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(struct crush_map *map, int ruleset, int type, int size)
  37 {
  38         int 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 != 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         BUG_ON(1);
 157         return 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, l;
 193         __u32 w;
 194         __u64 t;
 195
 196         /* start at root */
 197         n = bucket->num_nodes >> 1;
 198
 199         while (!terminal(n)) {
 200                 /* pick point in [0, w) */
 201                 w = bucket->node_weights[n];
 202                 t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
 203                                           bucket->h.id) * (__u64)w;
 204                 t = t >> 32;
 205
 206                 /* descend to the left or right? */
 207                 l = left(n);
 208                 if (t < bucket->node_weights[l])
 209                         n = l;
 210                 else
 211                         n = right(n);
 212         }
 213
 214         return bucket->h.items[n >> 1];
 215 }
 216
 217
 218 /* straw */
 219
 220 static int bucket_straw_choose(struct crush_bucket_straw *bucket,
 221                                int x, int r)
 222 {
 223         int i;
 224         int high = 0;
 225         __u64 high_draw = 0;
 226         __u64 draw;
 227
 228         for (i = 0; i < bucket->h.size; i++) {
 229                 draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
 230                 draw &= 0xffff;
 231                 draw *= bucket->straws[i];
 232                 if (i == 0 || draw > high_draw) {
 233                         high = i;
 234                         high_draw = draw;
 235                 }
 236         }
 237         return bucket->h.items[high];
 238 }
 239
 240 static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
 241 {
 242         dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
 243         switch (in->alg) {
 244         case CRUSH_BUCKET_UNIFORM:
 245                 return bucket_uniform_choose((struct crush_bucket_uniform *)in,
 246                                           x, r);
 247         case CRUSH_BUCKET_LIST:
 248                 return bucket_list_choose((struct crush_bucket_list *)in,
 249                                           x, r);
 250         case CRUSH_BUCKET_TREE:
 251                 return bucket_tree_choose((struct crush_bucket_tree *)in,
 252                                           x, r);
 253         case CRUSH_BUCKET_STRAW:
 254                 return bucket_straw_choose((struct crush_bucket_straw *)in,
 255                                            x, r);
 256         default:
 257                 BUG_ON(1);
 258                 return in->items[0];
 259         }
 260 }
 261
 262 /*
 263  * true if device is marked "out" (failed, fully offloaded)
 264  * of the cluster
 265  */
 266 static int is_out(struct crush_map *map, __u32 *weight, int item, int x)
 267 {
 268         if (weight[item] >= 0x10000)
 269                 return 0;
 270         if (weight[item] == 0)
 271                 return 1;
 272         if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
 273             < weight[item])
 274                 return 0;
 275         return 1;
 276 }
 277
 278 /**
 279  * crush_choose - choose numrep distinct items of given type
 280  * @map: the crush_map
 281  * @bucket: the bucket we are choose an item from
 282  * @x: crush input value
 283  * @numrep: the number of items to choose
 284  * @type: the type of item to choose
 285  * @out: pointer to output vector
 286  * @outpos: our position in that vector
 287  * @firstn: true if choosing "first n" items, false if choosing "indep"
 288  * @recurse_to_leaf: true if we want one device under each item of given type
 289  * @out2: second output vector for leaf items (if @recurse_to_leaf)
 290  */
 291 static int crush_choose(struct crush_map *map,
 292                         struct crush_bucket *bucket,
 293                         __u32 *weight,
 294                         int x, int numrep, int type,
 295                         int *out, int outpos,
 296                         int firstn, int recurse_to_leaf,
 297                         int *out2)
 298 {
 299         int rep;
 300         int ftotal, flocal;
 301         int retry_descent, retry_bucket, skip_rep;
 302         struct crush_bucket *in = bucket;
 303         int r;
 304         int i;
 305         int item = 0;
 306         int itemtype;
 307         int collide, reject;
 308         const int orig_tries = 5; /* attempts before we fall back to search */
 309
 310         dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
 311                 bucket->id, x, outpos, numrep);
 312
 313         for (rep = outpos; rep < numrep; rep++) {
 314                 /* keep trying until we get a non-out, non-colliding item */
 315                 ftotal = 0;
 316                 skip_rep = 0;
 317                 do {
 318                         retry_descent = 0;
 319                         in = bucket;               /* initial bucket */
 320
 321                         /* choose through intervening buckets */
 322                         flocal = 0;
 323                         do {
 324                                 collide = 0;
 325                                 retry_bucket = 0;
 326                                 r = rep;
 327                                 if (in->alg == CRUSH_BUCKET_UNIFORM) {
 328                                         /* be careful */
 329                                         if (firstn || numrep >= in->size)
 330                                                 /* r' = r + f_total */
 331                                                 r += ftotal;
 332                                         else if (in->size % numrep == 0)
 333                                                 /* r'=r+(n+1)*f_local */
 334                                                 r += (numrep+1) *
 335                                                         (flocal+ftotal);
 336                                         else
 337                                                 /* r' = r + n*f_local */
 338                                                 r += numrep * (flocal+ftotal);
 339                                 } else {
 340                                         if (firstn)
 341                                                 /* r' = r + f_total */
 342                                                 r += ftotal;
 343                                         else
 344                                                 /* r' = r + n*f_local */
 345                                                 r += numrep * (flocal+ftotal);
 346                                 }
 347
 348                                 /* bucket choose */
 349                                 if (in->size == 0) {
 350                                         reject = 1;
 351                                         goto reject;
 352                                 }
 353                                 if (flocal >= (in->size>>1) &&
 354                                     flocal > orig_tries)
 355                                         item = bucket_perm_choose(in, x, r);
 356                                 else
 357                                         item = crush_bucket_choose(in, x, r);
 358                                 BUG_ON(item >= map->max_devices);
 359
 360                                 /* desired type? */
 361                                 if (item < 0)
 362                                         itemtype = map->buckets[-1-item]->type;
 363                                 else
 364                                         itemtype = 0;
 365                                 dprintk("  item %d type %d\n", item, itemtype);
 366
 367                                 /* keep going? */
 368                                 if (itemtype != type) {
 369                                         BUG_ON(item >= 0 ||
 370                                                (-1-item) >= map->max_buckets);
 371                                         in = map->buckets[-1-item];
 372                                         retry_bucket = 1;
 373                                         continue;
 374                                 }
 375
 376                                 /* collision? */
 377                                 for (i = 0; i < outpos; i++) {
 378                                         if (out[i] == item) {
 379                                                 collide = 1;
 380                                                 break;
 381                                         }
 382                                 }
 383
 384                                 reject = 0;
 385                                 if (recurse_to_leaf) {
 386                                         if (item < 0) {
 387                                                 if (crush_choose(map,
 388                                                          map->buckets[-1-item],
 389                                                          weight,
 390                                                          x, outpos+1, 0,
 391                                                          out2, outpos,
 392                                                          firstn, 0,
 393                                                          NULL) <= outpos)
 394                                                         /* didn't get leaf */
 395                                                         reject = 1;
 396                                         } else {
 397                                                 /* we already have a leaf! */
 398                                                 out2[outpos] = item;
 399                                         }
 400                                 }
 401
 402                                 if (!reject) {
 403                                         /* out? */
 404                                         if (itemtype == 0)
 405                                                 reject = is_out(map, weight,
 406                                                                 item, x);
 407                                         else
 408                                                 reject = 0;
 409                                 }
 410
 411 reject:
 412                                 if (reject || collide) {
 413                                         ftotal++;
 414                                         flocal++;
 415
 416                                         if (collide && flocal < 3)
 417                                                 /* retry locally a few times */
 418                                                 retry_bucket = 1;
 419                                         else if (flocal < in->size + orig_tries)
 420                                                 /* exhaustive bucket search */
 421                                                 retry_bucket = 1;
 422                                         else if (ftotal < 20)
 423                                                 /* then retry descent */
 424                                                 retry_descent = 1;
 425                                         else
 426                                                 /* else give up */
 427                                                 skip_rep = 1;
 428                                         dprintk("  reject %d  collide %d  "
 429                                                 "ftotal %d  flocal %d\n",
 430                                                 reject, collide, ftotal,
 431                                                 flocal);
 432                                 }
 433                         } while (retry_bucket);
 434                 } while (retry_descent);
 435
 436                 if (skip_rep) {
 437                         dprintk("skip rep\n");
 438                         continue;
 439                 }
 440
 441                 dprintk("CHOOSE got %d\n", item);
 442                 out[outpos] = item;
 443                 outpos++;
 444         }
 445
 446         dprintk("CHOOSE returns %d\n", outpos);
 447         return outpos;
 448 }
 449
 450
 451 /**
 452  * crush_do_rule - calculate a mapping with the given input and rule
 453  * @map: the crush_map
 454  * @ruleno: the rule id
 455  * @x: hash input
 456  * @result: pointer to result vector
 457  * @result_max: maximum result size
 458  * @force: force initial replica choice; -1 for none
 459  */
 460 int crush_do_rule(struct crush_map *map,
 461                   int ruleno, int x, int *result, int result_max,
 462                   int force, __u32 *weight)
 463 {
 464         int result_len;
 465         int force_context[CRUSH_MAX_DEPTH];
 466         int force_pos = -1;
 467         int a[CRUSH_MAX_SET];
 468         int b[CRUSH_MAX_SET];
 469         int c[CRUSH_MAX_SET];
 470         int recurse_to_leaf;
 471         int *w;
 472         int wsize = 0;
 473         int *o;
 474         int osize;
 475         int *tmp;
 476         struct crush_rule *rule;
 477         int step;
 478         int i, j;
 479         int numrep;
 480         int firstn;
 481
 482         BUG_ON(ruleno >= map->max_rules);
 483
 484         rule = map->rules[ruleno];
 485         result_len = 0;
 486         w = a;
 487         o = b;
 488
 489         /*
 490          * determine hierarchical context of force, if any.  note
 491          * that this may or may not correspond to the specific types
 492          * referenced by the crush rule.
 493          */
 494         if (force >= 0 &&
 495             force < map->max_devices &&
 496             map->device_parents[force] != 0 &&
 497             !is_out(map, weight, force, x)) {
 498                 while (1) {
 499                         force_context[++force_pos] = force;
 500                         if (force >= 0)
 501                                 force = map->device_parents[force];
 502                         else
 503                                 force = map->bucket_parents[-1-force];
 504                         if (force == 0)
 505                                 break;
 506                 }
 507         }
 508
 509         for (step = 0; step < rule->len; step++) {
 510                 firstn = 0;
 511                 switch (rule->steps[step].op) {
 512                 case CRUSH_RULE_TAKE:
 513                         w[0] = rule->steps[step].arg1;
 514
 515                         /* find position in force_context/hierarchy */
 516                         while (force_pos >= 0 &&
 517                                force_context[force_pos] != w[0])
 518                                 force_pos--;
 519                         /* and move past it */
 520                         if (force_pos >= 0)
 521                                 force_pos--;
 522
 523                         wsize = 1;
 524                         break;
 525
 526                 case CRUSH_RULE_CHOOSE_LEAF_FIRSTN:
 527                 case CRUSH_RULE_CHOOSE_FIRSTN:
 528                         firstn = 1;
 529                 case CRUSH_RULE_CHOOSE_LEAF_INDEP:
 530                 case CRUSH_RULE_CHOOSE_INDEP:
 531                         BUG_ON(wsize == 0);
 532
 533                         recurse_to_leaf =
 534                                 rule->steps[step].op ==
 535                                  CRUSH_RULE_CHOOSE_LEAF_FIRSTN ||
 536                                 rule->steps[step].op ==
 537                                 CRUSH_RULE_CHOOSE_LEAF_INDEP;
 538
 539                         /* reset output */
 540                         osize = 0;
 541
 542                         for (i = 0; i < wsize; i++) {
 543                                 /*
 544                                  * see CRUSH_N, CRUSH_N_MINUS macros.
 545                                  * basically, numrep <= 0 means relative to
 546                                  * the provided result_max
 547                                  */
 548                                 numrep = rule->steps[step].arg1;
 549                                 if (numrep <= 0) {
 550                                         numrep += result_max;
 551                                         if (numrep <= 0)
 552                                                 continue;
 553                                 }
 554                                 j = 0;
 555                                 if (osize == 0 && force_pos >= 0) {
 556                                         /* skip any intermediate types */
 557                                         while (force_pos &&
 558                                                force_context[force_pos] < 0 &&
 559                                                rule->steps[step].arg2 !=
 560                                                map->buckets[-1 -
 561                                                force_context[force_pos]]->type)
 562                                                 force_pos--;
 563                                         o[osize] = force_context[force_pos];
 564                                         if (recurse_to_leaf)
 565                                                 c[osize] = force_context[0];
 566                                         j++;
 567                                         force_pos--;
 568                                 }
 569                                 osize += crush_choose(map,
 570                                                       map->buckets[-1-w[i]],
 571                                                       weight,
 572                                                       x, numrep,
 573                                                       rule->steps[step].arg2,
 574                                                       o+osize, j,
 575                                                       firstn,
 576                                                       recurse_to_leaf, c+osize);
 577                         }
 578
 579                         if (recurse_to_leaf)
 580                                 /* copy final _leaf_ values to output set */
 581                                 memcpy(o, c, osize*sizeof(*o));
 582
 583                         /* swap t and w arrays */
 584                         tmp = o;
 585                         o = w;
 586                         w = tmp;
 587                         wsize = osize;
 588                         break;
 589
 590
 591                 case CRUSH_RULE_EMIT:
 592                         for (i = 0; i < wsize && result_len < result_max; i++) {
 593                                 result[result_len] = w[i];
 594                                 result_len++;
 595                         }
 596                         wsize = 0;
 597                         break;
 598
 599                 default:
 600                         BUG_ON(1);
 601                 }
 602         }
 603         return result_len;
 604 }
 605
 606