1 files changed, 658 insertions, 0 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_traverse.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_traverse.c
new file mode 100644
index 0000000..db0869c
--- /dev/null
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_traverse.c
@@ -0,0 +1,658 @@
+/*
+ * 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.
+ * Copyright (c) 2013 by Delphix. All rights reserved.
+ */
+
+#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/dnode.h>
+#include <sys/spa.h>
+#include <sys/zio.h>
+#include <sys/dmu_impl.h>
+#include <sys/sa.h>
+#include <sys/sa_impl.h>
+#include <sys/callb.h>
+#include <sys/zfeature.h>
+
+int zfs_pd_blks_max = 100;
+
+typedef struct prefetch_data {
+	kmutex_t pd_mtx;
+	kcondvar_t pd_cv;
+	int pd_blks_max;
+	int pd_blks_fetched;
+	int pd_flags;
+	boolean_t pd_cancel;
+	boolean_t pd_exited;
+} prefetch_data_t;
+
+typedef struct traverse_data {
+	spa_t *td_spa;
+	uint64_t td_objset;
+	blkptr_t *td_rootbp;
+	uint64_t td_min_txg;
+	zbookmark_t *td_resume;
+	int td_flags;
+	prefetch_data_t *td_pfd;
+	blkptr_cb_t *td_func;
+	void *td_arg;
+} traverse_data_t;
+
+static int traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp,
+    uint64_t objset, uint64_t object);
+static void prefetch_dnode_metadata(traverse_data_t *td, const dnode_phys_t *,
+    uint64_t objset, uint64_t object);
+
+static int
+traverse_zil_block(zilog_t *zilog, blkptr_t *bp, void *arg, uint64_t claim_txg)
+{
+	traverse_data_t *td = arg;
+	zbookmark_t zb;
+
+	if (BP_IS_HOLE(bp))
+		return (0);
+
+	if (claim_txg == 0 && bp->blk_birth >= spa_first_txg(td->td_spa))
+		return (0);
+
+	SET_BOOKMARK(&zb, td->td_objset, ZB_ZIL_OBJECT, ZB_ZIL_LEVEL,
+	    bp->blk_cksum.zc_word[ZIL_ZC_SEQ]);
+
+	(void) td->td_func(td->td_spa, zilog, bp, &zb, NULL, td->td_arg);
+
+	return (0);
+}
+
+static int
+traverse_zil_record(zilog_t *zilog, lr_t *lrc, void *arg, uint64_t claim_txg)
+{
+	traverse_data_t *td = arg;
+
+	if (lrc->lrc_txtype == TX_WRITE) {
+		lr_write_t *lr = (lr_write_t *)lrc;
+		blkptr_t *bp = &lr->lr_blkptr;
+		zbookmark_t zb;
+
+		if (BP_IS_HOLE(bp))
+			return (0);
+
+		if (claim_txg == 0 || bp->blk_birth < claim_txg)
+			return (0);
+
+		SET_BOOKMARK(&zb, td->td_objset, lr->lr_foid,
+		    ZB_ZIL_LEVEL, lr->lr_offset / BP_GET_LSIZE(bp));
+
+		(void) td->td_func(td->td_spa, zilog, bp, &zb, NULL,
+		    td->td_arg);
+	}
+	return (0);
+}
+
+static void
+traverse_zil(traverse_data_t *td, zil_header_t *zh)
+{
+	uint64_t claim_txg = zh->zh_claim_txg;
+	zilog_t *zilog;
+
+	/*
+	 * We only want to visit blocks that have been claimed but not yet
+	 * replayed; plus, in read-only mode, blocks that are already stable.
+	 */
+	if (claim_txg == 0 && spa_writeable(td->td_spa))
+		return;
+
+	zilog = zil_alloc(spa_get_dsl(td->td_spa)->dp_meta_objset, zh);
+
+	(void) zil_parse(zilog, traverse_zil_block, traverse_zil_record, td,
+	    claim_txg);
+
+	zil_free(zilog);
+}
+
+typedef enum resume_skip {
+	RESUME_SKIP_ALL,
+	RESUME_SKIP_NONE,
+	RESUME_SKIP_CHILDREN
+} resume_skip_t;
+
+/*
+ * Returns RESUME_SKIP_ALL if td indicates that we are resuming a traversal and
+ * the block indicated by zb does not need to be visited at all. Returns
+ * RESUME_SKIP_CHILDREN if we are resuming a post traversal and we reach the
+ * resume point. This indicates that this block should be visited but not its
+ * children (since they must have been visited in a previous traversal).
+ * Otherwise returns RESUME_SKIP_NONE.
+ */
+static resume_skip_t
+resume_skip_check(traverse_data_t *td, const dnode_phys_t *dnp,
+    const zbookmark_t *zb)
+{
+	if (td->td_resume != NULL && !ZB_IS_ZERO(td->td_resume)) {
+		/*
+		 * If we already visited this bp & everything below,
+		 * don't bother doing it again.
+		 */
+		if (zbookmark_is_before(dnp, zb, td->td_resume))
+			return (RESUME_SKIP_ALL);
+
+		/*
+		 * If we found the block we're trying to resume from, zero
+		 * the bookmark out to indicate that we have resumed.
+		 */
+		ASSERT3U(zb->zb_object, <=, td->td_resume->zb_object);
+		if (bcmp(zb, td->td_resume, sizeof (*zb)) == 0) {
+			bzero(td->td_resume, sizeof (*zb));
+			if (td->td_flags & TRAVERSE_POST)
+				return (RESUME_SKIP_CHILDREN);
+		}
+	}
+	return (RESUME_SKIP_NONE);
+}
+
+static void
+traverse_pause(traverse_data_t *td, const zbookmark_t *zb)
+{
+	ASSERT(td->td_resume != NULL);
+	ASSERT0(zb->zb_level);
+	bcopy(zb, td->td_resume, sizeof (*td->td_resume));
+}
+
+static void
+traverse_prefetch_metadata(traverse_data_t *td,
+    const blkptr_t *bp, const zbookmark_t *zb)
+{
+	uint32_t flags = ARC_NOWAIT | ARC_PREFETCH;
+
+	if (!(td->td_flags & TRAVERSE_PREFETCH_METADATA))
+		return;
+	/*
+	 * If we are in the process of resuming, don't prefetch, because
+	 * some children will not be needed (and in fact may have already
+	 * been freed).
+	 */
+	if (td->td_resume != NULL && !ZB_IS_ZERO(td->td_resume))
+		return;
+	if (BP_IS_HOLE(bp) || bp->blk_birth <= td->td_min_txg)
+		return;
+	if (BP_GET_LEVEL(bp) == 0 && BP_GET_TYPE(bp) != DMU_OT_DNODE)
+		return;
+
+	(void) arc_read(NULL, td->td_spa, bp, NULL, NULL,
+	    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
+}
+
+static int
+traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
+    const blkptr_t *bp, const zbookmark_t *zb)
+{
+	zbookmark_t czb;
+	int err = 0, lasterr = 0;
+	arc_buf_t *buf = NULL;
+	prefetch_data_t *pd = td->td_pfd;
+	boolean_t hard = td->td_flags & TRAVERSE_HARD;
+	boolean_t pause = B_FALSE;
+
+	switch (resume_skip_check(td, dnp, zb)) {
+	case RESUME_SKIP_ALL:
+		return (0);
+	case RESUME_SKIP_CHILDREN:
+		goto post;
+	case RESUME_SKIP_NONE:
+		break;
+	default:
+		ASSERT(0);
+	}
+
+	if (bp->blk_birth == 0) {
+		if (spa_feature_is_active(td->td_spa, SPA_FEATURE_HOLE_BIRTH)) {
+			/*
+			 * Since this block has a birth time of 0 it must be a
+			 * hole created before the SPA_FEATURE_HOLE_BIRTH
+			 * feature was enabled.  If SPA_FEATURE_HOLE_BIRTH
+			 * was enabled before the min_txg for this traveral we
+			 * know the hole must have been created before the
+			 * min_txg for this traveral, so we can skip it. If
+			 * SPA_FEATURE_HOLE_BIRTH was enabled after the min_txg
+			 * for this traveral we cannot tell if the hole was
+			 * created before or after the min_txg for this
+			 * traversal, so we cannot skip it.
+			 */
+			uint64_t hole_birth_enabled_txg;
+			VERIFY(spa_feature_enabled_txg(td->td_spa,
+			    SPA_FEATURE_HOLE_BIRTH, &hole_birth_enabled_txg));
+			if (hole_birth_enabled_txg < td->td_min_txg)
+				return (0);
+		}
+	} else if (bp->blk_birth <= td->td_min_txg) {
+		return (0);
+	}
+
+	if (BP_IS_HOLE(bp)) {
+		err = td->td_func(td->td_spa, NULL, bp, zb, dnp, td->td_arg);
+		return (err);
+	}
+
+	if (pd && !pd->pd_exited &&
+	    ((pd->pd_flags & TRAVERSE_PREFETCH_DATA) ||
+	    BP_GET_TYPE(bp) == DMU_OT_DNODE || BP_GET_LEVEL(bp) > 0)) {
+		mutex_enter(&pd->pd_mtx);
+		ASSERT(pd->pd_blks_fetched >= 0);
+		while (pd->pd_blks_fetched == 0 && !pd->pd_exited)
+			cv_wait(&pd->pd_cv, &pd->pd_mtx);
+		pd->pd_blks_fetched--;
+		cv_broadcast(&pd->pd_cv);
+		mutex_exit(&pd->pd_mtx);
+	}
+
+	if (td->td_flags & TRAVERSE_PRE) {
+		err = td->td_func(td->td_spa, NULL, bp, zb, dnp,
+		    td->td_arg);
+		if (err == TRAVERSE_VISIT_NO_CHILDREN)
+			return (0);
+		if (err == ERESTART)
+			pause = B_TRUE; /* handle pausing at a common point */
+		if (err != 0)
+			goto post;
+	}
+
+	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, td->td_spa, bp, arc_getbuf_func, &buf,
+		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
+		if (err != 0)
+			return (err);
+		cbp = buf->b_data;
+
+		for (i = 0; i < epb; i++) {
+			SET_BOOKMARK(&czb, zb->zb_objset, zb->zb_object,
+			    zb->zb_level - 1,
+			    zb->zb_blkid * epb + i);
+			traverse_prefetch_metadata(td, &cbp[i], &czb);
+		}
+
+		/* recursively visitbp() blocks below this */
+		for (i = 0; i < epb; i++) {
+			SET_BOOKMARK(&czb, zb->zb_objset, zb->zb_object,
+			    zb->zb_level - 1,
+			    zb->zb_blkid * epb + i);
+			err = traverse_visitbp(td, dnp, &cbp[i], &czb);
+			if (err != 0) {
+				if (!hard)
+					break;
+				lasterr = err;
+			}
+		}
+	} else if (BP_GET_TYPE(bp) == DMU_OT_DNODE) {
+		uint32_t flags = ARC_WAIT;
+		int i;
+		int epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;
+
+		err = arc_read(NULL, td->td_spa, bp, arc_getbuf_func, &buf,
+		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
+		if (err != 0)
+			return (err);
+		dnp = buf->b_data;
+
+		for (i = 0; i < epb; i++) {
+			prefetch_dnode_metadata(td, &dnp[i], zb->zb_objset,
+			    zb->zb_blkid * epb + i);
+		}
+
+		/* recursively visitbp() blocks below this */
+		for (i = 0; i < epb; i++) {
+			err = traverse_dnode(td, &dnp[i], zb->zb_objset,
+			    zb->zb_blkid * epb + i);
+			if (err != 0) {
+				if (!hard)
+					break;
+				lasterr = err;
+			}
+		}
+	} else if (BP_GET_TYPE(bp) == DMU_OT_OBJSET) {
+		uint32_t flags = ARC_WAIT;
+		objset_phys_t *osp;
+		dnode_phys_t *dnp;
+
+		err = arc_read(NULL, td->td_spa, bp, arc_getbuf_func, &buf,
+		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
+		if (err != 0)
+			return (err);
+
+		osp = buf->b_data;
+		dnp = &osp->os_meta_dnode;
+		prefetch_dnode_metadata(td, dnp, zb->zb_objset,
+		    DMU_META_DNODE_OBJECT);
+		if (arc_buf_size(buf) >= sizeof (objset_phys_t)) {
+			prefetch_dnode_metadata(td, &osp->os_groupused_dnode,
+			    zb->zb_objset, DMU_GROUPUSED_OBJECT);
+			prefetch_dnode_metadata(td, &osp->os_userused_dnode,
+			    zb->zb_objset, DMU_USERUSED_OBJECT);
+		}
+
+		err = traverse_dnode(td, dnp, zb->zb_objset,
+		    DMU_META_DNODE_OBJECT);
+		if (err && hard) {
+			lasterr = err;
+			err = 0;
+		}
+		if (err == 0 && arc_buf_size(buf) >= sizeof (objset_phys_t)) {
+			dnp = &osp->os_groupused_dnode;
+			err = traverse_dnode(td, dnp, zb->zb_objset,
+			    DMU_GROUPUSED_OBJECT);
+		}
+		if (err && hard) {
+			lasterr = err;
+			err = 0;
+		}
+		if (err == 0 && arc_buf_size(buf) >= sizeof (objset_phys_t)) {
+			dnp = &osp->os_userused_dnode;
+			err = traverse_dnode(td, dnp, zb->zb_objset,
+			    DMU_USERUSED_OBJECT);
+		}
+	}
+
+	if (buf)
+		(void) arc_buf_remove_ref(buf, &buf);
+
+post:
+	if (err == 0 && (td->td_flags & TRAVERSE_POST)) {
+		err = td->td_func(td->td_spa, NULL, bp, zb, dnp, td->td_arg);
+		if (err == ERESTART)
+			pause = B_TRUE;
+	}
+
+	if (pause && td->td_resume != NULL) {
+		ASSERT3U(err, ==, ERESTART);
+		ASSERT(!hard);
+		traverse_pause(td, zb);
+	}
+
+	return (err != 0 ? err : lasterr);
+}
+
+static void
+prefetch_dnode_metadata(traverse_data_t *td, const dnode_phys_t *dnp,
+    uint64_t objset, uint64_t object)
+{
+	int j;
+	zbookmark_t czb;
+
+	for (j = 0; j < dnp->dn_nblkptr; j++) {
+		SET_BOOKMARK(&czb, objset, object, dnp->dn_nlevels - 1, j);
+		traverse_prefetch_metadata(td, &dnp->dn_blkptr[j], &czb);
+	}
+
+	if (dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR) {
+		SET_BOOKMARK(&czb, objset, object, 0, DMU_SPILL_BLKID);
+		traverse_prefetch_metadata(td, &dnp->dn_spill, &czb);
+	}
+}
+
+static int
+traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp,
+    uint64_t objset, uint64_t object)
+{
+	int j, err = 0, lasterr = 0;
+	zbookmark_t czb;
+	boolean_t hard = (td->td_flags & TRAVERSE_HARD);
+
+	for (j = 0; j < dnp->dn_nblkptr; j++) {
+		SET_BOOKMARK(&czb, objset, object, dnp->dn_nlevels - 1, j);
+		err = traverse_visitbp(td, dnp, &dnp->dn_blkptr[j], &czb);
+		if (err != 0) {
+			if (!hard)
+				break;
+			lasterr = err;
+		}
+	}
+
+	if (dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR) {
+		SET_BOOKMARK(&czb, objset, object, 0, DMU_SPILL_BLKID);
+		err = traverse_visitbp(td, dnp, &dnp->dn_spill, &czb);
+		if (err != 0) {
+			if (!hard)
+				return (err);
+			lasterr = err;
+		}
+	}
+	return (err != 0 ? err : lasterr);
+}
+
+/* ARGSUSED */
+static int
+traverse_prefetcher(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
+    const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
+{
+	prefetch_data_t *pfd = arg;
+	uint32_t aflags = ARC_NOWAIT | ARC_PREFETCH;
+
+	ASSERT(pfd->pd_blks_fetched >= 0);
+	if (pfd->pd_cancel)
+		return (SET_ERROR(EINTR));
+
+	if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp) ||
+	    !((pfd->pd_flags & TRAVERSE_PREFETCH_DATA) ||
+	    BP_GET_TYPE(bp) == DMU_OT_DNODE || BP_GET_LEVEL(bp) > 0) ||
+	    BP_GET_TYPE(bp) == DMU_OT_INTENT_LOG)
+		return (0);
+
+	mutex_enter(&pfd->pd_mtx);
+	while (!pfd->pd_cancel && pfd->pd_blks_fetched >= pfd->pd_blks_max)
+		cv_wait(&pfd->pd_cv, &pfd->pd_mtx);
+	pfd->pd_blks_fetched++;
+	cv_broadcast(&pfd->pd_cv);
+	mutex_exit(&pfd->pd_mtx);
+
+	(void) arc_read(NULL, spa, bp, NULL, NULL, ZIO_PRIORITY_ASYNC_READ,
+	    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE, &aflags, zb);
+
+	return (0);
+}
+
+static void
+traverse_prefetch_thread(void *arg)
+{
+	traverse_data_t *td_main = arg;
+	traverse_data_t td = *td_main;
+	zbookmark_t czb;
+
+	td.td_func = traverse_prefetcher;
+	td.td_arg = td_main->td_pfd;
+	td.td_pfd = NULL;
+
+	SET_BOOKMARK(&czb, td.td_objset,
+	    ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
+	(void) traverse_visitbp(&td, NULL, td.td_rootbp, &czb);
+
+	mutex_enter(&td_main->td_pfd->pd_mtx);
+	td_main->td_pfd->pd_exited = B_TRUE;
+	cv_broadcast(&td_main->td_pfd->pd_cv);
+	mutex_exit(&td_main->td_pfd->pd_mtx);
+}
+
+/*
+ * NB: dataset must not be changing on-disk (eg, is a snapshot or we are
+ * in syncing context).
+ */
+static int
+traverse_impl(spa_t *spa, dsl_dataset_t *ds, uint64_t objset, blkptr_t *rootbp,
+    uint64_t txg_start, zbookmark_t *resume, int flags,
+    blkptr_cb_t func, void *arg)
+{
+	traverse_data_t td;
+	prefetch_data_t pd = { 0 };
+	zbookmark_t czb;
+	int err;
+
+	ASSERT(ds == NULL || objset == ds->ds_object);
+	ASSERT(!(flags & TRAVERSE_PRE) || !(flags & TRAVERSE_POST));
+
+	/*
+	 * The data prefetching mechanism (the prefetch thread) is incompatible
+	 * with resuming from a bookmark.
+	 */
+	ASSERT(resume == NULL || !(flags & TRAVERSE_PREFETCH_DATA));
+
+	td.td_spa = spa;
+	td.td_objset = objset;
+	td.td_rootbp = rootbp;
+	td.td_min_txg = txg_start;
+	td.td_resume = resume;
+	td.td_func = func;
+	td.td_arg = arg;
+	td.td_pfd = &pd;
+	td.td_flags = flags;
+
+	pd.pd_blks_max = zfs_pd_blks_max;
+	pd.pd_flags = flags;
+	mutex_init(&pd.pd_mtx, NULL, MUTEX_DEFAULT, NULL);
+	cv_init(&pd.pd_cv, NULL, CV_DEFAULT, NULL);
+
+	/* See comment on ZIL traversal in dsl_scan_visitds. */
+	if (ds != NULL && !dsl_dataset_is_snapshot(ds) && !BP_IS_HOLE(rootbp)) {
+		uint32_t flags = ARC_WAIT;
+		objset_phys_t *osp;
+		arc_buf_t *buf;
+
+		err = arc_read(NULL, td.td_spa, rootbp,
+		    arc_getbuf_func, &buf,
+		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, NULL);
+		if (err != 0)
+			return (err);
+
+		osp = buf->b_data;
+		traverse_zil(&td, &osp->os_zil_header);
+		(void) arc_buf_remove_ref(buf, &buf);
+	}
+
+	if (!(flags & TRAVERSE_PREFETCH_DATA) ||
+	    0 == taskq_dispatch(system_taskq, traverse_prefetch_thread,
+	    &td, TQ_NOQUEUE))
+		pd.pd_exited = B_TRUE;
+
+	SET_BOOKMARK(&czb, td.td_objset,
+	    ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
+	err = traverse_visitbp(&td, NULL, rootbp, &czb);
+
+	mutex_enter(&pd.pd_mtx);
+	pd.pd_cancel = B_TRUE;
+	cv_broadcast(&pd.pd_cv);
+	while (!pd.pd_exited)
+		cv_wait(&pd.pd_cv, &pd.pd_mtx);
+	mutex_exit(&pd.pd_mtx);
+
+	mutex_destroy(&pd.pd_mtx);
+	cv_destroy(&pd.pd_cv);
+
+	return (err);
+}
+
+/*
+ * NB: dataset must not be changing on-disk (eg, is a snapshot or we are
+ * in syncing context).
+ */
+int
+traverse_dataset(dsl_dataset_t *ds, uint64_t txg_start, int flags,
+    blkptr_cb_t func, void *arg)
+{
+	return (traverse_impl(ds->ds_dir->dd_pool->dp_spa, ds, ds->ds_object,
+	    &ds->ds_phys->ds_bp, txg_start, NULL, flags, func, arg));
+}
+
+int
+traverse_dataset_destroyed(spa_t *spa, blkptr_t *blkptr,
+    uint64_t txg_start, zbookmark_t *resume, int flags,
+    blkptr_cb_t func, void *arg)
+{
+	return (traverse_impl(spa, NULL, ZB_DESTROYED_OBJSET,
+	    blkptr, txg_start, resume, flags, func, arg));
+}
+
+/*
+ * NB: pool must not be changing on-disk (eg, from zdb or sync context).
+ */
+int
+traverse_pool(spa_t *spa, uint64_t txg_start, int flags,
+    blkptr_cb_t func, void *arg)
+{
+	int err, lasterr = 0;
+	uint64_t obj;
+	dsl_pool_t *dp = spa_get_dsl(spa);
+	objset_t *mos = dp->dp_meta_objset;
+	boolean_t hard = (flags & TRAVERSE_HARD);
+
+	/* visit the MOS */
+	err = traverse_impl(spa, NULL, 0, spa_get_rootblkptr(spa),
+	    txg_start, NULL, flags, func, arg);
+	if (err != 0)
+		return (err);
+
+	/* visit each dataset */
+	for (obj = 1; err == 0 || (err != ESRCH && hard);
+	    err = dmu_object_next(mos, &obj, FALSE, txg_start)) {
+		dmu_object_info_t doi;
+
+		err = dmu_object_info(mos, obj, &doi);
+		if (err != 0) {
+			if (!hard)
+				return (err);
+			lasterr = err;
+			continue;
+		}
+
+		if (doi.doi_bonus_type == DMU_OT_DSL_DATASET) {
+			dsl_dataset_t *ds;
+			uint64_t txg = txg_start;
+
+			dsl_pool_config_enter(dp, FTAG);
+			err = dsl_dataset_hold_obj(dp, obj, FTAG, &ds);
+			dsl_pool_config_exit(dp, FTAG);
+			if (err != 0) {
+				if (!hard)
+					return (err);
+				lasterr = err;
+				continue;
+			}
+			if (ds->ds_phys->ds_prev_snap_txg > txg)
+				txg = ds->ds_phys->ds_prev_snap_txg;
+			err = traverse_dataset(ds, txg, flags, func, arg);
+			dsl_dataset_rele(ds, FTAG);
+			if (err != 0) {
+				if (!hard)
+					return (err);
+				lasterr = err;
+			}
+		}
+	}
+	if (err == ESRCH)
+		err = 0;
+	return (err != 0 ? err : lasterr);
+}