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dmu_send.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 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <sys/dmu.h>
#include <sys/dmu_impl.h>
#include <sys/dmu_tx.h>
#include <sys/dbuf.h>
#include <sys/dnode.h>
#include <sys/zfs_context.h>
#include <sys/dmu_objset.h>
#include <sys/dmu_traverse.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_pool.h>
#include <sys/dsl_synctask.h>
#include <sys/zfs_ioctl.h>
#include <sys/zap.h>
#include <sys/zio_checksum.h>

static char *dmu_recv_tag = "dmu_recv_tag";

struct backuparg {
      dmu_replay_record_t *drr;
      kthread_t *td;
      struct file *fp;
      offset_t *off;
      objset_t *os;
      zio_cksum_t zc;
      int err;
};

static int
dump_bytes(struct backuparg *ba, void *buf, int len)
{
      struct uio auio;
      struct iovec aiov;

      ASSERT3U(len % 8, ==, 0);

      fletcher_4_incremental_native(buf, len, &ba->zc);

      aiov.iov_base = buf;
      aiov.iov_len = len;
      auio.uio_iov = &aiov;
      auio.uio_iovcnt = 1;
      auio.uio_resid = len;
      auio.uio_segflg = UIO_SYSSPACE;
      auio.uio_rw = UIO_WRITE;
      auio.uio_offset = (off_t)-1;
      auio.uio_td = ba->td;
#ifdef _KERNEL
      if (ba->fp->f_type == DTYPE_VNODE)
            bwillwrite();
      ba->err = fo_write(ba->fp, &auio, ba->td->td_ucred, 0, ba->td);
#else
      fprintf(stderr, "%s: returning EOPNOTSUPP\n", __func__);
      ba->err = EOPNOTSUPP;
#endif
      *ba->off += len;

      return (ba->err);
}

static int
dump_free(struct backuparg *ba, uint64_t object, uint64_t offset,
    uint64_t length)
{
      /* write a FREE record */
      bzero(ba->drr, sizeof (dmu_replay_record_t));
      ba->drr->drr_type = DRR_FREE;
      ba->drr->drr_u.drr_free.drr_object = object;
      ba->drr->drr_u.drr_free.drr_offset = offset;
      ba->drr->drr_u.drr_free.drr_length = length;

      if (dump_bytes(ba, ba->drr, sizeof (dmu_replay_record_t)))
            return (EINTR);
      return (0);
}

static int
dump_data(struct backuparg *ba, dmu_object_type_t type,
    uint64_t object, uint64_t offset, int blksz, void *data)
{
      /* write a DATA record */
      bzero(ba->drr, sizeof (dmu_replay_record_t));
      ba->drr->drr_type = DRR_WRITE;
      ba->drr->drr_u.drr_write.drr_object = object;
      ba->drr->drr_u.drr_write.drr_type = type;
      ba->drr->drr_u.drr_write.drr_offset = offset;
      ba->drr->drr_u.drr_write.drr_length = blksz;

      if (dump_bytes(ba, ba->drr, sizeof (dmu_replay_record_t)))
            return (EINTR);
      if (dump_bytes(ba, data, blksz))
            return (EINTR);
      return (0);
}

static int
dump_freeobjects(struct backuparg *ba, uint64_t firstobj, uint64_t numobjs)
{
      /* write a FREEOBJECTS record */
      bzero(ba->drr, sizeof (dmu_replay_record_t));
      ba->drr->drr_type = DRR_FREEOBJECTS;
      ba->drr->drr_u.drr_freeobjects.drr_firstobj = firstobj;
      ba->drr->drr_u.drr_freeobjects.drr_numobjs = numobjs;

      if (dump_bytes(ba, ba->drr, sizeof (dmu_replay_record_t)))
            return (EINTR);
      return (0);
}

static int
dump_dnode(struct backuparg *ba, uint64_t object, dnode_phys_t *dnp)
{
      if (dnp == NULL || dnp->dn_type == DMU_OT_NONE)
            return (dump_freeobjects(ba, object, 1));

      /* write an OBJECT record */
      bzero(ba->drr, sizeof (dmu_replay_record_t));
      ba->drr->drr_type = DRR_OBJECT;
      ba->drr->drr_u.drr_object.drr_object = object;
      ba->drr->drr_u.drr_object.drr_type = dnp->dn_type;
      ba->drr->drr_u.drr_object.drr_bonustype = dnp->dn_bonustype;
      ba->drr->drr_u.drr_object.drr_blksz =
          dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT;
      ba->drr->drr_u.drr_object.drr_bonuslen = dnp->dn_bonuslen;
      ba->drr->drr_u.drr_object.drr_checksum = dnp->dn_checksum;
      ba->drr->drr_u.drr_object.drr_compress = dnp->dn_compress;

      if (dump_bytes(ba, ba->drr, sizeof (dmu_replay_record_t)))
            return (EINTR);

      if (dump_bytes(ba, DN_BONUS(dnp), P2ROUNDUP(dnp->dn_bonuslen, 8)))
            return (EINTR);

      /* free anything past the end of the file */
      if (dump_free(ba, object, (dnp->dn_maxblkid + 1) *
          (dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT), -1ULL))
            return (EINTR);
      if (ba->err)
            return (EINTR);
      return (0);
}

#define     BP_SPAN(dnp, level) \
      (((uint64_t)dnp->dn_datablkszsec) << (SPA_MINBLOCKSHIFT + \
      (level) * (dnp->dn_indblkshift - SPA_BLKPTRSHIFT)))

static int
backup_cb(spa_t *spa, blkptr_t *bp, const zbookmark_t *zb,
    const dnode_phys_t *dnp, void *arg)
{
      struct backuparg *ba = arg;
      dmu_object_type_t type = bp ? BP_GET_TYPE(bp) : DMU_OT_NONE;
      int err = 0;

      if (issig(JUSTLOOKING) && issig(FORREAL))
            return (EINTR);

      if (bp == NULL && zb->zb_object == 0) {
            uint64_t span = BP_SPAN(dnp, zb->zb_level);
            uint64_t dnobj = (zb->zb_blkid * span) >> DNODE_SHIFT;
            err = dump_freeobjects(ba, dnobj, span >> DNODE_SHIFT);
      } else if (bp == NULL) {
            uint64_t span = BP_SPAN(dnp, zb->zb_level);
            err = dump_free(ba, zb->zb_object, zb->zb_blkid * span, span);
      } else if (zb->zb_level > 0 || type == DMU_OT_OBJSET) {
            return (0);
      } else if (type == DMU_OT_DNODE) {
            dnode_phys_t *blk;
            int i;
            int blksz = BP_GET_LSIZE(bp);
            uint32_t aflags = ARC_WAIT;
            arc_buf_t *abuf;

            if (arc_read_nolock(NULL, spa, bp,
                arc_getbuf_func, &abuf, ZIO_PRIORITY_ASYNC_READ,
                ZIO_FLAG_CANFAIL, &aflags, zb) != 0)
                  return (EIO);

            blk = abuf->b_data;
            for (i = 0; i < blksz >> DNODE_SHIFT; i++) {
                  uint64_t dnobj = (zb->zb_blkid <<
                      (DNODE_BLOCK_SHIFT - DNODE_SHIFT)) + i;
                  err = dump_dnode(ba, dnobj, blk+i);
                  if (err)
                        break;
            }
            (void) arc_buf_remove_ref(abuf, &abuf);
      } else { /* it's a level-0 block of a regular object */
            uint32_t aflags = ARC_WAIT;
            arc_buf_t *abuf;
            int blksz = BP_GET_LSIZE(bp);

            if (arc_read_nolock(NULL, spa, bp,
                arc_getbuf_func, &abuf, ZIO_PRIORITY_ASYNC_READ,
                ZIO_FLAG_CANFAIL, &aflags, zb) != 0)
                  return (EIO);

            err = dump_data(ba, type, zb->zb_object, zb->zb_blkid * blksz,
                blksz, abuf->b_data);
            (void) arc_buf_remove_ref(abuf, &abuf);
      }

      ASSERT(err == 0 || err == EINTR);
      return (err);
}

int
dmu_sendbackup(objset_t *tosnap, objset_t *fromsnap, boolean_t fromorigin,
    struct file *fp, offset_t *off)
{
      dsl_dataset_t *ds = tosnap->os->os_dsl_dataset;
      dsl_dataset_t *fromds = fromsnap ? fromsnap->os->os_dsl_dataset : NULL;
      dmu_replay_record_t *drr;
      struct backuparg ba;
      int err;
      uint64_t fromtxg = 0;

      /* tosnap must be a snapshot */
      if (ds->ds_phys->ds_next_snap_obj == 0)
            return (EINVAL);

      /* fromsnap must be an earlier snapshot from the same fs as tosnap */
      if (fromds && (ds->ds_dir != fromds->ds_dir ||
          fromds->ds_phys->ds_creation_txg >= ds->ds_phys->ds_creation_txg))
            return (EXDEV);

      if (fromorigin) {
            dsl_pool_t *dp = ds->ds_dir->dd_pool;

            if (fromsnap)
                  return (EINVAL);

            if (dsl_dir_is_clone(ds->ds_dir)) {
                  rw_enter(&dp->dp_config_rwlock, RW_READER);
                  err = dsl_dataset_hold_obj(dp,
                      ds->ds_dir->dd_phys->dd_origin_obj, FTAG, &fromds);
                  rw_exit(&dp->dp_config_rwlock);
                  if (err)
                        return (err);
            } else {
                  fromorigin = B_FALSE;
            }
      }


      drr = kmem_zalloc(sizeof (dmu_replay_record_t), KM_SLEEP);
      drr->drr_type = DRR_BEGIN;
      drr->drr_u.drr_begin.drr_magic = DMU_BACKUP_MAGIC;
      drr->drr_u.drr_begin.drr_version = DMU_BACKUP_STREAM_VERSION;
      drr->drr_u.drr_begin.drr_creation_time =
          ds->ds_phys->ds_creation_time;
      drr->drr_u.drr_begin.drr_type = tosnap->os->os_phys->os_type;
      if (fromorigin)
            drr->drr_u.drr_begin.drr_flags |= DRR_FLAG_CLONE;
      drr->drr_u.drr_begin.drr_toguid = ds->ds_phys->ds_guid;
      if (ds->ds_phys->ds_flags & DS_FLAG_CI_DATASET)
            drr->drr_u.drr_begin.drr_flags |= DRR_FLAG_CI_DATA;

      if (fromds)
            drr->drr_u.drr_begin.drr_fromguid = fromds->ds_phys->ds_guid;
      dsl_dataset_name(ds, drr->drr_u.drr_begin.drr_toname);

      if (fromds)
            fromtxg = fromds->ds_phys->ds_creation_txg;
      if (fromorigin)
            dsl_dataset_rele(fromds, FTAG);

      ba.drr = drr;
      ba.td = curthread;
      ba.fp = fp;
      ba.os = tosnap;
      ba.off = off;
      ZIO_SET_CHECKSUM(&ba.zc, 0, 0, 0, 0);

      if (dump_bytes(&ba, drr, sizeof (dmu_replay_record_t))) {
            kmem_free(drr, sizeof (dmu_replay_record_t));
            return (ba.err);
      }

      err = traverse_dataset(ds, fromtxg, TRAVERSE_PRE | TRAVERSE_PREFETCH,
          backup_cb, &ba);

      if (err) {
            if (err == EINTR && ba.err)
                  err = ba.err;
            kmem_free(drr, sizeof (dmu_replay_record_t));
            return (err);
      }

      bzero(drr, sizeof (dmu_replay_record_t));
      drr->drr_type = DRR_END;
      drr->drr_u.drr_end.drr_checksum = ba.zc;

      if (dump_bytes(&ba, drr, sizeof (dmu_replay_record_t))) {
            kmem_free(drr, sizeof (dmu_replay_record_t));
            return (ba.err);
      }

      kmem_free(drr, sizeof (dmu_replay_record_t));

      return (0);
}

struct recvbeginsyncarg {
      const char *tofs;
      const char *tosnap;
      dsl_dataset_t *origin;
      uint64_t fromguid;
      dmu_objset_type_t type;
      void *tag;
      boolean_t force;
      uint64_t dsflags;
      char clonelastname[MAXNAMELEN];
      dsl_dataset_t *ds; /* the ds to recv into; returned from the syncfunc */
};

static dsl_dataset_t *
recv_full_sync_impl(dsl_pool_t *dp, uint64_t dsobj, dmu_objset_type_t type,
    cred_t *cr, dmu_tx_t *tx)
{
      dsl_dataset_t *ds;

      /* This should always work, since we just created it */
      /* XXX - create should return an owned ds */
      VERIFY(0 == dsl_dataset_own_obj(dp, dsobj,
          DS_MODE_INCONSISTENT, dmu_recv_tag, &ds));

      if (type != DMU_OST_NONE) {
            (void) dmu_objset_create_impl(dp->dp_spa,
                ds, &ds->ds_phys->ds_bp, type, tx);
      }

      spa_history_internal_log(LOG_DS_REPLAY_FULL_SYNC,
          dp->dp_spa, tx, cr, "dataset = %lld", dsobj);

      return (ds);
}

/* ARGSUSED */
static int
recv_full_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dir_t *dd = arg1;
      struct recvbeginsyncarg *rbsa = arg2;
      objset_t *mos = dd->dd_pool->dp_meta_objset;
      uint64_t val;
      int err;

      err = zap_lookup(mos, dd->dd_phys->dd_child_dir_zapobj,
          strrchr(rbsa->tofs, '/') + 1, sizeof (uint64_t), 1, &val);

      if (err != ENOENT)
            return (err ? err : EEXIST);

      if (rbsa->origin) {
            /* make sure it's a snap in the same pool */
            if (rbsa->origin->ds_dir->dd_pool != dd->dd_pool)
                  return (EXDEV);
            if (rbsa->origin->ds_phys->ds_num_children == 0)
                  return (EINVAL);
            if (rbsa->origin->ds_phys->ds_guid != rbsa->fromguid)
                  return (ENODEV);
      }

      return (0);
}

static void
recv_full_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dir_t *dd = arg1;
      struct recvbeginsyncarg *rbsa = arg2;
      uint64_t flags = DS_FLAG_INCONSISTENT | rbsa->dsflags;
      uint64_t dsobj;

      dsobj = dsl_dataset_create_sync(dd, strrchr(rbsa->tofs, '/') + 1,
          rbsa->origin, flags, cr, tx);

      rbsa->ds = recv_full_sync_impl(dd->dd_pool, dsobj,
          rbsa->origin ? DMU_OST_NONE : rbsa->type, cr, tx);
}

static int
recv_full_existing_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;
      struct recvbeginsyncarg *rbsa = arg2;
      int err;

      /* must be a head ds */
      if (ds->ds_phys->ds_next_snap_obj != 0)
            return (EINVAL);

      /* must not be a clone ds */
      if (dsl_dir_is_clone(ds->ds_dir))
            return (EINVAL);

      err = dsl_dataset_destroy_check(ds, rbsa->tag, tx);
      if (err)
            return (err);

      if (rbsa->origin) {
            /* make sure it's a snap in the same pool */
            if (rbsa->origin->ds_dir->dd_pool != ds->ds_dir->dd_pool)
                  return (EXDEV);
            if (rbsa->origin->ds_phys->ds_num_children == 0)
                  return (EINVAL);
            if (rbsa->origin->ds_phys->ds_guid != rbsa->fromguid)
                  return (ENODEV);
      }

      return (0);
}

static void
recv_full_existing_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;
      struct recvbeginsyncarg *rbsa = arg2;
      dsl_dir_t *dd = ds->ds_dir;
      uint64_t flags = DS_FLAG_INCONSISTENT | rbsa->dsflags;
      uint64_t dsobj;

      /*
       * NB: caller must provide an extra hold on the dsl_dir_t, so it
       * won't go away when dsl_dataset_destroy_sync() closes the
       * dataset.
       */
      dsl_dataset_destroy_sync(ds, rbsa->tag, cr, tx);

      dsobj = dsl_dataset_create_sync_dd(dd, rbsa->origin, flags, tx);

      rbsa->ds = recv_full_sync_impl(dd->dd_pool, dsobj,
          rbsa->origin ? DMU_OST_NONE : rbsa->type, cr, tx);
}

/* ARGSUSED */
static int
recv_incremental_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;
      struct recvbeginsyncarg *rbsa = arg2;
      int err;
      uint64_t val;

      /* must not have any changes since most recent snapshot */
      if (!rbsa->force && dsl_dataset_modified_since_lastsnap(ds))
            return (ETXTBSY);

      /* must already be a snapshot of this fs */
      if (ds->ds_phys->ds_prev_snap_obj == 0)
            return (ENODEV);

      /* most recent snapshot must match fromguid */
      if (ds->ds_prev->ds_phys->ds_guid != rbsa->fromguid)
            return (ENODEV);

      /* temporary clone name must not exist */
      err = zap_lookup(ds->ds_dir->dd_pool->dp_meta_objset,
          ds->ds_dir->dd_phys->dd_child_dir_zapobj,
          rbsa->clonelastname, 8, 1, &val);
      if (err == 0)
            return (EEXIST);
      if (err != ENOENT)
            return (err);

      /* new snapshot name must not exist */
      err = zap_lookup(ds->ds_dir->dd_pool->dp_meta_objset,
          ds->ds_phys->ds_snapnames_zapobj, rbsa->tosnap, 8, 1, &val);
      if (err == 0)
            return (EEXIST);
      if (err != ENOENT)
            return (err);
      return (0);
}

/* ARGSUSED */
static void
recv_online_incremental_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dataset_t *ohds = arg1;
      struct recvbeginsyncarg *rbsa = arg2;
      dsl_pool_t *dp = ohds->ds_dir->dd_pool;
      dsl_dataset_t *ods, *cds;
      uint64_t flags = DS_FLAG_INCONSISTENT | rbsa->dsflags;
      uint64_t dsobj;

      /* create the temporary clone */
      VERIFY(0 == dsl_dataset_hold_obj(dp, ohds->ds_phys->ds_prev_snap_obj,
          FTAG, &ods));
      dsobj = dsl_dataset_create_sync(ohds->ds_dir,
          rbsa->clonelastname, ods, flags, cr, tx);
      dsl_dataset_rele(ods, FTAG);

      /* open the temporary clone */
      VERIFY(0 == dsl_dataset_own_obj(dp, dsobj,
          DS_MODE_INCONSISTENT, dmu_recv_tag, &cds));

      /* copy the refquota from the target fs to the clone */
      if (ohds->ds_quota > 0)
            dsl_dataset_set_quota_sync(cds, &ohds->ds_quota, cr, tx);

      rbsa->ds = cds;

      spa_history_internal_log(LOG_DS_REPLAY_INC_SYNC,
          dp->dp_spa, tx, cr, "dataset = %lld", dsobj);
}

/* ARGSUSED */
static void
recv_offline_incremental_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;

      dmu_buf_will_dirty(ds->ds_dbuf, tx);
      ds->ds_phys->ds_flags |= DS_FLAG_INCONSISTENT;

      spa_history_internal_log(LOG_DS_REPLAY_INC_SYNC,
          ds->ds_dir->dd_pool->dp_spa, tx, cr, "dataset = %lld",
          ds->ds_object);
}

/*
 * NB: callers *MUST* call dmu_recv_stream() if dmu_recv_begin()
 * succeeds; otherwise we will leak the holds on the datasets.
 */
int
dmu_recv_begin(char *tofs, char *tosnap, struct drr_begin *drrb,
    boolean_t force, objset_t *origin, boolean_t online, dmu_recv_cookie_t *drc)
{
      int err = 0;
      boolean_t byteswap;
      struct recvbeginsyncarg rbsa;
      uint64_t version;
      int flags;
      dsl_dataset_t *ds;

      if (drrb->drr_magic == DMU_BACKUP_MAGIC)
            byteswap = FALSE;
      else if (drrb->drr_magic == BSWAP_64(DMU_BACKUP_MAGIC))
            byteswap = TRUE;
      else
            return (EINVAL);

      rbsa.tofs = tofs;
      rbsa.tosnap = tosnap;
      rbsa.origin = origin ? origin->os->os_dsl_dataset : NULL;
      rbsa.fromguid = drrb->drr_fromguid;
      rbsa.type = drrb->drr_type;
      rbsa.tag = FTAG;
      rbsa.dsflags = 0;
      version = drrb->drr_version;
      flags = drrb->drr_flags;

      if (byteswap) {
            rbsa.type = BSWAP_32(rbsa.type);
            rbsa.fromguid = BSWAP_64(rbsa.fromguid);
            version = BSWAP_64(version);
            flags = BSWAP_32(flags);
      }

      if (version != DMU_BACKUP_STREAM_VERSION ||
          rbsa.type >= DMU_OST_NUMTYPES ||
          ((flags & DRR_FLAG_CLONE) && origin == NULL))
            return (EINVAL);

      if (flags & DRR_FLAG_CI_DATA)
            rbsa.dsflags = DS_FLAG_CI_DATASET;

      bzero(drc, sizeof (dmu_recv_cookie_t));
      drc->drc_drrb = drrb;
      drc->drc_tosnap = tosnap;
      drc->drc_force = force;

      /*
       * Process the begin in syncing context.
       */
      if (rbsa.fromguid && !(flags & DRR_FLAG_CLONE) && !online) {
            /* offline incremental receive */
            err = dsl_dataset_own(tofs, 0, dmu_recv_tag, &ds);
            if (err)
                  return (err);

            /*
             * Only do the rollback if the most recent snapshot
             * matches the incremental source
             */
            if (force) {
                  if (ds->ds_prev == NULL ||
                      ds->ds_prev->ds_phys->ds_guid !=
                      rbsa.fromguid) {
                        dsl_dataset_disown(ds, dmu_recv_tag);
                        return (ENODEV);
                  }
                  (void) dsl_dataset_rollback(ds, DMU_OST_NONE);
            }
            rbsa.force = B_FALSE;
            err = dsl_sync_task_do(ds->ds_dir->dd_pool,
                recv_incremental_check,
                recv_offline_incremental_sync, ds, &rbsa, 1);
            if (err) {
                  dsl_dataset_disown(ds, dmu_recv_tag);
                  return (err);
            }
            drc->drc_logical_ds = drc->drc_real_ds = ds;
      } else if (rbsa.fromguid && !(flags & DRR_FLAG_CLONE)) {
            /* online incremental receive */

            /* tmp clone name is: tofs/%tosnap" */
            (void) snprintf(rbsa.clonelastname, sizeof (rbsa.clonelastname),
                "%%%s", tosnap);

            /* open the dataset we are logically receiving into */
            err = dsl_dataset_hold(tofs, dmu_recv_tag, &ds);
            if (err)
                  return (err);

            rbsa.force = force;
            err = dsl_sync_task_do(ds->ds_dir->dd_pool,
                recv_incremental_check,
                recv_online_incremental_sync, ds, &rbsa, 5);
            if (err) {
                  dsl_dataset_rele(ds, dmu_recv_tag);
                  return (err);
            }
            drc->drc_logical_ds = ds;
            drc->drc_real_ds = rbsa.ds;
      } else {
            /* create new fs -- full backup or clone */
            dsl_dir_t *dd = NULL;
            const char *tail;

            err = dsl_dir_open(tofs, FTAG, &dd, &tail);
            if (err)
                  return (err);
            if (tail == NULL) {
                  if (!force) {
                        dsl_dir_close(dd, FTAG);
                        return (EEXIST);
                  }

                  rw_enter(&dd->dd_pool->dp_config_rwlock, RW_READER);
                  err = dsl_dataset_own_obj(dd->dd_pool,
                      dd->dd_phys->dd_head_dataset_obj,
                      DS_MODE_INCONSISTENT, FTAG, &ds);
                  rw_exit(&dd->dd_pool->dp_config_rwlock);
                  if (err) {
                        dsl_dir_close(dd, FTAG);
                        return (err);
                  }

                  dsl_dataset_make_exclusive(ds, FTAG);
                  err = dsl_sync_task_do(dd->dd_pool,
                      recv_full_existing_check,
                      recv_full_existing_sync, ds, &rbsa, 5);
                  dsl_dataset_disown(ds, FTAG);
            } else {
                  err = dsl_sync_task_do(dd->dd_pool, recv_full_check,
                      recv_full_sync, dd, &rbsa, 5);
            }
            dsl_dir_close(dd, FTAG);
            if (err)
                  return (err);
            drc->drc_logical_ds = drc->drc_real_ds = rbsa.ds;
            drc->drc_newfs = B_TRUE;
      }

      return (0);
}

struct restorearg {
      int err;
      int byteswap;
      kthread_t *td;
      struct file *fp;
      char *buf;
      uint64_t voff;
      int bufsize; /* amount of memory allocated for buf */
      zio_cksum_t cksum;
};

static int
restore_bytes(struct restorearg *ra, void *buf, int len, off_t off, int *resid)
{
      struct uio auio;
      struct iovec aiov;
      int error;

      aiov.iov_base = buf;
      aiov.iov_len = len;
      auio.uio_iov = &aiov;
      auio.uio_iovcnt = 1;
      auio.uio_resid = len;
      auio.uio_segflg = UIO_SYSSPACE;
      auio.uio_rw = UIO_READ;
      auio.uio_offset = off;
      auio.uio_td = ra->td;
#ifdef _KERNEL
      error = fo_read(ra->fp, &auio, ra->td->td_ucred, FOF_OFFSET, ra->td);
#else
      fprintf(stderr, "%s: returning EOPNOTSUPP\n", __func__);
      error = EOPNOTSUPP;
#endif
      *resid = auio.uio_resid;
      return (error);
}

static void *
restore_read(struct restorearg *ra, int len)
{
      void *rv;
      int done = 0;

      /* some things will require 8-byte alignment, so everything must */
      ASSERT3U(len % 8, ==, 0);

      while (done < len) {
            int resid;

            ra->err = restore_bytes(ra, (caddr_t)ra->buf + done,
                len - done, ra->voff, &resid);

            if (resid == len - done)
                  ra->err = EINVAL;
            ra->voff += len - done - resid;
            done = len - resid;
            if (ra->err)
                  return (NULL);
      }

      ASSERT3U(done, ==, len);
      rv = ra->buf;
      if (ra->byteswap)
            fletcher_4_incremental_byteswap(rv, len, &ra->cksum);
      else
            fletcher_4_incremental_native(rv, len, &ra->cksum);
      return (rv);
}

static void
backup_byteswap(dmu_replay_record_t *drr)
{
#define     DO64(X) (drr->drr_u.X = BSWAP_64(drr->drr_u.X))
#define     DO32(X) (drr->drr_u.X = BSWAP_32(drr->drr_u.X))
      drr->drr_type = BSWAP_32(drr->drr_type);
      drr->drr_payloadlen = BSWAP_32(drr->drr_payloadlen);
      switch (drr->drr_type) {
      case DRR_BEGIN:
            DO64(drr_begin.drr_magic);
            DO64(drr_begin.drr_version);
            DO64(drr_begin.drr_creation_time);
            DO32(drr_begin.drr_type);
            DO32(drr_begin.drr_flags);
            DO64(drr_begin.drr_toguid);
            DO64(drr_begin.drr_fromguid);
            break;
      case DRR_OBJECT:
            DO64(drr_object.drr_object);
            /* DO64(drr_object.drr_allocation_txg); */
            DO32(drr_object.drr_type);
            DO32(drr_object.drr_bonustype);
            DO32(drr_object.drr_blksz);
            DO32(drr_object.drr_bonuslen);
            break;
      case DRR_FREEOBJECTS:
            DO64(drr_freeobjects.drr_firstobj);
            DO64(drr_freeobjects.drr_numobjs);
            break;
      case DRR_WRITE:
            DO64(drr_write.drr_object);
            DO32(drr_write.drr_type);
            DO64(drr_write.drr_offset);
            DO64(drr_write.drr_length);
            break;
      case DRR_FREE:
            DO64(drr_free.drr_object);
            DO64(drr_free.drr_offset);
            DO64(drr_free.drr_length);
            break;
      case DRR_END:
            DO64(drr_end.drr_checksum.zc_word[0]);
            DO64(drr_end.drr_checksum.zc_word[1]);
            DO64(drr_end.drr_checksum.zc_word[2]);
            DO64(drr_end.drr_checksum.zc_word[3]);
            break;
      }
#undef DO64
#undef DO32
}

static int
restore_object(struct restorearg *ra, objset_t *os, struct drr_object *drro)
{
      int err;
      dmu_tx_t *tx;
      void *data = NULL;

      if (drro->drr_type == DMU_OT_NONE ||
          drro->drr_type >= DMU_OT_NUMTYPES ||
          drro->drr_bonustype >= DMU_OT_NUMTYPES ||
          drro->drr_checksum >= ZIO_CHECKSUM_FUNCTIONS ||
          drro->drr_compress >= ZIO_COMPRESS_FUNCTIONS ||
          P2PHASE(drro->drr_blksz, SPA_MINBLOCKSIZE) ||
          drro->drr_blksz < SPA_MINBLOCKSIZE ||
          drro->drr_blksz > SPA_MAXBLOCKSIZE ||
          drro->drr_bonuslen > DN_MAX_BONUSLEN) {
            return (EINVAL);
      }

      err = dmu_object_info(os, drro->drr_object, NULL);

      if (err != 0 && err != ENOENT)
            return (EINVAL);

      if (drro->drr_bonuslen) {
            data = restore_read(ra, P2ROUNDUP(drro->drr_bonuslen, 8));
            if (ra->err)
                  return (ra->err);
      }

      if (err == ENOENT) {
            /* currently free, want to be allocated */
            tx = dmu_tx_create(os);
            dmu_tx_hold_bonus(tx, DMU_NEW_OBJECT);
            err = dmu_tx_assign(tx, TXG_WAIT);
            if (err) {
                  dmu_tx_abort(tx);
                  return (err);
            }
            err = dmu_object_claim(os, drro->drr_object,
                drro->drr_type, drro->drr_blksz,
                drro->drr_bonustype, drro->drr_bonuslen, tx);
            dmu_tx_commit(tx);
      } else {
            /* currently allocated, want to be allocated */
            err = dmu_object_reclaim(os, drro->drr_object,
                drro->drr_type, drro->drr_blksz,
                drro->drr_bonustype, drro->drr_bonuslen);
      }
      if (err)
            return (EINVAL);

      tx = dmu_tx_create(os);
      dmu_tx_hold_bonus(tx, drro->drr_object);
      err = dmu_tx_assign(tx, TXG_WAIT);
      if (err) {
            dmu_tx_abort(tx);
            return (err);
      }

      dmu_object_set_checksum(os, drro->drr_object, drro->drr_checksum, tx);
      dmu_object_set_compress(os, drro->drr_object, drro->drr_compress, tx);

      if (data != NULL) {
            dmu_buf_t *db;

            VERIFY(0 == dmu_bonus_hold(os, drro->drr_object, FTAG, &db));
            dmu_buf_will_dirty(db, tx);

            ASSERT3U(db->db_size, >=, drro->drr_bonuslen);
            bcopy(data, db->db_data, drro->drr_bonuslen);
            if (ra->byteswap) {
                  dmu_ot[drro->drr_bonustype].ot_byteswap(db->db_data,
                      drro->drr_bonuslen);
            }
            dmu_buf_rele(db, FTAG);
      }
      dmu_tx_commit(tx);
      return (0);
}

/* ARGSUSED */
static int
restore_freeobjects(struct restorearg *ra, objset_t *os,
    struct drr_freeobjects *drrfo)
{
      uint64_t obj;

      if (drrfo->drr_firstobj + drrfo->drr_numobjs < drrfo->drr_firstobj)
            return (EINVAL);

      for (obj = drrfo->drr_firstobj;
          obj < drrfo->drr_firstobj + drrfo->drr_numobjs;
          (void) dmu_object_next(os, &obj, FALSE, 0)) {
            int err;

            if (dmu_object_info(os, obj, NULL) != 0)
                  continue;

            err = dmu_free_object(os, obj);
            if (err)
                  return (err);
      }
      return (0);
}

static int
restore_write(struct restorearg *ra, objset_t *os,
    struct drr_write *drrw)
{
      dmu_tx_t *tx;
      void *data;
      int err;

      if (drrw->drr_offset + drrw->drr_length < drrw->drr_offset ||
          drrw->drr_type >= DMU_OT_NUMTYPES)
            return (EINVAL);

      data = restore_read(ra, drrw->drr_length);
      if (data == NULL)
            return (ra->err);

      if (dmu_object_info(os, drrw->drr_object, NULL) != 0)
            return (EINVAL);

      tx = dmu_tx_create(os);

      dmu_tx_hold_write(tx, drrw->drr_object,
          drrw->drr_offset, drrw->drr_length);
      err = dmu_tx_assign(tx, TXG_WAIT);
      if (err) {
            dmu_tx_abort(tx);
            return (err);
      }
      if (ra->byteswap)
            dmu_ot[drrw->drr_type].ot_byteswap(data, drrw->drr_length);
      dmu_write(os, drrw->drr_object,
          drrw->drr_offset, drrw->drr_length, data, tx);
      dmu_tx_commit(tx);
      return (0);
}

/* ARGSUSED */
static int
restore_free(struct restorearg *ra, objset_t *os,
    struct drr_free *drrf)
{
      int err;

      if (drrf->drr_length != -1ULL &&
          drrf->drr_offset + drrf->drr_length < drrf->drr_offset)
            return (EINVAL);

      if (dmu_object_info(os, drrf->drr_object, NULL) != 0)
            return (EINVAL);

      err = dmu_free_long_range(os, drrf->drr_object,
          drrf->drr_offset, drrf->drr_length);
      return (err);
}

void
dmu_recv_abort_cleanup(dmu_recv_cookie_t *drc)
{
      if (drc->drc_newfs || drc->drc_real_ds != drc->drc_logical_ds) {
            /*
             * online incremental or new fs: destroy the fs (which
             * may be a clone) that we created
             */
            (void) dsl_dataset_destroy(drc->drc_real_ds, dmu_recv_tag);
            if (drc->drc_real_ds != drc->drc_logical_ds)
                  dsl_dataset_rele(drc->drc_logical_ds, dmu_recv_tag);
      } else {
            /*
             * offline incremental: rollback to most recent snapshot.
             */
            (void) dsl_dataset_rollback(drc->drc_real_ds, DMU_OST_NONE);
            dsl_dataset_disown(drc->drc_real_ds, dmu_recv_tag);
      }
}

/*
 * NB: callers *must* call dmu_recv_end() if this succeeds.
 */
int
dmu_recv_stream(dmu_recv_cookie_t *drc, struct file *fp, offset_t *voffp)
{
      kthread_t *td = curthread;
      struct restorearg ra = { 0 };
      dmu_replay_record_t *drr;
      objset_t *os;
      zio_cksum_t pcksum;

      if (drc->drc_drrb->drr_magic == BSWAP_64(DMU_BACKUP_MAGIC))
            ra.byteswap = TRUE;

      {
            /* compute checksum of drr_begin record */
            dmu_replay_record_t *drr;
            drr = kmem_zalloc(sizeof (dmu_replay_record_t), KM_SLEEP);

            drr->drr_type = DRR_BEGIN;
            drr->drr_u.drr_begin = *drc->drc_drrb;
            if (ra.byteswap) {
                  fletcher_4_incremental_byteswap(drr,
                      sizeof (dmu_replay_record_t), &ra.cksum);
            } else {
                  fletcher_4_incremental_native(drr,
                      sizeof (dmu_replay_record_t), &ra.cksum);
            }
            kmem_free(drr, sizeof (dmu_replay_record_t));
      }

      if (ra.byteswap) {
            struct drr_begin *drrb = drc->drc_drrb;
            drrb->drr_magic = BSWAP_64(drrb->drr_magic);
            drrb->drr_version = BSWAP_64(drrb->drr_version);
            drrb->drr_creation_time = BSWAP_64(drrb->drr_creation_time);
            drrb->drr_type = BSWAP_32(drrb->drr_type);
            drrb->drr_toguid = BSWAP_64(drrb->drr_toguid);
            drrb->drr_fromguid = BSWAP_64(drrb->drr_fromguid);
      }

      ra.td = td;
      ra.fp = fp;
      ra.voff = *voffp;
      ra.bufsize = 1<<20;
      ra.buf = kmem_alloc(ra.bufsize, KM_SLEEP);

      /* these were verified in dmu_recv_begin */
      ASSERT(drc->drc_drrb->drr_version == DMU_BACKUP_STREAM_VERSION);
      ASSERT(drc->drc_drrb->drr_type < DMU_OST_NUMTYPES);

      /*
       * Open the objset we are modifying.
       */
      VERIFY(dmu_objset_open_ds(drc->drc_real_ds, DMU_OST_ANY, &os) == 0);

      ASSERT(drc->drc_real_ds->ds_phys->ds_flags & DS_FLAG_INCONSISTENT);

      /*
       * Read records and process them.
       */
      pcksum = ra.cksum;
      while (ra.err == 0 &&
          NULL != (drr = restore_read(&ra, sizeof (*drr)))) {
            if (issig(JUSTLOOKING) && issig(FORREAL)) {
                  ra.err = EINTR;
                  goto out;
            }

            if (ra.byteswap)
                  backup_byteswap(drr);

            switch (drr->drr_type) {
            case DRR_OBJECT:
            {
                  /*
                   * We need to make a copy of the record header,
                   * because restore_{object,write} may need to
                   * restore_read(), which will invalidate drr.
                   */
                  struct drr_object drro = drr->drr_u.drr_object;
                  ra.err = restore_object(&ra, os, &drro);
                  break;
            }
            case DRR_FREEOBJECTS:
            {
                  struct drr_freeobjects drrfo =
                      drr->drr_u.drr_freeobjects;
                  ra.err = restore_freeobjects(&ra, os, &drrfo);
                  break;
            }
            case DRR_WRITE:
            {
                  struct drr_write drrw = drr->drr_u.drr_write;
                  ra.err = restore_write(&ra, os, &drrw);
                  break;
            }
            case DRR_FREE:
            {
                  struct drr_free drrf = drr->drr_u.drr_free;
                  ra.err = restore_free(&ra, os, &drrf);
                  break;
            }
            case DRR_END:
            {
                  struct drr_end drre = drr->drr_u.drr_end;
                  /*
                   * We compare against the *previous* checksum
                   * value, because the stored checksum is of
                   * everything before the DRR_END record.
                   */
                  if (!ZIO_CHECKSUM_EQUAL(drre.drr_checksum, pcksum))
                        ra.err = ECKSUM;
                  goto out;
            }
            default:
                  ra.err = EINVAL;
                  goto out;
            }
            pcksum = ra.cksum;
      }
      ASSERT(ra.err != 0);

out:
      dmu_objset_close(os);

      if (ra.err != 0) {
            /*
             * rollback or destroy what we created, so we don't
             * leave it in the restoring state.
             */
            txg_wait_synced(drc->drc_real_ds->ds_dir->dd_pool, 0);
            dmu_recv_abort_cleanup(drc);
      }

      kmem_free(ra.buf, ra.bufsize);
      *voffp = ra.voff;
      return (ra.err);
}

struct recvendsyncarg {
      char *tosnap;
      uint64_t creation_time;
      uint64_t toguid;
};

static int
recv_end_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;
      struct recvendsyncarg *resa = arg2;

      return (dsl_dataset_snapshot_check(ds, resa->tosnap, tx));
}

static void
recv_end_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;
      struct recvendsyncarg *resa = arg2;

      dsl_dataset_snapshot_sync(ds, resa->tosnap, cr, tx);

      /* set snapshot's creation time and guid */
      dmu_buf_will_dirty(ds->ds_prev->ds_dbuf, tx);
      ds->ds_prev->ds_phys->ds_creation_time = resa->creation_time;
      ds->ds_prev->ds_phys->ds_guid = resa->toguid;
      ds->ds_prev->ds_phys->ds_flags &= ~DS_FLAG_INCONSISTENT;

      dmu_buf_will_dirty(ds->ds_dbuf, tx);
      ds->ds_phys->ds_flags &= ~DS_FLAG_INCONSISTENT;
}

int
dmu_recv_end(dmu_recv_cookie_t *drc)
{
      struct recvendsyncarg resa;
      dsl_dataset_t *ds = drc->drc_logical_ds;
      int err;

      /*
       * XXX hack; seems the ds is still dirty and
       * dsl_pool_zil_clean() expects it to have a ds_user_ptr
       * (and zil), but clone_swap() can close it.
       */
      txg_wait_synced(ds->ds_dir->dd_pool, 0);

      if (ds != drc->drc_real_ds) {
            /* we are doing an online recv */
            if (dsl_dataset_tryown(ds, FALSE, dmu_recv_tag)) {
                  err = dsl_dataset_clone_swap(drc->drc_real_ds, ds,
                      drc->drc_force);
                  if (err)
                        dsl_dataset_disown(ds, dmu_recv_tag);
            } else {
                  err = EBUSY;
                  dsl_dataset_rele(ds, dmu_recv_tag);
            }
            /* dsl_dataset_destroy() will disown the ds */
            (void) dsl_dataset_destroy(drc->drc_real_ds, dmu_recv_tag);
            if (err)
                  return (err);
      }

      resa.creation_time = drc->drc_drrb->drr_creation_time;
      resa.toguid = drc->drc_drrb->drr_toguid;
      resa.tosnap = drc->drc_tosnap;

      err = dsl_sync_task_do(ds->ds_dir->dd_pool,
          recv_end_check, recv_end_sync, ds, &resa, 3);
      if (err) {
            if (drc->drc_newfs) {
                  ASSERT(ds == drc->drc_real_ds);
                  (void) dsl_dataset_destroy(ds, dmu_recv_tag);
                  return (err);
            } else {
                  (void) dsl_dataset_rollback(ds, DMU_OST_NONE);
            }
      }

      /* release the hold from dmu_recv_begin */
      dsl_dataset_disown(ds, dmu_recv_tag);
      return (err);
}

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