fs/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 "crush.h"
  22 #include "hash.h"
  23
  24 /*
  25  * Implement the core CRUSH mapping algorithm.
  26  */
  27
  28 /**
  29  * crush_find_rule - find a crush_rule id for a given ruleset, type, and size.
  30  * @map: the crush_map
  31  * @ruleset: the storage ruleset id (user defined)
  32  * @type: storage ruleset type (user defined)
  33  * @size: output set size
  34  */
  35 int crush_find_rule(struct crush_map *map, int ruleset, int type, int size)
  36 {
  37         int i;
  38
  39         for (i = 0; i < map->max_rules; i++) {
  40                 if (map->rules[i] &&
  41                     map->rules[i]->mask.ruleset == ruleset &&
  42                     map->rules[i]->mask.type == type &&
  43                     map->rules[i]->mask.min_size <= size &&
  44                     map->rules[i]->mask.max_size >= size)
  45                         return i;
  46         }
  47         return -1;
  48 }
  49
  50
  51 /*
  52  * bucket choose methods
  53  *
  54  * For each bucket algorithm, we have a "choose" method that, given a
  55  * crush input @x and replica position (usually, position in output set) @r,
  56  * will produce an item in the bucket.
  57  */
  58
  59 /*
  60  * Choose based on a random permutation of the bucket.
  61  *
  62  * We used to use some prime number arithmetic to do this, but it
  63  * wasn't very random, and had some other bad behaviors.  Instead, we
  64  * calculate an actual random permutation of the bucket members.
  65  * Since this is expensive, we optimize for the r=0 case, which
  66  * captures the vast majority of calls.
  67  */
  68 static int bucket_perm_choose(struct crush_bucket *bucket,
  69                               int x, int r)
  70 {
  71         unsigned pr = r % bucket->size;
  72         unsigned i, s;
  73
  74         /* start a new permutation if @x has changed */
  75         if (bucket->perm_x != x || bucket->perm_n == 0) {
  76                 dprintk("bucket %d new x=%d\n", bucket->id, x);
  77                 bucket->perm_x = x;
  78
  79                 /* optimize common r=0 case */
  80                 if (pr == 0) {
  81                         s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
  82                                 bucket->size;
  83                         bucket->perm[0] = s;
  84                         bucket->perm_n = 0xffff;   /* magic value, see below */
  85                         goto out;
  86                 }
  87
  88                 for (i = 0; i < bucket->size; i++)
  89                         bucket->perm[i] = i;
  90                 bucket->perm_n = 0;
  91         } else if (bucket->perm_n == 0xffff) {
  92                 /* clean up after the r=0 case above */
  93                 for (i = 1; i < bucket->size; i++)
  94                         bucket->perm[i] = i;
  95                 bucket->perm[bucket->perm[0]] = 0;
  96                 bucket->perm_n = 1;
  97         }
  98
  99         /* calculate permutation up to pr */
 100         for (i = 0; i < bucket->perm_n; i++)
 101                 dprintk(" perm_choose have %d: %d\n", i, bucket->perm[i]);
 102         while (bucket->perm_n <= pr) {
 103                 unsigned p = bucket->perm_n;
 104                 /* no point in swapping the final entry */
 105                 if (p < bucket->size - 1) {
 106                         i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
 107                                 (bucket->size - p);
 108                         if (i) {
 109                                 unsigned t = bucket->perm[p + i];
 110                                 bucket->perm[p + i] = bucket->perm[p];
 111                                 bucket->perm[p] = t;
 112                         }
 113                         dprintk(" perm_choose swap %d with %d\n", p, p+i);
 114                 }
 115                 bucket->perm_n++;
 116         }
 117         for (i = 0; i < bucket->size; i++)
 118                 dprintk(" perm_choose  %d: %d\n", i, bucket->perm[i]);
 119
 120         s = bucket->perm[pr];
 121 out:
 122         dprintk(" perm_choose %d sz=%d x=%d r=%d (%d) s=%d\n", bucket->id,
 123                 bucket->size, x, r, pr, s);
 124         return bucket->items[s];
 125 }
 126
 127 /* uniform */
 128 static int bucket_uniform_choose(struct crush_bucket_uniform *bucket,
 129                                  int x, int r)
 130 {
 131         return bucket_perm_choose(&bucket->h, x, r);
 132 }
 133
 134 /* list */
 135 static int bucket_list_choose(struct crush_bucket_list *bucket,
 136                               int x, int r)
 137 {
 138         int i;
 139
 140         for (i = bucket->h.size-1; i >= 0; i--) {
 141                 __u64 w = crush_hash32_4(bucket->h.hash,x, bucket->h.items[i],
 142                                          r, bucket->h.id);
 143                 w &= 0xffff;
 144                 dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
 145                         "sw %x rand %llx",
 146                         i, x, r, bucket->h.items[i], bucket->item_weights[i],
 147                         bucket->sum_weights[i], w);
 148                 w *= bucket->sum_weights[i];
 149                 w = w >> 16;
 150                 /*dprintk(" scaled %llx\n", w);*/
 151                 if (w < bucket->item_weights[i])
 152                         return bucket->h.items[i];
 153         }
 154
 155         BUG_ON(1);
 156         return 0;
 157 }
 158
 159
 160 /* (binary) tree */
 161 static int height(int n)
 162 {
 163         int h = 0;
 164         while ((n & 1) == 0) {
 165                 h++;
 166                 n = n >> 1;
 167         }
 168         return h;
 169 }
 170
 171 static int left(int x)
 172 {
 173         int h = height(x);
 174         return x - (1 << (h-1));
 175 }
 176
 177 static int right(int x)
 178 {
 179         int h = height(x);
 180         return x + (1 << (h-1));
 181 }
 182
 183 static int terminal(int x)
 184 {
 185         return x & 1;
 186 }
 187
 188 static int bucket_tree_choose(struct crush_bucket_tree *bucket,
 189                               int x, int r)
 190 {
 191         int n, l;
 192         __u32 w;
 193         __u64 t;
 194
 195         /* start at root */
 196         n = bucket->num_nodes >> 1;
 197
 198         while (!terminal(n)) {
 199                 /* pick point in [0, w) */
 200                 w = bucket->node_weights[n];
 201                 t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
 202                                           bucket->h.id) * (__u64)w;
 203                 t = t >> 32;
 204
 205                 /* descend to the left or right? */
 206                 l = left(n);
 207                 if (t < bucket->node_weights[l])
 208                         n = l;
 209                 else
 210                         n = right(n);
 211         }
 212
 213         return bucket->h.items[n >> 1];
 214 }
 215
 216
 217 /* straw */
 218
 219 static int bucket_straw_choose(struct crush_bucket_straw *bucket,
 220                                int x, int r)
 221 {
 222         int i;
 223         int high = 0;
 224         __u64 high_draw = 0;
 225         __u64 draw;
 226
 227         for (i = 0; i < bucket->h.size; i++) {
 228                 draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
 229                 draw &= 0xffff;
 230                 draw *= bucket->straws[i];
 231                 if (i == 0 || draw > high_draw) {
 232                         high = i;
 233                         high_draw = draw;
 234                 }
 235         }
 236         return bucket->h.items[high];
 237 }
 238
 239 static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
 240 {
 241         dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
 242         switch (in->alg) {
 243         case CRUSH_BUCKET_UNIFORM:
 244                 return bucket_uniform_choose((struct crush_bucket_uniform *)in,
 245                                           x, r);
 246         case CRUSH_BUCKET_LIST:
 247                 return bucket_list_choose((struct crush_bucket_list *)in,
 248                                           x, r);
 249         case CRUSH_BUCKET_TREE:
 250                 return bucket_tree_choose((struct crush_bucket_tree *)in,
 251                                           x, r);
 252         case CRUSH_BUCKET_STRAW:
 253                 return bucket_straw_choose((struct crush_bucket_straw *)in,
 254                                            x, r);
 255         default:
 256                 BUG_ON(1);
 257                 return in->items[0];
 258         }
 259 }
 260
 261 /*
 262  * true if device is marked "out" (failed, fully offloaded)
 263  * of the cluster
 264  */
 265 static int is_out(struct crush_map *map, __u32 *weight, int item, int x)
 266 {
 267         if (weight[item] >= 0x10000)
 268                 return 0;
 269         if (weight[item] == 0)
 270                 return 1;
 271         if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
 272             < weight[item])
 273                 return 0;
 274         return 1;
 275 }
 276
 277 /**
 278  * crush_choose - choose numrep distinct items of given type
 279  * @map: the crush_map
 280  * @bucket: the bucket we are choose an item from
 281  * @x: crush input value
 282  * @numrep: the number of items to choose
 283  * @type: the type of item to choose
 284  * @out: pointer to output vector
 285  * @outpos: our position in that vector
 286  * @firstn: true if choosing "first n" items, false if choosing "indep"
 287  * @recurse_to_leaf: true if we want one device under each item of given type
 288  * @out2: second output vector for leaf items (if @recurse_to_leaf)
 289  */
 290 static int crush_choose(struct crush_map *map,
 291                         struct crush_bucket *bucket,
 292                         __u32 *weight,
 293                         int x, int numrep, int type,
 294                         int *out, int outpos,
 295                         int firstn, int recurse_to_leaf,
 296                         int *out2)
 297 {
 298         int rep;
 299         int ftotal, flocal;
 300         int retry_descent, retry_bucket, skip_rep;
 301         struct crush_bucket *in = bucket;
 302         int r;
 303         int i;
 304         int item = 0;
 305         int itemtype;
 306         int collide, reject;
 307         const int orig_tries = 5; /* attempts before we fall back to search */
 308
 309         dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
 310                 bucket->id, x, outpos, numrep);
 311
 312         for (rep = outpos; rep < numrep; rep++) {
 313                 /* keep trying until we get a non-out, non-colliding item */
 314                 ftotal = 0;
 315                 skip_rep = 0;
 316                 do {
 317                         retry_descent = 0;
 318                         in = bucket;               /* initial bucket */
 319
 320                         /* choose through intervening buckets */
 321                         flocal = 0;
 322                         do {
 323                                 collide = 0;
 324                                 retry_bucket = 0;
 325                                 r = rep;
 326                                 if (in->alg == CRUSH_BUCKET_UNIFORM) {
 327                                         /* be careful */
 328                                         if (firstn || numrep >= in->size)
 329                                                 /* r' = r + f_total */
 330                                                 r += ftotal;
 331                                         else if (in->size % numrep == 0)
 332                                                 /* r'=r+(n+1)*f_local */
 333                                                 r += (numrep+1) *
 334                                                         (flocal+ftotal);
 335                                         else
 336                                                 /* r' = r + n*f_local */
 337                                                 r += numrep * (flocal+ftotal);
 338                                 } else {
 339                                         if (firstn)
 340                                                 /* r' = r + f_total */
 341                                                 r += ftotal;
 342                                         else
 343                                                 /* r' = r + n*f_local */
 344                                                 r += numrep * (flocal+ftotal);
 345                                 }
 346
 347                                 /* bucket choose */
 348                                 if (in->size == 0) {
 349                                         reject = 1;
 350                                         goto reject;
 351                                 }
 352                                 if (flocal >= (in->size>>1) &&
 353                                     flocal > orig_tries)
 354                                         item = bucket_perm_choose(in, x, r);
 355                                 else
 356                                         item = crush_bucket_choose(in, x, r);
 357                                 BUG_ON(item >= map->max_devices);
 358
 359                                 /* desired type? */
 360                                 if (item < 0)
 361                                         itemtype = map->buckets[-1-item]->type;
 362                                 else
 363                                         itemtype = 0;
 364                                 dprintk("  item %d type %d\n", item, itemtype);
 365
 366                                 /* keep going? */
 367                                 if (itemtype != type) {
 368                                         BUG_ON(item >= 0 ||
 369                                                (-1-item) >= map->max_buckets);
 370                                         in = map->buckets[-1-item];
 371                                         retry_bucket = 1;
 372                                         continue;
 373                                 }
 374
 375                                 /* collision? */
 376                                 for (i = 0; i < outpos; i++) {
 377                                         if (out[i] == item) {
 378                                                 collide = 1;
 379                                                 break;
 380                                         }
 381                                 }
 382
 383                                 reject = 0;
 384                                 if (recurse_to_leaf) {
 385                                         if (item < 0) {
 386                                                 if (crush_choose(map,
 387                                                          map->buckets[-1-item],
 388                                                          weight,
 389                                                          x, outpos+1, 0,
 390                                                          out2, outpos,
 391                                                          firstn, 0,
 392                                                          NULL) <= outpos)
 393                                                         /* didn't get leaf */
 394                                                         reject = 1;
 395                                         } else {
 396                                                 /* we already have a leaf! */
 397                                                 out2[outpos] = item;
 398                                         }
 399                                 }
 400
 401                                 if (!reject) {
 402                                         /* out? */
 403                                         if (itemtype == 0)
 404                                                 reject = is_out(map, weight,
 405                                                                 item, x);
 406                                         else
 407                                                 reject = 0;
 408                                 }
 409
 410 reject:
 411                                 if (reject || collide) {
 412                                         ftotal++;
 413                                         flocal++;
 414
 415                                         if (collide && flocal < 3)
 416                                                 /* retry locally a few times */
 417                                                 retry_bucket = 1;
 418                                         else if (flocal < in->size + orig_tries)
 419                                                 /* exhaustive bucket search */
 420                                                 retry_bucket = 1;
 421                                         else if (ftotal < 20)
 422                                                 /* then retry descent */
 423                                                 retry_descent = 1;
 424                                         else
 425                                                 /* else give up */
 426                                                 skip_rep = 1;
 427                                         dprintk("  reject %d  collide %d  "
 428                                                 "ftotal %d  flocal %d\n",
 429                                                 reject, collide, ftotal,
 430                                                 flocal);
 431                                 }
 432                         } while (retry_bucket);
 433                 } while (retry_descent);
 434
 435                 if (skip_rep) {
 436                         dprintk("skip rep\n");
 437                         continue;
 438                 }
 439
 440                 dprintk("CHOOSE got %d\n", item);
 441                 out[outpos] = item;
 442                 outpos++;
 443         }
 444
 445         dprintk("CHOOSE returns %d\n", outpos);
 446         return outpos;
 447 }
 448
 449
 450 /**
 451  * crush_do_rule - calculate a mapping with the given input and rule
 452  * @map: the crush_map
 453  * @ruleno: the rule id
 454  * @x: hash input
 455  * @result: pointer to result vector
 456  * @result_max: maximum result size
 457  * @force: force initial replica choice; -1 for none
 458  */
 459 int crush_do_rule(struct crush_map *map,
 460                   int ruleno, int x, int *result, int result_max,
 461                   int force, __u32 *weight)
 462 {
 463         int result_len;
 464         int force_context[CRUSH_MAX_DEPTH];
 465         int force_pos = -1;
 466         int a[CRUSH_MAX_SET];
 467         int b[CRUSH_MAX_SET];
 468         int c[CRUSH_MAX_SET];
 469         int recurse_to_leaf;
 470         int *w;
 471         int wsize = 0;
 472         int *o;
 473         int osize;
 474         int *tmp;
 475         struct crush_rule *rule;
 476         int step;
 477         int i, j;
 478         int numrep;
 479         int firstn;
 480         int rc = -1;
 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                 if (force >= map->max_devices ||
 496                     map->device_parents[force] == 0) {
 497                         /*dprintk("CRUSH: forcefed device dne\n");*/
 498                         rc = -1;  /* force fed device dne */
 499                         goto out;
 500                 }
 501                 if (!is_out(map, weight, force, x)) {
 502                         while (1) {
 503                                 force_context[++force_pos] = force;
 504                                 if (force >= 0)
 505                                         force = map->device_parents[force];
 506                                 else
 507                                         force = map->bucket_parents[-1-force];
 508                                 if (force == 0)
 509                                         break;
 510                         }
 511                 }
 512         }
 513
 514         for (step = 0; step < rule->len; step++) {
 515                 firstn = 0;
 516                 switch (rule->steps[step].op) {
 517                 case CRUSH_RULE_TAKE:
 518                         w[0] = rule->steps[step].arg1;
 519                         if (force_pos >= 0) {
 520                                 BUG_ON(force_context[force_pos] != w[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         rc = result_len;
 604
 605 out:
 606         return rc;
 607 }
 608
 609