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dsl_scrub.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <sys/dsl_pool.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_prop.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_synctask.h>
#include <sys/dnode.h>
#include <sys/dmu_tx.h>
#include <sys/dmu_objset.h>
#include <sys/arc.h>
#include <sys/zap.h>
#include <sys/zio.h>
#include <sys/zfs_context.h>
#include <sys/fs/zfs.h>
#include <sys/zfs_znode.h>
#include <sys/spa_impl.h>
#include <sys/vdev_impl.h>
#include <sys/zil_impl.h>

typedef int (scrub_cb_t)(dsl_pool_t *, const blkptr_t *, const zbookmark_t *);

static scrub_cb_t dsl_pool_scrub_clean_cb;
static dsl_syncfunc_t dsl_pool_scrub_cancel_sync;

int zfs_scrub_min_time = 1; /* scrub for at least 1 sec each txg */
int zfs_resilver_min_time = 3; /* resilver for at least 3 sec each txg */
boolean_t zfs_no_scrub_io = B_FALSE; /* set to disable scrub i/o */

extern int zfs_txg_timeout;

static scrub_cb_t *scrub_funcs[SCRUB_FUNC_NUMFUNCS] = {
      NULL,
      dsl_pool_scrub_clean_cb
};

#define     SET_BOOKMARK(zb, objset, object, level, blkid)  \
{                                                       \
      (zb)->zb_objset = objset;                       \
      (zb)->zb_object = object;                       \
      (zb)->zb_level = level;                         \
      (zb)->zb_blkid = blkid;                         \
}

/* ARGSUSED */
static void
dsl_pool_scrub_setup_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_pool_t *dp = arg1;
      enum scrub_func *funcp = arg2;
      dmu_object_type_t ot = 0;
      boolean_t complete = B_FALSE;

      dsl_pool_scrub_cancel_sync(dp, &complete, cr, tx);

      ASSERT(dp->dp_scrub_func == SCRUB_FUNC_NONE);
      ASSERT(*funcp > SCRUB_FUNC_NONE);
      ASSERT(*funcp < SCRUB_FUNC_NUMFUNCS);

      dp->dp_scrub_min_txg = 0;
      dp->dp_scrub_max_txg = tx->tx_txg;

      if (*funcp == SCRUB_FUNC_CLEAN) {
            vdev_t *rvd = dp->dp_spa->spa_root_vdev;

            /* rewrite all disk labels */
            vdev_config_dirty(rvd);

            if (vdev_resilver_needed(rvd,
                &dp->dp_scrub_min_txg, &dp->dp_scrub_max_txg)) {
                  spa_event_notify(dp->dp_spa, NULL,
                      ESC_ZFS_RESILVER_START);
                  dp->dp_scrub_max_txg = MIN(dp->dp_scrub_max_txg,
                      tx->tx_txg);
            }

            /* zero out the scrub stats in all vdev_stat_t's */
            vdev_scrub_stat_update(rvd,
                dp->dp_scrub_min_txg ? POOL_SCRUB_RESILVER :
                POOL_SCRUB_EVERYTHING, B_FALSE);

            dp->dp_spa->spa_scrub_started = B_TRUE;
      }

      /* back to the generic stuff */

      if (dp->dp_blkstats == NULL) {
            dp->dp_blkstats =
                kmem_alloc(sizeof (zfs_all_blkstats_t), KM_SLEEP);
      }
      bzero(dp->dp_blkstats, sizeof (zfs_all_blkstats_t));

      if (spa_version(dp->dp_spa) < SPA_VERSION_DSL_SCRUB)
            ot = DMU_OT_ZAP_OTHER;

      dp->dp_scrub_func = *funcp;
      dp->dp_scrub_queue_obj = zap_create(dp->dp_meta_objset,
          ot ? ot : DMU_OT_SCRUB_QUEUE, DMU_OT_NONE, 0, tx);
      bzero(&dp->dp_scrub_bookmark, sizeof (zbookmark_t));
      dp->dp_scrub_restart = B_FALSE;
      dp->dp_spa->spa_scrub_errors = 0;

      VERIFY(0 == zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_FUNC, sizeof (uint32_t), 1,
          &dp->dp_scrub_func, tx));
      VERIFY(0 == zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_QUEUE, sizeof (uint64_t), 1,
          &dp->dp_scrub_queue_obj, tx));
      VERIFY(0 == zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_MIN_TXG, sizeof (uint64_t), 1,
          &dp->dp_scrub_min_txg, tx));
      VERIFY(0 == zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_MAX_TXG, sizeof (uint64_t), 1,
          &dp->dp_scrub_max_txg, tx));
      VERIFY(0 == zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_BOOKMARK, sizeof (uint64_t), 4,
          &dp->dp_scrub_bookmark, tx));
      VERIFY(0 == zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_ERRORS, sizeof (uint64_t), 1,
          &dp->dp_spa->spa_scrub_errors, tx));

      spa_history_internal_log(LOG_POOL_SCRUB, dp->dp_spa, tx, cr,
          "func=%u mintxg=%llu maxtxg=%llu",
          *funcp, dp->dp_scrub_min_txg, dp->dp_scrub_max_txg);
}

int
dsl_pool_scrub_setup(dsl_pool_t *dp, enum scrub_func func)
{
      return (dsl_sync_task_do(dp, NULL,
          dsl_pool_scrub_setup_sync, dp, &func, 0));
}

/* ARGSUSED */
static void
dsl_pool_scrub_cancel_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_pool_t *dp = arg1;
      boolean_t *completep = arg2;

      if (dp->dp_scrub_func == SCRUB_FUNC_NONE)
            return;

      mutex_enter(&dp->dp_scrub_cancel_lock);

      if (dp->dp_scrub_restart) {
            dp->dp_scrub_restart = B_FALSE;
            *completep = B_FALSE;
      }

      /* XXX this is scrub-clean specific */
      mutex_enter(&dp->dp_spa->spa_scrub_lock);
      while (dp->dp_spa->spa_scrub_inflight > 0) {
            cv_wait(&dp->dp_spa->spa_scrub_io_cv,
                &dp->dp_spa->spa_scrub_lock);
      }
      mutex_exit(&dp->dp_spa->spa_scrub_lock);
      dp->dp_spa->spa_scrub_started = B_FALSE;
      dp->dp_spa->spa_scrub_active = B_FALSE;

      dp->dp_scrub_func = SCRUB_FUNC_NONE;
      VERIFY(0 == dmu_object_free(dp->dp_meta_objset,
          dp->dp_scrub_queue_obj, tx));
      dp->dp_scrub_queue_obj = 0;
      bzero(&dp->dp_scrub_bookmark, sizeof (zbookmark_t));

      VERIFY(0 == zap_remove(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_QUEUE, tx));
      VERIFY(0 == zap_remove(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_MIN_TXG, tx));
      VERIFY(0 == zap_remove(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_MAX_TXG, tx));
      VERIFY(0 == zap_remove(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_BOOKMARK, tx));
      VERIFY(0 == zap_remove(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_FUNC, tx));
      VERIFY(0 == zap_remove(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_ERRORS, tx));

      spa_history_internal_log(LOG_POOL_SCRUB_DONE, dp->dp_spa, tx, cr,
          "complete=%u", *completep);

      /* below is scrub-clean specific */
      vdev_scrub_stat_update(dp->dp_spa->spa_root_vdev, POOL_SCRUB_NONE,
          *completep);
      /*
       * If the scrub/resilver completed, update all DTLs to reflect this.
       * Whether it succeeded or not, vacate all temporary scrub DTLs.
       */
      vdev_dtl_reassess(dp->dp_spa->spa_root_vdev, tx->tx_txg,
          *completep ? dp->dp_scrub_max_txg : 0, B_TRUE);
      if (dp->dp_scrub_min_txg && *completep)
            spa_event_notify(dp->dp_spa, NULL, ESC_ZFS_RESILVER_FINISH);
      spa_errlog_rotate(dp->dp_spa);

      /*
       * We may have finished replacing a device.
       * Let the async thread assess this and handle the detach.
       */
      spa_async_request(dp->dp_spa, SPA_ASYNC_RESILVER_DONE);

      dp->dp_scrub_min_txg = dp->dp_scrub_max_txg = 0;
      mutex_exit(&dp->dp_scrub_cancel_lock);
}

int
dsl_pool_scrub_cancel(dsl_pool_t *dp)
{
      boolean_t complete = B_FALSE;

      return (dsl_sync_task_do(dp, NULL,
          dsl_pool_scrub_cancel_sync, dp, &complete, 3));
}

int
dsl_free(zio_t *pio, dsl_pool_t *dp, uint64_t txg, const blkptr_t *bpp,
    zio_done_func_t *done, void *private, uint32_t arc_flags)
{
      /*
       * This function will be used by bp-rewrite wad to intercept frees.
       */
      return (arc_free(pio, dp->dp_spa, txg, (blkptr_t *)bpp,
          done, private, arc_flags));
}

static boolean_t
bookmark_is_zero(const zbookmark_t *zb)
{
      return (zb->zb_objset == 0 && zb->zb_object == 0 &&
          zb->zb_level == 0 && zb->zb_blkid == 0);
}

/* dnp is the dnode for zb1->zb_object */
static boolean_t
bookmark_is_before(dnode_phys_t *dnp, const zbookmark_t *zb1,
    const zbookmark_t *zb2)
{
      uint64_t zb1nextL0, zb2thisobj;

      ASSERT(zb1->zb_objset == zb2->zb_objset);
      ASSERT(zb1->zb_object != -1ULL);
      ASSERT(zb2->zb_level == 0);

      /*
       * A bookmark in the deadlist is considered to be after
       * everything else.
       */
      if (zb2->zb_object == -1ULL)
            return (B_TRUE);

      /* The objset_phys_t isn't before anything. */
      if (dnp == NULL)
            return (B_FALSE);

      zb1nextL0 = (zb1->zb_blkid + 1) <<
          ((zb1->zb_level) * (dnp->dn_indblkshift - SPA_BLKPTRSHIFT));

      zb2thisobj = zb2->zb_object ? zb2->zb_object :
          zb2->zb_blkid << (DNODE_BLOCK_SHIFT - DNODE_SHIFT);

      if (zb1->zb_object == 0) {
            uint64_t nextobj = zb1nextL0 *
                (dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT) >> DNODE_SHIFT;
            return (nextobj <= zb2thisobj);
      }

      if (zb1->zb_object < zb2thisobj)
            return (B_TRUE);
      if (zb1->zb_object > zb2thisobj)
            return (B_FALSE);
      if (zb2->zb_object == 0)
            return (B_FALSE);
      return (zb1nextL0 <= zb2->zb_blkid);
}

static boolean_t
scrub_pause(dsl_pool_t *dp, const zbookmark_t *zb)
{
      int elapsed_ticks;
      int mintime;

      if (dp->dp_scrub_pausing)
            return (B_TRUE); /* we're already pausing */

      if (!bookmark_is_zero(&dp->dp_scrub_bookmark))
            return (B_FALSE); /* we're resuming */

      /* We only know how to resume from level-0 blocks. */
      if (zb->zb_level != 0)
            return (B_FALSE);

      mintime = dp->dp_scrub_isresilver ? zfs_resilver_min_time :
          zfs_scrub_min_time;
      elapsed_ticks = lbolt64 - dp->dp_scrub_start_time;
      if (elapsed_ticks > hz * zfs_txg_timeout ||
          (elapsed_ticks > hz * mintime && txg_sync_waiting(dp))) {
            dprintf("pausing at %llx/%llx/%llx/%llx\n",
                (longlong_t)zb->zb_objset, (longlong_t)zb->zb_object,
                (longlong_t)zb->zb_level, (longlong_t)zb->zb_blkid);
            dp->dp_scrub_pausing = B_TRUE;
            dp->dp_scrub_bookmark = *zb;
            return (B_TRUE);
      }
      return (B_FALSE);
}

typedef struct zil_traverse_arg {
      dsl_pool_t  *zta_dp;
      zil_header_t      *zta_zh;
} zil_traverse_arg_t;

/* ARGSUSED */
static void
traverse_zil_block(zilog_t *zilog, blkptr_t *bp, void *arg, uint64_t claim_txg)
{
      zil_traverse_arg_t *zta = arg;
      dsl_pool_t *dp = zta->zta_dp;
      zil_header_t *zh = zta->zta_zh;
      zbookmark_t zb;

      if (bp->blk_birth <= dp->dp_scrub_min_txg)
            return;

      /*
       * One block ("stumpy") can be allocated a long time ago; we
       * want to visit that one because it has been allocated
       * (on-disk) even if it hasn't been claimed (even though for
       * plain scrub there's nothing to do to it).
       */
      if (claim_txg == 0 && bp->blk_birth >= spa_first_txg(dp->dp_spa))
            return;

      zb.zb_objset = zh->zh_log.blk_cksum.zc_word[ZIL_ZC_OBJSET];
      zb.zb_object = 0;
      zb.zb_level = -1;
      zb.zb_blkid = bp->blk_cksum.zc_word[ZIL_ZC_SEQ];
      VERIFY(0 == scrub_funcs[dp->dp_scrub_func](dp, bp, &zb));
}

/* ARGSUSED */
static void
traverse_zil_record(zilog_t *zilog, lr_t *lrc, void *arg, uint64_t claim_txg)
{
      if (lrc->lrc_txtype == TX_WRITE) {
            zil_traverse_arg_t *zta = arg;
            dsl_pool_t *dp = zta->zta_dp;
            zil_header_t *zh = zta->zta_zh;
            lr_write_t *lr = (lr_write_t *)lrc;
            blkptr_t *bp = &lr->lr_blkptr;
            zbookmark_t zb;

            if (bp->blk_birth <= dp->dp_scrub_min_txg)
                  return;

            /*
             * birth can be < claim_txg if this record's txg is
             * already txg sync'ed (but this log block contains
             * other records that are not synced)
             */
            if (claim_txg == 0 || bp->blk_birth < claim_txg)
                  return;

            zb.zb_objset = zh->zh_log.blk_cksum.zc_word[ZIL_ZC_OBJSET];
            zb.zb_object = lr->lr_foid;
            zb.zb_level = BP_GET_LEVEL(bp);
            zb.zb_blkid = lr->lr_offset / BP_GET_LSIZE(bp);
            VERIFY(0 == scrub_funcs[dp->dp_scrub_func](dp, bp, &zb));
      }
}

static void
traverse_zil(dsl_pool_t *dp, zil_header_t *zh)
{
      uint64_t claim_txg = zh->zh_claim_txg;
      zil_traverse_arg_t zta = { dp, zh };
      zilog_t *zilog;

      /*
       * We only want to visit blocks that have been claimed but not yet
       * replayed (or, in read-only mode, blocks that *would* be claimed).
       */
      if (claim_txg == 0 && (spa_mode & FWRITE))
            return;

      zilog = zil_alloc(dp->dp_meta_objset, zh);

      (void) zil_parse(zilog, traverse_zil_block, traverse_zil_record, &zta,
          claim_txg);

      zil_free(zilog);
}

static void
scrub_visitbp(dsl_pool_t *dp, dnode_phys_t *dnp,
    arc_buf_t *pbuf, blkptr_t *bp, const zbookmark_t *zb)
{
      int err;
      arc_buf_t *buf = NULL;

      if (bp->blk_birth == 0)
            return;

      if (bp->blk_birth <= dp->dp_scrub_min_txg)
            return;

      if (scrub_pause(dp, zb))
            return;

      if (!bookmark_is_zero(&dp->dp_scrub_bookmark)) {
            /*
             * If we already visited this bp & everything below (in
             * a prior txg), don't bother doing it again.
             */
            if (bookmark_is_before(dnp, zb, &dp->dp_scrub_bookmark))
                  return;

            /*
             * If we found the block we're trying to resume from, or
             * we went past it to a different object, zero it out to
             * indicate that it's OK to start checking for pausing
             * again.
             */
            if (bcmp(zb, &dp->dp_scrub_bookmark, sizeof (*zb)) == 0 ||
                zb->zb_object > dp->dp_scrub_bookmark.zb_object) {
                  dprintf("resuming at %llx/%llx/%llx/%llx\n",
                      (longlong_t)zb->zb_objset,
                      (longlong_t)zb->zb_object,
                      (longlong_t)zb->zb_level,
                      (longlong_t)zb->zb_blkid);
                  bzero(&dp->dp_scrub_bookmark, sizeof (*zb));
            }
      }

      if (BP_GET_LEVEL(bp) > 0) {
            uint32_t flags = ARC_WAIT;
            int i;
            blkptr_t *cbp;
            int epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT;

            err = arc_read(NULL, dp->dp_spa, bp, pbuf,
                arc_getbuf_func, &buf,
                ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
            if (err) {
                  mutex_enter(&dp->dp_spa->spa_scrub_lock);
                  dp->dp_spa->spa_scrub_errors++;
                  mutex_exit(&dp->dp_spa->spa_scrub_lock);
                  return;
            }
            cbp = buf->b_data;

            for (i = 0; i < epb; i++, cbp++) {
                  zbookmark_t czb;

                  SET_BOOKMARK(&czb, zb->zb_objset, zb->zb_object,
                      zb->zb_level - 1,
                      zb->zb_blkid * epb + i);
                  scrub_visitbp(dp, dnp, buf, cbp, &czb);
            }
      } else if (BP_GET_TYPE(bp) == DMU_OT_DNODE) {
            uint32_t flags = ARC_WAIT;
            dnode_phys_t *child_dnp;
            int i, j;
            int epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;

            err = arc_read(NULL, dp->dp_spa, bp, pbuf,
                arc_getbuf_func, &buf,
                ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
            if (err) {
                  mutex_enter(&dp->dp_spa->spa_scrub_lock);
                  dp->dp_spa->spa_scrub_errors++;
                  mutex_exit(&dp->dp_spa->spa_scrub_lock);
                  return;
            }
            child_dnp = buf->b_data;

            for (i = 0; i < epb; i++, child_dnp++) {
                  for (j = 0; j < child_dnp->dn_nblkptr; j++) {
                        zbookmark_t czb;

                        SET_BOOKMARK(&czb, zb->zb_objset,
                            zb->zb_blkid * epb + i,
                            child_dnp->dn_nlevels - 1, j);
                        scrub_visitbp(dp, child_dnp, buf,
                            &child_dnp->dn_blkptr[j], &czb);
                  }
            }
      } else if (BP_GET_TYPE(bp) == DMU_OT_OBJSET) {
            uint32_t flags = ARC_WAIT;
            objset_phys_t *osp;
            int j;

            err = arc_read_nolock(NULL, dp->dp_spa, bp,
                arc_getbuf_func, &buf,
                ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
            if (err) {
                  mutex_enter(&dp->dp_spa->spa_scrub_lock);
                  dp->dp_spa->spa_scrub_errors++;
                  mutex_exit(&dp->dp_spa->spa_scrub_lock);
                  return;
            }

            osp = buf->b_data;

            traverse_zil(dp, &osp->os_zil_header);

            for (j = 0; j < osp->os_meta_dnode.dn_nblkptr; j++) {
                  zbookmark_t czb;

                  SET_BOOKMARK(&czb, zb->zb_objset, 0,
                      osp->os_meta_dnode.dn_nlevels - 1, j);
                  scrub_visitbp(dp, &osp->os_meta_dnode, buf,
                      &osp->os_meta_dnode.dn_blkptr[j], &czb);
            }
      }

      (void) scrub_funcs[dp->dp_scrub_func](dp, bp, zb);
      if (buf)
            (void) arc_buf_remove_ref(buf, &buf);
}

static void
scrub_visit_rootbp(dsl_pool_t *dp, dsl_dataset_t *ds, blkptr_t *bp)
{
      zbookmark_t zb;

      SET_BOOKMARK(&zb, ds ? ds->ds_object : 0, 0, -1, 0);
      scrub_visitbp(dp, NULL, NULL, bp, &zb);
}

void
dsl_pool_ds_destroyed(dsl_dataset_t *ds, dmu_tx_t *tx)
{
      dsl_pool_t *dp = ds->ds_dir->dd_pool;

      if (dp->dp_scrub_func == SCRUB_FUNC_NONE)
            return;

      if (dp->dp_scrub_bookmark.zb_objset == ds->ds_object) {
            SET_BOOKMARK(&dp->dp_scrub_bookmark, -1, 0, 0, 0);
      } else if (zap_remove_int(dp->dp_meta_objset, dp->dp_scrub_queue_obj,
          ds->ds_object, tx) != 0) {
            return;
      }

      if (ds->ds_phys->ds_next_snap_obj != 0) {
            VERIFY(zap_add_int(dp->dp_meta_objset, dp->dp_scrub_queue_obj,
                ds->ds_phys->ds_next_snap_obj, tx) == 0);
      }
      ASSERT3U(ds->ds_phys->ds_num_children, <=, 1);
}

void
dsl_pool_ds_snapshotted(dsl_dataset_t *ds, dmu_tx_t *tx)
{
      dsl_pool_t *dp = ds->ds_dir->dd_pool;

      if (dp->dp_scrub_func == SCRUB_FUNC_NONE)
            return;

      ASSERT(ds->ds_phys->ds_prev_snap_obj != 0);

      if (dp->dp_scrub_bookmark.zb_objset == ds->ds_object) {
            dp->dp_scrub_bookmark.zb_objset =
                ds->ds_phys->ds_prev_snap_obj;
      } else if (zap_remove_int(dp->dp_meta_objset, dp->dp_scrub_queue_obj,
          ds->ds_object, tx) == 0) {
            VERIFY(zap_add_int(dp->dp_meta_objset, dp->dp_scrub_queue_obj,
                ds->ds_phys->ds_prev_snap_obj, tx) == 0);
      }
}

void
dsl_pool_ds_clone_swapped(dsl_dataset_t *ds1, dsl_dataset_t *ds2, dmu_tx_t *tx)
{
      dsl_pool_t *dp = ds1->ds_dir->dd_pool;

      if (dp->dp_scrub_func == SCRUB_FUNC_NONE)
            return;

      if (dp->dp_scrub_bookmark.zb_objset == ds1->ds_object) {
            dp->dp_scrub_bookmark.zb_objset = ds2->ds_object;
      } else if (dp->dp_scrub_bookmark.zb_objset == ds2->ds_object) {
            dp->dp_scrub_bookmark.zb_objset = ds1->ds_object;
      }

      if (zap_remove_int(dp->dp_meta_objset, dp->dp_scrub_queue_obj,
          ds1->ds_object, tx) == 0) {
            int err = zap_add_int(dp->dp_meta_objset,
                dp->dp_scrub_queue_obj, ds2->ds_object, tx);
            VERIFY(err == 0 || err == EEXIST);
            if (err == EEXIST) {
                  /* Both were there to begin with */
                  VERIFY(0 == zap_add_int(dp->dp_meta_objset,
                      dp->dp_scrub_queue_obj, ds1->ds_object, tx));
            }
      } else if (zap_remove_int(dp->dp_meta_objset, dp->dp_scrub_queue_obj,
          ds2->ds_object, tx) == 0) {
            VERIFY(0 == zap_add_int(dp->dp_meta_objset,
                dp->dp_scrub_queue_obj, ds1->ds_object, tx));
      }
}

struct enqueue_clones_arg {
      dmu_tx_t *tx;
      uint64_t originobj;
};

/* ARGSUSED */
static int
enqueue_clones_cb(spa_t *spa, uint64_t dsobj, const char *dsname, void *arg)
{
      struct enqueue_clones_arg *eca = arg;
      dsl_dataset_t *ds;
      int err;
      dsl_pool_t *dp;

      err = dsl_dataset_hold_obj(spa->spa_dsl_pool, dsobj, FTAG, &ds);
      if (err)
            return (err);
      dp = ds->ds_dir->dd_pool;

      if (ds->ds_dir->dd_phys->dd_origin_obj == eca->originobj) {
            while (ds->ds_phys->ds_prev_snap_obj != eca->originobj) {
                  dsl_dataset_t *prev;
                  err = dsl_dataset_hold_obj(dp,
                      ds->ds_phys->ds_prev_snap_obj, FTAG, &prev);

                  dsl_dataset_rele(ds, FTAG);
                  if (err)
                        return (err);
                  ds = prev;
            }
            VERIFY(zap_add_int(dp->dp_meta_objset, dp->dp_scrub_queue_obj,
                ds->ds_object, eca->tx) == 0);
      }
      dsl_dataset_rele(ds, FTAG);
      return (0);
}

static void
scrub_visitds(dsl_pool_t *dp, uint64_t dsobj, dmu_tx_t *tx)
{
      dsl_dataset_t *ds;
      uint64_t min_txg_save;

      VERIFY3U(0, ==, dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds));

      /*
       * Iterate over the bps in this ds.
       */
      min_txg_save = dp->dp_scrub_min_txg;
      dp->dp_scrub_min_txg =
          MAX(dp->dp_scrub_min_txg, ds->ds_phys->ds_prev_snap_txg);
      scrub_visit_rootbp(dp, ds, &ds->ds_phys->ds_bp);
      dp->dp_scrub_min_txg = min_txg_save;

      if (dp->dp_scrub_pausing)
            goto out;

      /*
       * Add descendent datasets to work queue.
       */
      if (ds->ds_phys->ds_next_snap_obj != 0) {
            VERIFY(zap_add_int(dp->dp_meta_objset, dp->dp_scrub_queue_obj,
                ds->ds_phys->ds_next_snap_obj, tx) == 0);
      }
      if (ds->ds_phys->ds_num_children > 1) {
            if (spa_version(dp->dp_spa) < SPA_VERSION_DSL_SCRUB) {
                  struct enqueue_clones_arg eca;
                  eca.tx = tx;
                  eca.originobj = ds->ds_object;

                  (void) dmu_objset_find_spa(ds->ds_dir->dd_pool->dp_spa,
                      NULL, enqueue_clones_cb, &eca, DS_FIND_CHILDREN);
            } else {
                  VERIFY(zap_join(dp->dp_meta_objset,
                      ds->ds_phys->ds_next_clones_obj,
                      dp->dp_scrub_queue_obj, tx) == 0);
            }
      }

out:
      dsl_dataset_rele(ds, FTAG);
}

/* ARGSUSED */
static int
enqueue_cb(spa_t *spa, uint64_t dsobj, const char *dsname, void *arg)
{
      dmu_tx_t *tx = arg;
      dsl_dataset_t *ds;
      int err;
      dsl_pool_t *dp;

      err = dsl_dataset_hold_obj(spa->spa_dsl_pool, dsobj, FTAG, &ds);
      if (err)
            return (err);

      dp = ds->ds_dir->dd_pool;

      while (ds->ds_phys->ds_prev_snap_obj != 0) {
            dsl_dataset_t *prev;
            err = dsl_dataset_hold_obj(dp, ds->ds_phys->ds_prev_snap_obj,
                FTAG, &prev);
            if (err) {
                  dsl_dataset_rele(ds, FTAG);
                  return (err);
            }

            /*
             * If this is a clone, we don't need to worry about it for now.
             */
            if (prev->ds_phys->ds_next_snap_obj != ds->ds_object) {
                  dsl_dataset_rele(ds, FTAG);
                  dsl_dataset_rele(prev, FTAG);
                  return (0);
            }
            dsl_dataset_rele(ds, FTAG);
            ds = prev;
      }

      VERIFY(zap_add_int(dp->dp_meta_objset, dp->dp_scrub_queue_obj,
          ds->ds_object, tx) == 0);
      dsl_dataset_rele(ds, FTAG);
      return (0);
}

void
dsl_pool_scrub_sync(dsl_pool_t *dp, dmu_tx_t *tx)
{
      zap_cursor_t zc;
      zap_attribute_t za;
      boolean_t complete = B_TRUE;

      if (dp->dp_scrub_func == SCRUB_FUNC_NONE)
            return;

      /* If the spa is not fully loaded, don't bother. */
      if (dp->dp_spa->spa_load_state != SPA_LOAD_NONE)
            return;

      if (dp->dp_scrub_restart) {
            enum scrub_func func = dp->dp_scrub_func;
            dp->dp_scrub_restart = B_FALSE;
            dsl_pool_scrub_setup_sync(dp, &func, kcred, tx);
      }

      if (dp->dp_spa->spa_root_vdev->vdev_stat.vs_scrub_type == 0) {
            /*
             * We must have resumed after rebooting; reset the vdev
             * stats to know that we're doing a scrub (although it
             * will think we're just starting now).
             */
            vdev_scrub_stat_update(dp->dp_spa->spa_root_vdev,
                dp->dp_scrub_min_txg ? POOL_SCRUB_RESILVER :
                POOL_SCRUB_EVERYTHING, B_FALSE);
      }

      dp->dp_scrub_pausing = B_FALSE;
      dp->dp_scrub_start_time = lbolt64;
      dp->dp_scrub_isresilver = (dp->dp_scrub_min_txg != 0);
      dp->dp_spa->spa_scrub_active = B_TRUE;

      if (dp->dp_scrub_bookmark.zb_objset == 0) {
            /* First do the MOS & ORIGIN */
            scrub_visit_rootbp(dp, NULL, &dp->dp_meta_rootbp);
            if (dp->dp_scrub_pausing)
                  goto out;

            if (spa_version(dp->dp_spa) < SPA_VERSION_DSL_SCRUB) {
                  VERIFY(0 == dmu_objset_find_spa(dp->dp_spa,
                      NULL, enqueue_cb, tx, DS_FIND_CHILDREN));
            } else {
                  scrub_visitds(dp, dp->dp_origin_snap->ds_object, tx);
            }
            ASSERT(!dp->dp_scrub_pausing);
      } else if (dp->dp_scrub_bookmark.zb_objset != -1ULL) {
            /*
             * If we were paused, continue from here.  Note if the
             * ds we were paused on was deleted, the zb_objset will
             * be -1, so we will skip this and find a new objset
             * below.
             */
            scrub_visitds(dp, dp->dp_scrub_bookmark.zb_objset, tx);
            if (dp->dp_scrub_pausing)
                  goto out;
      }

      /*
       * In case we were paused right at the end of the ds, zero the
       * bookmark so we don't think that we're still trying to resume.
       */
      bzero(&dp->dp_scrub_bookmark, sizeof (zbookmark_t));

      /* keep pulling things out of the zap-object-as-queue */
      while (zap_cursor_init(&zc, dp->dp_meta_objset, dp->dp_scrub_queue_obj),
          zap_cursor_retrieve(&zc, &za) == 0) {
            VERIFY(0 == zap_remove(dp->dp_meta_objset,
                dp->dp_scrub_queue_obj, za.za_name, tx));
            scrub_visitds(dp, za.za_first_integer, tx);
            if (dp->dp_scrub_pausing)
                  break;
            zap_cursor_fini(&zc);
      }
      zap_cursor_fini(&zc);
      if (dp->dp_scrub_pausing)
            goto out;

      /* done. */

      dsl_pool_scrub_cancel_sync(dp, &complete, kcred, tx);
      return;
out:
      VERIFY(0 == zap_update(dp->dp_meta_objset,
          DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_BOOKMARK, sizeof (uint64_t), 4,
          &dp->dp_scrub_bookmark, tx));
      VERIFY(0 == zap_update(dp->dp_meta_objset,
          DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SCRUB_ERRORS, sizeof (uint64_t), 1,
          &dp->dp_spa->spa_scrub_errors, tx));

      /* XXX this is scrub-clean specific */
      mutex_enter(&dp->dp_spa->spa_scrub_lock);
      while (dp->dp_spa->spa_scrub_inflight > 0) {
            cv_wait(&dp->dp_spa->spa_scrub_io_cv,
                &dp->dp_spa->spa_scrub_lock);
      }
      mutex_exit(&dp->dp_spa->spa_scrub_lock);
}

void
dsl_pool_scrub_restart(dsl_pool_t *dp)
{
      mutex_enter(&dp->dp_scrub_cancel_lock);
      dp->dp_scrub_restart = B_TRUE;
      mutex_exit(&dp->dp_scrub_cancel_lock);
}

/*
 * scrub consumers
 */

static void
count_block(zfs_all_blkstats_t *zab, const blkptr_t *bp)
{
      int i;

      /*
       * If we resume after a reboot, zab will be NULL; don't record
       * incomplete stats in that case.
       */
      if (zab == NULL)
            return;

      for (i = 0; i < 4; i++) {
            int l = (i < 2) ? BP_GET_LEVEL(bp) : DN_MAX_LEVELS;
            int t = (i & 1) ? BP_GET_TYPE(bp) : DMU_OT_TOTAL;
            zfs_blkstat_t *zb = &zab->zab_type[l][t];
            int equal;

            zb->zb_count++;
            zb->zb_asize += BP_GET_ASIZE(bp);
            zb->zb_lsize += BP_GET_LSIZE(bp);
            zb->zb_psize += BP_GET_PSIZE(bp);
            zb->zb_gangs += BP_COUNT_GANG(bp);

            switch (BP_GET_NDVAS(bp)) {
            case 2:
                  if (DVA_GET_VDEV(&bp->blk_dva[0]) ==
                      DVA_GET_VDEV(&bp->blk_dva[1]))
                        zb->zb_ditto_2_of_2_samevdev++;
                  break;
            case 3:
                  equal = (DVA_GET_VDEV(&bp->blk_dva[0]) ==
                      DVA_GET_VDEV(&bp->blk_dva[1])) +
                      (DVA_GET_VDEV(&bp->blk_dva[0]) ==
                      DVA_GET_VDEV(&bp->blk_dva[2])) +
                      (DVA_GET_VDEV(&bp->blk_dva[1]) ==
                      DVA_GET_VDEV(&bp->blk_dva[2]));
                  if (equal == 1)
                        zb->zb_ditto_2_of_3_samevdev++;
                  else if (equal == 3)
                        zb->zb_ditto_3_of_3_samevdev++;
                  break;
            }
      }
}

static void
dsl_pool_scrub_clean_done(zio_t *zio)
{
      spa_t *spa = zio->io_spa;

      zio_data_buf_free(zio->io_data, zio->io_size);

      mutex_enter(&spa->spa_scrub_lock);
      spa->spa_scrub_inflight--;
      cv_broadcast(&spa->spa_scrub_io_cv);

      if (zio->io_error && (zio->io_error != ECKSUM ||
          !(zio->io_flags & ZIO_FLAG_SPECULATIVE)))
            spa->spa_scrub_errors++;
      mutex_exit(&spa->spa_scrub_lock);
}

static int
dsl_pool_scrub_clean_cb(dsl_pool_t *dp,
    const blkptr_t *bp, const zbookmark_t *zb)
{
      size_t size = BP_GET_LSIZE(bp);
      int d;
      spa_t *spa = dp->dp_spa;
      boolean_t needs_io;
      int zio_flags = ZIO_FLAG_SCRUB_THREAD | ZIO_FLAG_CANFAIL;
      int zio_priority;

      count_block(dp->dp_blkstats, bp);

      if (dp->dp_scrub_isresilver == 0) {
            /* It's a scrub */
            zio_flags |= ZIO_FLAG_SCRUB;
            zio_priority = ZIO_PRIORITY_SCRUB;
            needs_io = B_TRUE;
      } else {
            /* It's a resilver */
            zio_flags |= ZIO_FLAG_RESILVER;
            zio_priority = ZIO_PRIORITY_RESILVER;
            needs_io = B_FALSE;
      }

      /* If it's an intent log block, failure is expected. */
      if (zb->zb_level == -1 && BP_GET_TYPE(bp) != DMU_OT_OBJSET)
            zio_flags |= ZIO_FLAG_SPECULATIVE;

      for (d = 0; d < BP_GET_NDVAS(bp); d++) {
            vdev_t *vd = vdev_lookup_top(spa,
                DVA_GET_VDEV(&bp->blk_dva[d]));

            /*
             * Keep track of how much data we've examined so that
             * zpool(1M) status can make useful progress reports.
             */
            mutex_enter(&vd->vdev_stat_lock);
            vd->vdev_stat.vs_scrub_examined +=
                DVA_GET_ASIZE(&bp->blk_dva[d]);
            mutex_exit(&vd->vdev_stat_lock);

            /* if it's a resilver, this may not be in the target range */
            if (!needs_io) {
                  if (DVA_GET_GANG(&bp->blk_dva[d])) {
                        /*
                         * Gang members may be spread across multiple
                         * vdevs, so the best we can do is look at the
                         * pool-wide DTL.
                         * XXX -- it would be better to change our
                         * allocation policy to ensure that this can't
                         * happen.
                         */
                        vd = spa->spa_root_vdev;
                  }
                  needs_io = vdev_dtl_contains(&vd->vdev_dtl_map,
                      bp->blk_birth, 1);
            }
      }

      if (needs_io && !zfs_no_scrub_io) {
            void *data = zio_data_buf_alloc(size);

            mutex_enter(&spa->spa_scrub_lock);
            while (spa->spa_scrub_inflight >= spa->spa_scrub_maxinflight)
                  cv_wait(&spa->spa_scrub_io_cv, &spa->spa_scrub_lock);
            spa->spa_scrub_inflight++;
            mutex_exit(&spa->spa_scrub_lock);

            zio_nowait(zio_read(NULL, spa, bp, data, size,
                dsl_pool_scrub_clean_done, NULL, zio_priority,
                zio_flags, zb));
      }

      /* do not relocate this block */
      return (0);
}

int
dsl_pool_scrub_clean(dsl_pool_t *dp)
{
      /*
       * Purge all vdev caches.  We do this here rather than in sync
       * context because this requires a writer lock on the spa_config
       * lock, which we can't do from sync context.  The
       * spa_scrub_reopen flag indicates that vdev_open() should not
       * attempt to start another scrub.
       */
      spa_config_enter(dp->dp_spa, SCL_ALL, FTAG, RW_WRITER);
      dp->dp_spa->spa_scrub_reopen = B_TRUE;
      vdev_reopen(dp->dp_spa->spa_root_vdev);
      dp->dp_spa->spa_scrub_reopen = B_FALSE;
      spa_config_exit(dp->dp_spa, SCL_ALL, FTAG);

      return (dsl_pool_scrub_setup(dp, SCRUB_FUNC_CLEAN));
}

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