linux/net/ceph/crush/mapper.c
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   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 */
  42int 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 */
  74static 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];
 128out:
 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 */
 135static 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 */
 142static 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 */
 169static 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
 179static int left(int x)
 180{
 181        int h = height(x);
 182        return x - (1 << (h-1));
 183}
 184
 185static int right(int x)
 186{
 187        int h = height(x);
 188        return x + (1 << (h-1));
 189}
 190
 191static int terminal(int x)
 192{
 193        return x & 1;
 194}
 195
 196static 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
 228static 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) */
 249static __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
 305static __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
 317static __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
 326static 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
 376static 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 */
 413static 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 */
 449static 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] : NULL),
 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
 593reject:
 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 */
 643static 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] : NULL),
 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 */
 848void 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 */
 894int 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}
1100