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  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  23  * Copyright (c) 2013 by Delphix. All rights reserved.
  24  */
  25 
  26 #include <sys/dsl_scan.h>
  27 #include <sys/dsl_pool.h>
  28 #include <sys/dsl_dataset.h>
  29 #include <sys/dsl_prop.h>
  30 #include <sys/dsl_dir.h>
  31 #include <sys/dsl_synctask.h>
  32 #include <sys/dnode.h>
  33 #include <sys/dmu_tx.h>
  34 #include <sys/dmu_objset.h>
  35 #include <sys/arc.h>
  36 #include <sys/zap.h>
  37 #include <sys/zio.h>
  38 #include <sys/zfs_context.h>
  39 #include <sys/fs/zfs.h>
  40 #include <sys/zfs_znode.h>
  41 #include <sys/spa_impl.h>
  42 #include <sys/vdev_impl.h>
  43 #include <sys/zil_impl.h>
  44 #include <sys/zio_checksum.h>
  45 #include <sys/ddt.h>
  46 #include <sys/sa.h>
  47 #include <sys/sa_impl.h>
  48 #include <sys/zfeature.h>
  49 #ifdef _KERNEL
  50 #include <sys/zfs_vfsops.h>
  51 #endif
  52 
  53 typedef int (scan_cb_t)(dsl_pool_t *, const blkptr_t *, const zbookmark_t *);
  54 
  55 static scan_cb_t dsl_scan_defrag_cb;
  56 static scan_cb_t dsl_scan_scrub_cb;
  57 static scan_cb_t dsl_scan_remove_cb;
  58 static void dsl_scan_cancel_sync(void *, dmu_tx_t *);
  59 static void dsl_scan_sync_state(dsl_scan_t *, dmu_tx_t *tx);
  60 
  61 int zfs_top_maxinflight = 32;           /* maximum I/Os per top-level */
  62 int zfs_resilver_delay = 2;             /* number of ticks to delay resilver */
  63 int zfs_scrub_delay = 4;                /* number of ticks to delay scrub */
  64 int zfs_scan_idle = 50;                 /* idle window in clock ticks */
  65 
  66 int zfs_scan_min_time_ms = 1000; /* min millisecs to scrub per txg */
  67 int zfs_free_min_time_ms = 1000; /* min millisecs to free per txg */
  68 int zfs_resilver_min_time_ms = 3000; /* min millisecs to resilver per txg */
  69 boolean_t zfs_no_scrub_io = B_FALSE; /* set to disable scrub i/o */
  70 boolean_t zfs_no_scrub_prefetch = B_FALSE; /* set to disable srub prefetching */
  71 enum ddt_class zfs_scrub_ddt_class_max = DDT_CLASS_DUPLICATE;
  72 int dsl_scan_delay_completion = B_FALSE; /* set to delay scan completion */
  73 
  74 #define DSL_SCAN_IS_SCRUB_RESILVER(scn) \
  75         ((scn)->scn_phys.scn_func == POOL_SCAN_SCRUB || \
  76         (scn)->scn_phys.scn_func == POOL_SCAN_RESILVER)
  77 
  78 extern int zfs_txg_timeout;
  79 
  80 /* the order has to match pool_scan_type */
  81 static scan_cb_t *scan_funcs[POOL_SCAN_FUNCS] = {
  82         NULL,
  83         dsl_scan_scrub_cb,      /* POOL_SCAN_SCRUB */
  84         dsl_scan_scrub_cb,      /* POOL_SCAN_RESILVER */
  85 };
  86 
  87 int
  88 dsl_scan_init(dsl_pool_t *dp, uint64_t txg)
  89 {
  90         int err;
  91         dsl_scan_t *scn;
  92         spa_t *spa = dp->dp_spa;
  93         uint64_t f;
  94 
  95         scn = dp->dp_scan = kmem_zalloc(sizeof (dsl_scan_t), KM_SLEEP);
  96         scn->scn_dp = dp;
  97 
  98         /*
  99          * It's possible that we're resuming a scan after a reboot so
 100          * make sure that the scan_async_destroying flag is initialized
 101          * appropriately.
 102          */
 103         ASSERT(!scn->scn_async_destroying);
 104         scn->scn_async_destroying = spa_feature_is_active(dp->dp_spa,
 105             &spa_feature_table[SPA_FEATURE_ASYNC_DESTROY]);
 106 
 107         err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
 108             "scrub_func", sizeof (uint64_t), 1, &f);
 109         if (err == 0) {
 110                 /*
 111                  * There was an old-style scrub in progress.  Restart a
 112                  * new-style scrub from the beginning.
 113                  */
 114                 scn->scn_restart_txg = txg;
 115                 zfs_dbgmsg("old-style scrub was in progress; "
 116                     "restarting new-style scrub in txg %llu",
 117                     scn->scn_restart_txg);
 118 
 119                 /*
 120                  * Load the queue obj from the old location so that it
 121                  * can be freed by dsl_scan_done().
 122                  */
 123                 (void) zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
 124                     "scrub_queue", sizeof (uint64_t), 1,
 125                     &scn->scn_phys.scn_queue_obj);
 126         } else {
 127                 err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
 128                     DMU_POOL_SCAN, sizeof (uint64_t), SCAN_PHYS_NUMINTS,
 129                     &scn->scn_phys);
 130                 if (err == ENOENT)
 131                         return (0);
 132                 else if (err)
 133                         return (err);
 134 
 135                 if (scn->scn_phys.scn_state == DSS_SCANNING &&
 136                     spa_prev_software_version(dp->dp_spa) < SPA_VERSION_SCAN) {
 137                         /*
 138                          * A new-type scrub was in progress on an old
 139                          * pool, and the pool was accessed by old
 140                          * software.  Restart from the beginning, since
 141                          * the old software may have changed the pool in
 142                          * the meantime.
 143                          */
 144                         scn->scn_restart_txg = txg;
 145                         zfs_dbgmsg("new-style scrub was modified "
 146                             "by old software; restarting in txg %llu",
 147                             scn->scn_restart_txg);
 148                 }
 149         }
 150 
 151         spa_scan_stat_init(spa);
 152         return (0);
 153 }
 154 
 155 void
 156 dsl_scan_fini(dsl_pool_t *dp)
 157 {
 158         if (dp->dp_scan) {
 159                 kmem_free(dp->dp_scan, sizeof (dsl_scan_t));
 160                 dp->dp_scan = NULL;
 161         }
 162 }
 163 
 164 /* ARGSUSED */
 165 static int
 166 dsl_scan_setup_check(void *arg, dmu_tx_t *tx)
 167 {
 168         dsl_scan_t *scn = dmu_tx_pool(tx)->dp_scan;
 169 
 170         if (scn->scn_phys.scn_state == DSS_SCANNING)
 171                 return (SET_ERROR(EBUSY));
 172 
 173         return (0);
 174 }
 175 
 176 static void
 177 dsl_scan_setup_sync(void *arg, dmu_tx_t *tx)
 178 {
 179         dsl_scan_t *scn = dmu_tx_pool(tx)->dp_scan;
 180         pool_scan_func_t *funcp = arg;
 181         dmu_object_type_t ot = 0;
 182         dsl_pool_t *dp = scn->scn_dp;
 183         spa_t *spa = dp->dp_spa;
 184 
 185         ASSERT(scn->scn_phys.scn_state != DSS_SCANNING);
 186         ASSERT(*funcp > POOL_SCAN_NONE && *funcp < POOL_SCAN_FUNCS);
 187         bzero(&scn->scn_phys, sizeof (scn->scn_phys));
 188         scn->scn_phys.scn_func = *funcp;
 189         scn->scn_phys.scn_state = DSS_SCANNING;
 190         scn->scn_phys.scn_min_txg = 0;
 191         scn->scn_phys.scn_max_txg = tx->tx_txg;
 192         scn->scn_phys.scn_ddt_class_max = DDT_CLASSES - 1; /* the entire DDT */
 193         scn->scn_phys.scn_start_time = gethrestime_sec();
 194         scn->scn_phys.scn_errors = 0;
 195         scn->scn_phys.scn_to_examine = spa->spa_root_vdev->vdev_stat.vs_alloc;
 196         scn->scn_restart_txg = 0;
 197         spa_scan_stat_init(spa);
 198 
 199         if (DSL_SCAN_IS_SCRUB_RESILVER(scn)) {
 200                 scn->scn_phys.scn_ddt_class_max = zfs_scrub_ddt_class_max;
 201 
 202                 /* rewrite all disk labels */
 203                 vdev_config_dirty(spa->spa_root_vdev);
 204 
 205                 if (vdev_resilver_needed(spa->spa_root_vdev,
 206                     &scn->scn_phys.scn_min_txg, &scn->scn_phys.scn_max_txg)) {
 207                         spa_event_notify(spa, NULL, ESC_ZFS_RESILVER_START);
 208                 } else {
 209                         spa_event_notify(spa, NULL, ESC_ZFS_SCRUB_START);
 210                 }
 211 
 212                 spa->spa_scrub_started = B_TRUE;
 213                 /*
 214                  * If this is an incremental scrub, limit the DDT scrub phase
 215                  * to just the auto-ditto class (for correctness); the rest
 216                  * of the scrub should go faster using top-down pruning.
 217                  */
 218                 if (scn->scn_phys.scn_min_txg > TXG_INITIAL)
 219                         scn->scn_phys.scn_ddt_class_max = DDT_CLASS_DITTO;
 220 
 221         }
 222 
 223         /* back to the generic stuff */
 224 
 225         if (dp->dp_blkstats == NULL) {
 226                 dp->dp_blkstats =
 227                     kmem_alloc(sizeof (zfs_all_blkstats_t), KM_SLEEP);
 228         }
 229         bzero(dp->dp_blkstats, sizeof (zfs_all_blkstats_t));
 230 
 231         if (spa_version(spa) < SPA_VERSION_DSL_SCRUB)
 232                 ot = DMU_OT_ZAP_OTHER;
 233 
 234         scn->scn_phys.scn_queue_obj = zap_create(dp->dp_meta_objset,
 235             ot ? ot : DMU_OT_SCAN_QUEUE, DMU_OT_NONE, 0, tx);
 236 
 237         dsl_scan_sync_state(scn, tx);
 238 
 239         spa_history_log_internal(spa, "scan setup", tx,
 240             "func=%u mintxg=%llu maxtxg=%llu",
 241             *funcp, scn->scn_phys.scn_min_txg, scn->scn_phys.scn_max_txg);
 242 }
 243 
 244 /* ARGSUSED */
 245 static void
 246 dsl_scan_done(dsl_scan_t *scn, boolean_t complete, dmu_tx_t *tx)
 247 {
 248         static const char *old_names[] = {
 249                 "scrub_bookmark",
 250                 "scrub_ddt_bookmark",
 251                 "scrub_ddt_class_max",
 252                 "scrub_queue",
 253                 "scrub_min_txg",
 254                 "scrub_max_txg",
 255                 "scrub_func",
 256                 "scrub_errors",
 257                 NULL
 258         };
 259 
 260         dsl_pool_t *dp = scn->scn_dp;
 261         spa_t *spa = dp->dp_spa;
 262         int i;
 263 
 264         /* Remove any remnants of an old-style scrub. */
 265         for (i = 0; old_names[i]; i++) {
 266                 (void) zap_remove(dp->dp_meta_objset,
 267                     DMU_POOL_DIRECTORY_OBJECT, old_names[i], tx);
 268         }
 269 
 270         if (scn->scn_phys.scn_queue_obj != 0) {
 271                 VERIFY(0 == dmu_object_free(dp->dp_meta_objset,
 272                     scn->scn_phys.scn_queue_obj, tx));
 273                 scn->scn_phys.scn_queue_obj = 0;
 274         }
 275 
 276         /*
 277          * If we were "restarted" from a stopped state, don't bother
 278          * with anything else.
 279          */
 280         if (scn->scn_phys.scn_state != DSS_SCANNING)
 281                 return;
 282 
 283         if (complete)
 284                 scn->scn_phys.scn_state = DSS_FINISHED;
 285         else
 286                 scn->scn_phys.scn_state = DSS_CANCELED;
 287 
 288         spa_history_log_internal(spa, "scan done", tx,
 289             "complete=%u", complete);
 290 
 291         if (DSL_SCAN_IS_SCRUB_RESILVER(scn)) {
 292                 mutex_enter(&spa->spa_scrub_lock);
 293                 while (spa->spa_scrub_inflight > 0) {
 294                         cv_wait(&spa->spa_scrub_io_cv,
 295                             &spa->spa_scrub_lock);
 296                 }
 297                 mutex_exit(&spa->spa_scrub_lock);
 298                 spa->spa_scrub_started = B_FALSE;
 299                 spa->spa_scrub_active = B_FALSE;
 300 
 301                 /*
 302                  * If the scrub/resilver completed, update all DTLs to
 303                  * reflect this.  Whether it succeeded or not, vacate
 304                  * all temporary scrub DTLs.
 305                  */
 306                 vdev_dtl_reassess(spa->spa_root_vdev, tx->tx_txg,
 307                     complete ? scn->scn_phys.scn_max_txg : 0, B_TRUE);
 308                 if (complete) {
 309                         spa_event_notify(spa, NULL, scn->scn_phys.scn_min_txg ?
 310                             ESC_ZFS_RESILVER_FINISH : ESC_ZFS_SCRUB_FINISH);
 311                 }
 312                 spa_errlog_rotate(spa);
 313 
 314                 /*
 315                  * We may have finished replacing a device.
 316                  * Let the async thread assess this and handle the detach.
 317                  */
 318                 spa_async_request(spa, SPA_ASYNC_RESILVER_DONE);
 319         }
 320 
 321         scn->scn_phys.scn_end_time = gethrestime_sec();
 322 }
 323 
 324 /* ARGSUSED */
 325 static int
 326 dsl_scan_cancel_check(void *arg, dmu_tx_t *tx)
 327 {
 328         dsl_scan_t *scn = dmu_tx_pool(tx)->dp_scan;
 329 
 330         if (scn->scn_phys.scn_state != DSS_SCANNING)
 331                 return (SET_ERROR(ENOENT));
 332         return (0);
 333 }
 334 
 335 /* ARGSUSED */
 336 static void
 337 dsl_scan_cancel_sync(void *arg, dmu_tx_t *tx)
 338 {
 339         dsl_scan_t *scn = dmu_tx_pool(tx)->dp_scan;
 340 
 341         dsl_scan_done(scn, B_FALSE, tx);
 342         dsl_scan_sync_state(scn, tx);
 343 }
 344 
 345 int
 346 dsl_scan_cancel(dsl_pool_t *dp)
 347 {
 348         return (dsl_sync_task(spa_name(dp->dp_spa), dsl_scan_cancel_check,
 349             dsl_scan_cancel_sync, NULL, 3));
 350 }
 351 
 352 static void dsl_scan_visitbp(blkptr_t *bp,
 353     const zbookmark_t *zb, dnode_phys_t *dnp, arc_buf_t *pbuf,
 354     dsl_dataset_t *ds, dsl_scan_t *scn, dmu_objset_type_t ostype,
 355     dmu_tx_t *tx);
 356 static void dsl_scan_visitdnode(dsl_scan_t *, dsl_dataset_t *ds,
 357     dmu_objset_type_t ostype,
 358     dnode_phys_t *dnp, arc_buf_t *buf, uint64_t object, dmu_tx_t *tx);
 359 
 360 void
 361 dsl_free(dsl_pool_t *dp, uint64_t txg, const blkptr_t *bp)
 362 {
 363         zio_free(dp->dp_spa, txg, bp);
 364 }
 365 
 366 void
 367 dsl_free_sync(zio_t *pio, dsl_pool_t *dp, uint64_t txg, const blkptr_t *bpp)
 368 {
 369         ASSERT(dsl_pool_sync_context(dp));
 370         zio_nowait(zio_free_sync(pio, dp->dp_spa, txg, bpp, pio->io_flags));
 371 }
 372 
 373 static uint64_t
 374 dsl_scan_ds_maxtxg(dsl_dataset_t *ds)
 375 {
 376         uint64_t smt = ds->ds_dir->dd_pool->dp_scan->scn_phys.scn_max_txg;
 377         if (dsl_dataset_is_snapshot(ds))
 378                 return (MIN(smt, ds->ds_phys->ds_creation_txg));
 379         return (smt);
 380 }
 381 
 382 static void
 383 dsl_scan_sync_state(dsl_scan_t *scn, dmu_tx_t *tx)
 384 {
 385         VERIFY0(zap_update(scn->scn_dp->dp_meta_objset,
 386             DMU_POOL_DIRECTORY_OBJECT,
 387             DMU_POOL_SCAN, sizeof (uint64_t), SCAN_PHYS_NUMINTS,
 388             &scn->scn_phys, tx));
 389 }
 390 
 391 static boolean_t
 392 dsl_scan_check_pause(dsl_scan_t *scn, const zbookmark_t *zb)
 393 {
 394         uint64_t elapsed_nanosecs;
 395         int mintime;
 396 
 397         /* we never skip user/group accounting objects */
 398         if (zb && (int64_t)zb->zb_object < 0)
 399                 return (B_FALSE);
 400 
 401         if (scn->scn_pausing)
 402                 return (B_TRUE); /* we're already pausing */
 403 
 404         if (!ZB_IS_ZERO(&scn->scn_phys.scn_bookmark))
 405                 return (B_FALSE); /* we're resuming */
 406 
 407         /* We only know how to resume from level-0 blocks. */
 408         if (zb && zb->zb_level != 0)
 409                 return (B_FALSE);
 410 
 411         mintime = (scn->scn_phys.scn_func == POOL_SCAN_RESILVER) ?
 412             zfs_resilver_min_time_ms : zfs_scan_min_time_ms;
 413         elapsed_nanosecs = gethrtime() - scn->scn_sync_start_time;
 414         if (elapsed_nanosecs / NANOSEC > zfs_txg_timeout ||
 415             (NSEC2MSEC(elapsed_nanosecs) > mintime &&
 416             txg_sync_waiting(scn->scn_dp)) ||
 417             spa_shutting_down(scn->scn_dp->dp_spa)) {
 418                 if (zb) {
 419                         dprintf("pausing at bookmark %llx/%llx/%llx/%llx\n",
 420                             (longlong_t)zb->zb_objset,
 421                             (longlong_t)zb->zb_object,
 422                             (longlong_t)zb->zb_level,
 423                             (longlong_t)zb->zb_blkid);
 424                         scn->scn_phys.scn_bookmark = *zb;
 425                 }
 426                 dprintf("pausing at DDT bookmark %llx/%llx/%llx/%llx\n",
 427                     (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_class,
 428                     (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_type,
 429                     (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_checksum,
 430                     (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_cursor);
 431                 scn->scn_pausing = B_TRUE;
 432                 return (B_TRUE);
 433         }
 434         return (B_FALSE);
 435 }
 436 
 437 typedef struct zil_scan_arg {
 438         dsl_pool_t      *zsa_dp;
 439         zil_header_t    *zsa_zh;
 440 } zil_scan_arg_t;
 441 
 442 /* ARGSUSED */
 443 static int
 444 dsl_scan_zil_block(zilog_t *zilog, blkptr_t *bp, void *arg, uint64_t claim_txg)
 445 {
 446         zil_scan_arg_t *zsa = arg;
 447         dsl_pool_t *dp = zsa->zsa_dp;
 448         dsl_scan_t *scn = dp->dp_scan;
 449         zil_header_t *zh = zsa->zsa_zh;
 450         zbookmark_t zb;
 451 
 452         if (bp->blk_birth <= scn->scn_phys.scn_cur_min_txg)
 453                 return (0);
 454 
 455         /*
 456          * One block ("stubby") can be allocated a long time ago; we
 457          * want to visit that one because it has been allocated
 458          * (on-disk) even if it hasn't been claimed (even though for
 459          * scrub there's nothing to do to it).
 460          */
 461         if (claim_txg == 0 && bp->blk_birth >= spa_first_txg(dp->dp_spa))
 462                 return (0);
 463 
 464         SET_BOOKMARK(&zb, zh->zh_log.blk_cksum.zc_word[ZIL_ZC_OBJSET],
 465             ZB_ZIL_OBJECT, ZB_ZIL_LEVEL, bp->blk_cksum.zc_word[ZIL_ZC_SEQ]);
 466 
 467         VERIFY(0 == scan_funcs[scn->scn_phys.scn_func](dp, bp, &zb));
 468         return (0);
 469 }
 470 
 471 /* ARGSUSED */
 472 static int
 473 dsl_scan_zil_record(zilog_t *zilog, lr_t *lrc, void *arg, uint64_t claim_txg)
 474 {
 475         if (lrc->lrc_txtype == TX_WRITE) {
 476                 zil_scan_arg_t *zsa = arg;
 477                 dsl_pool_t *dp = zsa->zsa_dp;
 478                 dsl_scan_t *scn = dp->dp_scan;
 479                 zil_header_t *zh = zsa->zsa_zh;
 480                 lr_write_t *lr = (lr_write_t *)lrc;
 481                 blkptr_t *bp = &lr->lr_blkptr;
 482                 zbookmark_t zb;
 483 
 484                 if (bp->blk_birth <= scn->scn_phys.scn_cur_min_txg)
 485                         return (0);
 486 
 487                 /*
 488                  * birth can be < claim_txg if this record's txg is
 489                  * already txg sync'ed (but this log block contains
 490                  * other records that are not synced)
 491                  */
 492                 if (claim_txg == 0 || bp->blk_birth < claim_txg)
 493                         return (0);
 494 
 495                 SET_BOOKMARK(&zb, zh->zh_log.blk_cksum.zc_word[ZIL_ZC_OBJSET],
 496                     lr->lr_foid, ZB_ZIL_LEVEL,
 497                     lr->lr_offset / BP_GET_LSIZE(bp));
 498 
 499                 VERIFY(0 == scan_funcs[scn->scn_phys.scn_func](dp, bp, &zb));
 500         }
 501         return (0);
 502 }
 503 
 504 static void
 505 dsl_scan_zil(dsl_pool_t *dp, zil_header_t *zh)
 506 {
 507         uint64_t claim_txg = zh->zh_claim_txg;
 508         zil_scan_arg_t zsa = { dp, zh };
 509         zilog_t *zilog;
 510 
 511         /*
 512          * We only want to visit blocks that have been claimed but not yet
 513          * replayed (or, in read-only mode, blocks that *would* be claimed).
 514          */
 515         if (claim_txg == 0 && spa_writeable(dp->dp_spa))
 516                 return;
 517 
 518         zilog = zil_alloc(dp->dp_meta_objset, zh);
 519 
 520         (void) zil_parse(zilog, dsl_scan_zil_block, dsl_scan_zil_record, &zsa,
 521             claim_txg);
 522 
 523         zil_free(zilog);
 524 }
 525 
 526 /* ARGSUSED */
 527 static void
 528 dsl_scan_prefetch(dsl_scan_t *scn, arc_buf_t *buf, blkptr_t *bp,
 529     uint64_t objset, uint64_t object, uint64_t blkid)
 530 {
 531         zbookmark_t czb;
 532         uint32_t flags = ARC_NOWAIT | ARC_PREFETCH;
 533 
 534         if (zfs_no_scrub_prefetch)
 535                 return;
 536 
 537         if (BP_IS_HOLE(bp) || bp->blk_birth <= scn->scn_phys.scn_min_txg ||
 538             (BP_GET_LEVEL(bp) == 0 && BP_GET_TYPE(bp) != DMU_OT_DNODE))
 539                 return;
 540 
 541         SET_BOOKMARK(&czb, objset, object, BP_GET_LEVEL(bp), blkid);
 542 
 543         (void) arc_read(scn->scn_zio_root, scn->scn_dp->dp_spa, bp,
 544             NULL, NULL, ZIO_PRIORITY_ASYNC_READ,
 545             ZIO_FLAG_CANFAIL | ZIO_FLAG_SCAN_THREAD, &flags, &czb);
 546 }
 547 
 548 static boolean_t
 549 dsl_scan_check_resume(dsl_scan_t *scn, const dnode_phys_t *dnp,
 550     const zbookmark_t *zb)
 551 {
 552         /*
 553          * We never skip over user/group accounting objects (obj<0)
 554          */
 555         if (!ZB_IS_ZERO(&scn->scn_phys.scn_bookmark) &&
 556             (int64_t)zb->zb_object >= 0) {
 557                 /*
 558                  * If we already visited this bp & everything below (in
 559                  * a prior txg sync), don't bother doing it again.
 560                  */
 561                 if (zbookmark_is_before(dnp, zb, &scn->scn_phys.scn_bookmark))
 562                         return (B_TRUE);
 563 
 564                 /*
 565                  * If we found the block we're trying to resume from, or
 566                  * we went past it to a different object, zero it out to
 567                  * indicate that it's OK to start checking for pausing
 568                  * again.
 569                  */
 570                 if (bcmp(zb, &scn->scn_phys.scn_bookmark, sizeof (*zb)) == 0 ||
 571                     zb->zb_object > scn->scn_phys.scn_bookmark.zb_object) {
 572                         dprintf("resuming at %llx/%llx/%llx/%llx\n",
 573                             (longlong_t)zb->zb_objset,
 574                             (longlong_t)zb->zb_object,
 575                             (longlong_t)zb->zb_level,
 576                             (longlong_t)zb->zb_blkid);
 577                         bzero(&scn->scn_phys.scn_bookmark, sizeof (*zb));
 578                 }
 579         }
 580         return (B_FALSE);
 581 }
 582 
 583 /*
 584  * Return nonzero on i/o error.
 585  * Return new buf to write out in *bufp.
 586  */
 587 static int
 588 dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
 589     dnode_phys_t *dnp, const blkptr_t *bp,
 590     const zbookmark_t *zb, dmu_tx_t *tx, arc_buf_t **bufp)
 591 {
 592         dsl_pool_t *dp = scn->scn_dp;
 593         int zio_flags = ZIO_FLAG_CANFAIL | ZIO_FLAG_SCAN_THREAD;
 594         int err;
 595 
 596         if (BP_GET_LEVEL(bp) > 0) {
 597                 uint32_t flags = ARC_WAIT;
 598                 int i;
 599                 blkptr_t *cbp;
 600                 int epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT;
 601 
 602                 err = arc_read(NULL, dp->dp_spa, bp, arc_getbuf_func, bufp,
 603                     ZIO_PRIORITY_ASYNC_READ, zio_flags, &flags, zb);
 604                 if (err) {
 605                         scn->scn_phys.scn_errors++;
 606                         return (err);
 607                 }
 608                 for (i = 0, cbp = (*bufp)->b_data; i < epb; i++, cbp++) {
 609                         dsl_scan_prefetch(scn, *bufp, cbp, zb->zb_objset,
 610                             zb->zb_object, zb->zb_blkid * epb + i);
 611                 }
 612                 for (i = 0, cbp = (*bufp)->b_data; i < epb; i++, cbp++) {
 613                         zbookmark_t czb;
 614 
 615                         SET_BOOKMARK(&czb, zb->zb_objset, zb->zb_object,
 616                             zb->zb_level - 1,
 617                             zb->zb_blkid * epb + i);
 618                         dsl_scan_visitbp(cbp, &czb, dnp,
 619                             *bufp, ds, scn, ostype, tx);
 620                 }
 621         } else if (BP_GET_TYPE(bp) == DMU_OT_USERGROUP_USED) {
 622                 uint32_t flags = ARC_WAIT;
 623 
 624                 err = arc_read(NULL, dp->dp_spa, bp, arc_getbuf_func, bufp,
 625                     ZIO_PRIORITY_ASYNC_READ, zio_flags, &flags, zb);
 626                 if (err) {
 627                         scn->scn_phys.scn_errors++;
 628                         return (err);
 629                 }
 630         } else if (BP_GET_TYPE(bp) == DMU_OT_DNODE) {
 631                 uint32_t flags = ARC_WAIT;
 632                 dnode_phys_t *cdnp;
 633                 int i, j;
 634                 int epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;
 635 
 636                 err = arc_read(NULL, dp->dp_spa, bp, arc_getbuf_func, bufp,
 637                     ZIO_PRIORITY_ASYNC_READ, zio_flags, &flags, zb);
 638                 if (err) {
 639                         scn->scn_phys.scn_errors++;
 640                         return (err);
 641                 }
 642                 for (i = 0, cdnp = (*bufp)->b_data; i < epb; i++, cdnp++) {
 643                         for (j = 0; j < cdnp->dn_nblkptr; j++) {
 644                                 blkptr_t *cbp = &cdnp->dn_blkptr[j];
 645                                 dsl_scan_prefetch(scn, *bufp, cbp,
 646                                     zb->zb_objset, zb->zb_blkid * epb + i, j);
 647                         }
 648                 }
 649                 for (i = 0, cdnp = (*bufp)->b_data; i < epb; i++, cdnp++) {
 650                         dsl_scan_visitdnode(scn, ds, ostype,
 651                             cdnp, *bufp, zb->zb_blkid * epb + i, tx);
 652                 }
 653 
 654         } else if (BP_GET_TYPE(bp) == DMU_OT_OBJSET) {
 655                 uint32_t flags = ARC_WAIT;
 656                 objset_phys_t *osp;
 657 
 658                 err = arc_read(NULL, dp->dp_spa, bp, arc_getbuf_func, bufp,
 659                     ZIO_PRIORITY_ASYNC_READ, zio_flags, &flags, zb);
 660                 if (err) {
 661                         scn->scn_phys.scn_errors++;
 662                         return (err);
 663                 }
 664 
 665                 osp = (*bufp)->b_data;
 666 
 667                 dsl_scan_visitdnode(scn, ds, osp->os_type,
 668                     &osp->os_meta_dnode, *bufp, DMU_META_DNODE_OBJECT, tx);
 669 
 670                 if (OBJSET_BUF_HAS_USERUSED(*bufp)) {
 671                         /*
 672                          * We also always visit user/group accounting
 673                          * objects, and never skip them, even if we are
 674                          * pausing.  This is necessary so that the space
 675                          * deltas from this txg get integrated.
 676                          */
 677                         dsl_scan_visitdnode(scn, ds, osp->os_type,
 678                             &osp->os_groupused_dnode, *bufp,
 679                             DMU_GROUPUSED_OBJECT, tx);
 680                         dsl_scan_visitdnode(scn, ds, osp->os_type,
 681                             &osp->os_userused_dnode, *bufp,
 682                             DMU_USERUSED_OBJECT, tx);
 683                 }
 684         }
 685 
 686         return (0);
 687 }
 688 
 689 static void
 690 dsl_scan_visitdnode(dsl_scan_t *scn, dsl_dataset_t *ds,
 691     dmu_objset_type_t ostype, dnode_phys_t *dnp, arc_buf_t *buf,
 692     uint64_t object, dmu_tx_t *tx)
 693 {
 694         int j;
 695 
 696         for (j = 0; j < dnp->dn_nblkptr; j++) {
 697                 zbookmark_t czb;
 698 
 699                 SET_BOOKMARK(&czb, ds ? ds->ds_object : 0, object,
 700                     dnp->dn_nlevels - 1, j);
 701                 dsl_scan_visitbp(&dnp->dn_blkptr[j],
 702                     &czb, dnp, buf, ds, scn, ostype, tx);
 703         }
 704 
 705         if (dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR) {
 706                 zbookmark_t czb;
 707                 SET_BOOKMARK(&czb, ds ? ds->ds_object : 0, object,
 708                     0, DMU_SPILL_BLKID);
 709                 dsl_scan_visitbp(&dnp->dn_spill,
 710                     &czb, dnp, buf, ds, scn, ostype, tx);
 711         }
 712 }
 713 
 714 /*
 715  * The arguments are in this order because mdb can only print the
 716  * first 5; we want them to be useful.
 717  */
 718 static void
 719 dsl_scan_visitbp(blkptr_t *bp, const zbookmark_t *zb,
 720     dnode_phys_t *dnp, arc_buf_t *pbuf,
 721     dsl_dataset_t *ds, dsl_scan_t *scn, dmu_objset_type_t ostype,
 722     dmu_tx_t *tx)
 723 {
 724         dsl_pool_t *dp = scn->scn_dp;
 725         arc_buf_t *buf = NULL;
 726         blkptr_t bp_toread = *bp;
 727 
 728         /* ASSERT(pbuf == NULL || arc_released(pbuf)); */
 729 
 730         if (dsl_scan_check_pause(scn, zb))
 731                 return;
 732 
 733         if (dsl_scan_check_resume(scn, dnp, zb))
 734                 return;
 735 
 736         if (bp->blk_birth == 0)
 737                 return;
 738 
 739         scn->scn_visited_this_txg++;
 740 
 741         dprintf_bp(bp,
 742             "visiting ds=%p/%llu zb=%llx/%llx/%llx/%llx buf=%p bp=%p",
 743             ds, ds ? ds->ds_object : 0,
 744             zb->zb_objset, zb->zb_object, zb->zb_level, zb->zb_blkid,
 745             pbuf, bp);
 746 
 747         if (bp->blk_birth <= scn->scn_phys.scn_cur_min_txg)
 748                 return;
 749 
 750         if (dsl_scan_recurse(scn, ds, ostype, dnp, &bp_toread, zb, tx,
 751             &buf) != 0)
 752                 return;
 753 
 754         /*
 755          * If dsl_scan_ddt() has aready visited this block, it will have
 756          * already done any translations or scrubbing, so don't call the
 757          * callback again.
 758          */
 759         if (ddt_class_contains(dp->dp_spa,
 760             scn->scn_phys.scn_ddt_class_max, bp)) {
 761                 ASSERT(buf == NULL);
 762                 return;
 763         }
 764 
 765         /*
 766          * If this block is from the future (after cur_max_txg), then we
 767          * are doing this on behalf of a deleted snapshot, and we will
 768          * revisit the future block on the next pass of this dataset.
 769          * Don't scan it now unless we need to because something
 770          * under it was modified.
 771          */
 772         if (bp->blk_birth <= scn->scn_phys.scn_cur_max_txg) {
 773                 scan_funcs[scn->scn_phys.scn_func](dp, bp, zb);
 774         }
 775         if (buf)
 776                 (void) arc_buf_remove_ref(buf, &buf);
 777 }
 778 
 779 static void
 780 dsl_scan_visit_rootbp(dsl_scan_t *scn, dsl_dataset_t *ds, blkptr_t *bp,
 781     dmu_tx_t *tx)
 782 {
 783         zbookmark_t zb;
 784 
 785         SET_BOOKMARK(&zb, ds ? ds->ds_object : DMU_META_OBJSET,
 786             ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
 787         dsl_scan_visitbp(bp, &zb, NULL, NULL,
 788             ds, scn, DMU_OST_NONE, tx);
 789 
 790         dprintf_ds(ds, "finished scan%s", "");
 791 }
 792 
 793 void
 794 dsl_scan_ds_destroyed(dsl_dataset_t *ds, dmu_tx_t *tx)
 795 {
 796         dsl_pool_t *dp = ds->ds_dir->dd_pool;
 797         dsl_scan_t *scn = dp->dp_scan;
 798         uint64_t mintxg;
 799 
 800         if (scn->scn_phys.scn_state != DSS_SCANNING)
 801                 return;
 802 
 803         if (scn->scn_phys.scn_bookmark.zb_objset == ds->ds_object) {
 804                 if (dsl_dataset_is_snapshot(ds)) {
 805                         /* Note, scn_cur_{min,max}_txg stays the same. */
 806                         scn->scn_phys.scn_bookmark.zb_objset =
 807                             ds->ds_phys->ds_next_snap_obj;
 808                         zfs_dbgmsg("destroying ds %llu; currently traversing; "
 809                             "reset zb_objset to %llu",
 810                             (u_longlong_t)ds->ds_object,
 811                             (u_longlong_t)ds->ds_phys->ds_next_snap_obj);
 812                         scn->scn_phys.scn_flags |= DSF_VISIT_DS_AGAIN;
 813                 } else {
 814                         SET_BOOKMARK(&scn->scn_phys.scn_bookmark,
 815                             ZB_DESTROYED_OBJSET, 0, 0, 0);
 816                         zfs_dbgmsg("destroying ds %llu; currently traversing; "
 817                             "reset bookmark to -1,0,0,0",
 818                             (u_longlong_t)ds->ds_object);
 819                 }
 820         } else if (zap_lookup_int_key(dp->dp_meta_objset,
 821             scn->scn_phys.scn_queue_obj, ds->ds_object, &mintxg) == 0) {
 822                 ASSERT3U(ds->ds_phys->ds_num_children, <=, 1);
 823                 VERIFY3U(0, ==, zap_remove_int(dp->dp_meta_objset,
 824                     scn->scn_phys.scn_queue_obj, ds->ds_object, tx));
 825                 if (dsl_dataset_is_snapshot(ds)) {
 826                         /*
 827                          * We keep the same mintxg; it could be >
 828                          * ds_creation_txg if the previous snapshot was
 829                          * deleted too.
 830                          */
 831                         VERIFY(zap_add_int_key(dp->dp_meta_objset,
 832                             scn->scn_phys.scn_queue_obj,
 833                             ds->ds_phys->ds_next_snap_obj, mintxg, tx) == 0);
 834                         zfs_dbgmsg("destroying ds %llu; in queue; "
 835                             "replacing with %llu",
 836                             (u_longlong_t)ds->ds_object,
 837                             (u_longlong_t)ds->ds_phys->ds_next_snap_obj);
 838                 } else {
 839                         zfs_dbgmsg("destroying ds %llu; in queue; removing",
 840                             (u_longlong_t)ds->ds_object);
 841                 }
 842         } else {
 843                 zfs_dbgmsg("destroying ds %llu; ignoring",
 844                     (u_longlong_t)ds->ds_object);
 845         }
 846 
 847         /*
 848          * dsl_scan_sync() should be called after this, and should sync
 849          * out our changed state, but just to be safe, do it here.
 850          */
 851         dsl_scan_sync_state(scn, tx);
 852 }
 853 
 854 void
 855 dsl_scan_ds_snapshotted(dsl_dataset_t *ds, dmu_tx_t *tx)
 856 {
 857         dsl_pool_t *dp = ds->ds_dir->dd_pool;
 858         dsl_scan_t *scn = dp->dp_scan;
 859         uint64_t mintxg;
 860 
 861         if (scn->scn_phys.scn_state != DSS_SCANNING)
 862                 return;
 863 
 864         ASSERT(ds->ds_phys->ds_prev_snap_obj != 0);
 865 
 866         if (scn->scn_phys.scn_bookmark.zb_objset == ds->ds_object) {
 867                 scn->scn_phys.scn_bookmark.zb_objset =
 868                     ds->ds_phys->ds_prev_snap_obj;
 869                 zfs_dbgmsg("snapshotting ds %llu; currently traversing; "
 870                     "reset zb_objset to %llu",
 871                     (u_longlong_t)ds->ds_object,
 872                     (u_longlong_t)ds->ds_phys->ds_prev_snap_obj);
 873         } else if (zap_lookup_int_key(dp->dp_meta_objset,
 874             scn->scn_phys.scn_queue_obj, ds->ds_object, &mintxg) == 0) {
 875                 VERIFY3U(0, ==, zap_remove_int(dp->dp_meta_objset,
 876                     scn->scn_phys.scn_queue_obj, ds->ds_object, tx));
 877                 VERIFY(zap_add_int_key(dp->dp_meta_objset,
 878                     scn->scn_phys.scn_queue_obj,
 879                     ds->ds_phys->ds_prev_snap_obj, mintxg, tx) == 0);
 880                 zfs_dbgmsg("snapshotting ds %llu; in queue; "
 881                     "replacing with %llu",
 882                     (u_longlong_t)ds->ds_object,
 883                     (u_longlong_t)ds->ds_phys->ds_prev_snap_obj);
 884         }
 885         dsl_scan_sync_state(scn, tx);
 886 }
 887 
 888 void
 889 dsl_scan_ds_clone_swapped(dsl_dataset_t *ds1, dsl_dataset_t *ds2, dmu_tx_t *tx)
 890 {
 891         dsl_pool_t *dp = ds1->ds_dir->dd_pool;
 892         dsl_scan_t *scn = dp->dp_scan;
 893         uint64_t mintxg;
 894 
 895         if (scn->scn_phys.scn_state != DSS_SCANNING)
 896                 return;
 897 
 898         if (scn->scn_phys.scn_bookmark.zb_objset == ds1->ds_object) {
 899                 scn->scn_phys.scn_bookmark.zb_objset = ds2->ds_object;
 900                 zfs_dbgmsg("clone_swap ds %llu; currently traversing; "
 901                     "reset zb_objset to %llu",
 902                     (u_longlong_t)ds1->ds_object,
 903                     (u_longlong_t)ds2->ds_object);
 904         } else if (scn->scn_phys.scn_bookmark.zb_objset == ds2->ds_object) {
 905                 scn->scn_phys.scn_bookmark.zb_objset = ds1->ds_object;
 906                 zfs_dbgmsg("clone_swap ds %llu; currently traversing; "
 907                     "reset zb_objset to %llu",
 908                     (u_longlong_t)ds2->ds_object,
 909                     (u_longlong_t)ds1->ds_object);
 910         }
 911 
 912         if (zap_lookup_int_key(dp->dp_meta_objset, scn->scn_phys.scn_queue_obj,
 913             ds1->ds_object, &mintxg) == 0) {
 914                 int err;
 915 
 916                 ASSERT3U(mintxg, ==, ds1->ds_phys->ds_prev_snap_txg);
 917                 ASSERT3U(mintxg, ==, ds2->ds_phys->ds_prev_snap_txg);
 918                 VERIFY3U(0, ==, zap_remove_int(dp->dp_meta_objset,
 919                     scn->scn_phys.scn_queue_obj, ds1->ds_object, tx));
 920                 err = zap_add_int_key(dp->dp_meta_objset,
 921                     scn->scn_phys.scn_queue_obj, ds2->ds_object, mintxg, tx);
 922                 VERIFY(err == 0 || err == EEXIST);
 923                 if (err == EEXIST) {
 924                         /* Both were there to begin with */
 925                         VERIFY(0 == zap_add_int_key(dp->dp_meta_objset,
 926                             scn->scn_phys.scn_queue_obj,
 927                             ds1->ds_object, mintxg, tx));
 928                 }
 929                 zfs_dbgmsg("clone_swap ds %llu; in queue; "
 930                     "replacing with %llu",
 931                     (u_longlong_t)ds1->ds_object,
 932                     (u_longlong_t)ds2->ds_object);
 933         } else if (zap_lookup_int_key(dp->dp_meta_objset,
 934             scn->scn_phys.scn_queue_obj, ds2->ds_object, &mintxg) == 0) {
 935                 ASSERT3U(mintxg, ==, ds1->ds_phys->ds_prev_snap_txg);
 936                 ASSERT3U(mintxg, ==, ds2->ds_phys->ds_prev_snap_txg);
 937                 VERIFY3U(0, ==, zap_remove_int(dp->dp_meta_objset,
 938                     scn->scn_phys.scn_queue_obj, ds2->ds_object, tx));
 939                 VERIFY(0 == zap_add_int_key(dp->dp_meta_objset,
 940                     scn->scn_phys.scn_queue_obj, ds1->ds_object, mintxg, tx));
 941                 zfs_dbgmsg("clone_swap ds %llu; in queue; "
 942                     "replacing with %llu",
 943                     (u_longlong_t)ds2->ds_object,
 944                     (u_longlong_t)ds1->ds_object);
 945         }
 946 
 947         dsl_scan_sync_state(scn, tx);
 948 }
 949 
 950 struct enqueue_clones_arg {
 951         dmu_tx_t *tx;
 952         uint64_t originobj;
 953 };
 954 
 955 /* ARGSUSED */
 956 static int
 957 enqueue_clones_cb(dsl_pool_t *dp, dsl_dataset_t *hds, void *arg)
 958 {
 959         struct enqueue_clones_arg *eca = arg;
 960         dsl_dataset_t *ds;
 961         int err;
 962         dsl_scan_t *scn = dp->dp_scan;
 963 
 964         if (hds->ds_dir->dd_phys->dd_origin_obj != eca->originobj)
 965                 return (0);
 966 
 967         err = dsl_dataset_hold_obj(dp, hds->ds_object, FTAG, &ds);
 968         if (err)
 969                 return (err);
 970 
 971         while (ds->ds_phys->ds_prev_snap_obj != eca->originobj) {
 972                 dsl_dataset_t *prev;
 973                 err = dsl_dataset_hold_obj(dp,
 974                     ds->ds_phys->ds_prev_snap_obj, FTAG, &prev);
 975 
 976                 dsl_dataset_rele(ds, FTAG);
 977                 if (err)
 978                         return (err);
 979                 ds = prev;
 980         }
 981         VERIFY(zap_add_int_key(dp->dp_meta_objset,
 982             scn->scn_phys.scn_queue_obj, ds->ds_object,
 983             ds->ds_phys->ds_prev_snap_txg, eca->tx) == 0);
 984         dsl_dataset_rele(ds, FTAG);
 985         return (0);
 986 }
 987 
 988 static void
 989 dsl_scan_visitds(dsl_scan_t *scn, uint64_t dsobj, dmu_tx_t *tx)
 990 {
 991         dsl_pool_t *dp = scn->scn_dp;
 992         dsl_dataset_t *ds;
 993         objset_t *os;
 994 
 995         VERIFY3U(0, ==, dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds));
 996 
 997         if (dmu_objset_from_ds(ds, &os))
 998                 goto out;
 999 
1000         /*
1001          * Only the ZIL in the head (non-snapshot) is valid.  Even though
1002          * snapshots can have ZIL block pointers (which may be the same
1003          * BP as in the head), they must be ignored.  So we traverse the
1004          * ZIL here, rather than in scan_recurse(), because the regular
1005          * snapshot block-sharing rules don't apply to it.
1006          */
1007         if (DSL_SCAN_IS_SCRUB_RESILVER(scn) && !dsl_dataset_is_snapshot(ds))
1008                 dsl_scan_zil(dp, &os->os_zil_header);
1009 
1010         /*
1011          * Iterate over the bps in this ds.
1012          */
1013         dmu_buf_will_dirty(ds->ds_dbuf, tx);
1014         dsl_scan_visit_rootbp(scn, ds, &ds->ds_phys->ds_bp, tx);
1015 
1016         char *dsname = kmem_alloc(ZFS_MAXNAMELEN, KM_SLEEP);
1017         dsl_dataset_name(ds, dsname);
1018         zfs_dbgmsg("scanned dataset %llu (%s) with min=%llu max=%llu; "
1019             "pausing=%u",
1020             (longlong_t)dsobj, dsname,
1021             (longlong_t)scn->scn_phys.scn_cur_min_txg,
1022             (longlong_t)scn->scn_phys.scn_cur_max_txg,
1023             (int)scn->scn_pausing);
1024         kmem_free(dsname, ZFS_MAXNAMELEN);
1025 
1026         if (scn->scn_pausing)
1027                 goto out;
1028 
1029         /*
1030          * We've finished this pass over this dataset.
1031          */
1032 
1033         /*
1034          * If we did not completely visit this dataset, do another pass.
1035          */
1036         if (scn->scn_phys.scn_flags & DSF_VISIT_DS_AGAIN) {
1037                 zfs_dbgmsg("incomplete pass; visiting again");
1038                 scn->scn_phys.scn_flags &= ~DSF_VISIT_DS_AGAIN;
1039                 VERIFY(zap_add_int_key(dp->dp_meta_objset,
1040                     scn->scn_phys.scn_queue_obj, ds->ds_object,
1041                     scn->scn_phys.scn_cur_max_txg, tx) == 0);
1042                 goto out;
1043         }
1044 
1045         /*
1046          * Add descendent datasets to work queue.
1047          */
1048         if (ds->ds_phys->ds_next_snap_obj != 0) {
1049                 VERIFY(zap_add_int_key(dp->dp_meta_objset,
1050                     scn->scn_phys.scn_queue_obj, ds->ds_phys->ds_next_snap_obj,
1051                     ds->ds_phys->ds_creation_txg, tx) == 0);
1052         }
1053         if (ds->ds_phys->ds_num_children > 1) {
1054                 boolean_t usenext = B_FALSE;
1055                 if (ds->ds_phys->ds_next_clones_obj != 0) {
1056                         uint64_t count;
1057                         /*
1058                          * A bug in a previous version of the code could
1059                          * cause upgrade_clones_cb() to not set
1060                          * ds_next_snap_obj when it should, leading to a
1061                          * missing entry.  Therefore we can only use the
1062                          * next_clones_obj when its count is correct.
1063                          */
1064                         int err = zap_count(dp->dp_meta_objset,
1065                             ds->ds_phys->ds_next_clones_obj, &count);
1066                         if (err == 0 &&
1067                             count == ds->ds_phys->ds_num_children - 1)
1068                                 usenext = B_TRUE;
1069                 }
1070 
1071                 if (usenext) {
1072                         VERIFY0(zap_join_key(dp->dp_meta_objset,
1073                             ds->ds_phys->ds_next_clones_obj,
1074                             scn->scn_phys.scn_queue_obj,
1075                             ds->ds_phys->ds_creation_txg, tx));
1076                 } else {
1077                         struct enqueue_clones_arg eca;
1078                         eca.tx = tx;
1079                         eca.originobj = ds->ds_object;
1080 
1081                         VERIFY0(dmu_objset_find_dp(dp, dp->dp_root_dir_obj,
1082                             enqueue_clones_cb, &eca, DS_FIND_CHILDREN));
1083                 }
1084         }
1085 
1086 out:
1087         dsl_dataset_rele(ds, FTAG);
1088 }
1089 
1090 /* ARGSUSED */
1091 static int
1092 enqueue_cb(dsl_pool_t *dp, dsl_dataset_t *hds, void *arg)
1093 {
1094         dmu_tx_t *tx = arg;
1095         dsl_dataset_t *ds;
1096         int err;
1097         dsl_scan_t *scn = dp->dp_scan;
1098 
1099         err = dsl_dataset_hold_obj(dp, hds->ds_object, FTAG, &ds);
1100         if (err)
1101                 return (err);
1102 
1103         while (ds->ds_phys->ds_prev_snap_obj != 0) {
1104                 dsl_dataset_t *prev;
1105                 err = dsl_dataset_hold_obj(dp, ds->ds_phys->ds_prev_snap_obj,
1106                     FTAG, &prev);
1107                 if (err) {
1108                         dsl_dataset_rele(ds, FTAG);
1109                         return (err);
1110                 }
1111 
1112                 /*
1113                  * If this is a clone, we don't need to worry about it for now.
1114                  */
1115                 if (prev->ds_phys->ds_next_snap_obj != ds->ds_object) {
1116                         dsl_dataset_rele(ds, FTAG);
1117                         dsl_dataset_rele(prev, FTAG);
1118                         return (0);
1119                 }
1120                 dsl_dataset_rele(ds, FTAG);
1121                 ds = prev;
1122         }
1123 
1124         VERIFY(zap_add_int_key(dp->dp_meta_objset, scn->scn_phys.scn_queue_obj,
1125             ds->ds_object, ds->ds_phys->ds_prev_snap_txg, tx) == 0);
1126         dsl_dataset_rele(ds, FTAG);
1127         return (0);
1128 }
1129 
1130 /*
1131  * Scrub/dedup interaction.
1132  *
1133  * If there are N references to a deduped block, we don't want to scrub it
1134  * N times -- ideally, we should scrub it exactly once.
1135  *
1136  * We leverage the fact that the dde's replication class (enum ddt_class)
1137  * is ordered from highest replication class (DDT_CLASS_DITTO) to lowest
1138  * (DDT_CLASS_UNIQUE) so that we may walk the DDT in that order.
1139  *
1140  * To prevent excess scrubbing, the scrub begins by walking the DDT
1141  * to find all blocks with refcnt > 1, and scrubs each of these once.
1142  * Since there are two replication classes which contain blocks with
1143  * refcnt > 1, we scrub the highest replication class (DDT_CLASS_DITTO) first.
1144  * Finally the top-down scrub begins, only visiting blocks with refcnt == 1.
1145  *
1146  * There would be nothing more to say if a block's refcnt couldn't change
1147  * during a scrub, but of course it can so we must account for changes
1148  * in a block's replication class.
1149  *
1150  * Here's an example of what can occur:
1151  *
1152  * If a block has refcnt > 1 during the DDT scrub phase, but has refcnt == 1
1153  * when visited during the top-down scrub phase, it will be scrubbed twice.
1154  * This negates our scrub optimization, but is otherwise harmless.
1155  *
1156  * If a block has refcnt == 1 during the DDT scrub phase, but has refcnt > 1
1157  * on each visit during the top-down scrub phase, it will never be scrubbed.
1158  * To catch this, ddt_sync_entry() notifies the scrub code whenever a block's
1159  * reference class transitions to a higher level (i.e DDT_CLASS_UNIQUE to
1160  * DDT_CLASS_DUPLICATE); if it transitions from refcnt == 1 to refcnt > 1
1161  * while a scrub is in progress, it scrubs the block right then.
1162  */
1163 static void
1164 dsl_scan_ddt(dsl_scan_t *scn, dmu_tx_t *tx)
1165 {
1166         ddt_bookmark_t *ddb = &scn->scn_phys.scn_ddt_bookmark;
1167         ddt_entry_t dde = { 0 };
1168         int error;
1169         uint64_t n = 0;
1170 
1171         while ((error = ddt_walk(scn->scn_dp->dp_spa, ddb, &dde)) == 0) {
1172                 ddt_t *ddt;
1173 
1174                 if (ddb->ddb_class > scn->scn_phys.scn_ddt_class_max)
1175                         break;
1176                 dprintf("visiting ddb=%llu/%llu/%llu/%llx\n",
1177                     (longlong_t)ddb->ddb_class,
1178                     (longlong_t)ddb->ddb_type,
1179                     (longlong_t)ddb->ddb_checksum,
1180                     (longlong_t)ddb->ddb_cursor);
1181 
1182                 /* There should be no pending changes to the dedup table */
1183                 ddt = scn->scn_dp->dp_spa->spa_ddt[ddb->ddb_checksum];
1184                 ASSERT(avl_first(&ddt->ddt_tree) == NULL);
1185 
1186                 dsl_scan_ddt_entry(scn, ddb->ddb_checksum, &dde, tx);
1187                 n++;
1188 
1189                 if (dsl_scan_check_pause(scn, NULL))
1190                         break;
1191         }
1192 
1193         zfs_dbgmsg("scanned %llu ddt entries with class_max = %u; pausing=%u",
1194             (longlong_t)n, (int)scn->scn_phys.scn_ddt_class_max,
1195             (int)scn->scn_pausing);
1196 
1197         ASSERT(error == 0 || error == ENOENT);
1198         ASSERT(error != ENOENT ||
1199             ddb->ddb_class > scn->scn_phys.scn_ddt_class_max);
1200 }
1201 
1202 /* ARGSUSED */
1203 void
1204 dsl_scan_ddt_entry(dsl_scan_t *scn, enum zio_checksum checksum,
1205     ddt_entry_t *dde, dmu_tx_t *tx)
1206 {
1207         const ddt_key_t *ddk = &dde->dde_key;
1208         ddt_phys_t *ddp = dde->dde_phys;
1209         blkptr_t bp;
1210         zbookmark_t zb = { 0 };
1211 
1212         if (scn->scn_phys.scn_state != DSS_SCANNING)
1213                 return;
1214 
1215         for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
1216                 if (ddp->ddp_phys_birth == 0 ||
1217                     ddp->ddp_phys_birth > scn->scn_phys.scn_cur_max_txg)
1218                         continue;
1219                 ddt_bp_create(checksum, ddk, ddp, &bp);
1220 
1221                 scn->scn_visited_this_txg++;
1222                 scan_funcs[scn->scn_phys.scn_func](scn->scn_dp, &bp, &zb);
1223         }
1224 }
1225 
1226 static void
1227 dsl_scan_visit(dsl_scan_t *scn, dmu_tx_t *tx)
1228 {
1229         dsl_pool_t *dp = scn->scn_dp;
1230         zap_cursor_t zc;
1231         zap_attribute_t za;
1232 
1233         if (scn->scn_phys.scn_ddt_bookmark.ddb_class <=
1234             scn->scn_phys.scn_ddt_class_max) {
1235                 scn->scn_phys.scn_cur_min_txg = scn->scn_phys.scn_min_txg;
1236                 scn->scn_phys.scn_cur_max_txg = scn->scn_phys.scn_max_txg;
1237                 dsl_scan_ddt(scn, tx);
1238                 if (scn->scn_pausing)
1239                         return;
1240         }
1241 
1242         if (scn->scn_phys.scn_bookmark.zb_objset == DMU_META_OBJSET) {
1243                 /* First do the MOS & ORIGIN */
1244 
1245                 scn->scn_phys.scn_cur_min_txg = scn->scn_phys.scn_min_txg;
1246                 scn->scn_phys.scn_cur_max_txg = scn->scn_phys.scn_max_txg;
1247                 dsl_scan_visit_rootbp(scn, NULL,
1248                     &dp->dp_meta_rootbp, tx);
1249                 spa_set_rootblkptr(dp->dp_spa, &dp->dp_meta_rootbp);
1250                 if (scn->scn_pausing)
1251                         return;
1252 
1253                 if (spa_version(dp->dp_spa) < SPA_VERSION_DSL_SCRUB) {
1254                         VERIFY0(dmu_objset_find_dp(dp, dp->dp_root_dir_obj,
1255                             enqueue_cb, tx, DS_FIND_CHILDREN));
1256                 } else {
1257                         dsl_scan_visitds(scn,
1258                             dp->dp_origin_snap->ds_object, tx);
1259                 }
1260                 ASSERT(!scn->scn_pausing);
1261         } else if (scn->scn_phys.scn_bookmark.zb_objset !=
1262             ZB_DESTROYED_OBJSET) {
1263                 /*
1264                  * If we were paused, continue from here.  Note if the
1265                  * ds we were paused on was deleted, the zb_objset may
1266                  * be -1, so we will skip this and find a new objset
1267                  * below.
1268                  */
1269                 dsl_scan_visitds(scn, scn->scn_phys.scn_bookmark.zb_objset, tx);
1270                 if (scn->scn_pausing)
1271                         return;
1272         }
1273 
1274         /*
1275          * In case we were paused right at the end of the ds, zero the
1276          * bookmark so we don't think that we're still trying to resume.
1277          */
1278         bzero(&scn->scn_phys.scn_bookmark, sizeof (zbookmark_t));
1279 
1280         /* keep pulling things out of the zap-object-as-queue */
1281         while (zap_cursor_init(&zc, dp->dp_meta_objset,
1282             scn->scn_phys.scn_queue_obj),
1283             zap_cursor_retrieve(&zc, &za) == 0) {
1284                 dsl_dataset_t *ds;
1285                 uint64_t dsobj;
1286 
1287                 dsobj = strtonum(za.za_name, NULL);
1288                 VERIFY3U(0, ==, zap_remove_int(dp->dp_meta_objset,
1289                     scn->scn_phys.scn_queue_obj, dsobj, tx));
1290 
1291                 /* Set up min/max txg */
1292                 VERIFY3U(0, ==, dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds));
1293                 if (za.za_first_integer != 0) {
1294                         scn->scn_phys.scn_cur_min_txg =
1295                             MAX(scn->scn_phys.scn_min_txg,
1296                             za.za_first_integer);
1297                 } else {
1298                         scn->scn_phys.scn_cur_min_txg =
1299                             MAX(scn->scn_phys.scn_min_txg,
1300                             ds->ds_phys->ds_prev_snap_txg);
1301                 }
1302                 scn->scn_phys.scn_cur_max_txg = dsl_scan_ds_maxtxg(ds);
1303                 dsl_dataset_rele(ds, FTAG);
1304 
1305                 dsl_scan_visitds(scn, dsobj, tx);
1306                 zap_cursor_fini(&zc);
1307                 if (scn->scn_pausing)
1308                         return;
1309         }
1310         zap_cursor_fini(&zc);
1311 }
1312 
1313 static boolean_t
1314 dsl_scan_free_should_pause(dsl_scan_t *scn)
1315 {
1316         uint64_t elapsed_nanosecs;
1317 
1318         elapsed_nanosecs = gethrtime() - scn->scn_sync_start_time;
1319         return (elapsed_nanosecs / NANOSEC > zfs_txg_timeout ||
1320             (NSEC2MSEC(elapsed_nanosecs) > zfs_free_min_time_ms &&
1321             txg_sync_waiting(scn->scn_dp)) ||
1322             spa_shutting_down(scn->scn_dp->dp_spa));
1323 }
1324 
1325 static int
1326 dsl_scan_free_block_cb(void *arg, const blkptr_t *bp, dmu_tx_t *tx)
1327 {
1328         dsl_scan_t *scn = arg;
1329 
1330         if (!scn->scn_is_bptree ||
1331             (BP_GET_LEVEL(bp) == 0 && BP_GET_TYPE(bp) != DMU_OT_OBJSET)) {
1332                 if (dsl_scan_free_should_pause(scn))
1333                         return (SET_ERROR(ERESTART));
1334         }
1335 
1336         zio_nowait(zio_free_sync(scn->scn_zio_root, scn->scn_dp->dp_spa,
1337             dmu_tx_get_txg(tx), bp, 0));
1338         dsl_dir_diduse_space(tx->tx_pool->dp_free_dir, DD_USED_HEAD,
1339             -bp_get_dsize_sync(scn->scn_dp->dp_spa, bp),
1340             -BP_GET_PSIZE(bp), -BP_GET_UCSIZE(bp), tx);
1341         scn->scn_visited_this_txg++;
1342         return (0);
1343 }
1344 
1345 boolean_t
1346 dsl_scan_active(dsl_scan_t *scn)
1347 {
1348         spa_t *spa = scn->scn_dp->dp_spa;
1349         uint64_t used = 0, comp, uncomp;
1350 
1351         if (spa->spa_load_state != SPA_LOAD_NONE)
1352                 return (B_FALSE);
1353         if (spa_shutting_down(spa))
1354                 return (B_FALSE);
1355 
1356         if (scn->scn_phys.scn_state == DSS_SCANNING ||
1357             scn->scn_async_destroying)
1358                 return (B_TRUE);
1359 
1360         if (spa_version(scn->scn_dp->dp_spa) >= SPA_VERSION_DEADLISTS) {
1361                 (void) bpobj_space(&scn->scn_dp->dp_free_bpobj,
1362                     &used, &comp, &uncomp);
1363         }
1364         return (used != 0);
1365 }
1366 
1367 void
1368 dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
1369 {
1370         dsl_scan_t *scn = dp->dp_scan;
1371         spa_t *spa = dp->dp_spa;
1372         int err;
1373 
1374         /*
1375          * Check for scn_restart_txg before checking spa_load_state, so
1376          * that we can restart an old-style scan while the pool is being
1377          * imported (see dsl_scan_init).
1378          */
1379         if (scn->scn_restart_txg != 0 &&
1380             scn->scn_restart_txg <= tx->tx_txg) {
1381                 pool_scan_func_t func = POOL_SCAN_SCRUB;
1382                 dsl_scan_done(scn, B_FALSE, tx);
1383                 if (vdev_resilver_needed(spa->spa_root_vdev, NULL, NULL))
1384                         func = POOL_SCAN_RESILVER;
1385                 zfs_dbgmsg("restarting scan func=%u txg=%llu",
1386                     func, tx->tx_txg);
1387                 dsl_scan_setup_sync(&func, tx);
1388         }
1389 
1390         if (!dsl_scan_active(scn) ||
1391             spa_sync_pass(dp->dp_spa) > 1)
1392                 return;
1393 
1394         scn->scn_visited_this_txg = 0;
1395         scn->scn_pausing = B_FALSE;
1396         scn->scn_sync_start_time = gethrtime();
1397         spa->spa_scrub_active = B_TRUE;
1398 
1399         /*
1400          * First process the free list.  If we pause the free, don't do
1401          * any scanning.  This ensures that there is no free list when
1402          * we are scanning, so the scan code doesn't have to worry about
1403          * traversing it.
1404          */
1405         if (spa_version(dp->dp_spa) >= SPA_VERSION_DEADLISTS) {
1406                 scn->scn_is_bptree = B_FALSE;
1407                 scn->scn_zio_root = zio_root(dp->dp_spa, NULL,
1408                     NULL, ZIO_FLAG_MUSTSUCCEED);
1409                 err = bpobj_iterate(&dp->dp_free_bpobj,
1410                     dsl_scan_free_block_cb, scn, tx);
1411                 VERIFY3U(0, ==, zio_wait(scn->scn_zio_root));
1412 
1413                 if (err == 0 && spa_feature_is_active(spa,
1414                     &spa_feature_table[SPA_FEATURE_ASYNC_DESTROY])) {
1415                         ASSERT(scn->scn_async_destroying);
1416                         scn->scn_is_bptree = B_TRUE;
1417                         scn->scn_zio_root = zio_root(dp->dp_spa, NULL,
1418                             NULL, ZIO_FLAG_MUSTSUCCEED);
1419                         err = bptree_iterate(dp->dp_meta_objset,
1420                             dp->dp_bptree_obj, B_TRUE, dsl_scan_free_block_cb,
1421                             scn, tx);
1422                         VERIFY0(zio_wait(scn->scn_zio_root));
1423 
1424                         if (err == 0) {
1425                                 zfeature_info_t *feat = &spa_feature_table
1426                                     [SPA_FEATURE_ASYNC_DESTROY];
1427                                 /* finished; deactivate async destroy feature */
1428                                 spa_feature_decr(spa, feat, tx);
1429                                 ASSERT(!spa_feature_is_active(spa, feat));
1430                                 VERIFY0(zap_remove(dp->dp_meta_objset,
1431                                     DMU_POOL_DIRECTORY_OBJECT,
1432                                     DMU_POOL_BPTREE_OBJ, tx));
1433                                 VERIFY0(bptree_free(dp->dp_meta_objset,
1434                                     dp->dp_bptree_obj, tx));
1435                                 dp->dp_bptree_obj = 0;
1436                                 scn->scn_async_destroying = B_FALSE;
1437                         }
1438                 }
1439                 if (scn->scn_visited_this_txg) {
1440                         zfs_dbgmsg("freed %llu blocks in %llums from "
1441                             "free_bpobj/bptree txg %llu",
1442                             (longlong_t)scn->scn_visited_this_txg,
1443                             (longlong_t)
1444                             NSEC2MSEC(gethrtime() - scn->scn_sync_start_time),
1445                             (longlong_t)tx->tx_txg);
1446                         scn->scn_visited_this_txg = 0;
1447                         /*
1448                          * Re-sync the ddt so that we can further modify
1449                          * it when doing bprewrite.
1450                          */
1451                         ddt_sync(spa, tx->tx_txg);
1452                 }
1453                 if (err == ERESTART)
1454                         return;
1455         }
1456 
1457         if (scn->scn_phys.scn_state != DSS_SCANNING)
1458                 return;
1459 
1460         if (scn->scn_phys.scn_ddt_bookmark.ddb_class <=
1461             scn->scn_phys.scn_ddt_class_max) {
1462                 zfs_dbgmsg("doing scan sync txg %llu; "
1463                     "ddt bm=%llu/%llu/%llu/%llx",
1464                     (longlong_t)tx->tx_txg,
1465                     (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_class,
1466                     (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_type,
1467                     (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_checksum,
1468                     (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_cursor);
1469                 ASSERT(scn->scn_phys.scn_bookmark.zb_objset == 0);
1470                 ASSERT(scn->scn_phys.scn_bookmark.zb_object == 0);
1471                 ASSERT(scn->scn_phys.scn_bookmark.zb_level == 0);
1472                 ASSERT(scn->scn_phys.scn_bookmark.zb_blkid == 0);
1473         } else {
1474                 zfs_dbgmsg("doing scan sync txg %llu; bm=%llu/%llu/%llu/%llu",
1475                     (longlong_t)tx->tx_txg,
1476                     (longlong_t)scn->scn_phys.scn_bookmark.zb_objset,
1477                     (longlong_t)scn->scn_phys.scn_bookmark.zb_object,
1478                     (longlong_t)scn->scn_phys.scn_bookmark.zb_level,
1479                     (longlong_t)scn->scn_phys.scn_bookmark.zb_blkid);
1480         }
1481 
1482         scn->scn_zio_root = zio_root(dp->dp_spa, NULL,
1483             NULL, ZIO_FLAG_CANFAIL);
1484         dsl_pool_config_enter(dp, FTAG);
1485         dsl_scan_visit(scn, tx);
1486         dsl_pool_config_exit(dp, FTAG);
1487         (void) zio_wait(scn->scn_zio_root);
1488         scn->scn_zio_root = NULL;
1489 
1490         zfs_dbgmsg("visited %llu blocks in %llums",
1491             (longlong_t)scn->scn_visited_this_txg,
1492             (longlong_t)NSEC2MSEC(gethrtime() - scn->scn_sync_start_time));
1493 
1494         if (!scn->scn_pausing) {
1495                 /* finished with scan. */
1496                 zfs_dbgmsg("finished scan txg %llu", (longlong_t)tx->tx_txg);
1497                 dsl_scan_done(scn, B_TRUE, tx);
1498         }
1499 
1500         if (DSL_SCAN_IS_SCRUB_RESILVER(scn)) {
1501                 mutex_enter(&spa->spa_scrub_lock);
1502                 while (spa->spa_scrub_inflight > 0) {
1503                         cv_wait(&spa->spa_scrub_io_cv,
1504                             &spa->spa_scrub_lock);
1505                 }
1506                 mutex_exit(&spa->spa_scrub_lock);
1507         }
1508 
1509         dsl_scan_sync_state(scn, tx);
1510 }
1511 
1512 /*
1513  * This will start a new scan, or restart an existing one.
1514  */
1515 void
1516 dsl_resilver_restart(dsl_pool_t *dp, uint64_t txg)
1517 {
1518         if (txg == 0) {
1519                 dmu_tx_t *tx;
1520                 tx = dmu_tx_create_dd(dp->dp_mos_dir);
1521                 VERIFY(0 == dmu_tx_assign(tx, TXG_WAIT));
1522 
1523                 txg = dmu_tx_get_txg(tx);
1524                 dp->dp_scan->scn_restart_txg = txg;
1525                 dmu_tx_commit(tx);
1526         } else {
1527                 dp->dp_scan->scn_restart_txg = txg;
1528         }
1529         zfs_dbgmsg("restarting resilver txg=%llu", txg);
1530 }
1531 
1532 boolean_t
1533 dsl_scan_resilvering(dsl_pool_t *dp)
1534 {
1535         return (dp->dp_scan->scn_phys.scn_state == DSS_SCANNING &&
1536             dp->dp_scan->scn_phys.scn_func == POOL_SCAN_RESILVER);
1537 }
1538 
1539 /*
1540  * scrub consumers
1541  */
1542 
1543 static void
1544 count_block(zfs_all_blkstats_t *zab, const blkptr_t *bp)
1545 {
1546         int i;
1547 
1548         /*
1549          * If we resume after a reboot, zab will be NULL; don't record
1550          * incomplete stats in that case.
1551          */
1552         if (zab == NULL)
1553                 return;
1554 
1555         for (i = 0; i < 4; i++) {
1556                 int l = (i < 2) ? BP_GET_LEVEL(bp) : DN_MAX_LEVELS;
1557                 int t = (i & 1) ? BP_GET_TYPE(bp) : DMU_OT_TOTAL;
1558                 if (t & DMU_OT_NEWTYPE)
1559                         t = DMU_OT_OTHER;
1560                 zfs_blkstat_t *zb = &zab->zab_type[l][t];
1561                 int equal;
1562 
1563                 zb->zb_count++;
1564                 zb->zb_asize += BP_GET_ASIZE(bp);
1565                 zb->zb_lsize += BP_GET_LSIZE(bp);
1566                 zb->zb_psize += BP_GET_PSIZE(bp);
1567                 zb->zb_gangs += BP_COUNT_GANG(bp);
1568 
1569                 switch (BP_GET_NDVAS(bp)) {
1570                 case 2:
1571                         if (DVA_GET_VDEV(&bp->blk_dva[0]) ==
1572                             DVA_GET_VDEV(&bp->blk_dva[1]))
1573                                 zb->zb_ditto_2_of_2_samevdev++;
1574                         break;
1575                 case 3:
1576                         equal = (DVA_GET_VDEV(&bp->blk_dva[0]) ==
1577                             DVA_GET_VDEV(&bp->blk_dva[1])) +
1578                             (DVA_GET_VDEV(&bp->blk_dva[0]) ==
1579                             DVA_GET_VDEV(&bp->blk_dva[2])) +
1580                             (DVA_GET_VDEV(&bp->blk_dva[1]) ==
1581                             DVA_GET_VDEV(&bp->blk_dva[2]));
1582                         if (equal == 1)
1583                                 zb->zb_ditto_2_of_3_samevdev++;
1584                         else if (equal == 3)
1585                                 zb->zb_ditto_3_of_3_samevdev++;
1586                         break;
1587                 }
1588         }
1589 }
1590 
1591 static void
1592 dsl_scan_scrub_done(zio_t *zio)
1593 {
1594         spa_t *spa = zio->io_spa;
1595 
1596         zio_data_buf_free(zio->io_data, zio->io_size);
1597 
1598         mutex_enter(&spa->spa_scrub_lock);
1599         spa->spa_scrub_inflight--;
1600         cv_broadcast(&spa->spa_scrub_io_cv);
1601 
1602         if (zio->io_error && (zio->io_error != ECKSUM ||
1603             !(zio->io_flags & ZIO_FLAG_SPECULATIVE))) {
1604                 spa->spa_dsl_pool->dp_scan->scn_phys.scn_errors++;
1605         }
1606         mutex_exit(&spa->spa_scrub_lock);
1607 }
1608 
1609 static int
1610 dsl_scan_scrub_cb(dsl_pool_t *dp,
1611     const blkptr_t *bp, const zbookmark_t *zb)
1612 {
1613         dsl_scan_t *scn = dp->dp_scan;
1614         size_t size = BP_GET_PSIZE(bp);
1615         spa_t *spa = dp->dp_spa;
1616         uint64_t phys_birth = BP_PHYSICAL_BIRTH(bp);
1617         boolean_t needs_io;
1618         int zio_flags = ZIO_FLAG_SCAN_THREAD | ZIO_FLAG_RAW | ZIO_FLAG_CANFAIL;
1619         int zio_priority;
1620         int scan_delay = 0;
1621 
1622         if (phys_birth <= scn->scn_phys.scn_min_txg ||
1623             phys_birth >= scn->scn_phys.scn_max_txg)
1624                 return (0);
1625 
1626         count_block(dp->dp_blkstats, bp);
1627 
1628         ASSERT(DSL_SCAN_IS_SCRUB_RESILVER(scn));
1629         if (scn->scn_phys.scn_func == POOL_SCAN_SCRUB) {
1630                 zio_flags |= ZIO_FLAG_SCRUB;
1631                 zio_priority = ZIO_PRIORITY_SCRUB;
1632                 needs_io = B_TRUE;
1633                 scan_delay = zfs_scrub_delay;
1634         } else {
1635                 ASSERT3U(scn->scn_phys.scn_func, ==, POOL_SCAN_RESILVER);
1636                 zio_flags |= ZIO_FLAG_RESILVER;
1637                 zio_priority = ZIO_PRIORITY_RESILVER;
1638                 needs_io = B_FALSE;
1639                 scan_delay = zfs_resilver_delay;
1640         }
1641 
1642         /* If it's an intent log block, failure is expected. */
1643         if (zb->zb_level == ZB_ZIL_LEVEL)
1644                 zio_flags |= ZIO_FLAG_SPECULATIVE;
1645 
1646         for (int d = 0; d < BP_GET_NDVAS(bp); d++) {
1647                 vdev_t *vd = vdev_lookup_top(spa,
1648                     DVA_GET_VDEV(&bp->blk_dva[d]));
1649 
1650                 /*
1651                  * Keep track of how much data we've examined so that
1652                  * zpool(1M) status can make useful progress reports.
1653                  */
1654                 scn->scn_phys.scn_examined += DVA_GET_ASIZE(&bp->blk_dva[d]);
1655                 spa->spa_scan_pass_exam += DVA_GET_ASIZE(&bp->blk_dva[d]);
1656 
1657                 /* if it's a resilver, this may not be in the target range */
1658                 if (!needs_io) {
1659                         if (DVA_GET_GANG(&bp->blk_dva[d])) {
1660                                 /*
1661                                  * Gang members may be spread across multiple
1662                                  * vdevs, so the best estimate we have is the
1663                                  * scrub range, which has already been checked.
1664                                  * XXX -- it would be better to change our
1665                                  * allocation policy to ensure that all
1666                                  * gang members reside on the same vdev.
1667                                  */
1668                                 needs_io = B_TRUE;
1669                         } else {
1670                                 needs_io = vdev_dtl_contains(vd, DTL_PARTIAL,
1671                                     phys_birth, 1);
1672                         }
1673                 }
1674         }
1675 
1676         if (needs_io && !zfs_no_scrub_io) {
1677                 vdev_t *rvd = spa->spa_root_vdev;
1678                 uint64_t maxinflight = rvd->vdev_children * zfs_top_maxinflight;
1679                 void *data = zio_data_buf_alloc(size);
1680 
1681                 mutex_enter(&spa->spa_scrub_lock);
1682                 while (spa->spa_scrub_inflight >= maxinflight)
1683                         cv_wait(&spa->spa_scrub_io_cv, &spa->spa_scrub_lock);
1684                 spa->spa_scrub_inflight++;
1685                 mutex_exit(&spa->spa_scrub_lock);
1686 
1687                 /*
1688                  * If we're seeing recent (zfs_scan_idle) "important" I/Os
1689                  * then throttle our workload to limit the impact of a scan.
1690                  */
1691                 if (ddi_get_lbolt64() - spa->spa_last_io <= zfs_scan_idle)
1692                         delay(scan_delay);
1693 
1694                 zio_nowait(zio_read(NULL, spa, bp, data, size,
1695                     dsl_scan_scrub_done, NULL, zio_priority,
1696                     zio_flags, zb));
1697         }
1698 
1699         /* do not relocate this block */
1700         return (0);
1701 }
1702 
1703 int
1704 dsl_scan(dsl_pool_t *dp, pool_scan_func_t func)
1705 {
1706         spa_t *spa = dp->dp_spa;
1707 
1708         /*
1709          * Purge all vdev caches and probe all devices.  We do this here
1710          * rather than in sync context because this requires a writer lock
1711          * on the spa_config lock, which we can't do from sync context.  The
1712          * spa_scrub_reopen flag indicates that vdev_open() should not
1713          * attempt to start another scrub.
1714          */
1715         spa_vdev_state_enter(spa, SCL_NONE);
1716         spa->spa_scrub_reopen = B_TRUE;
1717         vdev_reopen(spa->spa_root_vdev);
1718         spa->spa_scrub_reopen = B_FALSE;
1719         (void) spa_vdev_state_exit(spa, NULL, 0);
1720 
1721         return (dsl_sync_task(spa_name(spa), dsl_scan_setup_check,
1722             dsl_scan_setup_sync, &func, 0));
1723 }