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 # include <linux/crush/mapper.h>
  21 #else
  22 # include "crush_compat.h"
  23 # include "crush.h"
  24 # include "hash.h"
  25 # include "mapper.h"
  26 #endif
  27 #include "crush_ln_table.h"
  28
  29 #define dprintk(args...) /* printf(args) */
  30
  31 /*
  32  * Implement the core CRUSH mapping algorithm.
  33  */
  34
  35 /**
  36  * crush_find_rule - find a crush_rule id for a given ruleset, type, and size.
  37  * @map: the crush_map
  38  * @ruleset: the storage ruleset id (user defined)
  39  * @type: storage ruleset type (user defined)
  40  * @size: output set size
  41  */
  42 int crush_find_rule(const struct crush_map *map, int ruleset, int type, int size)
  43 {
  44         __u32 i;
  45
  46         for (i = 0; i < map->max_rules; i++) {
  47                 if (map->rules[i] &&
  48                     map->rules[i]->mask.ruleset == ruleset &&
  49                     map->rules[i]->mask.type == type &&
  50                     map->rules[i]->mask.min_size <= size &&
  51                     map->rules[i]->mask.max_size >= size)
  52                         return i;
  53         }
  54         return -1;
  55 }
  56
  57 /*
  58  * bucket choose methods
  59  *
  60  * For each bucket algorithm, we have a "choose" method that, given a
  61  * crush input @x and replica position (usually, position in output set) @r,
  62  * will produce an item in the bucket.
  63  */
  64
  65 /*
  66  * Choose based on a random permutation of the bucket.
  67  *
  68  * We used to use some prime number arithmetic to do this, but it
  69  * wasn't very random, and had some other bad behaviors.  Instead, we
  70  * calculate an actual random permutation of the bucket members.
  71  * Since this is expensive, we optimize for the r=0 case, which
  72  * captures the vast majority of calls.
  73  */
  74 static int bucket_perm_choose(const struct crush_bucket *bucket,
  75                               struct crush_work_bucket *work,
  76                               int x, int r)
  77 {
  78         unsigned int pr = r % bucket->size;
  79         unsigned int i, s;
  80
  81         /* start a new permutation if @x has changed */
  82         if (work->perm_x != (__u32)x || work->perm_n == 0) {
  83                 dprintk("bucket %d new x=%d\n", bucket->id, x);
  84                 work->perm_x = x;
  85
  86                 /* optimize common r=0 case */
  87                 if (pr == 0) {
  88                         s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
  89                                 bucket->size;
  90                         work->perm[0] = s;
  91                         work->perm_n = 0xffff;   /* magic value, see below */
  92                         goto out;
  93                 }
  94
  95                 for (i = 0; i < bucket->size; i++)
  96                         work->perm[i] = i;
  97                 work->perm_n = 0;
  98         } else if (work->perm_n == 0xffff) {
  99                 /* clean up after the r=0 case above */
 100                 for (i = 1; i < bucket->size; i++)
 101                         work->perm[i] = i;
 102                 work->perm[work->perm[0]] = 0;
 103                 work->perm_n = 1;
 104         }
 105
 106         /* calculate permutation up to pr */
 107         for (i = 0; i < work->perm_n; i++)
 108                 dprintk(" perm_choose have %d: %d\n", i, work->perm[i]);
 109         while (work->perm_n <= pr) {
 110                 unsigned int p = work->perm_n;
 111                 /* no point in swapping the final entry */
 112                 if (p < bucket->size - 1) {
 113                         i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
 114                                 (bucket->size - p);
 115                         if (i) {
 116                                 unsigned int t = work->perm[p + i];
 117                                 work->perm[p + i] = work->perm[p];
 118                                 work->perm[p] = t;
 119                         }
 120                         dprintk(" perm_choose swap %d with %d\n", p, p+i);
 121                 }
 122                 work->perm_n++;
 123         }
 124         for (i = 0; i < bucket->size; i++)
 125                 dprintk(" perm_choose  %d: %d\n", i, work->perm[i]);
 126
 127         s = work->perm[pr];
 128 out:
 129         dprintk(" perm_choose %d sz=%d x=%d r=%d (%d) s=%d\n", bucket->id,
 130                 bucket->size, x, r, pr, s);
 131         return bucket->items[s];
 132 }
 133
 134 /* uniform */
 135 static int bucket_uniform_choose(const struct crush_bucket_uniform *bucket,
 136                                  struct crush_work_bucket *work, int x, int r)
 137 {
 138         return bucket_perm_choose(&bucket->h, work, x, r);
 139 }
 140
 141 /* list */
 142 static int bucket_list_choose(const struct crush_bucket_list *bucket,
 143                               int x, int r)
 144 {
 145         int i;
 146
 147         for (i = bucket->h.size-1; i >= 0; i--) {
 148                 __u64 w = crush_hash32_4(bucket->h.hash, x, bucket->h.items[i],
 149                                          r, bucket->h.id);
 150                 w &= 0xffff;
 151                 dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
 152                         "sw %x rand %llx",
 153                         i, x, r, bucket->h.items[i], bucket->item_weights[i],
 154                         bucket->sum_weights[i], w);
 155                 w *= bucket->sum_weights[i];
 156                 w = w >> 16;
 157                 /*dprintk(" scaled %llx\n", w);*/
 158                 if (w < bucket->item_weights[i]) {
 159                         return bucket->h.items[i];
 160                 }
 161         }
 162
 163         dprintk("bad list sums for bucket %d\n", bucket->h.id);
 164         return bucket->h.items[0];
 165 }
 166
 167
 168 /* (binary) tree */
 169 static int height(int n)
 170 {
 171         int h = 0;
 172         while ((n & 1) == 0) {
 173                 h++;
 174                 n = n >> 1;
 175         }
 176         return h;
 177 }
 178
 179 static int left(int x)
 180 {
 181         int h = height(x);
 182         return x - (1 << (h-1));
 183 }
 184
 185 static int right(int x)
 186 {
 187         int h = height(x);
 188         return x + (1 << (h-1));
 189 }
 190
 191 static int terminal(int x)
 192 {
 193         return x & 1;
 194 }
 195
 196 static int bucket_tree_choose(const struct crush_bucket_tree *bucket,
 197                               int x, int r)
 198 {
 199         int n;
 200         __u32 w;
 201         __u64 t;
 202
 203         /* start at root */
 204         n = bucket->num_nodes >> 1;
 205
 206         while (!terminal(n)) {
 207                 int l;
 208                 /* pick point in [0, w) */
 209                 w = bucket->node_weights[n];
 210                 t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
 211                                           bucket->h.id) * (__u64)w;
 212                 t = t >> 32;
 213
 214                 /* descend to the left or right? */
 215                 l = left(n);
 216                 if (t < bucket->node_weights[l])
 217                         n = l;
 218                 else
 219                         n = right(n);
 220         }
 221
 222         return bucket->h.items[n >> 1];
 223 }
 224
 225
 226 /* straw */
 227
 228 static int bucket_straw_choose(const struct crush_bucket_straw *bucket,
 229                                int x, int r)
 230 {
 231         __u32 i;
 232         int high = 0;
 233         __u64 high_draw = 0;
 234         __u64 draw;
 235
 236         for (i = 0; i < bucket->h.size; i++) {
 237                 draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
 238                 draw &= 0xffff;
 239                 draw *= bucket->straws[i];
 240                 if (i == 0 || draw > high_draw) {
 241                         high = i;
 242                         high_draw = draw;
 243                 }
 244         }
 245         return bucket->h.items[high];
 246 }
 247
 248 /* compute 2^44*log2(input+1) */
 249 static __u64 crush_ln(unsigned int xin)
 250 {
 251         unsigned int x = xin;
 252         int iexpon, index1, index2;
 253         __u64 RH, LH, LL, xl64, result;
 254
 255         x++;
 256
 257         /* normalize input */
 258         iexpon = 15;
 259
 260         /*
 261          * figure out number of bits we need to shift and
 262          * do it in one step instead of iteratively
 263          */
 264         if (!(x & 0x18000)) {
 265                 int bits = __builtin_clz(x & 0x1FFFF) - 16;
 266                 x <<= bits;
 267                 iexpon = 15 - bits;
 268         }
 269
 270         index1 = (x >> 8) << 1;
 271         /* RH ~ 2^56/index1 */
 272         RH = __RH_LH_tbl[index1 - 256];
 273         /* LH ~ 2^48 * log2(index1/256) */
 274         LH = __RH_LH_tbl[index1 + 1 - 256];
 275
 276         /* RH*x ~ 2^48 * (2^15 + xf), xf<2^8 */
 277         xl64 = (__s64)x * RH;
 278         xl64 >>= 48;
 279
 280         result = iexpon;
 281         result <<= (12 + 32);
 282
 283         index2 = xl64 & 0xff;
 284         /* LL ~ 2^48*log2(1.0+index2/2^15) */
 285         LL = __LL_tbl[index2];
 286
 287         LH = LH + LL;
 288
 289         LH >>= (48 - 12 - 32);
 290         result += LH;
 291
 292         return result;
 293 }
 294
 295
 296 /*
 297  * straw2
 298  *
 299  * for reference, see:
 300  *
 301  * http://en.wikipedia.org/wiki/Exponential_distribution#Distribution_of_the_minimum_of_exponential_random_variables
 302  *
 303  */
 304
 305 static __u32 *get_choose_arg_weights(const struct crush_bucket_straw2 *bucket,
 306                                      const struct crush_choose_arg *arg,
 307                                      int position)
 308 {
 309         if (!arg || !arg->weight_set)
 310                 return bucket->item_weights;
 311
 312         if (position >= arg->weight_set_size)
 313                 position = arg->weight_set_size - 1;
 314         return arg->weight_set[position].weights;
 315 }
 316
 317 static __s32 *get_choose_arg_ids(const struct crush_bucket_straw2 *bucket,
 318                                  const struct crush_choose_arg *arg)
 319 {
 320         if (!arg || !arg->ids)
 321                 return bucket->h.items;
 322
 323         return arg->ids;
 324 }
 325
 326 static int bucket_straw2_choose(const struct crush_bucket_straw2 *bucket,
 327                                 int x, int r,
 328                                 const struct crush_choose_arg *arg,
 329                                 int position)
 330 {
 331         unsigned int i, high = 0;
 332         unsigned int u;
 333         __s64 ln, draw, high_draw = 0;
 334         __u32 *weights = get_choose_arg_weights(bucket, arg, position);
 335         __s32 *ids = get_choose_arg_ids(bucket, arg);
 336
 337         for (i = 0; i < bucket->h.size; i++) {
 338                 dprintk("weight 0x%x item %d\n", weights[i], ids[i]);
 339                 if (weights[i]) {
 340                         u = crush_hash32_3(bucket->h.hash, x, ids[i], r);
 341                         u &= 0xffff;
 342
 343                         /*
 344                          * for some reason slightly less than 0x10000 produces
 345                          * a slightly more accurate distribution... probably a
 346                          * rounding effect.
 347                          *
 348                          * the natural log lookup table maps [0,0xffff]
 349                          * (corresponding to real numbers [1/0x10000, 1] to
 350                          * [0, 0xffffffffffff] (corresponding to real numbers
 351                          * [-11.090355,0]).
 352                          */
 353                         ln = crush_ln(u) - 0x1000000000000ll;
 354
 355                         /*
 356                          * divide by 16.16 fixed-point weight.  note
 357                          * that the ln value is negative, so a larger
 358                          * weight means a larger (less negative) value
 359                          * for draw.
 360                          */
 361                         draw = div64_s64(ln, weights[i]);
 362                 } else {
 363                         draw = S64_MIN;
 364                 }
 365
 366                 if (i == 0 || draw > high_draw) {
 367                         high = i;
 368                         high_draw = draw;
 369                 }
 370         }
 371
 372         return bucket->h.items[high];
 373 }
 374
 375
 376 static int crush_bucket_choose(const struct crush_bucket *in,
 377                                struct crush_work_bucket *work,
 378                                int x, int r,
 379                                const struct crush_choose_arg *arg,
 380                                int position)
 381 {
 382         dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
 383         BUG_ON(in->size == 0);
 384         switch (in->alg) {
 385         case CRUSH_BUCKET_UNIFORM:
 386                 return bucket_uniform_choose(
 387                         (const struct crush_bucket_uniform *)in,
 388                         work, x, r);
 389         case CRUSH_BUCKET_LIST:
 390                 return bucket_list_choose((const struct crush_bucket_list *)in,
 391                                           x, r);
 392         case CRUSH_BUCKET_TREE:
 393                 return bucket_tree_choose((const struct crush_bucket_tree *)in,
 394                                           x, r);
 395         case CRUSH_BUCKET_STRAW:
 396                 return bucket_straw_choose(
 397                         (const struct crush_bucket_straw *)in,
 398                         x, r);
 399         case CRUSH_BUCKET_STRAW2:
 400                 return bucket_straw2_choose(
 401                         (const struct crush_bucket_straw2 *)in,
 402                         x, r, arg, position);
 403         default:
 404                 dprintk("unknown bucket %d alg %d\n", in->id, in->alg);
 405                 return in->items[0];
 406         }
 407 }
 408
 409 /*
 410  * true if device is marked "out" (failed, fully offloaded)
 411  * of the cluster
 412  */
 413 static int is_out(const struct crush_map *map,
 414                   const __u32 *weight, int weight_max,
 415                   int item, int x)
 416 {
 417         if (item >= weight_max)
 418                 return 1;
 419         if (weight[item] >= 0x10000)
 420                 return 0;
 421         if (weight[item] == 0)
 422                 return 1;
 423         if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
 424             < weight[item])
 425                 return 0;
 426         return 1;
 427 }
 428
 429 /**
 430  * crush_choose_firstn - choose numrep distinct items of given type
 431  * @map: the crush_map
 432  * @bucket: the bucket we are choose an item from
 433  * @x: crush input value
 434  * @numrep: the number of items to choose
 435  * @type: the type of item to choose
 436  * @out: pointer to output vector
 437  * @outpos: our position in that vector
 438  * @out_size: size of the out vector
 439  * @tries: number of attempts to make
 440  * @recurse_tries: number of attempts to have recursive chooseleaf make
 441  * @local_retries: localized retries
 442  * @local_fallback_retries: localized fallback retries
 443  * @recurse_to_leaf: true if we want one device under each item of given type (chooseleaf instead of choose)
 444  * @stable: stable mode starts rep=0 in the recursive call for all replicas
 445  * @vary_r: pass r to recursive calls
 446  * @out2: second output vector for leaf items (if @recurse_to_leaf)
 447  * @parent_r: r value passed from the parent
 448  */
 449 static int crush_choose_firstn(const struct crush_map *map,
 450                                struct crush_work *work,
 451                                const struct crush_bucket *bucket,
 452                                const __u32 *weight, int weight_max,
 453                                int x, int numrep, int type,
 454                                int *out, int outpos,
 455                                int out_size,
 456                                unsigned int tries,
 457                                unsigned int recurse_tries,
 458                                unsigned int local_retries,
 459                                unsigned int local_fallback_retries,
 460                                int recurse_to_leaf,
 461                                unsigned int vary_r,
 462                                unsigned int stable,
 463                                int *out2,
 464                                int parent_r,
 465                                const struct crush_choose_arg *choose_args)
 466 {
 467         int rep;
 468         unsigned int ftotal, flocal;
 469         int retry_descent, retry_bucket, skip_rep;
 470         const struct crush_bucket *in = bucket;
 471         int r;
 472         int i;
 473         int item = 0;
 474         int itemtype;
 475         int collide, reject;
 476         int count = out_size;
 477
 478         dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d tries %d recurse_tries %d local_retries %d local_fallback_retries %d parent_r %d stable %d\n",
 479                 recurse_to_leaf ? "_LEAF" : "",
 480                 bucket->id, x, outpos, numrep,
 481                 tries, recurse_tries, local_retries, local_fallback_retries,
 482                 parent_r, stable);
 483
 484         for (rep = stable ? 0 : outpos; rep < numrep && count > 0 ; rep++) {
 485                 /* keep trying until we get a non-out, non-colliding item */
 486                 ftotal = 0;
 487                 skip_rep = 0;
 488                 do {
 489                         retry_descent = 0;
 490                         in = bucket;               /* initial bucket */
 491
 492                         /* choose through intervening buckets */
 493                         flocal = 0;
 494                         do {
 495                                 collide = 0;
 496                                 retry_bucket = 0;
 497                                 r = rep + parent_r;
 498                                 /* r' = r + f_total */
 499                                 r += ftotal;
 500
 501                                 /* bucket choose */
 502                                 if (in->size == 0) {
 503                                         reject = 1;
 504                                         goto reject;
 505                                 }
 506                                 if (local_fallback_retries > 0 &&
 507                                     flocal >= (in->size>>1) &&
 508                                     flocal > local_fallback_retries)
 509                                         item = bucket_perm_choose(
 510                                                 in, work->work[-1-in->id],
 511                                                 x, r);
 512                                 else
 513                                         item = crush_bucket_choose(
 514                                                 in, work->work[-1-in->id],
 515                                                 x, r,
 516                                                 (choose_args ?
 517                                                  &choose_args[-1-in->id] : 0),
 518                                                 outpos);
 519                                 if (item >= map->max_devices) {
 520                                         dprintk("   bad item %d\n", item);
 521                                         skip_rep = 1;
 522                                         break;
 523                                 }
 524
 525                                 /* desired type? */
 526                                 if (item < 0)
 527                                         itemtype = map->buckets[-1-item]->type;
 528                                 else
 529                                         itemtype = 0;
 530                                 dprintk("  item %d type %d\n", item, itemtype);
 531
 532                                 /* keep going? */
 533                                 if (itemtype != type) {
 534                                         if (item >= 0 ||
 535                                             (-1-item) >= map->max_buckets) {
 536                                                 dprintk("   bad item type %d\n", type);
 537                                                 skip_rep = 1;
 538                                                 break;
 539                                         }
 540                                         in = map->buckets[-1-item];
 541                                         retry_bucket = 1;
 542                                         continue;
 543                                 }
 544
 545                                 /* collision? */
 546                                 for (i = 0; i < outpos; i++) {
 547                                         if (out[i] == item) {
 548                                                 collide = 1;
 549                                                 break;
 550                                         }
 551                                 }
 552
 553                                 reject = 0;
 554                                 if (!collide && recurse_to_leaf) {
 555                                         if (item < 0) {
 556                                                 int sub_r;
 557                                                 if (vary_r)
 558                                                         sub_r = r >> (vary_r-1);
 559                                                 else
 560                                                         sub_r = 0;
 561                                                 if (crush_choose_firstn(
 562                                                             map,
 563                                                             work,
 564                                                             map->buckets[-1-item],
 565                                                             weight, weight_max,
 566                                                             x, stable ? 1 : outpos+1, 0,
 567                                                             out2, outpos, count,
 568                                                             recurse_tries, 0,
 569                                                             local_retries,
 570                                                             local_fallback_retries,
 571                                                             0,
 572                                                             vary_r,
 573                                                             stable,
 574                                                             NULL,
 575                                                             sub_r,
 576                                                             choose_args) <= outpos)
 577                                                         /* didn't get leaf */
 578                                                         reject = 1;
 579                                         } else {
 580                                                 /* we already have a leaf! */
 581                                                 out2[outpos] = item;
 582                                         }
 583                                 }
 584
 585                                 if (!reject && !collide) {
 586                                         /* out? */
 587                                         if (itemtype == 0)
 588                                                 reject = is_out(map, weight,
 589                                                                 weight_max,
 590                                                                 item, x);
 591                                 }
 592
 593 reject:
 594                                 if (reject || collide) {
 595                                         ftotal++;
 596                                         flocal++;
 597
 598                                         if (collide && flocal <= local_retries)
 599                                                 /* retry locally a few times */
 600                                                 retry_bucket = 1;
 601                                         else if (local_fallback_retries > 0 &&
 602                                                  flocal <= in->size + local_fallback_retries)
 603                                                 /* exhaustive bucket search */
 604                                                 retry_bucket = 1;
 605                                         else if (ftotal < tries)
 606                                                 /* then retry descent */
 607                                                 retry_descent = 1;
 608                                         else
 609                                                 /* else give up */
 610                                                 skip_rep = 1;
 611                                         dprintk("  reject %d  collide %d  "
 612                                                 "ftotal %u  flocal %u\n",
 613                                                 reject, collide, ftotal,
 614                                                 flocal);
 615                                 }
 616                         } while (retry_bucket);
 617                 } while (retry_descent);
 618
 619                 if (skip_rep) {
 620                         dprintk("skip rep\n");
 621                         continue;
 622                 }
 623
 624                 dprintk("CHOOSE got %d\n", item);
 625                 out[outpos] = item;
 626                 outpos++;
 627                 count--;
 628 #ifndef __KERNEL__
 629                 if (map->choose_tries && ftotal <= map->choose_total_tries)
 630                         map->choose_tries[ftotal]++;
 631 #endif
 632         }
 633
 634         dprintk("CHOOSE returns %d\n", outpos);
 635         return outpos;
 636 }
 637
 638
 639 /**
 640  * crush_choose_indep: alternative breadth-first positionally stable mapping
 641  *
 642  */
 643 static void crush_choose_indep(const struct crush_map *map,
 644                                struct crush_work *work,
 645                                const struct crush_bucket *bucket,
 646                                const __u32 *weight, int weight_max,
 647                                int x, int left, int numrep, int type,
 648                                int *out, int outpos,
 649                                unsigned int tries,
 650                                unsigned int recurse_tries,
 651                                int recurse_to_leaf,
 652                                int *out2,
 653                                int parent_r,
 654                                const struct crush_choose_arg *choose_args)
 655 {
 656         const struct crush_bucket *in = bucket;
 657         int endpos = outpos + left;
 658         int rep;
 659         unsigned int ftotal;
 660         int r;
 661         int i;
 662         int item = 0;
 663         int itemtype;
 664         int collide;
 665
 666         dprintk("CHOOSE%s INDEP bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
 667                 bucket->id, x, outpos, numrep);
 668
 669         /* initially my result is undefined */
 670         for (rep = outpos; rep < endpos; rep++) {
 671                 out[rep] = CRUSH_ITEM_UNDEF;
 672                 if (out2)
 673                         out2[rep] = CRUSH_ITEM_UNDEF;
 674         }
 675
 676         for (ftotal = 0; left > 0 && ftotal < tries; ftotal++) {
 677 #ifdef DEBUG_INDEP
 678                 if (out2 && ftotal) {
 679                         dprintk("%u %d a: ", ftotal, left);
 680                         for (rep = outpos; rep < endpos; rep++) {
 681                                 dprintk(" %d", out[rep]);
 682                         }
 683                         dprintk("\n");
 684                         dprintk("%u %d b: ", ftotal, left);
 685                         for (rep = outpos; rep < endpos; rep++) {
 686                                 dprintk(" %d", out2[rep]);
 687                         }
 688                         dprintk("\n");
 689                 }
 690 #endif
 691                 for (rep = outpos; rep < endpos; rep++) {
 692                         if (out[rep] != CRUSH_ITEM_UNDEF)
 693                                 continue;
 694
 695                         in = bucket;  /* initial bucket */
 696
 697                         /* choose through intervening buckets */
 698                         for (;;) {
 699                                 /* note: we base the choice on the position
 700                                  * even in the nested call.  that means that
 701                                  * if the first layer chooses the same bucket
 702                                  * in a different position, we will tend to
 703                                  * choose a different item in that bucket.
 704                                  * this will involve more devices in data
 705                                  * movement and tend to distribute the load.
 706                                  */
 707                                 r = rep + parent_r;
 708
 709                                 /* be careful */
 710                                 if (in->alg == CRUSH_BUCKET_UNIFORM &&
 711                                     in->size % numrep == 0)
 712                                         /* r'=r+(n+1)*f_total */
 713                                         r += (numrep+1) * ftotal;
 714                                 else
 715                                         /* r' = r + n*f_total */
 716                                         r += numrep * ftotal;
 717
 718                                 /* bucket choose */
 719                                 if (in->size == 0) {
 720                                         dprintk("   empty bucket\n");
 721                                         break;
 722                                 }
 723
 724                                 item = crush_bucket_choose(
 725                                         in, work->work[-1-in->id],
 726                                         x, r,
 727                                         (choose_args ?
 728                                          &choose_args[-1-in->id] : 0),
 729                                         outpos);
 730                                 if (item >= map->max_devices) {
 731                                         dprintk("   bad item %d\n", item);
 732                                         out[rep] = CRUSH_ITEM_NONE;
 733                                         if (out2)
 734                                                 out2[rep] = CRUSH_ITEM_NONE;
 735                                         left--;
 736                                         break;
 737                                 }
 738
 739                                 /* desired type? */
 740                                 if (item < 0)
 741                                         itemtype = map->buckets[-1-item]->type;
 742                                 else
 743                                         itemtype = 0;
 744                                 dprintk("  item %d type %d\n", item, itemtype);
 745
 746                                 /* keep going? */
 747                                 if (itemtype != type) {
 748                                         if (item >= 0 ||
 749                                             (-1-item) >= map->max_buckets) {
 750                                                 dprintk("   bad item type %d\n", type);
 751                                                 out[rep] = CRUSH_ITEM_NONE;
 752                                                 if (out2)
 753                                                         out2[rep] =
 754                                                                 CRUSH_ITEM_NONE;
 755                                                 left--;
 756                                                 break;
 757                                         }
 758                                         in = map->buckets[-1-item];
 759                                         continue;
 760                                 }
 761
 762                                 /* collision? */
 763                                 collide = 0;
 764                                 for (i = outpos; i < endpos; i++) {
 765                                         if (out[i] == item) {
 766                                                 collide = 1;
 767                                                 break;
 768                                         }
 769                                 }
 770                                 if (collide)
 771                                         break;
 772
 773                                 if (recurse_to_leaf) {
 774                                         if (item < 0) {
 775                                                 crush_choose_indep(
 776                                                         map,
 777                                                         work,
 778                                                         map->buckets[-1-item],
 779                                                         weight, weight_max,
 780                                                         x, 1, numrep, 0,
 781                                                         out2, rep,
 782                                                         recurse_tries, 0,
 783                                                         0, NULL, r,
 784                                                         choose_args);
 785                                                 if (out2[rep] == CRUSH_ITEM_NONE) {
 786                                                         /* placed nothing; no leaf */
 787                                                         break;
 788                                                 }
 789                                         } else {
 790                                                 /* we already have a leaf! */
 791                                                 out2[rep] = item;
 792                                         }
 793                                 }
 794
 795                                 /* out? */
 796                                 if (itemtype == 0 &&
 797                                     is_out(map, weight, weight_max, item, x))
 798                                         break;
 799
 800                                 /* yay! */
 801                                 out[rep] = item;
 802                                 left--;
 803                                 break;
 804                         }
 805                 }
 806         }
 807         for (rep = outpos; rep < endpos; rep++) {
 808                 if (out[rep] == CRUSH_ITEM_UNDEF) {
 809                         out[rep] = CRUSH_ITEM_NONE;
 810                 }
 811                 if (out2 && out2[rep] == CRUSH_ITEM_UNDEF) {
 812                         out2[rep] = CRUSH_ITEM_NONE;
 813                 }
 814         }
 815 #ifndef __KERNEL__
 816         if (map->choose_tries && ftotal <= map->choose_total_tries)
 817                 map->choose_tries[ftotal]++;
 818 #endif
 819 #ifdef DEBUG_INDEP
 820         if (out2) {
 821                 dprintk("%u %d a: ", ftotal, left);
 822                 for (rep = outpos; rep < endpos; rep++) {
 823                         dprintk(" %d", out[rep]);
 824                 }
 825                 dprintk("\n");
 826                 dprintk("%u %d b: ", ftotal, left);
 827                 for (rep = outpos; rep < endpos; rep++) {
 828                         dprintk(" %d", out2[rep]);
 829                 }
 830                 dprintk("\n");
 831         }
 832 #endif
 833 }
 834
 835
 836 /*
 837  * This takes a chunk of memory and sets it up to be a shiny new
 838  * working area for a CRUSH placement computation. It must be called
 839  * on any newly allocated memory before passing it in to
 840  * crush_do_rule. It may be used repeatedly after that, so long as the
 841  * map has not changed. If the map /has/ changed, you must make sure
 842  * the working size is no smaller than what was allocated and re-run
 843  * crush_init_workspace.
 844  *
 845  * If you do retain the working space between calls to crush, make it
 846  * thread-local.
 847  */
 848 void crush_init_workspace(const struct crush_map *map, void *v)
 849 {
 850         struct crush_work *w = v;
 851         __s32 b;
 852
 853         /*
 854          * We work by moving through the available space and setting
 855          * values and pointers as we go.
 856          *
 857          * It's a bit like Forth's use of the 'allot' word since we
 858          * set the pointer first and then reserve the space for it to
 859          * point to by incrementing the point.
 860          */
 861         v += sizeof(struct crush_work);
 862         w->work = v;
 863         v += map->max_buckets * sizeof(struct crush_work_bucket *);
 864         for (b = 0; b < map->max_buckets; ++b) {
 865                 if (!map->buckets[b])
 866                         continue;
 867
 868                 w->work[b] = v;
 869                 switch (map->buckets[b]->alg) {
 870                 default:
 871                         v += sizeof(struct crush_work_bucket);
 872                         break;
 873                 }
 874                 w->work[b]->perm_x = 0;
 875                 w->work[b]->perm_n = 0;
 876                 w->work[b]->perm = v;
 877                 v += map->buckets[b]->size * sizeof(__u32);
 878         }
 879         BUG_ON(v - (void *)w != map->working_size);
 880 }
 881
 882 /**
 883  * crush_do_rule - calculate a mapping with the given input and rule
 884  * @map: the crush_map
 885  * @ruleno: the rule id
 886  * @x: hash input
 887  * @result: pointer to result vector
 888  * @result_max: maximum result size
 889  * @weight: weight vector (for map leaves)
 890  * @weight_max: size of weight vector
 891  * @cwin: pointer to at least crush_work_size() bytes of memory
 892  * @choose_args: weights and ids for each known bucket
 893  */
 894 int crush_do_rule(const struct crush_map *map,
 895                   int ruleno, int x, int *result, int result_max,
 896                   const __u32 *weight, int weight_max,
 897                   void *cwin, const struct crush_choose_arg *choose_args)
 898 {
 899         int result_len;
 900         struct crush_work *cw = cwin;
 901         int *a = cwin + map->working_size;
 902         int *b = a + result_max;
 903         int *c = b + result_max;
 904         int *w = a;
 905         int *o = b;
 906         int recurse_to_leaf;
 907         int wsize = 0;
 908         int osize;
 909         int *tmp;
 910         const struct crush_rule *rule;
 911         __u32 step;
 912         int i, j;
 913         int numrep;
 914         int out_size;
 915         /*
 916          * the original choose_total_tries value was off by one (it
 917          * counted "retries" and not "tries").  add one.
 918          */
 919         int choose_tries = map->choose_total_tries + 1;
 920         int choose_leaf_tries = 0;
 921         /*
 922          * the local tries values were counted as "retries", though,
 923          * and need no adjustment
 924          */
 925         int choose_local_retries = map->choose_local_tries;
 926         int choose_local_fallback_retries = map->choose_local_fallback_tries;
 927
 928         int vary_r = map->chooseleaf_vary_r;
 929         int stable = map->chooseleaf_stable;
 930
 931         if ((__u32)ruleno >= map->max_rules) {
 932                 dprintk(" bad ruleno %d\n", ruleno);
 933                 return 0;
 934         }
 935
 936         rule = map->rules[ruleno];
 937         result_len = 0;
 938
 939         for (step = 0; step < rule->len; step++) {
 940                 int firstn = 0;
 941                 const struct crush_rule_step *curstep = &rule->steps[step];
 942
 943                 switch (curstep->op) {
 944                 case CRUSH_RULE_TAKE:
 945                         if ((curstep->arg1 >= 0 &&
 946                              curstep->arg1 < map->max_devices) ||
 947                             (-1-curstep->arg1 >= 0 &&
 948                              -1-curstep->arg1 < map->max_buckets &&
 949                              map->buckets[-1-curstep->arg1])) {
 950                                 w[0] = curstep->arg1;
 951                                 wsize = 1;
 952                         } else {
 953                                 dprintk(" bad take value %d\n", curstep->arg1);
 954                         }
 955                         break;
 956
 957                 case CRUSH_RULE_SET_CHOOSE_TRIES:
 958                         if (curstep->arg1 > 0)
 959                                 choose_tries = curstep->arg1;
 960                         break;
 961
 962                 case CRUSH_RULE_SET_CHOOSELEAF_TRIES:
 963                         if (curstep->arg1 > 0)
 964                                 choose_leaf_tries = curstep->arg1;
 965                         break;
 966
 967                 case CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES:
 968                         if (curstep->arg1 >= 0)
 969                                 choose_local_retries = curstep->arg1;
 970                         break;
 971
 972                 case CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES:
 973                         if (curstep->arg1 >= 0)
 974                                 choose_local_fallback_retries = curstep->arg1;
 975                         break;
 976
 977                 case CRUSH_RULE_SET_CHOOSELEAF_VARY_R:
 978                         if (curstep->arg1 >= 0)
 979                                 vary_r = curstep->arg1;
 980                         break;
 981
 982                 case CRUSH_RULE_SET_CHOOSELEAF_STABLE:
 983                         if (curstep->arg1 >= 0)
 984                                 stable = curstep->arg1;
 985                         break;
 986
 987                 case CRUSH_RULE_CHOOSELEAF_FIRSTN:
 988                 case CRUSH_RULE_CHOOSE_FIRSTN:
 989                         firstn = 1;
 990                         /* fall through */
 991                 case CRUSH_RULE_CHOOSELEAF_INDEP:
 992                 case CRUSH_RULE_CHOOSE_INDEP:
 993                         if (wsize == 0)
 994                                 break;
 995
 996                         recurse_to_leaf =
 997                                 curstep->op ==
 998                                  CRUSH_RULE_CHOOSELEAF_FIRSTN ||
 999                                 curstep->op ==
1000                                 CRUSH_RULE_CHOOSELEAF_INDEP;
1001
1002                         /* reset output */
1003                         osize = 0;
1004
1005                         for (i = 0; i < wsize; i++) {
1006                                 int bno;
1007                                 numrep = curstep->arg1;
1008                                 if (numrep <= 0) {
1009                                         numrep += result_max;
1010                                         if (numrep <= 0)
1011                                                 continue;
1012                                 }
1013                                 j = 0;
1014                                 /* make sure bucket id is valid */
1015                                 bno = -1 - w[i];
1016                                 if (bno < 0 || bno >= map->max_buckets) {
1017                                         /* w[i] is probably CRUSH_ITEM_NONE */
1018                                         dprintk("  bad w[i] %d\n", w[i]);
1019                                         continue;
1020                                 }
1021                                 if (firstn) {
1022                                         int recurse_tries;
1023                                         if (choose_leaf_tries)
1024                                                 recurse_tries =
1025                                                         choose_leaf_tries;
1026                                         else if (map->chooseleaf_descend_once)
1027                                                 recurse_tries = 1;
1028                                         else
1029                                                 recurse_tries = choose_tries;
1030                                         osize += crush_choose_firstn(
1031                                                 map,
1032                                                 cw,
1033                                                 map->buckets[bno],
1034                                                 weight, weight_max,
1035                                                 x, numrep,
1036                                                 curstep->arg2,
1037                                                 o+osize, j,
1038                                                 result_max-osize,
1039                                                 choose_tries,
1040                                                 recurse_tries,
1041                                                 choose_local_retries,
1042                                                 choose_local_fallback_retries,
1043                                                 recurse_to_leaf,
1044                                                 vary_r,
1045                                                 stable,
1046                                                 c+osize,
1047                                                 0,
1048                                                 choose_args);
1049                                 } else {
1050                                         out_size = ((numrep < (result_max-osize)) ?
1051                                                     numrep : (result_max-osize));
1052                                         crush_choose_indep(
1053                                                 map,
1054                                                 cw,
1055                                                 map->buckets[bno],
1056                                                 weight, weight_max,
1057                                                 x, out_size, numrep,
1058                                                 curstep->arg2,
1059                                                 o+osize, j,
1060                                                 choose_tries,
1061                                                 choose_leaf_tries ?
1062                                                    choose_leaf_tries : 1,
1063                                                 recurse_to_leaf,
1064                                                 c+osize,
1065                                                 0,
1066                                                 choose_args);
1067                                         osize += out_size;
1068                                 }
1069                         }
1070
1071                         if (recurse_to_leaf)
1072                                 /* copy final _leaf_ values to output set */
1073                                 memcpy(o, c, osize*sizeof(*o));
1074
1075                         /* swap o and w arrays */
1076                         tmp = o;
1077                         o = w;
1078                         w = tmp;
1079                         wsize = osize;
1080                         break;
1081
1082
1083                 case CRUSH_RULE_EMIT:
1084                         for (i = 0; i < wsize && result_len < result_max; i++) {
1085                                 result[result_len] = w[i];
1086                                 result_len++;
1087                         }
1088                         wsize = 0;
1089                         break;
1090
1091                 default:
1092                         dprintk(" unknown op %d at step %d\n",
1093                                 curstep->op, step);
1094                         break;
1095                 }
1096         }
1097
1098         return result_len;
1099 }