reject = 0;
 498                                 if (!collide && recurse_to_leaf) {
 499                                         if (item < 0) {
 500                                                 int sub_r;
 501                                                 if (vary_r)
 502                                                         sub_r = r >> (vary_r-1);
 503                                                 else
 504                                                         sub_r = 0;
 505                                                 if (crush_choose_firstn(map,
 506                                                          map->buckets[-1-item],
 507                                                          weight, weight_max,
 508                                                          x, outpos+1, 0,
 509                                                          out2, outpos, count,
 510                                                          recurse_tries, 0,
 511                                                          local_retries,
 512                                                          local_fallback_retries,
 513                                                          0,
 514                                                          vary_r,
 515                                                          NULL,
 516                                                          sub_r) <= outpos)
 517                                                         /* didn't get leaf */
 518                                                         reject = 1;
 519                                         } else {
 520                                                 /* we already have a leaf! */
 521                                                 out2[outpos] = item;
 522                                         }
 523                                 }
 524
 525                                 if (!reject) {
 526                                         /* out? */
 527                                         if (itemtype == 0)
 528                                                 reject = is_out(map, weight,
 529                                                                 weight_max,
 530                                                                 item, x);
 531                                         else
 532                                                 reject = 0;
 533                                 }
 534
 535 reject:
 536                                 if (reject || collide) {
 537                                         ftotal++;
 538                                         flocal++;
 539
 540                                         if (collide && flocal <= local_retries)
 541                                                 /* retry locally a few times */
 542                                                 retry_bucket = 1;
 543                                         else if (local_fallback_retries > 0 &&
 544                                                  flocal <= in->size + local_fallback_retries)
 545                                                 /* exhaustive bucket search */
 546                                                 retry_bucket = 1;
 547                                         else if (ftotal < tries)
 548                                                 /* then retry descent */
 549                                                 retry_descent = 1;
 550                                         else
 551                                                 /* else give up */
 552                                                 skip_rep = 1;
 553                                         dprintk("  reject %d  collide %d  "
 554                                                 "ftotal %u  flocal %u\n",
 555                                                 reject, collide, ftotal,
 556                                                 flocal);
 557                                 }
 558                         } while (retry_bucket);
 559                 } while (retry_descent);
 560
 561                 if (skip_rep) {
 562                         dprintk("skip rep\n");
 563                         continue;
 564                 }
 565
 566                 dprintk("CHOOSE got %d\n", item);
 567                 out[outpos] = item;
 568                 outpos++;
 569                 count--;
 570         }
 571
 572         dprintk("CHOOSE returns %d\n", outpos);
 573         return outpos;
 574 }
 575
 576
 577 /**
 578  * crush_choose_indep: alternative breadth-first positionally stable mapping
 579  *
 580  */
 581 static void crush_choose_indep(const struct crush_map *map,
 582                                struct crush_bucket *bucket,
 583                                const __u32 *weight, int weight_max,
 584                                int x, int left, int numrep, int type,
 585                                int *out, int outpos,
 586                                unsigned int tries,
 587                                unsigned int recurse_tries,
 588                                int recurse_to_leaf,
 589                                int *out2,
 590                                int parent_r)
 591 {
 592         struct crush_bucket *in = bucket;
 593         int endpos = outpos + left;
 594         int rep;
 595         unsigned int ftotal;
 596         int r;
 597         int i;
 598         int item = 0;
 599         int itemtype;
 600         int collide;
 601
 602         dprintk("CHOOSE%s INDEP bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
 603                 bucket->id, x, outpos, numrep);
 604
 605         /* initially my result is undefined */
 606         for (rep = outpos; rep < endpos; rep++) {
 607                 out[rep] = CRUSH_ITEM_UNDEF;
 608                 if (out2)
 609                         out2[rep] = CRUSH_ITEM_UNDEF;
 610         }
 611
 612         for (ftotal = 0; left > 0 && ftotal < tries; ftotal++) {
 613                 for (rep = outpos; rep < endpos; rep++) {
 614                         if (out[rep] != CRUSH_ITEM_UNDEF)
 615                                 continue;
 616
 617                         in = bucket;  /* initial bucket */
 618
 619                         /* choose through intervening buckets */
 620                         for (;;) {
 621                                 /* note: we base the choice on the position
 622                                  * even in the nested call.  that means that
 623                                  * if the first layer chooses the same bucket
 624                                  * in a different position, we will tend to
 625                                  * choose a different item in that bucket.
 626                                  * this will involve more devices in data
 627                                  * movement and tend to distribute the load.
 628                                  */
 629                                 r = rep + parent_r;
 630
 631                                 /* be careful */
 632                                 if (in->alg == CRUSH_BUCKET_UNIFORM &&
 633                                     in->size % numrep == 0)
 634                                         /* r'=r+(n+1)*f_total */
 635                                         r += (numrep+1) * ftotal;
 636                                 else
 637                                         /* r' = r + n*f_total */
 638                                         r += numrep * ftotal;
 639
 640                                 /* bucket choose */
 641                                 if (in->size == 0) {
 642                                         dprintk("   empty bucket\n");
 643                                         break;
 644                                 }
 645
 646                                 item = crush_bucket_choose(in, x, r);
 647                                 if (item >= map->max_devices) {
 648                                         dprintk("   bad item %d\n", item);
 649                                         out[rep] = CRUSH_ITEM_NONE;
 650                                         if (out2)
 651                                                 out2[rep] = CRUSH_ITEM_NONE;
 652                                         left--;
 653                                         break;
 654                                 }
 655
 656                                 /* desired type? */
 657                                 if (item < 0)
 658                                         itemtype = map->buckets[-1-item]->type;
 659                                 else
 660                                         itemtype = 0;
 661                                 dprintk("  item %d type %d\n", item, itemtype);
 662
 663                                 /* keep going? */
 664                                 if (itemtype != type) {
 665                                         if (item >= 0 ||
 666                                             (-1-item) >= map->max_buckets) {
 667                                                 dprintk("   bad item type %d\n", type);
 668                                                 out[rep] = CRUSH_ITEM_NONE;
 669                                                 if (out2)
 670                                                         out2[rep] =
 671                                                                 CRUSH_ITEM_NONE;
 672                                                 left--;
 673                                                 break;
 674                                         }
 675                                         in = map->buckets[-1-item];
 676                                         continue;
 677                                 }
 678
 679                                 /* collision? */
 680                                 collide = 0;
 681                                 for (i = outpos; i < endpos; i++) {
 682                                         if (out[i] == item) {
 683                                                 collide = 1;
 684                                                 break;
 685                                         }
 686                                 }
 687                                 if (collide)
 688                                         break;
 689
 690                                 if (recurse_to_leaf) {
 691                                         if (item < 0) {
 692                                                 crush_choose_indep(map,
 693                                                    map->buckets[-1-item],
 694                                                    weight, weight_max,
 695                                                    x, 1, numrep, 0,
 696                                                    out2, rep,
 697                                                    recurse_tries, 0,
 698                                                    0, NULL, r);
 699                                                 if (out2[rep] == CRUSH_ITEM_NONE) {
 700                                                         /* placed nothing; no leaf */
 701                                                         break;
 702                                                 }
 703                                         } else {
 704                                                 /* we already have a leaf! */
 705                                                 out2[rep] = item;
 706                                         }
 707                                 }
 708
 709                                 /* out? */
 710                                 if (itemtype == 0 &&
 711                                     is_out(map, weight, weight_max, item, x))
 712                                         break;
 713
 714                                 /* yay! */
 715                                 out[rep] = item;
 716                                 left--;
 717                                 break;
 718                         }
 719                 }
 720         }
 721         for (rep = outpos; rep < endpos; rep++) {
 722                 if (out[rep] == CRUSH_ITEM_UNDEF) {
 723                         out[rep] = CRUSH_ITEM_NONE;
 724                 }
 725                 if (out2 && out2[rep] == CRUSH_ITEM_UNDEF) {
 726                         out2[rep] = CRUSH_ITEM_NONE;
 727                 }
 728         }
 729 }
 730
 731 /**
 732  * crush_do_rule - calculate a mapping with the given input and rule
 733  * @map: the crush_map
 734  * @ruleno: the rule id
 735  * @x: hash input
 736  * @result: pointer to result vector
 737  * @result_max: maximum result size
 738  * @weight: weight vector (for map leaves)
 739  * @weight_max: size of weight vector
 740  * @scratch: scratch vector for private use; must be >= 3 * result_max
 741  */
 742 int crush_do_rule(const struct crush_map *map,
 743                   int ruleno, int x, int *result, int result_max,
 744                   const __u32 *weight, int weight_max,
 745                   int *scratch)
 746 {
 747         int result_len;
 748         int *a = scratch;
 749         int *b = scratch + result_max;
 750         int *c = scratch + result_max*2;
 751         int recurse_to_leaf;
 752         int *w;
 753         int wsize = 0;
 754         int *o;
 755         int osize;
 756         int *tmp;
 757         struct crush_rule *rule;
 758         __u32 step;
 759         int i, j;
 760         int numrep;
 761         int out_size;
 762         /*
 763          * the original choose_total_tries value was off by one (it
 764          * counted "retries" and not "tries").  add one.
 765          */
 766         int choose_tries = map->choose_total_tries + 1;
 767         int choose_leaf_tries = 0;
 768         /*
 769          * the local tries values were counted as "retries", though,
 770          * and need no adjustment
 771          */
 772         int choose_local_retries = map->choose_local_tries;
 773         int choose_local_fallback_retries = map->choose_local_fallback_tries;
 774
 775         int vary_r = map->chooseleaf_vary_r;
 776
 777         if ((__u32)ruleno >= map->max_rules) {
 778                 dprintk(" bad ruleno %d\n", ruleno);
 779                 return 0;
 780         }
 781
 782         rule = map->rules[ruleno];
 783         result_len = 0;
 784         w = a;
 785         o = b;
 786
 787         for (step = 0; step < rule->len; step++) {
 788                 int firstn = 0;
 789                 struct crush_rule_step *curstep = &rule->steps[step];
 790
 791                 switch (curstep->op) {
 792                 case CRUSH_RULE_TAKE:
 793                         w[0] = curstep->arg1;
 794                         wsize = 1;
 795                         break;
 796
 797                 case CRUSH_RULE_SET_CHOOSE_TRIES:
 798                         if (curstep->arg1 > 0)
 799                                 choose_tries = curstep->arg1;
 800                         break;
 801
 802                 case CRUSH_RULE_SET_CHOOSELEAF_TRIES:
 803                         if (curstep->arg1 > 0)
 804                                 choose_leaf_tries = curstep->arg1;
 805                         break;
 806
 807                 case CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES:
 808                         if (curstep->arg1 >= 0)
 809                                 choose_local_retries = curstep->arg1;
 810                         break;
 811
 812                 case CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES:
 813                         if (curstep->arg1 >= 0)
 814                                 choose_local_fallback_retries = curstep->arg1;
 815                         break;
 816
 817                 case CRUSH_RULE_SET_CHOOSELEAF_VARY_R:
 818                         if (curstep->arg1 >= 0)
 819                                 vary_r = curstep->arg1;
 820                         break;
 821
 822                 case CRUSH_RULE_CHOOSELEAF_FIRSTN:
 823                 case CRUSH_RULE_CHOOSE_FIRSTN:
 824                         firstn = 1;
 825                         /* fall through */
 826                 case CRUSH_RULE_CHOOSELEAF_INDEP:
 827                 case CRUSH_RULE_CHOOSE_INDEP:
 828                         if (wsize == 0)
 829                                 break;
 830
 831                         recurse_to_leaf =
 832                                 curstep->op ==
 833                                  CRUSH_RULE_CHOOSELEAF_FIRSTN ||
 834                                 curstep->op ==
 835                                 CRUSH_RULE_CHOOSELEAF_INDEP;
 836
 837                         /* reset output */
 838                         osize = 0;
 839
 840                         for (i = 0; i < wsize; i++) {
 841                                 /*
 842                                  * see CRUSH_N, CRUSH_N_MINUS macros.
 843                                  * basically, numrep <= 0 means relative to
 844                                  * the provided result_max
 845                                  */
 846                                 numrep = curstep->arg1;
 847                                 if (numrep <= 0) {
 848                                         numrep += result_max;
 849                                         if (numrep <= 0)
 850                                                 continue;
 851                                 }
 852                                 j = 0;
 853                                 if (firstn) {
 854                                         int recurse_tries;
 855                                         if (choose_leaf_tries)
 856                                                 recurse_tries =
 857                                                         choose_leaf_tries;
 858                                         else if (map->chooseleaf_descend_once)
 859                                                 recurse_tries = 1;
 860                                         else
 861                                                 recurse_tries = choose_tries;
 862                                         osize += crush_choose_firstn(
 863                                                 map,
 864                                                 map->buckets[-1-w[i]],
 865                                                 weight, weight_max,
 866                                                 x, numrep,
 867                                                 curstep->arg2,
 868                                                 o+osize, j,
 869                                                 result_max-osize,
 870                                                 choose_tries,
 871                                                 recurse_tries,
 872                                                 choose_local_retries,
 873                                                 choose_local_fallback_retries,
 874                                                 recurse_to_leaf,
 875                                                 vary_r,
 876                                                 c+osize,
 877                                                 0);
 878                                 } else {
 879                                         out_size = ((numrep < (result_max-osize)) ?
 880                                                     numrep : (result_max-osize));
 881                                         crush_choose_indep(
 882                                                 map,
 883                                                 map->buckets[-1-w[i]],
 884                                                 weight, weight_max,
 885                                                 x, out_size, numrep,
 886                                                 curstep->arg2,
 887                                                 o+osize, j,
 888                                                 choose_tries,
 889                                                 choose_leaf_tries ?
 890                                                    choose_leaf_tries : 1,
 891                                                 recurse_to_leaf,
 892                                                 c+osize,
 893                                                 0);
 894                                         osize += out_size;
 895                                 }
 896                         }
 897
 898                         if (recurse_to_leaf)
 899                                 /* copy final _leaf_ values to output set */
 900                                 memcpy(o, c, osize*sizeof(*o));
 901
 902                         /* swap o and w arrays */
 903                         tmp = o;
 904                         o = w;
 905                         w = tmp;
 906                         wsize = osize;
 907                         break;
 908
 909
 910                 case CRUSH_RULE_EMIT:
 911                         for (i = 0; i < wsize && result_len < result_max; i++) {
 912                                 result[result_len] = w[i];
 913                                 result_len++;
 914                         }
 915                         wsize = 0;
 916                         break;
 917
 918                 default:
 919                         dprintk(" unknown op %d at step %d\n",
 920                                 curstep->op, step);
 921                         break;
 922                 }
 923         }
 924         return result_len;
 925 }
 926
 927