1 files changed, 848 insertions, 0 deletions

diff --git a/uts/common/fs/zfs/dsl_pool.c b/uts/common/fs/zfs/dsl_pool.c
new file mode 100644
index 000000000000..700cc962865d
--- /dev/null
+++ b/uts/common/fs/zfs/dsl_pool.c
@@ -0,0 +1,848 @@
+/*
+ * 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ */
+
+#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/dsl_scan.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/dsl_deadlist.h>
+
+int zfs_no_write_throttle = 0;
+int zfs_write_limit_shift = 3;			/* 1/8th of physical memory */
+int zfs_txg_synctime_ms = 1000;		/* target millisecs to sync a txg */
+
+uint64_t zfs_write_limit_min = 32 << 20;	/* min write limit is 32MB */
+uint64_t zfs_write_limit_max = 0;		/* max data payload per txg */
+uint64_t zfs_write_limit_inflated = 0;
+uint64_t zfs_write_limit_override = 0;
+
+kmutex_t zfs_write_limit_lock;
+
+static pgcnt_t old_physmem = 0;
+
+int
+dsl_pool_open_special_dir(dsl_pool_t *dp, const char *name, dsl_dir_t **ddp)
+{
+	uint64_t obj;
+	int err;
+
+	err = zap_lookup(dp->dp_meta_objset,
+	    dp->dp_root_dir->dd_phys->dd_child_dir_zapobj,
+	    name, sizeof (obj), 1, &obj);
+	if (err)
+		return (err);
+
+	return (dsl_dir_open_obj(dp, obj, name, dp, ddp));
+}
+
+static dsl_pool_t *
+dsl_pool_open_impl(spa_t *spa, uint64_t txg)
+{
+	dsl_pool_t *dp;
+	blkptr_t *bp = spa_get_rootblkptr(spa);
+
+	dp = kmem_zalloc(sizeof (dsl_pool_t), KM_SLEEP);
+	dp->dp_spa = spa;
+	dp->dp_meta_rootbp = *bp;
+	rw_init(&dp->dp_config_rwlock, NULL, RW_DEFAULT, NULL);
+	dp->dp_write_limit = zfs_write_limit_min;
+	txg_init(dp, txg);
+
+	txg_list_create(&dp->dp_dirty_datasets,
+	    offsetof(dsl_dataset_t, ds_dirty_link));
+	txg_list_create(&dp->dp_dirty_dirs,
+	    offsetof(dsl_dir_t, dd_dirty_link));
+	txg_list_create(&dp->dp_sync_tasks,
+	    offsetof(dsl_sync_task_group_t, dstg_node));
+	list_create(&dp->dp_synced_datasets, sizeof (dsl_dataset_t),
+	    offsetof(dsl_dataset_t, ds_synced_link));
+
+	mutex_init(&dp->dp_lock, NULL, MUTEX_DEFAULT, NULL);
+
+	dp->dp_vnrele_taskq = taskq_create("zfs_vn_rele_taskq", 1, minclsyspri,
+	    1, 4, 0);
+
+	return (dp);
+}
+
+int
+dsl_pool_open(spa_t *spa, uint64_t txg, dsl_pool_t **dpp)
+{
+	int err;
+	dsl_pool_t *dp = dsl_pool_open_impl(spa, txg);
+	dsl_dir_t *dd;
+	dsl_dataset_t *ds;
+	uint64_t obj;
+
+	rw_enter(&dp->dp_config_rwlock, RW_WRITER);
+	err = dmu_objset_open_impl(spa, NULL, &dp->dp_meta_rootbp,
+	    &dp->dp_meta_objset);
+	if (err)
+		goto out;
+
+	err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
+	    DMU_POOL_ROOT_DATASET, sizeof (uint64_t), 1,
+	    &dp->dp_root_dir_obj);
+	if (err)
+		goto out;
+
+	err = dsl_dir_open_obj(dp, dp->dp_root_dir_obj,
+	    NULL, dp, &dp->dp_root_dir);
+	if (err)
+		goto out;
+
+	err = dsl_pool_open_special_dir(dp, MOS_DIR_NAME, &dp->dp_mos_dir);
+	if (err)
+		goto out;
+
+	if (spa_version(spa) >= SPA_VERSION_ORIGIN) {
+		err = dsl_pool_open_special_dir(dp, ORIGIN_DIR_NAME, &dd);
+		if (err)
+			goto out;
+		err = dsl_dataset_hold_obj(dp, dd->dd_phys->dd_head_dataset_obj,
+		    FTAG, &ds);
+		if (err == 0) {
+			err = dsl_dataset_hold_obj(dp,
+			    ds->ds_phys->ds_prev_snap_obj, dp,
+			    &dp->dp_origin_snap);
+			dsl_dataset_rele(ds, FTAG);
+		}
+		dsl_dir_close(dd, dp);
+		if (err)
+			goto out;
+	}
+
+	if (spa_version(spa) >= SPA_VERSION_DEADLISTS) {
+		err = dsl_pool_open_special_dir(dp, FREE_DIR_NAME,
+		    &dp->dp_free_dir);
+		if (err)
+			goto out;
+
+		err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
+		    DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj);
+		if (err)
+			goto out;
+		VERIFY3U(0, ==, bpobj_open(&dp->dp_free_bpobj,
+		    dp->dp_meta_objset, obj));
+	}
+
+	err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
+	    DMU_POOL_TMP_USERREFS, sizeof (uint64_t), 1,
+	    &dp->dp_tmp_userrefs_obj);
+	if (err == ENOENT)
+		err = 0;
+	if (err)
+		goto out;
+
+	err = dsl_scan_init(dp, txg);
+
+out:
+	rw_exit(&dp->dp_config_rwlock);
+	if (err)
+		dsl_pool_close(dp);
+	else
+		*dpp = dp;
+
+	return (err);
+}
+
+void
+dsl_pool_close(dsl_pool_t *dp)
+{
+	/* drop our references from dsl_pool_open() */
+
+	/*
+	 * Since we held the origin_snap from "syncing" context (which
+	 * includes pool-opening context), it actually only got a "ref"
+	 * and not a hold, so just drop that here.
+	 */
+	if (dp->dp_origin_snap)
+		dsl_dataset_drop_ref(dp->dp_origin_snap, dp);
+	if (dp->dp_mos_dir)
+		dsl_dir_close(dp->dp_mos_dir, dp);
+	if (dp->dp_free_dir)
+		dsl_dir_close(dp->dp_free_dir, dp);
+	if (dp->dp_root_dir)
+		dsl_dir_close(dp->dp_root_dir, dp);
+
+	bpobj_close(&dp->dp_free_bpobj);
+
+	/* undo the dmu_objset_open_impl(mos) from dsl_pool_open() */
+	if (dp->dp_meta_objset)
+		dmu_objset_evict(dp->dp_meta_objset);
+
+	txg_list_destroy(&dp->dp_dirty_datasets);
+	txg_list_destroy(&dp->dp_sync_tasks);
+	txg_list_destroy(&dp->dp_dirty_dirs);
+	list_destroy(&dp->dp_synced_datasets);
+
+	arc_flush(dp->dp_spa);
+	txg_fini(dp);
+	dsl_scan_fini(dp);
+	rw_destroy(&dp->dp_config_rwlock);
+	mutex_destroy(&dp->dp_lock);
+	taskq_destroy(dp->dp_vnrele_taskq);
+	if (dp->dp_blkstats)
+		kmem_free(dp->dp_blkstats, sizeof (zfs_all_blkstats_t));
+	kmem_free(dp, sizeof (dsl_pool_t));
+}
+
+dsl_pool_t *
+dsl_pool_create(spa_t *spa, nvlist_t *zplprops, uint64_t txg)
+{
+	int err;
+	dsl_pool_t *dp = dsl_pool_open_impl(spa, txg);
+	dmu_tx_t *tx = dmu_tx_create_assigned(dp, txg);
+	objset_t *os;
+	dsl_dataset_t *ds;
+	uint64_t obj;
+
+	/* create and open the MOS (meta-objset) */
+	dp->dp_meta_objset = dmu_objset_create_impl(spa,
+	    NULL, &dp->dp_meta_rootbp, DMU_OST_META, tx);
+
+	/* create the pool directory */
+	err = zap_create_claim(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
+	    DMU_OT_OBJECT_DIRECTORY, DMU_OT_NONE, 0, tx);
+	ASSERT3U(err, ==, 0);
+
+	/* Initialize scan structures */
+	VERIFY3U(0, ==, dsl_scan_init(dp, txg));
+
+	/* create and open the root dir */
+	dp->dp_root_dir_obj = dsl_dir_create_sync(dp, NULL, NULL, tx);
+	VERIFY(0 == dsl_dir_open_obj(dp, dp->dp_root_dir_obj,
+	    NULL, dp, &dp->dp_root_dir));
+
+	/* create and open the meta-objset dir */
+	(void) dsl_dir_create_sync(dp, dp->dp_root_dir, MOS_DIR_NAME, tx);
+	VERIFY(0 == dsl_pool_open_special_dir(dp,
+	    MOS_DIR_NAME, &dp->dp_mos_dir));
+
+	if (spa_version(spa) >= SPA_VERSION_DEADLISTS) {
+		/* create and open the free dir */
+		(void) dsl_dir_create_sync(dp, dp->dp_root_dir,
+		    FREE_DIR_NAME, tx);
+		VERIFY(0 == dsl_pool_open_special_dir(dp,
+		    FREE_DIR_NAME, &dp->dp_free_dir));
+
+		/* create and open the free_bplist */
+		obj = bpobj_alloc(dp->dp_meta_objset, SPA_MAXBLOCKSIZE, tx);
+		VERIFY(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
+		    DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj, tx) == 0);
+		VERIFY3U(0, ==, bpobj_open(&dp->dp_free_bpobj,
+		    dp->dp_meta_objset, obj));
+	}
+
+	if (spa_version(spa) >= SPA_VERSION_DSL_SCRUB)
+		dsl_pool_create_origin(dp, tx);
+
+	/* create the root dataset */
+	obj = dsl_dataset_create_sync_dd(dp->dp_root_dir, NULL, 0, tx);
+
+	/* create the root objset */
+	VERIFY(0 == dsl_dataset_hold_obj(dp, obj, FTAG, &ds));
+	os = dmu_objset_create_impl(dp->dp_spa, ds,
+	    dsl_dataset_get_blkptr(ds), DMU_OST_ZFS, tx);
+#ifdef _KERNEL
+	zfs_create_fs(os, kcred, zplprops, tx);
+#endif
+	dsl_dataset_rele(ds, FTAG);
+
+	dmu_tx_commit(tx);
+
+	return (dp);
+}
+
+static int
+deadlist_enqueue_cb(void *arg, const blkptr_t *bp, dmu_tx_t *tx)
+{
+	dsl_deadlist_t *dl = arg;
+	dsl_deadlist_insert(dl, bp, tx);
+	return (0);
+}
+
+void
+dsl_pool_sync(dsl_pool_t *dp, uint64_t txg)
+{
+	zio_t *zio;
+	dmu_tx_t *tx;
+	dsl_dir_t *dd;
+	dsl_dataset_t *ds;
+	dsl_sync_task_group_t *dstg;
+	objset_t *mos = dp->dp_meta_objset;
+	hrtime_t start, write_time;
+	uint64_t data_written;
+	int err;
+
+	/*
+	 * We need to copy dp_space_towrite() before doing
+	 * dsl_sync_task_group_sync(), because
+	 * dsl_dataset_snapshot_reserve_space() will increase
+	 * dp_space_towrite but not actually write anything.
+	 */
+	data_written = dp->dp_space_towrite[txg & TXG_MASK];
+
+	tx = dmu_tx_create_assigned(dp, txg);
+
+	dp->dp_read_overhead = 0;
+	start = gethrtime();
+
+	zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
+	while (ds = txg_list_remove(&dp->dp_dirty_datasets, txg)) {
+		/*
+		 * We must not sync any non-MOS datasets twice, because
+		 * we may have taken a snapshot of them.  However, we
+		 * may sync newly-created datasets on pass 2.
+		 */
+		ASSERT(!list_link_active(&ds->ds_synced_link));
+		list_insert_tail(&dp->dp_synced_datasets, ds);
+		dsl_dataset_sync(ds, zio, tx);
+	}
+	DTRACE_PROBE(pool_sync__1setup);
+	err = zio_wait(zio);
+
+	write_time = gethrtime() - start;
+	ASSERT(err == 0);
+	DTRACE_PROBE(pool_sync__2rootzio);
+
+	for (ds = list_head(&dp->dp_synced_datasets); ds;
+	    ds = list_next(&dp->dp_synced_datasets, ds))
+		dmu_objset_do_userquota_updates(ds->ds_objset, tx);
+
+	/*
+	 * Sync the datasets again to push out the changes due to
+	 * userspace updates.  This must be done before we process the
+	 * sync tasks, because that could cause a snapshot of a dataset
+	 * whose ds_bp will be rewritten when we do this 2nd sync.
+	 */
+	zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
+	while (ds = txg_list_remove(&dp->dp_dirty_datasets, txg)) {
+		ASSERT(list_link_active(&ds->ds_synced_link));
+		dmu_buf_rele(ds->ds_dbuf, ds);
+		dsl_dataset_sync(ds, zio, tx);
+	}
+	err = zio_wait(zio);
+
+	/*
+	 * Move dead blocks from the pending deadlist to the on-disk
+	 * deadlist.
+	 */
+	for (ds = list_head(&dp->dp_synced_datasets); ds;
+	    ds = list_next(&dp->dp_synced_datasets, ds)) {
+		bplist_iterate(&ds->ds_pending_deadlist,
+		    deadlist_enqueue_cb, &ds->ds_deadlist, tx);
+	}
+
+	while (dstg = txg_list_remove(&dp->dp_sync_tasks, txg)) {
+		/*
+		 * No more sync tasks should have been added while we
+		 * were syncing.
+		 */
+		ASSERT(spa_sync_pass(dp->dp_spa) == 1);
+		dsl_sync_task_group_sync(dstg, tx);
+	}
+	DTRACE_PROBE(pool_sync__3task);
+
+	start = gethrtime();
+	while (dd = txg_list_remove(&dp->dp_dirty_dirs, txg))
+		dsl_dir_sync(dd, tx);
+	write_time += gethrtime() - start;
+
+	start = gethrtime();
+	if (list_head(&mos->os_dirty_dnodes[txg & TXG_MASK]) != NULL ||
+	    list_head(&mos->os_free_dnodes[txg & TXG_MASK]) != NULL) {
+		zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
+		dmu_objset_sync(mos, zio, tx);
+		err = zio_wait(zio);
+		ASSERT(err == 0);
+		dprintf_bp(&dp->dp_meta_rootbp, "meta objset rootbp is %s", "");
+		spa_set_rootblkptr(dp->dp_spa, &dp->dp_meta_rootbp);
+	}
+	write_time += gethrtime() - start;
+	DTRACE_PROBE2(pool_sync__4io, hrtime_t, write_time,
+	    hrtime_t, dp->dp_read_overhead);
+	write_time -= dp->dp_read_overhead;
+
+	dmu_tx_commit(tx);
+
+	dp->dp_space_towrite[txg & TXG_MASK] = 0;
+	ASSERT(dp->dp_tempreserved[txg & TXG_MASK] == 0);
+
+	/*
+	 * If the write limit max has not been explicitly set, set it
+	 * to a fraction of available physical memory (default 1/8th).
+	 * Note that we must inflate the limit because the spa
+	 * inflates write sizes to account for data replication.
+	 * Check this each sync phase to catch changing memory size.
+	 */
+	if (physmem != old_physmem && zfs_write_limit_shift) {
+		mutex_enter(&zfs_write_limit_lock);
+		old_physmem = physmem;
+		zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
+		zfs_write_limit_inflated = MAX(zfs_write_limit_min,
+		    spa_get_asize(dp->dp_spa, zfs_write_limit_max));
+		mutex_exit(&zfs_write_limit_lock);
+	}
+
+	/*
+	 * Attempt to keep the sync time consistent by adjusting the
+	 * amount of write traffic allowed into each transaction group.
+	 * Weight the throughput calculation towards the current value:
+	 * 	thru = 3/4 old_thru + 1/4 new_thru
+	 *
+	 * Note: write_time is in nanosecs, so write_time/MICROSEC
+	 * yields millisecs
+	 */
+	ASSERT(zfs_write_limit_min > 0);
+	if (data_written > zfs_write_limit_min / 8 && write_time > MICROSEC) {
+		uint64_t throughput = data_written / (write_time / MICROSEC);
+
+		if (dp->dp_throughput)
+			dp->dp_throughput = throughput / 4 +
+			    3 * dp->dp_throughput / 4;
+		else
+			dp->dp_throughput = throughput;
+		dp->dp_write_limit = MIN(zfs_write_limit_inflated,
+		    MAX(zfs_write_limit_min,
+		    dp->dp_throughput * zfs_txg_synctime_ms));
+	}
+}
+
+void
+dsl_pool_sync_done(dsl_pool_t *dp, uint64_t txg)
+{
+	dsl_dataset_t *ds;
+	objset_t *os;
+
+	while (ds = list_head(&dp->dp_synced_datasets)) {
+		list_remove(&dp->dp_synced_datasets, ds);
+		os = ds->ds_objset;
+		zil_clean(os->os_zil, txg);
+		ASSERT(!dmu_objset_is_dirty(os, txg));
+		dmu_buf_rele(ds->ds_dbuf, ds);
+	}
+	ASSERT(!dmu_objset_is_dirty(dp->dp_meta_objset, txg));
+}
+
+/*
+ * TRUE if the current thread is the tx_sync_thread or if we
+ * are being called from SPA context during pool initialization.
+ */
+int
+dsl_pool_sync_context(dsl_pool_t *dp)
+{
+	return (curthread == dp->dp_tx.tx_sync_thread ||
+	    spa_get_dsl(dp->dp_spa) == NULL);
+}
+
+uint64_t
+dsl_pool_adjustedsize(dsl_pool_t *dp, boolean_t netfree)
+{
+	uint64_t space, resv;
+
+	/*
+	 * Reserve about 1.6% (1/64), or at least 32MB, for allocation
+	 * efficiency.
+	 * XXX The intent log is not accounted for, so it must fit
+	 * within this slop.
+	 *
+	 * If we're trying to assess whether it's OK to do a free,
+	 * cut the reservation in half to allow forward progress
+	 * (e.g. make it possible to rm(1) files from a full pool).
+	 */
+	space = spa_get_dspace(dp->dp_spa);
+	resv = MAX(space >> 6, SPA_MINDEVSIZE >> 1);
+	if (netfree)
+		resv >>= 1;
+
+	return (space - resv);
+}
+
+int
+dsl_pool_tempreserve_space(dsl_pool_t *dp, uint64_t space, dmu_tx_t *tx)
+{
+	uint64_t reserved = 0;
+	uint64_t write_limit = (zfs_write_limit_override ?
+	    zfs_write_limit_override : dp->dp_write_limit);
+
+	if (zfs_no_write_throttle) {
+		atomic_add_64(&dp->dp_tempreserved[tx->tx_txg & TXG_MASK],
+		    space);
+		return (0);
+	}
+
+	/*
+	 * Check to see if we have exceeded the maximum allowed IO for
+	 * this transaction group.  We can do this without locks since
+	 * a little slop here is ok.  Note that we do the reserved check
+	 * with only half the requested reserve: this is because the
+	 * reserve requests are worst-case, and we really don't want to
+	 * throttle based off of worst-case estimates.
+	 */
+	if (write_limit > 0) {
+		reserved = dp->dp_space_towrite[tx->tx_txg & TXG_MASK]
+		    + dp->dp_tempreserved[tx->tx_txg & TXG_MASK] / 2;
+
+		if (reserved && reserved > write_limit)
+			return (ERESTART);
+	}
+
+	atomic_add_64(&dp->dp_tempreserved[tx->tx_txg & TXG_MASK], space);
+
+	/*
+	 * If this transaction group is over 7/8ths capacity, delay
+	 * the caller 1 clock tick.  This will slow down the "fill"
+	 * rate until the sync process can catch up with us.
+	 */
+	if (reserved && reserved > (write_limit - (write_limit >> 3)))
+		txg_delay(dp, tx->tx_txg, 1);
+
+	return (0);
+}
+
+void
+dsl_pool_tempreserve_clear(dsl_pool_t *dp, int64_t space, dmu_tx_t *tx)
+{
+	ASSERT(dp->dp_tempreserved[tx->tx_txg & TXG_MASK] >= space);
+	atomic_add_64(&dp->dp_tempreserved[tx->tx_txg & TXG_MASK], -space);
+}
+
+void
+dsl_pool_memory_pressure(dsl_pool_t *dp)
+{
+	uint64_t space_inuse = 0;
+	int i;
+
+	if (dp->dp_write_limit == zfs_write_limit_min)
+		return;
+
+	for (i = 0; i < TXG_SIZE; i++) {
+		space_inuse += dp->dp_space_towrite[i];
+		space_inuse += dp->dp_tempreserved[i];
+	}
+	dp->dp_write_limit = MAX(zfs_write_limit_min,
+	    MIN(dp->dp_write_limit, space_inuse / 4));
+}
+
+void
+dsl_pool_willuse_space(dsl_pool_t *dp, int64_t space, dmu_tx_t *tx)
+{
+	if (space > 0) {
+		mutex_enter(&dp->dp_lock);
+		dp->dp_space_towrite[tx->tx_txg & TXG_MASK] += space;
+		mutex_exit(&dp->dp_lock);
+	}
+}
+
+/* ARGSUSED */
+static int
+upgrade_clones_cb(spa_t *spa, uint64_t dsobj, const char *dsname, void *arg)
+{
+	dmu_tx_t *tx = arg;
+	dsl_dataset_t *ds, *prev = NULL;
+	int err;
+	dsl_pool_t *dp = spa_get_dsl(spa);
+
+	err = dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds);
+	if (err)
+		return (err);
+
+	while (ds->ds_phys->ds_prev_snap_obj != 0) {
+		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 (prev->ds_phys->ds_next_snap_obj != ds->ds_object)
+			break;
+		dsl_dataset_rele(ds, FTAG);
+		ds = prev;
+		prev = NULL;
+	}
+
+	if (prev == NULL) {
+		prev = dp->dp_origin_snap;
+
+		/*
+		 * The $ORIGIN can't have any data, or the accounting
+		 * will be wrong.
+		 */
+		ASSERT(prev->ds_phys->ds_bp.blk_birth == 0);
+
+		/* The origin doesn't get attached to itself */
+		if (ds->ds_object == prev->ds_object) {
+			dsl_dataset_rele(ds, FTAG);
+			return (0);
+		}
+
+		dmu_buf_will_dirty(ds->ds_dbuf, tx);
+		ds->ds_phys->ds_prev_snap_obj = prev->ds_object;
+		ds->ds_phys->ds_prev_snap_txg = prev->ds_phys->ds_creation_txg;
+
+		dmu_buf_will_dirty(ds->ds_dir->dd_dbuf, tx);
+		ds->ds_dir->dd_phys->dd_origin_obj = prev->ds_object;
+
+		dmu_buf_will_dirty(prev->ds_dbuf, tx);
+		prev->ds_phys->ds_num_children++;
+
+		if (ds->ds_phys->ds_next_snap_obj == 0) {
+			ASSERT(ds->ds_prev == NULL);
+			VERIFY(0 == dsl_dataset_hold_obj(dp,
+			    ds->ds_phys->ds_prev_snap_obj, ds, &ds->ds_prev));
+		}
+	}
+
+	ASSERT(ds->ds_dir->dd_phys->dd_origin_obj == prev->ds_object);
+	ASSERT(ds->ds_phys->ds_prev_snap_obj == prev->ds_object);
+
+	if (prev->ds_phys->ds_next_clones_obj == 0) {
+		dmu_buf_will_dirty(prev->ds_dbuf, tx);
+		prev->ds_phys->ds_next_clones_obj =
+		    zap_create(dp->dp_meta_objset,
+		    DMU_OT_NEXT_CLONES, DMU_OT_NONE, 0, tx);
+	}
+	VERIFY(0 == zap_add_int(dp->dp_meta_objset,
+	    prev->ds_phys->ds_next_clones_obj, ds->ds_object, tx));
+
+	dsl_dataset_rele(ds, FTAG);
+	if (prev != dp->dp_origin_snap)
+		dsl_dataset_rele(prev, FTAG);
+	return (0);
+}
+
+void
+dsl_pool_upgrade_clones(dsl_pool_t *dp, dmu_tx_t *tx)
+{
+	ASSERT(dmu_tx_is_syncing(tx));
+	ASSERT(dp->dp_origin_snap != NULL);
+
+	VERIFY3U(0, ==, dmu_objset_find_spa(dp->dp_spa, NULL, upgrade_clones_cb,
+	    tx, DS_FIND_CHILDREN));
+}
+
+/* ARGSUSED */
+static int
+upgrade_dir_clones_cb(spa_t *spa, uint64_t dsobj, const char *dsname, void *arg)
+{
+	dmu_tx_t *tx = arg;
+	dsl_dataset_t *ds;
+	dsl_pool_t *dp = spa_get_dsl(spa);
+	objset_t *mos = dp->dp_meta_objset;
+
+	VERIFY3U(0, ==, dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds));
+
+	if (ds->ds_dir->dd_phys->dd_origin_obj) {
+		dsl_dataset_t *origin;
+
+		VERIFY3U(0, ==, dsl_dataset_hold_obj(dp,
+		    ds->ds_dir->dd_phys->dd_origin_obj, FTAG, &origin));
+
+		if (origin->ds_dir->dd_phys->dd_clones == 0) {
+			dmu_buf_will_dirty(origin->ds_dir->dd_dbuf, tx);
+			origin->ds_dir->dd_phys->dd_clones = zap_create(mos,
+			    DMU_OT_DSL_CLONES, DMU_OT_NONE, 0, tx);
+		}
+
+		VERIFY3U(0, ==, zap_add_int(dp->dp_meta_objset,
+		    origin->ds_dir->dd_phys->dd_clones, dsobj, tx));
+
+		dsl_dataset_rele(origin, FTAG);
+	}
+
+	dsl_dataset_rele(ds, FTAG);
+	return (0);
+}
+
+void
+dsl_pool_upgrade_dir_clones(dsl_pool_t *dp, dmu_tx_t *tx)
+{
+	ASSERT(dmu_tx_is_syncing(tx));
+	uint64_t obj;
+
+	(void) dsl_dir_create_sync(dp, dp->dp_root_dir, FREE_DIR_NAME, tx);
+	VERIFY(0 == dsl_pool_open_special_dir(dp,
+	    FREE_DIR_NAME, &dp->dp_free_dir));
+
+	/*
+	 * We can't use bpobj_alloc(), because spa_version() still
+	 * returns the old version, and we need a new-version bpobj with
+	 * subobj support.  So call dmu_object_alloc() directly.
+	 */
+	obj = dmu_object_alloc(dp->dp_meta_objset, DMU_OT_BPOBJ,
+	    SPA_MAXBLOCKSIZE, DMU_OT_BPOBJ_HDR, sizeof (bpobj_phys_t), tx);
+	VERIFY3U(0, ==, zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
+	    DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj, tx));
+	VERIFY3U(0, ==, bpobj_open(&dp->dp_free_bpobj,
+	    dp->dp_meta_objset, obj));
+
+	VERIFY3U(0, ==, dmu_objset_find_spa(dp->dp_spa, NULL,
+	    upgrade_dir_clones_cb, tx, DS_FIND_CHILDREN));
+}
+
+void
+dsl_pool_create_origin(dsl_pool_t *dp, dmu_tx_t *tx)
+{
+	uint64_t dsobj;
+	dsl_dataset_t *ds;
+
+	ASSERT(dmu_tx_is_syncing(tx));
+	ASSERT(dp->dp_origin_snap == NULL);
+
+	/* create the origin dir, ds, & snap-ds */
+	rw_enter(&dp->dp_config_rwlock, RW_WRITER);
+	dsobj = dsl_dataset_create_sync(dp->dp_root_dir, ORIGIN_DIR_NAME,
+	    NULL, 0, kcred, tx);
+	VERIFY(0 == dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds));
+	dsl_dataset_snapshot_sync(ds, ORIGIN_DIR_NAME, tx);
+	VERIFY(0 == dsl_dataset_hold_obj(dp, ds->ds_phys->ds_prev_snap_obj,
+	    dp, &dp->dp_origin_snap));
+	dsl_dataset_rele(ds, FTAG);
+	rw_exit(&dp->dp_config_rwlock);
+}
+
+taskq_t *
+dsl_pool_vnrele_taskq(dsl_pool_t *dp)
+{
+	return (dp->dp_vnrele_taskq);
+}
+
+/*
+ * Walk through the pool-wide zap object of temporary snapshot user holds
+ * and release them.
+ */
+void
+dsl_pool_clean_tmp_userrefs(dsl_pool_t *dp)
+{
+	zap_attribute_t za;
+	zap_cursor_t zc;
+	objset_t *mos = dp->dp_meta_objset;
+	uint64_t zapobj = dp->dp_tmp_userrefs_obj;
+
+	if (zapobj == 0)
+		return;
+	ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS);
+
+	for (zap_cursor_init(&zc, mos, zapobj);
+	    zap_cursor_retrieve(&zc, &za) == 0;
+	    zap_cursor_advance(&zc)) {
+		char *htag;
+		uint64_t dsobj;
+
+		htag = strchr(za.za_name, '-');
+		*htag = '\0';
+		++htag;
+		dsobj = strtonum(za.za_name, NULL);
+		(void) dsl_dataset_user_release_tmp(dp, dsobj, htag, B_FALSE);
+	}
+	zap_cursor_fini(&zc);
+}
+
+/*
+ * Create the pool-wide zap object for storing temporary snapshot holds.
+ */
+void
+dsl_pool_user_hold_create_obj(dsl_pool_t *dp, dmu_tx_t *tx)
+{
+	objset_t *mos = dp->dp_meta_objset;
+
+	ASSERT(dp->dp_tmp_userrefs_obj == 0);
+	ASSERT(dmu_tx_is_syncing(tx));
+
+	dp->dp_tmp_userrefs_obj = zap_create(mos, DMU_OT_USERREFS,
+	    DMU_OT_NONE, 0, tx);
+
+	VERIFY(zap_add(mos, DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_TMP_USERREFS,
+	    sizeof (uint64_t), 1, &dp->dp_tmp_userrefs_obj, tx) == 0);
+}
+
+static int
+dsl_pool_user_hold_rele_impl(dsl_pool_t *dp, uint64_t dsobj,
+    const char *tag, uint64_t *now, dmu_tx_t *tx, boolean_t holding)
+{
+	objset_t *mos = dp->dp_meta_objset;
+	uint64_t zapobj = dp->dp_tmp_userrefs_obj;
+	char *name;
+	int error;
+
+	ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS);
+	ASSERT(dmu_tx_is_syncing(tx));
+
+	/*
+	 * If the pool was created prior to SPA_VERSION_USERREFS, the
+	 * zap object for temporary holds might not exist yet.
+	 */
+	if (zapobj == 0) {
+		if (holding) {
+			dsl_pool_user_hold_create_obj(dp, tx);
+			zapobj = dp->dp_tmp_userrefs_obj;
+		} else {
+			return (ENOENT);
+		}
+	}
+
+	name = kmem_asprintf("%llx-%s", (u_longlong_t)dsobj, tag);
+	if (holding)
+		error = zap_add(mos, zapobj, name, 8, 1, now, tx);
+	else
+		error = zap_remove(mos, zapobj, name, tx);
+	strfree(name);
+
+	return (error);
+}
+
+/*
+ * Add a temporary hold for the given dataset object and tag.
+ */
+int
+dsl_pool_user_hold(dsl_pool_t *dp, uint64_t dsobj, const char *tag,
+    uint64_t *now, dmu_tx_t *tx)
+{
+	return (dsl_pool_user_hold_rele_impl(dp, dsobj, tag, now, tx, B_TRUE));
+}
+
+/*
+ * Release a temporary hold for the given dataset object and tag.
+ */
+int
+dsl_pool_user_release(dsl_pool_t *dp, uint64_t dsobj, const char *tag,
+    dmu_tx_t *tx)
+{
+	return (dsl_pool_user_hold_rele_impl(dp, dsobj, tag, NULL,
+	    tx, B_FALSE));
+}