module/zfs/ddt.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
  24  * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  25  */
  26
  27 #include <sys/zfs_context.h>
  28 #include <sys/spa.h>
  29 #include <sys/spa_impl.h>
  30 #include <sys/zio.h>
  31 #include <sys/ddt.h>
  32 #include <sys/zap.h>
  33 #include <sys/dmu_tx.h>
  34 #include <sys/arc.h>
  35 #include <sys/dsl_pool.h>
  36 #include <sys/zio_checksum.h>
  37 #include <sys/zio_compress.h>
  38 #include <sys/dsl_scan.h>
  39 #include <sys/abd.h>
  40
  41 static kmem_cache_t *ddt_cache;
  42 static kmem_cache_t *ddt_entry_cache;
  43
  44 /*
  45  * Enable/disable prefetching of dedup-ed blocks which are going to be freed.
  46  */
  47 int zfs_dedup_prefetch = 0;
  48
  49 static const ddt_ops_t *ddt_ops[DDT_TYPES] = {
  50         &ddt_zap_ops,
  51 };
  52
  53 static const char *ddt_class_name[DDT_CLASSES] = {
  54         "ditto",
  55         "duplicate",
  56         "unique",
  57 };
  58
  59 static void
  60 ddt_object_create(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
  61     dmu_tx_t *tx)
  62 {
  63         spa_t *spa = ddt->ddt_spa;
  64         objset_t *os = ddt->ddt_os;
  65         uint64_t *objectp = &ddt->ddt_object[type][class];
  66         boolean_t prehash = zio_checksum_table[ddt->ddt_checksum].ci_flags &
  67             ZCHECKSUM_FLAG_DEDUP;
  68         char name[DDT_NAMELEN];
  69
  70         ddt_object_name(ddt, type, class, name);
  71
  72         ASSERT(*objectp == 0);
  73         VERIFY(ddt_ops[type]->ddt_op_create(os, objectp, tx, prehash) == 0);
  74         ASSERT(*objectp != 0);
  75
  76         VERIFY(zap_add(os, DMU_POOL_DIRECTORY_OBJECT, name,
  77             sizeof (uint64_t), 1, objectp, tx) == 0);
  78
  79         VERIFY(zap_add(os, spa->spa_ddt_stat_object, name,
  80             sizeof (uint64_t), sizeof (ddt_histogram_t) / sizeof (uint64_t),
  81             &ddt->ddt_histogram[type][class], tx) == 0);
  82 }
  83
  84 static void
  85 ddt_object_destroy(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
  86     dmu_tx_t *tx)
  87 {
  88         spa_t *spa = ddt->ddt_spa;
  89         objset_t *os = ddt->ddt_os;
  90         uint64_t *objectp = &ddt->ddt_object[type][class];
  91         uint64_t count;
  92         char name[DDT_NAMELEN];
  93
  94         ddt_object_name(ddt, type, class, name);
  95
  96         ASSERT(*objectp != 0);
  97         ASSERT(ddt_histogram_empty(&ddt->ddt_histogram[type][class]));
  98         VERIFY(ddt_object_count(ddt, type, class, &count) == 0 && count == 0);
  99         VERIFY(zap_remove(os, DMU_POOL_DIRECTORY_OBJECT, name, tx) == 0);
 100         VERIFY(zap_remove(os, spa->spa_ddt_stat_object, name, tx) == 0);
 101         VERIFY(ddt_ops[type]->ddt_op_destroy(os, *objectp, tx) == 0);
 102         bzero(&ddt->ddt_object_stats[type][class], sizeof (ddt_object_t));
 103
 104         *objectp = 0;
 105 }
 106
 107 static int
 108 ddt_object_load(ddt_t *ddt, enum ddt_type type, enum ddt_class class)
 109 {
 110         ddt_object_t *ddo = &ddt->ddt_object_stats[type][class];
 111         dmu_object_info_t doi;
 112         uint64_t count;
 113         char name[DDT_NAMELEN];
 114         int error;
 115
 116         ddt_object_name(ddt, type, class, name);
 117
 118         error = zap_lookup(ddt->ddt_os, DMU_POOL_DIRECTORY_OBJECT, name,
 119             sizeof (uint64_t), 1, &ddt->ddt_object[type][class]);
 120         if (error != 0)
 121                 return (error);
 122
 123         error = zap_lookup(ddt->ddt_os, ddt->ddt_spa->spa_ddt_stat_object, name,
 124             sizeof (uint64_t), sizeof (ddt_histogram_t) / sizeof (uint64_t),
 125             &ddt->ddt_histogram[type][class]);
 126         if (error != 0)
 127                 return (error);
 128
 129         /*
 130          * Seed the cached statistics.
 131          */
 132         error = ddt_object_info(ddt, type, class, &doi);
 133         if (error)
 134                 return (error);
 135
 136         error = ddt_object_count(ddt, type, class, &count);
 137         if (error)
 138                 return (error);
 139
 140         ddo->ddo_count = count;
 141         ddo->ddo_dspace = doi.doi_physical_blocks_512 << 9;
 142         ddo->ddo_mspace = doi.doi_fill_count * doi.doi_data_block_size;
 143
 144         return (0);
 145 }
 146
 147 static void
 148 ddt_object_sync(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 149     dmu_tx_t *tx)
 150 {
 151         ddt_object_t *ddo = &ddt->ddt_object_stats[type][class];
 152         dmu_object_info_t doi;
 153         uint64_t count;
 154         char name[DDT_NAMELEN];
 155
 156         ddt_object_name(ddt, type, class, name);
 157
 158         VERIFY(zap_update(ddt->ddt_os, ddt->ddt_spa->spa_ddt_stat_object, name,
 159             sizeof (uint64_t), sizeof (ddt_histogram_t) / sizeof (uint64_t),
 160             &ddt->ddt_histogram[type][class], tx) == 0);
 161
 162         /*
 163          * Cache DDT statistics; this is the only time they'll change.
 164          */
 165         VERIFY(ddt_object_info(ddt, type, class, &doi) == 0);
 166         VERIFY(ddt_object_count(ddt, type, class, &count) == 0);
 167
 168         ddo->ddo_count = count;
 169         ddo->ddo_dspace = doi.doi_physical_blocks_512 << 9;
 170         ddo->ddo_mspace = doi.doi_fill_count * doi.doi_data_block_size;
 171 }
 172
 173 static int
 174 ddt_object_lookup(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 175     ddt_entry_t *dde)
 176 {
 177         if (!ddt_object_exists(ddt, type, class))
 178                 return (SET_ERROR(ENOENT));
 179
 180         return (ddt_ops[type]->ddt_op_lookup(ddt->ddt_os,
 181             ddt->ddt_object[type][class], dde));
 182 }
 183
 184 static void
 185 ddt_object_prefetch(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 186     ddt_entry_t *dde)
 187 {
 188         if (!ddt_object_exists(ddt, type, class))
 189                 return;
 190
 191         ddt_ops[type]->ddt_op_prefetch(ddt->ddt_os,
 192             ddt->ddt_object[type][class], dde);
 193 }
 194
 195 int
 196 ddt_object_update(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 197     ddt_entry_t *dde, dmu_tx_t *tx)
 198 {
 199         ASSERT(ddt_object_exists(ddt, type, class));
 200
 201         return (ddt_ops[type]->ddt_op_update(ddt->ddt_os,
 202             ddt->ddt_object[type][class], dde, tx));
 203 }
 204
 205 static int
 206 ddt_object_remove(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 207     ddt_entry_t *dde, dmu_tx_t *tx)
 208 {
 209         ASSERT(ddt_object_exists(ddt, type, class));
 210
 211         return (ddt_ops[type]->ddt_op_remove(ddt->ddt_os,
 212             ddt->ddt_object[type][class], dde, tx));
 213 }
 214
 215 int
 216 ddt_object_walk(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 217     uint64_t *walk, ddt_entry_t *dde)
 218 {
 219         ASSERT(ddt_object_exists(ddt, type, class));
 220
 221         return (ddt_ops[type]->ddt_op_walk(ddt->ddt_os,
 222             ddt->ddt_object[type][class], dde, walk));
 223 }
 224
 225 int
 226 ddt_object_count(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 227     uint64_t *count)
 228 {
 229         ASSERT(ddt_object_exists(ddt, type, class));
 230
 231         return (ddt_ops[type]->ddt_op_count(ddt->ddt_os,
 232             ddt->ddt_object[type][class], count));
 233 }
 234
 235 int
 236 ddt_object_info(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 237     dmu_object_info_t *doi)
 238 {
 239         if (!ddt_object_exists(ddt, type, class))
 240                 return (SET_ERROR(ENOENT));
 241
 242         return (dmu_object_info(ddt->ddt_os, ddt->ddt_object[type][class],
 243             doi));
 244 }
 245
 246 boolean_t
 247 ddt_object_exists(ddt_t *ddt, enum ddt_type type, enum ddt_class class)
 248 {
 249         return (!!ddt->ddt_object[type][class]);
 250 }
 251
 252 void
 253 ddt_object_name(ddt_t *ddt, enum ddt_type type, enum ddt_class class,
 254     char *name)
 255 {
 256         (void) sprintf(name, DMU_POOL_DDT,
 257             zio_checksum_table[ddt->ddt_checksum].ci_name,
 258             ddt_ops[type]->ddt_op_name, ddt_class_name[class]);
 259 }
 260
 261 void
 262 ddt_bp_fill(const ddt_phys_t *ddp, blkptr_t *bp, uint64_t txg)
 263 {
 264         ASSERT(txg != 0);
 265
 266         for (int d = 0; d < SPA_DVAS_PER_BP; d++)
 267                 bp->blk_dva[d] = ddp->ddp_dva[d];
 268         BP_SET_BIRTH(bp, txg, ddp->ddp_phys_birth);
 269 }
 270
 271 /*
 272  * The bp created via this function may be used for repairs and scrub, but it
 273  * will be missing the salt / IV required to do a full decrypting read.
 274  */
 275 void
 276 ddt_bp_create(enum zio_checksum checksum,
 277     const ddt_key_t *ddk, const ddt_phys_t *ddp, blkptr_t *bp)
 278 {
 279         BP_ZERO(bp);
 280
 281         if (ddp != NULL)
 282                 ddt_bp_fill(ddp, bp, ddp->ddp_phys_birth);
 283
 284         bp->blk_cksum = ddk->ddk_cksum;
 285
 286         BP_SET_LSIZE(bp, DDK_GET_LSIZE(ddk));
 287         BP_SET_PSIZE(bp, DDK_GET_PSIZE(ddk));
 288         BP_SET_COMPRESS(bp, DDK_GET_COMPRESS(ddk));
 289         BP_SET_CRYPT(bp, DDK_GET_CRYPT(ddk));
 290         BP_SET_FILL(bp, 1);
 291         BP_SET_CHECKSUM(bp, checksum);
 292         BP_SET_TYPE(bp, DMU_OT_DEDUP);
 293         BP_SET_LEVEL(bp, 0);
 294         BP_SET_DEDUP(bp, 0);
 295         BP_SET_BYTEORDER(bp, ZFS_HOST_BYTEORDER);
 296 }
 297
 298 void
 299 ddt_key_fill(ddt_key_t *ddk, const blkptr_t *bp)
 300 {
 301         ddk->ddk_cksum = bp->blk_cksum;
 302         ddk->ddk_prop = 0;
 303
 304         ASSERT(BP_IS_ENCRYPTED(bp) || !BP_USES_CRYPT(bp));
 305
 306         DDK_SET_LSIZE(ddk, BP_GET_LSIZE(bp));
 307         DDK_SET_PSIZE(ddk, BP_GET_PSIZE(bp));
 308         DDK_SET_COMPRESS(ddk, BP_GET_COMPRESS(bp));
 309         DDK_SET_CRYPT(ddk, BP_USES_CRYPT(bp));
 310 }
 311
 312 void
 313 ddt_phys_fill(ddt_phys_t *ddp, const blkptr_t *bp)
 314 {
 315         ASSERT(ddp->ddp_phys_birth == 0);
 316
 317         for (int d = 0; d < SPA_DVAS_PER_BP; d++)
 318                 ddp->ddp_dva[d] = bp->blk_dva[d];
 319         ddp->ddp_phys_birth = BP_PHYSICAL_BIRTH(bp);
 320 }
 321
 322 void
 323 ddt_phys_clear(ddt_phys_t *ddp)
 324 {
 325         bzero(ddp, sizeof (*ddp));
 326 }
 327
 328 void
 329 ddt_phys_addref(ddt_phys_t *ddp)
 330 {
 331         ddp->ddp_refcnt++;
 332 }
 333
 334 void
 335 ddt_phys_decref(ddt_phys_t *ddp)
 336 {
 337         if (ddp) {
 338                 ASSERT(ddp->ddp_refcnt > 0);
 339                 ddp->ddp_refcnt--;
 340         }
 341 }
 342
 343 void
 344 ddt_phys_free(ddt_t *ddt, ddt_key_t *ddk, ddt_phys_t *ddp, uint64_t txg)
 345 {
 346         blkptr_t blk;
 347
 348         ddt_bp_create(ddt->ddt_checksum, ddk, ddp, &blk);
 349         ddt_phys_clear(ddp);
 350         zio_free(ddt->ddt_spa, txg, &blk);
 351 }
 352
 353 ddt_phys_t *
 354 ddt_phys_select(const ddt_entry_t *dde, const blkptr_t *bp)
 355 {
 356         ddt_phys_t *ddp = (ddt_phys_t *)dde->dde_phys;
 357
 358         for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
 359                 if (DVA_EQUAL(BP_IDENTITY(bp), &ddp->ddp_dva[0]) &&
 360                     BP_PHYSICAL_BIRTH(bp) == ddp->ddp_phys_birth)
 361                         return (ddp);
 362         }
 363         return (NULL);
 364 }
 365
 366 uint64_t
 367 ddt_phys_total_refcnt(const ddt_entry_t *dde)
 368 {
 369         uint64_t refcnt = 0;
 370
 371         for (int p = DDT_PHYS_SINGLE; p <= DDT_PHYS_TRIPLE; p++)
 372                 refcnt += dde->dde_phys[p].ddp_refcnt;
 373
 374         return (refcnt);
 375 }
 376
 377 static void
 378 ddt_stat_generate(ddt_t *ddt, ddt_entry_t *dde, ddt_stat_t *dds)
 379 {
 380         spa_t *spa = ddt->ddt_spa;
 381         ddt_phys_t *ddp = dde->dde_phys;
 382         ddt_key_t *ddk = &dde->dde_key;
 383         uint64_t lsize = DDK_GET_LSIZE(ddk);
 384         uint64_t psize = DDK_GET_PSIZE(ddk);
 385
 386         bzero(dds, sizeof (*dds));
 387
 388         for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
 389                 uint64_t dsize = 0;
 390                 uint64_t refcnt = ddp->ddp_refcnt;
 391
 392                 if (ddp->ddp_phys_birth == 0)
 393                         continue;
 394
 395                 for (int d = 0; d < DDE_GET_NDVAS(dde); d++)
 396                         dsize += dva_get_dsize_sync(spa, &ddp->ddp_dva[d]);
 397
 398                 dds->dds_blocks += 1;
 399                 dds->dds_lsize += lsize;
 400                 dds->dds_psize += psize;
 401                 dds->dds_dsize += dsize;
 402
 403                 dds->dds_ref_blocks += refcnt;
 404                 dds->dds_ref_lsize += lsize * refcnt;
 405                 dds->dds_ref_psize += psize * refcnt;
 406                 dds->dds_ref_dsize += dsize * refcnt;
 407         }
 408 }
 409
 410 void
 411 ddt_stat_add(ddt_stat_t *dst, const ddt_stat_t *src, uint64_t neg)
 412 {
 413         const uint64_t *s = (const uint64_t *)src;
 414         uint64_t *d = (uint64_t *)dst;
 415         uint64_t *d_end = (uint64_t *)(dst + 1);
 416
 417         ASSERT(neg == 0 || neg == -1ULL);       /* add or subtract */
 418
 419         while (d < d_end)
 420                 *d++ += (*s++ ^ neg) - neg;
 421 }
 422
 423 static void
 424 ddt_stat_update(ddt_t *ddt, ddt_entry_t *dde, uint64_t neg)
 425 {
 426         ddt_stat_t dds;
 427         ddt_histogram_t *ddh;
 428         int bucket;
 429
 430         ddt_stat_generate(ddt, dde, &dds);
 431
 432         bucket = highbit64(dds.dds_ref_blocks) - 1;
 433         ASSERT(bucket >= 0);
 434
 435         ddh = &ddt->ddt_histogram[dde->dde_type][dde->dde_class];
 436
 437         ddt_stat_add(&ddh->ddh_stat[bucket], &dds, neg);
 438 }
 439
 440 void
 441 ddt_histogram_add(ddt_histogram_t *dst, const ddt_histogram_t *src)
 442 {
 443         for (int h = 0; h < 64; h++)
 444                 ddt_stat_add(&dst->ddh_stat[h], &src->ddh_stat[h], 0);
 445 }
 446
 447 void
 448 ddt_histogram_stat(ddt_stat_t *dds, const ddt_histogram_t *ddh)
 449 {
 450         bzero(dds, sizeof (*dds));
 451
 452         for (int h = 0; h < 64; h++)
 453                 ddt_stat_add(dds, &ddh->ddh_stat[h], 0);
 454 }
 455
 456 boolean_t
 457 ddt_histogram_empty(const ddt_histogram_t *ddh)
 458 {
 459         const uint64_t *s = (const uint64_t *)ddh;
 460         const uint64_t *s_end = (const uint64_t *)(ddh + 1);
 461
 462         while (s < s_end)
 463                 if (*s++ != 0)
 464                         return (B_FALSE);
 465
 466         return (B_TRUE);
 467 }
 468
 469 void
 470 ddt_get_dedup_object_stats(spa_t *spa, ddt_object_t *ddo_total)
 471 {
 472         /* Sum the statistics we cached in ddt_object_sync(). */
 473         for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 474                 ddt_t *ddt = spa->spa_ddt[c];
 475                 for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
 476                         for (enum ddt_class class = 0; class < DDT_CLASSES;
 477                             class++) {
 478                                 ddt_object_t *ddo =
 479                                     &ddt->ddt_object_stats[type][class];
 480                                 ddo_total->ddo_count += ddo->ddo_count;
 481                                 ddo_total->ddo_dspace += ddo->ddo_dspace;
 482                                 ddo_total->ddo_mspace += ddo->ddo_mspace;
 483                         }
 484                 }
 485         }
 486
 487         /* ... and compute the averages. */
 488         if (ddo_total->ddo_count != 0) {
 489                 ddo_total->ddo_dspace /= ddo_total->ddo_count;
 490                 ddo_total->ddo_mspace /= ddo_total->ddo_count;
 491         }
 492 }
 493
 494 void
 495 ddt_get_dedup_histogram(spa_t *spa, ddt_histogram_t *ddh)
 496 {
 497         for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 498                 ddt_t *ddt = spa->spa_ddt[c];
 499                 for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
 500                         for (enum ddt_class class = 0; class < DDT_CLASSES;
 501                             class++) {
 502                                 ddt_histogram_add(ddh,
 503                                     &ddt->ddt_histogram_cache[type][class]);
 504                         }
 505                 }
 506         }
 507 }
 508
 509 void
 510 ddt_get_dedup_stats(spa_t *spa, ddt_stat_t *dds_total)
 511 {
 512         ddt_histogram_t *ddh_total;
 513
 514         ddh_total = kmem_zalloc(sizeof (ddt_histogram_t), KM_SLEEP);
 515         ddt_get_dedup_histogram(spa, ddh_total);
 516         ddt_histogram_stat(dds_total, ddh_total);
 517         kmem_free(ddh_total, sizeof (ddt_histogram_t));
 518 }
 519
 520 uint64_t
 521 ddt_get_dedup_dspace(spa_t *spa)
 522 {
 523         ddt_stat_t dds_total;
 524
 525         if (spa->spa_dedup_dspace != ~0ULL)
 526                 return (spa->spa_dedup_dspace);
 527
 528         bzero(&dds_total, sizeof (ddt_stat_t));
 529
 530         /* Calculate and cache the stats */
 531         ddt_get_dedup_stats(spa, &dds_total);
 532         spa->spa_dedup_dspace = dds_total.dds_ref_dsize - dds_total.dds_dsize;
 533         return (spa->spa_dedup_dspace);
 534 }
 535
 536 uint64_t
 537 ddt_get_pool_dedup_ratio(spa_t *spa)
 538 {
 539         ddt_stat_t dds_total = { 0 };
 540
 541         ddt_get_dedup_stats(spa, &dds_total);
 542         if (dds_total.dds_dsize == 0)
 543                 return (100);
 544
 545         return (dds_total.dds_ref_dsize * 100 / dds_total.dds_dsize);
 546 }
 547
 548 int
 549 ddt_ditto_copies_needed(ddt_t *ddt, ddt_entry_t *dde, ddt_phys_t *ddp_willref)
 550 {
 551         spa_t *spa = ddt->ddt_spa;
 552         uint64_t total_refcnt = 0;
 553         uint64_t ditto = spa->spa_dedup_ditto;
 554         int total_copies = 0;
 555         int desired_copies = 0;
 556         int copies_needed = 0;
 557
 558         for (int p = DDT_PHYS_SINGLE; p <= DDT_PHYS_TRIPLE; p++) {
 559                 ddt_phys_t *ddp = &dde->dde_phys[p];
 560                 zio_t *zio = dde->dde_lead_zio[p];
 561                 uint64_t refcnt = ddp->ddp_refcnt;      /* committed refs */
 562                 if (zio != NULL)
 563                         refcnt += zio->io_parent_count; /* pending refs */
 564                 if (ddp == ddp_willref)
 565                         refcnt++;                       /* caller's ref */
 566                 if (refcnt != 0) {
 567                         total_refcnt += refcnt;
 568                         total_copies += p;
 569                 }
 570         }
 571
 572         if (ditto == 0 || ditto > UINT32_MAX)
 573                 ditto = UINT32_MAX;
 574
 575         if (total_refcnt >= 1)
 576                 desired_copies++;
 577         if (total_refcnt >= ditto)
 578                 desired_copies++;
 579         if (total_refcnt >= ditto * ditto)
 580                 desired_copies++;
 581
 582         copies_needed = MAX(desired_copies, total_copies) - total_copies;
 583
 584         /* encrypted blocks store their IV in DVA[2] */
 585         if (DDK_GET_CRYPT(&dde->dde_key))
 586                 copies_needed = MIN(copies_needed, SPA_DVAS_PER_BP - 1);
 587
 588         return (copies_needed);
 589 }
 590
 591 int
 592 ddt_ditto_copies_present(ddt_entry_t *dde)
 593 {
 594         ddt_phys_t *ddp = &dde->dde_phys[DDT_PHYS_DITTO];
 595         dva_t *dva = ddp->ddp_dva;
 596         int copies = 0 - DVA_GET_GANG(dva);
 597
 598         for (int d = 0; d < DDE_GET_NDVAS(dde); d++, dva++)
 599                 if (DVA_IS_VALID(dva))
 600                         copies++;
 601
 602         ASSERT(copies >= 0 && copies < SPA_DVAS_PER_BP);
 603
 604         return (copies);
 605 }
 606
 607 size_t
 608 ddt_compress(void *src, uchar_t *dst, size_t s_len, size_t d_len)
 609 {
 610         uchar_t *version = dst++;
 611         int cpfunc = ZIO_COMPRESS_ZLE;
 612         zio_compress_info_t *ci = &zio_compress_table[cpfunc];
 613         size_t c_len;
 614
 615         ASSERT(d_len >= s_len + 1);     /* no compression plus version byte */
 616
 617         c_len = ci->ci_compress(src, dst, s_len, d_len - 1, ci->ci_level);
 618
 619         if (c_len == s_len) {
 620                 cpfunc = ZIO_COMPRESS_OFF;
 621                 bcopy(src, dst, s_len);
 622         }
 623
 624         *version = cpfunc;
 625         /* CONSTCOND */
 626         if (ZFS_HOST_BYTEORDER)
 627                 *version |= DDT_COMPRESS_BYTEORDER_MASK;
 628
 629         return (c_len + 1);
 630 }
 631
 632 void
 633 ddt_decompress(uchar_t *src, void *dst, size_t s_len, size_t d_len)
 634 {
 635         uchar_t version = *src++;
 636         int cpfunc = version & DDT_COMPRESS_FUNCTION_MASK;
 637         zio_compress_info_t *ci = &zio_compress_table[cpfunc];
 638
 639         if (ci->ci_decompress != NULL)
 640                 (void) ci->ci_decompress(src, dst, s_len, d_len, ci->ci_level);
 641         else
 642                 bcopy(src, dst, d_len);
 643
 644         if (((version & DDT_COMPRESS_BYTEORDER_MASK) != 0) !=
 645             (ZFS_HOST_BYTEORDER != 0))
 646                 byteswap_uint64_array(dst, d_len);
 647 }
 648
 649 ddt_t *
 650 ddt_select_by_checksum(spa_t *spa, enum zio_checksum c)
 651 {
 652         return (spa->spa_ddt[c]);
 653 }
 654
 655 ddt_t *
 656 ddt_select(spa_t *spa, const blkptr_t *bp)
 657 {
 658         return (spa->spa_ddt[BP_GET_CHECKSUM(bp)]);
 659 }
 660
 661 void
 662 ddt_enter(ddt_t *ddt)
 663 {
 664         mutex_enter(&ddt->ddt_lock);
 665 }
 666
 667 void
 668 ddt_exit(ddt_t *ddt)
 669 {
 670         mutex_exit(&ddt->ddt_lock);
 671 }
 672
 673 void
 674 ddt_init(void)
 675 {
 676         ddt_cache = kmem_cache_create("ddt_cache",
 677             sizeof (ddt_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
 678         ddt_entry_cache = kmem_cache_create("ddt_entry_cache",
 679             sizeof (ddt_entry_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
 680 }
 681
 682 void
 683 ddt_fini(void)
 684 {
 685         kmem_cache_destroy(ddt_entry_cache);
 686         kmem_cache_destroy(ddt_cache);
 687 }
 688
 689 static ddt_entry_t *
 690 ddt_alloc(const ddt_key_t *ddk)
 691 {
 692         ddt_entry_t *dde;
 693
 694         dde = kmem_cache_alloc(ddt_entry_cache, KM_SLEEP);
 695         bzero(dde, sizeof (ddt_entry_t));
 696         cv_init(&dde->dde_cv, NULL, CV_DEFAULT, NULL);
 697
 698         dde->dde_key = *ddk;
 699
 700         return (dde);
 701 }
 702
 703 static void
 704 ddt_free(ddt_entry_t *dde)
 705 {
 706         ASSERT(!dde->dde_loading);
 707
 708         for (int p = 0; p < DDT_PHYS_TYPES; p++)
 709                 ASSERT(dde->dde_lead_zio[p] == NULL);
 710
 711         if (dde->dde_repair_abd != NULL)
 712                 abd_free(dde->dde_repair_abd);
 713
 714         cv_destroy(&dde->dde_cv);
 715         kmem_cache_free(ddt_entry_cache, dde);
 716 }
 717
 718 void
 719 ddt_remove(ddt_t *ddt, ddt_entry_t *dde)
 720 {
 721         ASSERT(MUTEX_HELD(&ddt->ddt_lock));
 722
 723         avl_remove(&ddt->ddt_tree, dde);
 724         ddt_free(dde);
 725 }
 726
 727 ddt_entry_t *
 728 ddt_lookup(ddt_t *ddt, const blkptr_t *bp, boolean_t add)
 729 {
 730         ddt_entry_t *dde, dde_search;
 731         enum ddt_type type;
 732         enum ddt_class class;
 733         avl_index_t where;
 734         int error;
 735
 736         ASSERT(MUTEX_HELD(&ddt->ddt_lock));
 737
 738         ddt_key_fill(&dde_search.dde_key, bp);
 739
 740         dde = avl_find(&ddt->ddt_tree, &dde_search, &where);
 741         if (dde == NULL) {
 742                 if (!add)
 743                         return (NULL);
 744                 dde = ddt_alloc(&dde_search.dde_key);
 745                 avl_insert(&ddt->ddt_tree, dde, where);
 746         }
 747
 748         while (dde->dde_loading)
 749                 cv_wait(&dde->dde_cv, &ddt->ddt_lock);
 750
 751         if (dde->dde_loaded)
 752                 return (dde);
 753
 754         dde->dde_loading = B_TRUE;
 755
 756         ddt_exit(ddt);
 757
 758         error = ENOENT;
 759
 760         for (type = 0; type < DDT_TYPES; type++) {
 761                 for (class = 0; class < DDT_CLASSES; class++) {
 762                         error = ddt_object_lookup(ddt, type, class, dde);
 763                         if (error != ENOENT) {
 764                                 ASSERT0(error);
 765                                 break;
 766                         }
 767                 }
 768                 if (error != ENOENT)
 769                         break;
 770         }
 771
 772         ddt_enter(ddt);
 773
 774         ASSERT(dde->dde_loaded == B_FALSE);
 775         ASSERT(dde->dde_loading == B_TRUE);
 776
 777         dde->dde_type = type;   /* will be DDT_TYPES if no entry found */
 778         dde->dde_class = class; /* will be DDT_CLASSES if no entry found */
 779         dde->dde_loaded = B_TRUE;
 780         dde->dde_loading = B_FALSE;
 781
 782         if (error == 0)
 783                 ddt_stat_update(ddt, dde, -1ULL);
 784
 785         cv_broadcast(&dde->dde_cv);
 786
 787         return (dde);
 788 }
 789
 790 void
 791 ddt_prefetch(spa_t *spa, const blkptr_t *bp)
 792 {
 793         ddt_t *ddt;
 794         ddt_entry_t dde;
 795
 796         if (!zfs_dedup_prefetch || bp == NULL || !BP_GET_DEDUP(bp))
 797                 return;
 798
 799         /*
 800          * We only remove the DDT once all tables are empty and only
 801          * prefetch dedup blocks when there are entries in the DDT.
 802          * Thus no locking is required as the DDT can't disappear on us.
 803          */
 804         ddt = ddt_select(spa, bp);
 805         ddt_key_fill(&dde.dde_key, bp);
 806
 807         for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
 808                 for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
 809                         ddt_object_prefetch(ddt, type, class, &dde);
 810                 }
 811         }
 812 }
 813
 814 /*
 815  * Opaque struct used for ddt_key comparison
 816  */
 817 #define DDT_KEY_CMP_LEN (sizeof (ddt_key_t) / sizeof (uint16_t))
 818
 819 typedef struct ddt_key_cmp {
 820         uint16_t        u16[DDT_KEY_CMP_LEN];
 821 } ddt_key_cmp_t;
 822
 823 int
 824 ddt_entry_compare(const void *x1, const void *x2)
 825 {
 826         const ddt_entry_t *dde1 = x1;
 827         const ddt_entry_t *dde2 = x2;
 828         const ddt_key_cmp_t *k1 = (const ddt_key_cmp_t *)&dde1->dde_key;
 829         const ddt_key_cmp_t *k2 = (const ddt_key_cmp_t *)&dde2->dde_key;
 830         int32_t cmp = 0;
 831
 832         for (int i = 0; i < DDT_KEY_CMP_LEN; i++) {
 833                 cmp = (int32_t)k1->u16[i] - (int32_t)k2->u16[i];
 834                 if (likely(cmp))
 835                         break;
 836         }
 837
 838         return (AVL_ISIGN(cmp));
 839 }
 840
 841 static ddt_t *
 842 ddt_table_alloc(spa_t *spa, enum zio_checksum c)
 843 {
 844         ddt_t *ddt;
 845
 846         ddt = kmem_cache_alloc(ddt_cache, KM_SLEEP);
 847         bzero(ddt, sizeof (ddt_t));
 848
 849         mutex_init(&ddt->ddt_lock, NULL, MUTEX_DEFAULT, NULL);
 850         avl_create(&ddt->ddt_tree, ddt_entry_compare,
 851             sizeof (ddt_entry_t), offsetof(ddt_entry_t, dde_node));
 852         avl_create(&ddt->ddt_repair_tree, ddt_entry_compare,
 853             sizeof (ddt_entry_t), offsetof(ddt_entry_t, dde_node));
 854         ddt->ddt_checksum = c;
 855         ddt->ddt_spa = spa;
 856         ddt->ddt_os = spa->spa_meta_objset;
 857
 858         return (ddt);
 859 }
 860
 861 static void
 862 ddt_table_free(ddt_t *ddt)
 863 {
 864         ASSERT(avl_numnodes(&ddt->ddt_tree) == 0);
 865         ASSERT(avl_numnodes(&ddt->ddt_repair_tree) == 0);
 866         avl_destroy(&ddt->ddt_tree);
 867         avl_destroy(&ddt->ddt_repair_tree);
 868         mutex_destroy(&ddt->ddt_lock);
 869         kmem_cache_free(ddt_cache, ddt);
 870 }
 871
 872 void
 873 ddt_create(spa_t *spa)
 874 {
 875         spa->spa_dedup_checksum = ZIO_DEDUPCHECKSUM;
 876
 877         for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++)
 878                 spa->spa_ddt[c] = ddt_table_alloc(spa, c);
 879 }
 880
 881 int
 882 ddt_load(spa_t *spa)
 883 {
 884         int error;
 885
 886         ddt_create(spa);
 887
 888         error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
 889             DMU_POOL_DDT_STATS, sizeof (uint64_t), 1,
 890             &spa->spa_ddt_stat_object);
 891
 892         if (error)
 893                 return (error == ENOENT ? 0 : error);
 894
 895         for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 896                 ddt_t *ddt = spa->spa_ddt[c];
 897                 for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
 898                         for (enum ddt_class class = 0; class < DDT_CLASSES;
 899                             class++) {
 900                                 error = ddt_object_load(ddt, type, class);
 901                                 if (error != 0 && error != ENOENT)
 902                                         return (error);
 903                         }
 904                 }
 905
 906                 /*
 907                  * Seed the cached histograms.
 908                  */
 909                 bcopy(ddt->ddt_histogram, &ddt->ddt_histogram_cache,
 910                     sizeof (ddt->ddt_histogram));
 911                 spa->spa_dedup_dspace = ~0ULL;
 912         }
 913
 914         return (0);
 915 }
 916
 917 void
 918 ddt_unload(spa_t *spa)
 919 {
 920         for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 921                 if (spa->spa_ddt[c]) {
 922                         ddt_table_free(spa->spa_ddt[c]);
 923                         spa->spa_ddt[c] = NULL;
 924                 }
 925         }
 926 }
 927
 928 boolean_t
 929 ddt_class_contains(spa_t *spa, enum ddt_class max_class, const blkptr_t *bp)
 930 {
 931         ddt_t *ddt;
 932         ddt_entry_t *dde;
 933
 934         if (!BP_GET_DEDUP(bp))
 935                 return (B_FALSE);
 936
 937         if (max_class == DDT_CLASS_UNIQUE)
 938                 return (B_TRUE);
 939
 940         ddt = spa->spa_ddt[BP_GET_CHECKSUM(bp)];
 941         dde = kmem_cache_alloc(ddt_entry_cache, KM_SLEEP);
 942
 943         ddt_key_fill(&(dde->dde_key), bp);
 944
 945         for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
 946                 for (enum ddt_class class = 0; class <= max_class; class++) {
 947                         if (ddt_object_lookup(ddt, type, class, dde) == 0) {
 948                                 kmem_cache_free(ddt_entry_cache, dde);
 949                                 return (B_TRUE);
 950                         }
 951                 }
 952         }
 953
 954         kmem_cache_free(ddt_entry_cache, dde);
 955         return (B_FALSE);
 956 }
 957
 958 ddt_entry_t *
 959 ddt_repair_start(ddt_t *ddt, const blkptr_t *bp)
 960 {
 961         ddt_key_t ddk;
 962         ddt_entry_t *dde;
 963
 964         ddt_key_fill(&ddk, bp);
 965
 966         dde = ddt_alloc(&ddk);
 967
 968         for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
 969                 for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
 970                         /*
 971                          * We can only do repair if there are multiple copies
 972                          * of the block.  For anything in the UNIQUE class,
 973                          * there's definitely only one copy, so don't even try.
 974                          */
 975                         if (class != DDT_CLASS_UNIQUE &&
 976                             ddt_object_lookup(ddt, type, class, dde) == 0)
 977                                 return (dde);
 978                 }
 979         }
 980
 981         bzero(dde->dde_phys, sizeof (dde->dde_phys));
 982
 983         return (dde);
 984 }
 985
 986 void
 987 ddt_repair_done(ddt_t *ddt, ddt_entry_t *dde)
 988 {
 989         avl_index_t where;
 990
 991         ddt_enter(ddt);
 992
 993         if (dde->dde_repair_abd != NULL && spa_writeable(ddt->ddt_spa) &&
 994             avl_find(&ddt->ddt_repair_tree, dde, &where) == NULL)
 995                 avl_insert(&ddt->ddt_repair_tree, dde, where);
 996         else
 997                 ddt_free(dde);
 998
 999         ddt_exit(ddt);
1000 }
1001
1002 static void
1003 ddt_repair_entry_done(zio_t *zio)
1004 {
1005         ddt_entry_t *rdde = zio->io_private;
1006
1007         ddt_free(rdde);
1008 }
1009
1010 static void
1011 ddt_repair_entry(ddt_t *ddt, ddt_entry_t *dde, ddt_entry_t *rdde, zio_t *rio)
1012 {
1013         ddt_phys_t *ddp = dde->dde_phys;
1014         ddt_phys_t *rddp = rdde->dde_phys;
1015         ddt_key_t *ddk = &dde->dde_key;
1016         ddt_key_t *rddk = &rdde->dde_key;
1017         zio_t *zio;
1018         blkptr_t blk;
1019
1020         zio = zio_null(rio, rio->io_spa, NULL,
1021             ddt_repair_entry_done, rdde, rio->io_flags);
1022
1023         for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++, rddp++) {
1024                 if (ddp->ddp_phys_birth == 0 ||
1025                     ddp->ddp_phys_birth != rddp->ddp_phys_birth ||
1026                     bcmp(ddp->ddp_dva, rddp->ddp_dva, sizeof (ddp->ddp_dva)))
1027                         continue;
1028                 ddt_bp_create(ddt->ddt_checksum, ddk, ddp, &blk);
1029                 zio_nowait(zio_rewrite(zio, zio->io_spa, 0, &blk,
1030                     rdde->dde_repair_abd, DDK_GET_PSIZE(rddk), NULL, NULL,
1031                     ZIO_PRIORITY_SYNC_WRITE, ZIO_DDT_CHILD_FLAGS(zio), NULL));
1032         }
1033
1034         zio_nowait(zio);
1035 }
1036
1037 static void
1038 ddt_repair_table(ddt_t *ddt, zio_t *rio)
1039 {
1040         spa_t *spa = ddt->ddt_spa;
1041         ddt_entry_t *dde, *rdde_next, *rdde;
1042         avl_tree_t *t = &ddt->ddt_repair_tree;
1043         blkptr_t blk;
1044
1045         if (spa_sync_pass(spa) > 1)
1046                 return;
1047
1048         ddt_enter(ddt);
1049         for (rdde = avl_first(t); rdde != NULL; rdde = rdde_next) {
1050                 rdde_next = AVL_NEXT(t, rdde);
1051                 avl_remove(&ddt->ddt_repair_tree, rdde);
1052                 ddt_exit(ddt);
1053                 ddt_bp_create(ddt->ddt_checksum, &rdde->dde_key, NULL, &blk);
1054                 dde = ddt_repair_start(ddt, &blk);
1055                 ddt_repair_entry(ddt, dde, rdde, rio);
1056                 ddt_repair_done(ddt, dde);
1057                 ddt_enter(ddt);
1058         }
1059         ddt_exit(ddt);
1060 }
1061
1062 static void
1063 ddt_sync_entry(ddt_t *ddt, ddt_entry_t *dde, dmu_tx_t *tx, uint64_t txg)
1064 {
1065         dsl_pool_t *dp = ddt->ddt_spa->spa_dsl_pool;
1066         ddt_phys_t *ddp = dde->dde_phys;
1067         ddt_key_t *ddk = &dde->dde_key;
1068         enum ddt_type otype = dde->dde_type;
1069         enum ddt_type ntype = DDT_TYPE_CURRENT;
1070         enum ddt_class oclass = dde->dde_class;
1071         enum ddt_class nclass;
1072         uint64_t total_refcnt = 0;
1073
1074         ASSERT(dde->dde_loaded);
1075         ASSERT(!dde->dde_loading);
1076
1077         for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
1078                 ASSERT(dde->dde_lead_zio[p] == NULL);
1079                 if (ddp->ddp_phys_birth == 0) {
1080                         ASSERT(ddp->ddp_refcnt == 0);
1081                         continue;
1082                 }
1083                 if (p == DDT_PHYS_DITTO) {
1084                         if (ddt_ditto_copies_needed(ddt, dde, NULL) == 0)
1085                                 ddt_phys_free(ddt, ddk, ddp, txg);
1086                         continue;
1087                 }
1088                 if (ddp->ddp_refcnt == 0)
1089                         ddt_phys_free(ddt, ddk, ddp, txg);
1090                 total_refcnt += ddp->ddp_refcnt;
1091         }
1092
1093         if (dde->dde_phys[DDT_PHYS_DITTO].ddp_phys_birth != 0)
1094                 nclass = DDT_CLASS_DITTO;
1095         else if (total_refcnt > 1)
1096                 nclass = DDT_CLASS_DUPLICATE;
1097         else
1098                 nclass = DDT_CLASS_UNIQUE;
1099
1100         if (otype != DDT_TYPES &&
1101             (otype != ntype || oclass != nclass || total_refcnt == 0)) {
1102                 VERIFY(ddt_object_remove(ddt, otype, oclass, dde, tx) == 0);
1103                 ASSERT(ddt_object_lookup(ddt, otype, oclass, dde) == ENOENT);
1104         }
1105
1106         if (total_refcnt != 0) {
1107                 dde->dde_type = ntype;
1108                 dde->dde_class = nclass;
1109                 ddt_stat_update(ddt, dde, 0);
1110                 if (!ddt_object_exists(ddt, ntype, nclass))
1111                         ddt_object_create(ddt, ntype, nclass, tx);
1112                 VERIFY(ddt_object_update(ddt, ntype, nclass, dde, tx) == 0);
1113
1114                 /*
1115                  * If the class changes, the order that we scan this bp
1116                  * changes.  If it decreases, we could miss it, so
1117                  * scan it right now.  (This covers both class changing
1118                  * while we are doing ddt_walk(), and when we are
1119                  * traversing.)
1120                  */
1121                 if (nclass < oclass) {
1122                         dsl_scan_ddt_entry(dp->dp_scan,
1123                             ddt->ddt_checksum, dde, tx);
1124                 }
1125         }
1126 }
1127
1128 static void
1129 ddt_sync_table(ddt_t *ddt, dmu_tx_t *tx, uint64_t txg)
1130 {
1131         spa_t *spa = ddt->ddt_spa;
1132         ddt_entry_t *dde;
1133         void *cookie = NULL;
1134
1135         if (avl_numnodes(&ddt->ddt_tree) == 0)
1136                 return;
1137
1138         ASSERT(spa->spa_uberblock.ub_version >= SPA_VERSION_DEDUP);
1139
1140         if (spa->spa_ddt_stat_object == 0) {
1141                 spa->spa_ddt_stat_object = zap_create_link(ddt->ddt_os,
1142                     DMU_OT_DDT_STATS, DMU_POOL_DIRECTORY_OBJECT,
1143                     DMU_POOL_DDT_STATS, tx);
1144         }
1145
1146         while ((dde = avl_destroy_nodes(&ddt->ddt_tree, &cookie)) != NULL) {
1147                 ddt_sync_entry(ddt, dde, tx, txg);
1148                 ddt_free(dde);
1149         }
1150
1151         for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
1152                 uint64_t add, count = 0;
1153                 for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
1154                         if (ddt_object_exists(ddt, type, class)) {
1155                                 ddt_object_sync(ddt, type, class, tx);
1156                                 VERIFY(ddt_object_count(ddt, type, class,
1157                                     &add) == 0);
1158                                 count += add;
1159                         }
1160                 }
1161                 for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
1162                         if (count == 0 && ddt_object_exists(ddt, type, class))
1163                                 ddt_object_destroy(ddt, type, class, tx);
1164                 }
1165         }
1166
1167         bcopy(ddt->ddt_histogram, &ddt->ddt_histogram_cache,
1168             sizeof (ddt->ddt_histogram));
1169         spa->spa_dedup_dspace = ~0ULL;
1170 }
1171
1172 void
1173 ddt_sync(spa_t *spa, uint64_t txg)
1174 {
1175         dsl_scan_t *scn = spa->spa_dsl_pool->dp_scan;
1176         dmu_tx_t *tx;
1177         zio_t *rio;
1178
1179         ASSERT(spa_syncing_txg(spa) == txg);
1180
1181         tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
1182
1183         rio = zio_root(spa, NULL, NULL,
1184             ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE | ZIO_FLAG_SELF_HEAL);
1185
1186         /*
1187          * This function may cause an immediate scan of ddt blocks (see
1188          * the comment above dsl_scan_ddt() for details). We set the
1189          * scan's root zio here so that we can wait for any scan IOs in
1190          * addition to the regular ddt IOs.
1191          */
1192         ASSERT3P(scn->scn_zio_root, ==, NULL);
1193         scn->scn_zio_root = rio;
1194
1195         for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
1196                 ddt_t *ddt = spa->spa_ddt[c];
1197                 if (ddt == NULL)
1198                         continue;
1199                 ddt_sync_table(ddt, tx, txg);
1200                 ddt_repair_table(ddt, rio);
1201         }
1202
1203         (void) zio_wait(rio);
1204         scn->scn_zio_root = NULL;
1205
1206         dmu_tx_commit(tx);
1207 }
1208
1209 int
1210 ddt_walk(spa_t *spa, ddt_bookmark_t *ddb, ddt_entry_t *dde)
1211 {
1212         do {
1213                 do {
1214                         do {
1215                                 ddt_t *ddt = spa->spa_ddt[ddb->ddb_checksum];
1216                                 int error = ENOENT;
1217                                 if (ddt_object_exists(ddt, ddb->ddb_type,
1218                                     ddb->ddb_class)) {
1219                                         error = ddt_object_walk(ddt,
1220                                             ddb->ddb_type, ddb->ddb_class,
1221                                             &ddb->ddb_cursor, dde);
1222                                 }
1223                                 dde->dde_type = ddb->ddb_type;
1224                                 dde->dde_class = ddb->ddb_class;
1225                                 if (error == 0)
1226                                         return (0);
1227                                 if (error != ENOENT)
1228                                         return (error);
1229                                 ddb->ddb_cursor = 0;
1230                         } while (++ddb->ddb_checksum < ZIO_CHECKSUM_FUNCTIONS);
1231                         ddb->ddb_checksum = 0;
1232                 } while (++ddb->ddb_type < DDT_TYPES);
1233                 ddb->ddb_type = 0;
1234         } while (++ddb->ddb_class < DDT_CLASSES);
1235
1236         return (SET_ERROR(ENOENT));
1237 }
1238
1239 #if defined(_KERNEL) && defined(HAVE_SPL)
1240 module_param(zfs_dedup_prefetch, int, 0644);
1241 MODULE_PARM_DESC(zfs_dedup_prefetch, "Enable prefetching dedup-ed blks");
1242 #endif