Illumos #3464

3464 zfs synctask code needs restructuring
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>

References:
  https://www.illumos.org/issues/3464
  illumos/illumos-gate@3b2aab1880

Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1495

cmd/zdb/zdb.c

@@ -1725,7 +1725,9 @@ dump_dir(objset_t *os)
 	int print_header = 1;
 	int i, error;
 
+	dsl_pool_config_enter(dmu_objset_pool(os), FTAG);
 	dmu_objset_fast_stat(os, &dds);
+	dsl_pool_config_exit(dmu_objset_pool(os), FTAG);
 
 	if (dds.dds_type < DMU_OST_NUMTYPES)
 		type = objset_types[dds.dds_type];
@@ -2171,7 +2173,6 @@ zdb_blkptr_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 
 		zio_nowait(zio_read(NULL, spa, bp, data, size,
 		    zdb_blkptr_done, zcb, ZIO_PRIORITY_ASYNC_READ, flags, zb));
-
 	}
 
 	zcb->zcb_readfails = 0;
@@ -2365,8 +2366,10 @@ dump_block_stats(spa_t *spa)
 	 */
 	(void) bpobj_iterate_nofree(&spa->spa_deferred_bpobj,
 	    count_block_cb, &zcb, NULL);
-	(void) bpobj_iterate_nofree(&spa->spa_dsl_pool->dp_free_bpobj,
-	    count_block_cb, &zcb, NULL);
+	if (spa_version(spa) >= SPA_VERSION_DEADLISTS) {
+		(void) bpobj_iterate_nofree(&spa->spa_dsl_pool->dp_free_bpobj,
+		    count_block_cb, &zcb, NULL);
+	}
 	if (spa_feature_is_active(spa,
 	    &spa_feature_table[SPA_FEATURE_ASYNC_DESTROY])) {
 		VERIFY3U(0, ==, bptree_iterate(spa->spa_meta_objset,

cmd/zfs/zfs_main.c

@@ -892,6 +892,7 @@ typedef struct destroy_cbdata {
 	boolean_t	cb_parsable;
 	boolean_t	cb_dryrun;
 	nvlist_t	*cb_nvl;
+	nvlist_t	*cb_batchedsnaps;
 
 	/* first snap in contiguous run */
 	char		*cb_firstsnap;
@@ -988,9 +989,27 @@ destroy_callback(zfs_handle_t *zhp, void *data)
 		zfs_close(zhp);
 		return (0);
 	}
+	if (cb->cb_dryrun) {
+		zfs_close(zhp);
+		return (0);
+	}
 
-	if (!cb->cb_dryrun) {
-		if (zfs_unmount(zhp, NULL, cb->cb_force ? MS_FORCE : 0) != 0 ||
+	/*
+	 * We batch up all contiguous snapshots (even of different
+	 * filesystems) and destroy them with one ioctl.  We can't
+	 * simply do all snap deletions and then all fs deletions,
+	 * because we must delete a clone before its origin.
+	 */
+	if (zfs_get_type(zhp) == ZFS_TYPE_SNAPSHOT) {
+		fnvlist_add_boolean(cb->cb_batchedsnaps, name);
+	} else {
+		int error = zfs_destroy_snaps_nvl(g_zfs,
+		    cb->cb_batchedsnaps, B_FALSE);
+		fnvlist_free(cb->cb_batchedsnaps);
+		cb->cb_batchedsnaps = fnvlist_alloc();
+
+		if (error != 0 ||
+		    zfs_unmount(zhp, NULL, cb->cb_force ? MS_FORCE : 0) != 0 ||
 		    zfs_destroy(zhp, cb->cb_defer_destroy) != 0) {
 			zfs_close(zhp);
 			return (-1);
@@ -1146,8 +1165,10 @@ static int
 zfs_do_destroy(int argc, char **argv)
 {
 	destroy_cbdata_t cb = { 0 };
+	int rv = 0;
+	int err = 0;
 	int c;
-	zfs_handle_t *zhp;
+	zfs_handle_t *zhp = NULL;
 	char *at;
 	zfs_type_t type = ZFS_TYPE_DATASET;
 
@@ -1201,11 +1222,9 @@ zfs_do_destroy(int argc, char **argv)
 
 	at = strchr(argv[0], '@');
 	if (at != NULL) {
-		int err = 0;
 
 		/* Build the list of snaps to destroy in cb_nvl. */
-		if (nvlist_alloc(&cb.cb_nvl, NV_UNIQUE_NAME, 0) != 0)
-			nomem();
+		cb.cb_nvl = fnvlist_alloc();
 
 		*at = '\0';
 		zhp = zfs_open(g_zfs, argv[0],
@@ -1216,17 +1235,15 @@ zfs_do_destroy(int argc, char **argv)
 		cb.cb_snapspec = at + 1;
 		if (gather_snapshots(zfs_handle_dup(zhp), &cb) != 0 ||
 		    cb.cb_error) {
-			zfs_close(zhp);
-			nvlist_free(cb.cb_nvl);
-			return (1);
+			rv = 1;
+			goto out;
 		}
 
 		if (nvlist_empty(cb.cb_nvl)) {
 			(void) fprintf(stderr, gettext("could not find any "
 			    "snapshots to destroy; check snapshot names.\n"));
-			zfs_close(zhp);
-			nvlist_free(cb.cb_nvl);
-			return (1);
+			rv = 1;
+			goto out;
 		}
 
 		if (cb.cb_verbose) {
@@ -1245,18 +1262,26 @@ zfs_do_destroy(int argc, char **argv)
 		}
 
 		if (!cb.cb_dryrun) {
-			if (cb.cb_doclones)
+			if (cb.cb_doclones) {
+				cb.cb_batchedsnaps = fnvlist_alloc();
 				err = destroy_clones(&cb);
+				if (err == 0) {
+					err = zfs_destroy_snaps_nvl(g_zfs,
+					    cb.cb_batchedsnaps, B_FALSE);
+				}
+				if (err != 0) {
+					rv = 1;
+					goto out;
+				}
+			}
 			if (err == 0) {
-				err = zfs_destroy_snaps_nvl(zhp, cb.cb_nvl,
+				err = zfs_destroy_snaps_nvl(g_zfs, cb.cb_nvl,
 				    cb.cb_defer_destroy);
 			}
 		}
 
-		zfs_close(zhp);
-		nvlist_free(cb.cb_nvl);
 		if (err != 0)
-			return (1);
+			rv = 1;
 	} else {
 		/* Open the given dataset */
 		if ((zhp = zfs_open(g_zfs, argv[0], type)) == NULL)
@@ -1277,8 +1302,8 @@ zfs_do_destroy(int argc, char **argv)
 			    zfs_get_name(zhp));
 			(void) fprintf(stderr, gettext("use 'zpool destroy %s' "
 			    "to destroy the pool itself\n"), zfs_get_name(zhp));
-			zfs_close(zhp);
-			return (1);
+			rv = 1;
+			goto out;
 		}
 
 		/*
@@ -1288,30 +1313,42 @@ zfs_do_destroy(int argc, char **argv)
 		if (!cb.cb_doclones &&
 		    zfs_iter_dependents(zhp, B_TRUE, destroy_check_dependent,
 		    &cb) != 0) {
-			zfs_close(zhp);
-			return (1);
+			rv = 1;
+			goto out;
 		}
 
 		if (cb.cb_error) {
-			zfs_close(zhp);
-			return (1);
+			rv = 1;
+			goto out;
 		}
 
+		cb.cb_batchedsnaps = fnvlist_alloc();
 		if (zfs_iter_dependents(zhp, B_FALSE, destroy_callback,
 		    &cb) != 0) {
-			zfs_close(zhp);
-			return (1);
+			rv = 1;
+			goto out;
 		}
 
 		/*
 		 * Do the real thing.  The callback will close the
 		 * handle regardless of whether it succeeds or not.
 		 */
-		if (destroy_callback(zhp, &cb) != 0)
-			return (1);
+		err = destroy_callback(zhp, &cb);
+		zhp = NULL;
+		if (err == 0) {
+			err = zfs_destroy_snaps_nvl(g_zfs,
+			    cb.cb_batchedsnaps, cb.cb_defer_destroy);
+		}
+		if (err != 0)
+			rv = 1;
 	}
 
-	return (0);
+out:
+	fnvlist_free(cb.cb_batchedsnaps);
+	fnvlist_free(cb.cb_nvl);
+	if (zhp != NULL)
+		zfs_close(zhp);
+	return (rv);
 }
 
 static boolean_t
@@ -5081,28 +5118,12 @@ cleanup2:
 	return (error);
 }
 
-/*
- * zfs allow [-r] [-t] <tag> <snap> ...
- *
- *	-r	Recursively hold
- *	-t	Temporary hold (hidden option)
- *
- * Apply a user-hold with the given tag to the list of snapshots.
- */
 static int
 zfs_do_allow(int argc, char **argv)
 {
 	return (zfs_do_allow_unallow_impl(argc, argv, B_FALSE));
 }
 
-/*
- * zfs unallow [-r] [-t] <tag> <snap> ...
- *
- *	-r	Recursively hold
- *	-t	Temporary hold (hidden option)
- *
- * Apply a user-hold with the given tag to the list of snapshots.
- */
 static int
 zfs_do_unallow(int argc, char **argv)
 {
@@ -5116,7 +5137,6 @@ zfs_do_hold_rele_impl(int argc, char **argv, boolean_t holding)
 	int i;
 	const char *tag;
 	boolean_t recursive = B_FALSE;
-	boolean_t temphold = B_FALSE;
 	const char *opts = holding ? "rt" : "r";
 	int c;
 
@@ -5126,9 +5146,6 @@ zfs_do_hold_rele_impl(int argc, char **argv, boolean_t holding)
 		case 'r':
 			recursive = B_TRUE;
 			break;
-		case 't':
-			temphold = B_TRUE;
-			break;
 		case '?':
 			(void) fprintf(stderr, gettext("invalid option '%c'\n"),
 			    optopt);
@@ -5177,7 +5194,7 @@ zfs_do_hold_rele_impl(int argc, char **argv, boolean_t holding)
 		}
 		if (holding) {
 			if (zfs_hold(zhp, delim+1, tag, recursive,
-			    temphold, B_FALSE, -1, 0, 0) != 0)
+			    B_FALSE, -1) != 0)
 				++errors;
 		} else {
 			if (zfs_release(zhp, delim+1, tag, recursive) != 0)
@@ -5193,7 +5210,6 @@ zfs_do_hold_rele_impl(int argc, char **argv, boolean_t holding)
  * zfs hold [-r] [-t] <tag> <snap> ...
  *
  *	-r	Recursively hold
- *	-t	Temporary hold (hidden option)
  *
  * Apply a user-hold with the given tag to the list of snapshots.
  */

cmd/zhack/zhack.c

@@ -46,6 +46,7 @@
 #include <sys/zio_checksum.h>
 #include <sys/zio_compress.h>
 #include <sys/zfeature.h>
+#include <sys/dmu_tx.h>
 #undef ZFS_MAXNAMELEN
 #include <libzfs.h>
 
@@ -123,7 +124,7 @@ import_pool(const char *target, boolean_t readonly)
 	spa_t *spa;
 	nvpair_t *elem;
 	nvlist_t *props;
-	const char *name;
+	char *name;
 
 	kernel_init(readonly ? FREAD : (FREAD | FWRITE));
 	g_zfs = libzfs_init();
@@ -273,10 +274,10 @@ zhack_do_feature_stat(int argc, char **argv)
 }
 
 static void
-feature_enable_sync(void *arg1, void *arg2, dmu_tx_t *tx)
+feature_enable_sync(void *arg, dmu_tx_t *tx)
 {
-	spa_t *spa = arg1;
-	zfeature_info_t *feature = arg2;
+	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
+	zfeature_info_t *feature = arg;
 
 	spa_feature_enable(spa, feature, tx);
 	spa_history_log_internal(spa, "zhack enable feature", tx,
@@ -344,8 +345,8 @@ zhack_do_feature_enable(int argc, char **argv)
 	if (0 == zap_contains(mos, spa->spa_feat_desc_obj, feature.fi_guid))
 		fatal("feature already enabled: %s", feature.fi_guid);
 
-	VERIFY3U(0, ==, dsl_sync_task_do(spa->spa_dsl_pool, NULL,
-	    feature_enable_sync, spa, &feature, 5));
+	VERIFY0(dsl_sync_task(spa_name(spa), NULL,
+	    feature_enable_sync, &feature, 5));
 
 	spa_close(spa, FTAG);
 
@@ -353,10 +354,10 @@ zhack_do_feature_enable(int argc, char **argv)
 }
 
 static void
-feature_incr_sync(void *arg1, void *arg2, dmu_tx_t *tx)
+feature_incr_sync(void *arg, dmu_tx_t *tx)
 {
-	spa_t *spa = arg1;
-	zfeature_info_t *feature = arg2;
+	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
+	zfeature_info_t *feature = arg;
 
 	spa_feature_incr(spa, feature, tx);
 	spa_history_log_internal(spa, "zhack feature incr", tx,
@@ -364,10 +365,10 @@ feature_incr_sync(void *arg1, void *arg2, dmu_tx_t *tx)
 }
 
 static void
-feature_decr_sync(void *arg1, void *arg2, dmu_tx_t *tx)
+feature_decr_sync(void *arg, dmu_tx_t *tx)
 {
-	spa_t *spa = arg1;
-	zfeature_info_t *feature = arg2;
+	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
+	zfeature_info_t *feature = arg;
 
 	spa_feature_decr(spa, feature, tx);
 	spa_history_log_internal(spa, "zhack feature decr", tx,
@@ -442,8 +443,8 @@ zhack_do_feature_ref(int argc, char **argv)
 	if (decr && !spa_feature_is_active(spa, &feature))
 		fatal("feature refcount already 0: %s", feature.fi_guid);
 
-	VERIFY3U(0, ==, dsl_sync_task_do(spa->spa_dsl_pool, NULL,
-	    decr ? feature_decr_sync : feature_incr_sync, spa, &feature, 5));
+	VERIFY0(dsl_sync_task(spa_name(spa), NULL,
+	    decr ? feature_decr_sync : feature_incr_sync, &feature, 5));
 
 	spa_close(spa, FTAG);
 }

cmd/ztest/ztest.c

@@ -106,10 +106,12 @@
 #include <sys/metaslab_impl.h>
 #include <sys/dsl_prop.h>
 #include <sys/dsl_dataset.h>
+#include <sys/dsl_destroy.h>
 #include <sys/dsl_scan.h>
 #include <sys/zio_checksum.h>
 #include <sys/refcount.h>
 #include <sys/zfeature.h>
+#include <sys/dsl_userhold.h>
 #include <stdio.h>
 #include <stdio_ext.h>
 #include <stdlib.h>
@@ -367,7 +369,7 @@ ztest_info_t ztest_info[] = {
 	{ ztest_scrub,				1,	&zopt_rarely	},
 	{ ztest_spa_upgrade,			1,	&zopt_rarely	},
 	{ ztest_dsl_dataset_promote_busy,	1,	&zopt_rarely	},
-	{ ztest_vdev_attach_detach,		1,	&zopt_rarely	},
+	{ ztest_vdev_attach_detach,		1,	&zopt_sometimes	},
 	{ ztest_vdev_LUN_growth,		1,	&zopt_rarely	},
 	{ ztest_vdev_add_remove,		1,
 	    &ztest_opts.zo_vdevtime				},
@@ -1031,9 +1033,8 @@ ztest_dsl_prop_set_uint64(char *osname, zfs_prop_t prop, uint64_t value,
 	uint64_t curval;
 	int error;
 
-	error = dsl_prop_set(osname, propname,
-	    (inherit ? ZPROP_SRC_NONE : ZPROP_SRC_LOCAL),
-	    sizeof (value), 1, &value);
+	error = dsl_prop_set_int(osname, propname,
+	    (inherit ? ZPROP_SRC_NONE : ZPROP_SRC_LOCAL), value);
 
 	if (error == ENOSPC) {
 		ztest_record_enospc(FTAG);
@@ -1042,8 +1043,7 @@ ztest_dsl_prop_set_uint64(char *osname, zfs_prop_t prop, uint64_t value,
 	ASSERT0(error);
 
 	setpoint = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);
-	VERIFY3U(dsl_prop_get(osname, propname, sizeof (curval),
-	    1, &curval, setpoint), ==, 0);
+	VERIFY0(dsl_prop_get_integer(osname, propname, &curval, setpoint));
 
 	if (ztest_opts.zo_verbose >= 6) {
 		VERIFY(zfs_prop_index_to_string(prop, curval, &valname) == 0);
@@ -2484,8 +2484,7 @@ ztest_vdev_add_remove(ztest_ds_t *zd, uint64_t id)
 	int error;
 
 	mutex_enter(&ztest_vdev_lock);
-	leaves =
-		MAX(zs->zs_mirrors + zs->zs_splits, 1) * ztest_opts.zo_raidz;
+	leaves = MAX(zs->zs_mirrors + zs->zs_splits, 1) * ztest_opts.zo_raidz;
 
 	spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
 
@@ -2507,7 +2506,7 @@ ztest_vdev_add_remove(ztest_ds_t *zd, uint64_t id)
 		 * prevent a race between removing a slog (dmu_objset_find)
 		 * and destroying a dataset. Removing the slog will
 		 * grab a reference on the dataset which may cause
-		 * dmu_objset_destroy() to fail with EBUSY thus
+		 * dsl_destroy_head() to fail with EBUSY thus
 		 * leaving the dataset in an inconsistent state.
 		 */
 		rw_enter(&ztest_name_lock, RW_WRITER);
@@ -3196,7 +3195,7 @@ ztest_objset_destroy_cb(const char *name, void *arg)
 	/*
 	 * Verify that the dataset contains a directory object.
 	 */
-	VERIFY3U(0, ==, dmu_objset_hold(name, FTAG, &os));
+	VERIFY0(dmu_objset_own(name, DMU_OST_OTHER, B_TRUE, FTAG, &os));
 	error = dmu_object_info(os, ZTEST_DIROBJ, &doi);
 	if (error != ENOENT) {
 		/* We could have crashed in the middle of destroying it */
@@ -3204,12 +3203,16 @@ ztest_objset_destroy_cb(const char *name, void *arg)
 		ASSERT3U(doi.doi_type, ==, DMU_OT_ZAP_OTHER);
 		ASSERT3S(doi.doi_physical_blocks_512, >=, 0);
 	}
-	dmu_objset_rele(os, FTAG);
+	dmu_objset_disown(os, FTAG);
 
 	/*
 	 * Destroy the dataset.
 	 */
-	VERIFY3U(0, ==, dmu_objset_destroy(name, B_FALSE));
+	if (strchr(name, '@') != NULL) {
+		VERIFY0(dsl_destroy_snapshot(name, B_FALSE));
+	} else {
+		VERIFY0(dsl_destroy_head(name));
+	}
 	return (0);
 }
 
@@ -3219,16 +3222,17 @@ ztest_snapshot_create(char *osname, uint64_t id)
 	char snapname[MAXNAMELEN];
 	int error;
 
-	(void) snprintf(snapname, MAXNAMELEN, "%s@%llu", osname,
-	    (u_longlong_t)id);
+	(void) snprintf(snapname, sizeof (snapname), "%llu", (u_longlong_t)id);
 
-	error = dmu_objset_snapshot_one(osname, strchr(snapname, '@') + 1);
+	error = dmu_objset_snapshot_one(osname, snapname);
 	if (error == ENOSPC) {
 		ztest_record_enospc(FTAG);
 		return (B_FALSE);
 	}
-	if (error != 0 && error != EEXIST)
-		fatal(0, "ztest_snapshot_create(%s) = %d", snapname, error);
+	if (error != 0 && error != EEXIST) {
+		fatal(0, "ztest_snapshot_create(%s@%s) = %d", osname,
+		    snapname, error);
+	}
 	return (B_TRUE);
 }
 
@@ -3241,7 +3245,7 @@ ztest_snapshot_destroy(char *osname, uint64_t id)
 	(void) snprintf(snapname, MAXNAMELEN, "%s@%llu", osname,
 	    (u_longlong_t)id);
 
-	error = dmu_objset_destroy(snapname, B_FALSE);
+	error = dsl_destroy_snapshot(snapname, B_FALSE);
 	if (error != 0 && error != ENOENT)
 		fatal(0, "ztest_snapshot_destroy(%s) = %d", snapname, error);
 	return (B_TRUE);
@@ -3269,7 +3273,7 @@ ztest_dmu_objset_create_destroy(ztest_ds_t *zd, uint64_t id)
 
 	/*
 	 * If this dataset exists from a previous run, process its replay log
-	 * half of the time.  If we don't replay it, then dmu_objset_destroy()
+	 * half of the time.  If we don't replay it, then dsl_destroy_head()
 	 * (invoked from ztest_objset_destroy_cb()) should just throw it away.
 	 */
 	if (ztest_random(2) == 0 &&
@@ -3291,7 +3295,8 @@ ztest_dmu_objset_create_destroy(ztest_ds_t *zd, uint64_t id)
 	/*
 	 * Verify that the destroyed dataset is no longer in the namespace.
 	 */
-	VERIFY3U(ENOENT, ==, dmu_objset_hold(name, FTAG, &os));
+	VERIFY3U(ENOENT, ==, dmu_objset_own(name, DMU_OST_OTHER, B_TRUE,
+	    FTAG, &os));
 
 	/*
 	 * Verify that we can create a new dataset.
@@ -3305,8 +3310,7 @@ ztest_dmu_objset_create_destroy(ztest_ds_t *zd, uint64_t id)
 		fatal(0, "dmu_objset_create(%s) = %d", name, error);
 	}
 
-	VERIFY3U(0, ==,
-	    dmu_objset_own(name, DMU_OST_OTHER, B_FALSE, FTAG, &os));
+	VERIFY0(dmu_objset_own(name, DMU_OST_OTHER, B_FALSE, FTAG, &os));
 
 	ztest_zd_init(zdtmp, NULL, os);
 
@@ -3396,21 +3400,21 @@ ztest_dsl_dataset_cleanup(char *osname, uint64_t id)
 	(void) snprintf(snap3name, MAXNAMELEN, "%s@s3_%llu",
 	    clone1name, (u_longlong_t)id);
 
-	error = dmu_objset_destroy(clone2name, B_FALSE);
+	error = dsl_destroy_head(clone2name);
 	if (error && error != ENOENT)
-		fatal(0, "dmu_objset_destroy(%s) = %d", clone2name, error);
-	error = dmu_objset_destroy(snap3name, B_FALSE);
+		fatal(0, "dsl_destroy_head(%s) = %d", clone2name, error);
+	error = dsl_destroy_snapshot(snap3name, B_FALSE);
 	if (error && error != ENOENT)
-		fatal(0, "dmu_objset_destroy(%s) = %d", snap3name, error);
-	error = dmu_objset_destroy(snap2name, B_FALSE);
+		fatal(0, "dsl_destroy_snapshot(%s) = %d", snap3name, error);
+	error = dsl_destroy_snapshot(snap2name, B_FALSE);
 	if (error && error != ENOENT)
-		fatal(0, "dmu_objset_destroy(%s) = %d", snap2name, error);
-	error = dmu_objset_destroy(clone1name, B_FALSE);
+		fatal(0, "dsl_destroy_snapshot(%s) = %d", snap2name, error);
+	error = dsl_destroy_head(clone1name);
 	if (error && error != ENOENT)
-		fatal(0, "dmu_objset_destroy(%s) = %d", clone1name, error);
-	error = dmu_objset_destroy(snap1name, B_FALSE);
+		fatal(0, "dsl_destroy_head(%s) = %d", clone1name, error);
+	error = dsl_destroy_snapshot(snap1name, B_FALSE);
 	if (error && error != ENOENT)
-		fatal(0, "dmu_objset_destroy(%s) = %d", snap1name, error);
+		fatal(0, "dsl_destroy_snapshot(%s) = %d", snap1name, error);
 
 	umem_free(snap1name, MAXNAMELEN);
 	umem_free(clone1name, MAXNAMELEN);
@@ -3425,8 +3429,7 @@ ztest_dsl_dataset_cleanup(char *osname, uint64_t id)
 void
 ztest_dsl_dataset_promote_busy(ztest_ds_t *zd, uint64_t id)
 {
-	objset_t *clone;
-	dsl_dataset_t *ds;
+	objset_t *os;
 	char *snap1name;
 	char *clone1name;
 	char *snap2name;
@@ -3465,12 +3468,7 @@ ztest_dsl_dataset_promote_busy(ztest_ds_t *zd, uint64_t id)
 		fatal(0, "dmu_take_snapshot(%s) = %d", snap1name, error);
 	}
 
-	error = dmu_objset_hold(snap1name, FTAG, &clone);
-	if (error)
-		fatal(0, "dmu_open_snapshot(%s) = %d", snap1name, error);
-
-	error = dmu_objset_clone(clone1name, dmu_objset_ds(clone), 0);
-	dmu_objset_rele(clone, FTAG);
+	error = dmu_objset_clone(clone1name, snap1name);
 	if (error) {
 		if (error == ENOSPC) {
 			ztest_record_enospc(FTAG);
@@ -3497,12 +3495,7 @@ ztest_dsl_dataset_promote_busy(ztest_ds_t *zd, uint64_t id)
 		fatal(0, "dmu_open_snapshot(%s) = %d", snap3name, error);
 	}
 
-	error = dmu_objset_hold(snap3name, FTAG, &clone);
-	if (error)
-		fatal(0, "dmu_open_snapshot(%s) = %d", snap3name, error);
-
-	error = dmu_objset_clone(clone2name, dmu_objset_ds(clone), 0);
-	dmu_objset_rele(clone, FTAG);
+	error = dmu_objset_clone(clone2name, snap3name);
 	if (error) {
 		if (error == ENOSPC) {
 			ztest_record_enospc(FTAG);
@@ -3511,14 +3504,14 @@ ztest_dsl_dataset_promote_busy(ztest_ds_t *zd, uint64_t id)
 		fatal(0, "dmu_objset_create(%s) = %d", clone2name, error);
 	}
 
-	error = dsl_dataset_own(snap2name, B_FALSE, FTAG, &ds);
+	error = dmu_objset_own(snap2name, DMU_OST_ANY, B_TRUE, FTAG, &os);
 	if (error)
-		fatal(0, "dsl_dataset_own(%s) = %d", snap2name, error);
+		fatal(0, "dmu_objset_own(%s) = %d", snap2name, error);
 	error = dsl_dataset_promote(clone2name, NULL);
 	if (error != EBUSY)
 		fatal(0, "dsl_dataset_promote(%s), %d, not EBUSY", clone2name,
 		    error);
-	dsl_dataset_disown(ds, FTAG);
+	dmu_objset_disown(os, FTAG);
 
 out:
 	ztest_dsl_dataset_cleanup(osname, id);
@@ -4392,7 +4385,7 @@ ztest_zap_parallel(ztest_ds_t *zd, uint64_t id)
 	}
 
 	count = -1ULL;
-	VERIFY(zap_count(os, object, &count) == 0);
+	VERIFY0(zap_count(os, object, &count));
 	ASSERT(count != -1ULL);
 
 	/*
@@ -4710,6 +4703,22 @@ ztest_spa_prop_get_set(ztest_ds_t *zd, uint64_t id)
 	(void) rw_exit(&ztest_name_lock);
 }
 
+static int
+user_release_one(const char *snapname, const char *holdname)
+{
+	nvlist_t *snaps, *holds;
+	int error;
+
+	snaps = fnvlist_alloc();
+	holds = fnvlist_alloc();
+	fnvlist_add_boolean(holds, holdname);
+	fnvlist_add_nvlist(snaps, snapname, holds);
+	fnvlist_free(holds);
+	error = dsl_dataset_user_release(snaps, NULL);
+	fnvlist_free(snaps);
+	return (error);
+}
+
 /*
  * Test snapshot hold/release and deferred destroy.
  */
@@ -4724,22 +4733,30 @@ ztest_dmu_snapshot_hold(ztest_ds_t *zd, uint64_t id)
 	char clonename[100];
 	char tag[100];
 	char osname[MAXNAMELEN];
+	nvlist_t *holds;
 
 	(void) rw_enter(&ztest_name_lock, RW_READER);
 
 	dmu_objset_name(os, osname);
 
-	(void) snprintf(snapname, 100, "sh1_%llu", (u_longlong_t)id);
-	(void) snprintf(fullname, 100, "%s@%s", osname, snapname);
-	(void) snprintf(clonename, 100, "%s/ch1_%llu",osname,(u_longlong_t)id);
-	(void) snprintf(tag, 100, "tag_%llu", (u_longlong_t)id);
+	(void) snprintf(snapname, sizeof (snapname), "sh1_%llu", (long long unsigned int)id);
+	(void) snprintf(fullname, sizeof (fullname), "%s@%s", osname, snapname);
+	(void) snprintf(clonename, sizeof (clonename),
+	    "%s/ch1_%llu", osname, (long long unsigned int)id);
+	(void) snprintf(tag, sizeof (tag), "tag_%llu", (long long unsigned int)id);
 
 	/*
 	 * Clean up from any previous run.
 	 */
-	(void) dmu_objset_destroy(clonename, B_FALSE);
-	(void) dsl_dataset_user_release(osname, snapname, tag, B_FALSE);
-	(void) dmu_objset_destroy(fullname, B_FALSE);
+	error = dsl_destroy_head(clonename);
+	if (error != ENOENT)
+		ASSERT0(error);
+	error = user_release_one(fullname, tag);
+	if (error != ESRCH && error != ENOENT)
+		ASSERT0(error);
+	error = dsl_destroy_snapshot(fullname, B_FALSE);
+	if (error != ENOENT)
+		ASSERT0(error);
 
 	/*
 	 * Create snapshot, clone it, mark snap for deferred destroy,
@@ -4754,12 +4771,7 @@ ztest_dmu_snapshot_hold(ztest_ds_t *zd, uint64_t id)
 		fatal(0, "dmu_objset_snapshot(%s) = %d", fullname, error);
 	}
 
-	error = dmu_objset_hold(fullname, FTAG, &origin);
-	if (error)
-		fatal(0, "dmu_objset_hold(%s) = %d", fullname, error);
-
-	error = dmu_objset_clone(clonename, dmu_objset_ds(origin), 0);
-	dmu_objset_rele(origin, FTAG);
+	error = dmu_objset_clone(clonename, fullname);
 	if (error) {
 		if (error == ENOSPC) {
 			ztest_record_enospc("dmu_objset_clone");
@@ -4768,15 +4780,15 @@ ztest_dmu_snapshot_hold(ztest_ds_t *zd, uint64_t id)
 		fatal(0, "dmu_objset_clone(%s) = %d", clonename, error);
 	}
 
-	error = dmu_objset_destroy(fullname, B_TRUE);
+	error = dsl_destroy_snapshot(fullname, B_TRUE);
 	if (error) {
-		fatal(0, "dmu_objset_destroy(%s, B_TRUE) = %d",
+		fatal(0, "dsl_destroy_snapshot(%s, B_TRUE) = %d",
 		    fullname, error);
 	}
 
-	error = dmu_objset_destroy(clonename, B_FALSE);
+	error = dsl_destroy_head(clonename);
 	if (error)
-		fatal(0, "dmu_objset_destroy(%s) = %d", clonename, error);
+		fatal(0, "dsl_destroy_head(%s) = %d", clonename, error);
 
 	error = dmu_objset_hold(fullname, FTAG, &origin);
 	if (error != ENOENT)
@@ -4796,28 +4808,31 @@ ztest_dmu_snapshot_hold(ztest_ds_t *zd, uint64_t id)
 		fatal(0, "dmu_objset_snapshot(%s) = %d", fullname, error);
 	}
 
-	error = dsl_dataset_user_hold(osname, snapname, tag, B_FALSE,
-	    B_TRUE, -1);
+	holds = fnvlist_alloc();
+	fnvlist_add_string(holds, fullname, tag);
+	error = dsl_dataset_user_hold(holds, 0, NULL);
+	fnvlist_free(holds);
+
 	if (error)
 		fatal(0, "dsl_dataset_user_hold(%s)", fullname, tag);
 
-	error = dmu_objset_destroy(fullname, B_FALSE);
+	error = dsl_destroy_snapshot(fullname, B_FALSE);
 	if (error != EBUSY) {
-		fatal(0, "dmu_objset_destroy(%s, B_FALSE) = %d",
+		fatal(0, "dsl_destroy_snapshot(%s, B_FALSE) = %d",
 		    fullname, error);
 	}
 
-	error = dmu_objset_destroy(fullname, B_TRUE);
+	error = dsl_destroy_snapshot(fullname, B_TRUE);
 	if (error) {
-		fatal(0, "dmu_objset_destroy(%s, B_TRUE) = %d",
+		fatal(0, "dsl_destroy_snapshot(%s, B_TRUE) = %d",
 		    fullname, error);
 	}
 
-	error = dsl_dataset_user_release(osname, snapname, tag, B_FALSE);
+	error = user_release_one(fullname, tag);
 	if (error)
-		fatal(0, "dsl_dataset_user_release(%s)", fullname, tag);
+		fatal(0, "user_release_one(%s)", fullname, tag);
 
-	VERIFY(dmu_objset_hold(fullname, FTAG, &origin) == ENOENT);
+	VERIFY3U(dmu_objset_hold(fullname, FTAG, &origin), ==, ENOENT);
 
 out:
 	(void) rw_exit(&ztest_name_lock);
@@ -4947,7 +4962,7 @@ ztest_fault_inject(ztest_ds_t *zd, uint64_t id)
 			 * prevent a race between offlining a slog and
 			 * destroying a dataset. Offlining the slog will
 			 * grab a reference on the dataset which may cause
-			 * dmu_objset_destroy() to fail with EBUSY thus
+			 * dsl_destroy_head() to fail with EBUSY thus
 			 * leaving the dataset in an inconsistent state.
 			 */
 			if (islog)
@@ -5084,8 +5099,12 @@ ztest_ddt_repair(ztest_ds_t *zd, uint64_t id)
 	 */
 	for (i = 0; i < copies; i++) {
 		uint64_t offset = i * blocksize;
-		VERIFY(dmu_buf_hold(os, object, offset, FTAG, &db,
-		    DMU_READ_NO_PREFETCH) == 0);
+		int error = dmu_buf_hold(os, object, offset, FTAG, &db,
+		    DMU_READ_NO_PREFETCH);
+		if (error != 0) {
+			fatal(B_FALSE, "dmu_buf_hold(%p, %llu, %llu) = %u",
+			    os, (long long)object, (long long) offset, error);
+		}
 		ASSERT(db->db_offset == offset);
 		ASSERT(db->db_size == blocksize);
 		ASSERT(ztest_pattern_match(db->db_data, db->db_size, pattern) ||
@@ -5300,6 +5319,7 @@ ztest_spa_import_export(char *oldname, char *newname)
 	nvlist_t *config, *newconfig;
 	uint64_t pool_guid;
 	spa_t *spa;
+	int error;
 
 	if (ztest_opts.zo_verbose >= 4) {
 		(void) printf("import/export: old = %s, new = %s\n",
@@ -5344,7 +5364,12 @@ ztest_spa_import_export(char *oldname, char *newname)
 	/*
 	 * Import it under the new name.
 	 */
-	VERIFY3U(0, ==, spa_import(newname, config, NULL, 0));
+	error = spa_import(newname, config, NULL, 0);
+	if (error != 0) {
+		dump_nvlist(config, 0);
+		fatal(B_FALSE, "couldn't import pool %s as %s: error %u",
+		    oldname, newname, error);
+	}
 
 	ztest_walk_pool_directory("pools after import");
 
@@ -5551,7 +5576,7 @@ ztest_dataset_open(int d)
 	}
 	ASSERT(error == 0 || error == EEXIST);
 
-	VERIFY0(dmu_objset_hold(name, zd, &os));
+	VERIFY0(dmu_objset_own(name, DMU_OST_OTHER, B_FALSE, zd, &os));
 	(void) rw_exit(&ztest_name_lock);
 
 	ztest_zd_init(zd, ZTEST_GET_SHARED_DS(d), os);
@@ -5592,7 +5617,7 @@ ztest_dataset_close(int d)
 	ztest_ds_t *zd = &ztest_ds[d];
 
 	zil_close(zd->zd_zilog);
-	dmu_objset_rele(zd->zd_os, zd);
+	dmu_objset_disown(zd->zd_os, zd);
 
 	ztest_zd_fini(zd);
 }
@@ -5638,13 +5663,14 @@ ztest_run(ztest_shared_t *zs)
 	 * Open our pool.
 	 */
 	kernel_init(FREAD | FWRITE);
-	VERIFY(spa_open(ztest_opts.zo_pool, &spa, FTAG) == 0);
+	VERIFY0(spa_open(ztest_opts.zo_pool, &spa, FTAG));
 	spa->spa_debug = B_TRUE;
 	ztest_spa = spa;
 
-	VERIFY3U(0, ==, dmu_objset_hold(ztest_opts.zo_pool, FTAG, &os));
+	VERIFY0(dmu_objset_own(ztest_opts.zo_pool,
+	    DMU_OST_ANY, B_TRUE, FTAG, &os));
 	zs->zs_guid = dmu_objset_fsid_guid(os);
-	dmu_objset_rele(os, FTAG);
+	dmu_objset_disown(os, FTAG);
 
 	spa->spa_dedup_ditto = 2 * ZIO_DEDUPDITTO_MIN;