--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/usr/src/uts/common/fs/zfs/dnode.c	Mon Oct 31 11:33:35 2005 -0800
@@ -0,0 +1,1304 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License, Version 1.0 only
+ * (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 2005 Sun Microsystems, Inc.  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#pragma ident	"%Z%%M%	%I%	%E% SMI"
+
+#include <sys/zfs_context.h>
+#include <sys/dbuf.h>
+#include <sys/dnode.h>
+#include <sys/dmu.h>
+#include <sys/dmu_impl.h>
+#include <sys/dmu_tx.h>
+#include <sys/dmu_objset.h>
+#include <sys/dsl_dir.h>
+#include <sys/dsl_dataset.h>
+#include <sys/spa.h>
+#include <sys/zio.h>
+#include <sys/dmu_zfetch.h>
+
+static int free_range_compar(const void *node1, const void *node2);
+
+static kmem_cache_t *dnode_cache;
+
+static dnode_phys_t dnode_phys_zero;
+
+int zfs_default_bs = SPA_MINBLOCKSHIFT;
+int zfs_default_ibs = DN_MAX_INDBLKSHIFT;
+
+/* ARGSUSED */
+static int
+dnode_cons(void *arg, void *unused, int kmflag)
+{
+	int i;
+	dnode_t *dn = arg;
+	bzero(dn, sizeof (dnode_t));
+
+	rw_init(&dn->dn_struct_rwlock, NULL, RW_DEFAULT, NULL);
+	mutex_init(&dn->dn_mtx, NULL, MUTEX_DEFAULT, NULL);
+	mutex_init(&dn->dn_dbufs_mtx, NULL, MUTEX_DEFAULT, NULL);
+	refcount_create(&dn->dn_holds);
+	refcount_create(&dn->dn_tx_holds);
+
+	for (i = 0; i < TXG_SIZE; i++) {
+		avl_create(&dn->dn_ranges[i], free_range_compar,
+		    sizeof (free_range_t),
+		    offsetof(struct free_range, fr_node));
+		list_create(&dn->dn_dirty_dbufs[i],
+		    sizeof (dmu_buf_impl_t),
+		    offsetof(dmu_buf_impl_t, db_dirty_node[i]));
+	}
+
+	list_create(&dn->dn_dbufs, sizeof (dmu_buf_impl_t),
+	    offsetof(dmu_buf_impl_t, db_link));
+
+	return (0);
+}
+
+/* ARGSUSED */
+static void
+dnode_dest(void *arg, void *unused)
+{
+	int i;
+	dnode_t *dn = arg;
+
+	rw_destroy(&dn->dn_struct_rwlock);
+	mutex_destroy(&dn->dn_mtx);
+	mutex_destroy(&dn->dn_dbufs_mtx);
+	refcount_destroy(&dn->dn_holds);
+	refcount_destroy(&dn->dn_tx_holds);
+
+	for (i = 0; i < TXG_SIZE; i++) {
+		avl_destroy(&dn->dn_ranges[i]);
+		list_destroy(&dn->dn_dirty_dbufs[i]);
+	}
+
+	list_destroy(&dn->dn_dbufs);
+}
+
+void
+dnode_init(void)
+{
+	dnode_cache = kmem_cache_create("dnode_t",
+	    sizeof (dnode_t),
+	    0, dnode_cons, dnode_dest, NULL, NULL, NULL, 0);
+}
+
+void
+dnode_fini(void)
+{
+	kmem_cache_destroy(dnode_cache);
+}
+
+
+void
+dnode_verify(dnode_t *dn)
+{
+#ifdef ZFS_DEBUG
+	int drop_struct_lock = FALSE;
+
+	ASSERT(dn->dn_phys);
+	ASSERT(dn->dn_objset);
+
+	ASSERT(dn->dn_phys->dn_type < DMU_OT_NUMTYPES);
+
+	if (!(zfs_flags & ZFS_DEBUG_DNODE_VERIFY))
+		return;
+
+	if (!RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
+		rw_enter(&dn->dn_struct_rwlock, RW_READER);
+		drop_struct_lock = TRUE;
+	}
+	if (dn->dn_phys->dn_type != DMU_OT_NONE || dn->dn_allocated_txg != 0) {
+		int i;
+		ASSERT3U(dn->dn_indblkshift, >=, 0);
+		ASSERT3U(dn->dn_indblkshift, <=, SPA_MAXBLOCKSHIFT);
+		if (dn->dn_datablkshift) {
+			ASSERT3U(dn->dn_datablkshift, >=, SPA_MINBLOCKSHIFT);
+			ASSERT3U(dn->dn_datablkshift, <=, SPA_MAXBLOCKSHIFT);
+			ASSERT3U(1<<dn->dn_datablkshift, ==, dn->dn_datablksz);
+		}
+		ASSERT3U(dn->dn_nlevels, <=, 30);
+		ASSERT3U(dn->dn_type, <=, DMU_OT_NUMTYPES);
+		ASSERT3U(dn->dn_nblkptr, >=, 1);
+		ASSERT3U(dn->dn_nblkptr, <=, DN_MAX_NBLKPTR);
+		ASSERT3U(dn->dn_bonuslen, <=, DN_MAX_BONUSLEN);
+		ASSERT3U(dn->dn_datablksz, ==,
+		    dn->dn_datablkszsec << SPA_MINBLOCKSHIFT);
+		ASSERT3U(ISP2(dn->dn_datablksz), ==, dn->dn_datablkshift != 0);
+		ASSERT3U((dn->dn_nblkptr - 1) * sizeof (blkptr_t) +
+		    dn->dn_bonuslen, <=, DN_MAX_BONUSLEN);
+		for (i = 0; i < TXG_SIZE; i++) {
+			ASSERT3U(dn->dn_next_nlevels[i], <=, dn->dn_nlevels);
+		}
+	}
+	if (dn->dn_phys->dn_type != DMU_OT_NONE)
+		ASSERT3U(dn->dn_phys->dn_nlevels, <=, dn->dn_nlevels);
+	ASSERT(IS_DNODE_DNODE(dn->dn_object) || dn->dn_dbuf);
+	if (dn->dn_dbuf != NULL) {
+		ASSERT3P(dn->dn_phys, ==,
+		    (dnode_phys_t *)dn->dn_dbuf->db.db_data +
+		    (dn->dn_object % (dn->dn_dbuf->db.db_size >> DNODE_SHIFT)));
+	}
+	if (drop_struct_lock)
+		rw_exit(&dn->dn_struct_rwlock);
+#endif
+}
+
+void
+dnode_byteswap(dnode_phys_t *dnp)
+{
+	uint64_t *buf64 = (void*)&dnp->dn_blkptr;
+	int i;
+
+	if (dnp->dn_type == DMU_OT_NONE) {
+		bzero(dnp, sizeof (dnode_phys_t));
+		return;
+	}
+
+	dnp->dn_type = BSWAP_8(dnp->dn_type);
+	dnp->dn_indblkshift = BSWAP_8(dnp->dn_indblkshift);
+	dnp->dn_nlevels = BSWAP_8(dnp->dn_nlevels);
+	dnp->dn_nblkptr = BSWAP_8(dnp->dn_nblkptr);
+	dnp->dn_bonustype = BSWAP_8(dnp->dn_bonustype);
+	dnp->dn_checksum = BSWAP_8(dnp->dn_checksum);
+	dnp->dn_compress = BSWAP_8(dnp->dn_compress);
+	dnp->dn_datablkszsec = BSWAP_16(dnp->dn_datablkszsec);
+	dnp->dn_bonuslen = BSWAP_16(dnp->dn_bonuslen);
+	dnp->dn_maxblkid = BSWAP_64(dnp->dn_maxblkid);
+	dnp->dn_secphys = BSWAP_64(dnp->dn_secphys);
+
+	/*
+	 * dn_nblkptr is only one byte, so it's OK to read it in either
+	 * byte order.  We can't read dn_bouslen.
+	 */
+	ASSERT(dnp->dn_indblkshift <= SPA_MAXBLOCKSHIFT);
+	ASSERT(dnp->dn_nblkptr <= DN_MAX_NBLKPTR);
+	for (i = 0; i < dnp->dn_nblkptr * sizeof (blkptr_t)/8; i++)
+		buf64[i] = BSWAP_64(buf64[i]);
+
+	/*
+	 * OK to check dn_bonuslen for zero, because it won't matter if
+	 * we have the wrong byte order.  This is necessary because the
+	 * dnode dnode is smaller than a regular dnode.
+	 */
+	if (dnp->dn_bonuslen != 0) {
+		/*
+		 * Note that the bonus length calculated here may be
+		 * longer than the actual bonus buffer.  This is because
+		 * we always put the bonus buffer after the last block
+		 * pointer (instead of packing it against the end of the
+		 * dnode buffer).
+		 */
+		int off = (dnp->dn_nblkptr-1) * sizeof (blkptr_t);
+		size_t len = DN_MAX_BONUSLEN - off;
+		dmu_ot[dnp->dn_bonustype].ot_byteswap(dnp->dn_bonus + off, len);
+	}
+}
+
+void
+dnode_buf_byteswap(void *vbuf, size_t size)
+{
+	dnode_phys_t *buf = vbuf;
+	int i;
+
+	ASSERT3U(sizeof (dnode_phys_t), ==, (1<<DNODE_SHIFT));
+	ASSERT((size & (sizeof (dnode_phys_t)-1)) == 0);
+
+	size >>= DNODE_SHIFT;
+	for (i = 0; i < size; i++) {
+		dnode_byteswap(buf);
+		buf++;
+	}
+}
+
+static int
+free_range_compar(const void *node1, const void *node2)
+{
+	const free_range_t *rp1 = node1;
+	const free_range_t *rp2 = node2;
+
+	if (rp1->fr_blkid < rp2->fr_blkid)
+		return (-1);
+	else if (rp1->fr_blkid > rp2->fr_blkid)
+		return (1);
+	else return (0);
+}
+
+static void
+dnode_setdblksz(dnode_t *dn, int size)
+{
+	ASSERT3U(P2PHASE(size, SPA_MINBLOCKSIZE), ==, 0);
+	ASSERT3U(size, <=, SPA_MAXBLOCKSIZE);
+	ASSERT3U(size, >=, SPA_MINBLOCKSIZE);
+	ASSERT3U(size >> SPA_MINBLOCKSHIFT, <,
+	    1<<(sizeof (dn->dn_phys->dn_datablkszsec) * 8));
+	dn->dn_datablksz = size;
+	dn->dn_datablkszsec = size >> SPA_MINBLOCKSHIFT;
+	dn->dn_datablkshift = ISP2(size) ? highbit(size - 1) : 0;
+}
+
+static dnode_t *
+dnode_create(objset_impl_t *os, dnode_phys_t *dnp, dmu_buf_impl_t *db,
+    uint64_t object)
+{
+	dnode_t *dn = kmem_cache_alloc(dnode_cache, KM_SLEEP);
+	(void) dnode_cons(dn, NULL, 0); /* XXX */
+
+	dn->dn_objset = os;
+	dn->dn_object = object;
+	dn->dn_dbuf = db;
+	dn->dn_phys = dnp;
+
+	if (dnp->dn_datablkszsec)
+		dnode_setdblksz(dn, dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT);
+	dn->dn_indblkshift = dnp->dn_indblkshift;
+	dn->dn_nlevels = dnp->dn_nlevels;
+	dn->dn_type = dnp->dn_type;
+	dn->dn_nblkptr = dnp->dn_nblkptr;
+	dn->dn_checksum = dnp->dn_checksum;
+	dn->dn_compress = dnp->dn_compress;
+	dn->dn_bonustype = dnp->dn_bonustype;
+	dn->dn_bonuslen = dnp->dn_bonuslen;
+	dn->dn_maxblkid = dnp->dn_maxblkid;
+
+	dmu_zfetch_init(&dn->dn_zfetch, dn);
+
+	ASSERT(dn->dn_phys->dn_type < DMU_OT_NUMTYPES);
+	mutex_enter(&os->os_lock);
+	list_insert_head(&os->os_dnodes, dn);
+	mutex_exit(&os->os_lock);
+
+	return (dn);
+}
+
+static void
+dnode_destroy(dnode_t *dn)
+{
+	objset_impl_t *os = dn->dn_objset;
+
+	mutex_enter(&os->os_lock);
+	list_remove(&os->os_dnodes, dn);
+	mutex_exit(&os->os_lock);
+
+	if (dn->dn_dirtyctx_firstset) {
+		kmem_free(dn->dn_dirtyctx_firstset, 1);
+		dn->dn_dirtyctx_firstset = NULL;
+	}
+	dmu_zfetch_rele(&dn->dn_zfetch);
+	kmem_cache_free(dnode_cache, dn);
+}
+
+void
+dnode_allocate(dnode_t *dn, dmu_object_type_t ot, int blocksize, int ibs,
+	dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
+{
+	int i;
+
+	if (blocksize == 0)
+		blocksize = 1 << zfs_default_bs;
+
+	blocksize = MIN(MAX(blocksize, SPA_MINBLOCKSIZE), SPA_MAXBLOCKSIZE);
+
+	if (ibs == 0)
+		ibs = zfs_default_ibs;
+
+	ibs = MIN(MAX(ibs, DN_MIN_INDBLKSHIFT), DN_MAX_INDBLKSHIFT);
+
+	dprintf("os=%p obj=%llu txg=%llu blocksize=%d ibs=%d\n", dn->dn_objset,
+	    dn->dn_object, tx->tx_txg, blocksize, ibs);
+
+	ASSERT(dn->dn_type == DMU_OT_NONE);
+	ASSERT(bcmp(dn->dn_phys, &dnode_phys_zero, sizeof (dnode_phys_t)) == 0);
+	ASSERT(dn->dn_phys->dn_type == DMU_OT_NONE);
+	ASSERT(ot != DMU_OT_NONE);
+	ASSERT3U(ot, <, DMU_OT_NUMTYPES);
+	ASSERT((bonustype == DMU_OT_NONE && bonuslen == 0) ||
+	    (bonustype != DMU_OT_NONE && bonuslen != 0));
+	ASSERT3U(bonustype, <, DMU_OT_NUMTYPES);
+	ASSERT3U(bonuslen, <=, DN_MAX_BONUSLEN);
+	ASSERT(dn->dn_type == DMU_OT_NONE);
+	ASSERT3U(dn->dn_maxblkid, ==, 0);
+	ASSERT3U(dn->dn_allocated_txg, ==, 0);
+	ASSERT3U(dn->dn_assigned_txg, ==, 0);
+	ASSERT(refcount_is_zero(&dn->dn_tx_holds));
+	ASSERT3U(refcount_count(&dn->dn_holds), <=, 1);
+	ASSERT3P(list_head(&dn->dn_dbufs), ==, NULL);
+
+	for (i = 0; i < TXG_SIZE; i++) {
+		ASSERT3U(dn->dn_next_nlevels[i], ==, 0);
+		ASSERT3U(dn->dn_next_indblkshift[i], ==, 0);
+		ASSERT3U(dn->dn_dirtyblksz[i], ==, 0);
+		ASSERT3P(list_head(&dn->dn_dirty_dbufs[i]), ==, NULL);
+		ASSERT3U(avl_numnodes(&dn->dn_ranges[i]), ==, 0);
+	}
+
+	dn->dn_type = ot;
+	dnode_setdblksz(dn, blocksize);
+	dn->dn_indblkshift = ibs;
+	dn->dn_nlevels = 1;
+	dn->dn_nblkptr = 1 + ((DN_MAX_BONUSLEN - bonuslen) >> SPA_BLKPTRSHIFT);
+	dn->dn_bonustype = bonustype;
+	dn->dn_bonuslen = bonuslen;
+	dn->dn_checksum = ZIO_CHECKSUM_INHERIT;
+	dn->dn_compress = ZIO_COMPRESS_INHERIT;
+	dn->dn_dirtyctx = 0;
+
+	dn->dn_free_txg = 0;
+	if (dn->dn_dirtyctx_firstset) {
+		kmem_free(dn->dn_dirtyctx_firstset, 1);
+		dn->dn_dirtyctx_firstset = NULL;
+	}
+
+	dn->dn_allocated_txg = tx->tx_txg;
+	dnode_setdirty(dn, tx);
+}
+
+void
+dnode_reallocate(dnode_t *dn, dmu_object_type_t ot, int blocksize,
+    dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
+{
+	dmu_buf_impl_t *db = NULL;
+
+	ASSERT3U(blocksize, >=, SPA_MINBLOCKSIZE);
+	ASSERT3U(blocksize, <=, SPA_MAXBLOCKSIZE);
+	ASSERT3U(blocksize % SPA_MINBLOCKSIZE, ==, 0);
+	ASSERT3P(list_head(&dn->dn_dbufs), ==, NULL);
+	ASSERT(!(dn->dn_object & DMU_PRIVATE_OBJECT) || dmu_tx_private_ok(tx));
+	ASSERT(tx->tx_txg != 0);
+	ASSERT((bonustype == DMU_OT_NONE && bonuslen == 0) ||
+	    (bonustype != DMU_OT_NONE && bonuslen != 0));
+	ASSERT3U(bonustype, <, DMU_OT_NUMTYPES);
+	ASSERT3U(bonuslen, <=, DN_MAX_BONUSLEN);
+	ASSERT(dn->dn_dirtyblksz[0] == 0);
+	ASSERT(dn->dn_dirtyblksz[1] == 0);
+	ASSERT(dn->dn_dirtyblksz[2] == 0);
+	ASSERT(dn->dn_dirtyblksz[3] == 0);
+
+	/*
+	 * XXX I should really have a generation number to tell if we
+	 * need to do this...
+	 */
+	if (blocksize != dn->dn_datablksz ||
+	    dn->dn_bonustype != bonustype || dn->dn_bonuslen != bonuslen) {
+		/* free all old data */
+		dnode_free_range(dn, 0, -1ULL, tx);
+	}
+
+	/* change blocksize */
+	rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
+	dnode_setdblksz(dn, blocksize);
+	dnode_setdirty(dn, tx);
+	/* don't need dd_dirty_mtx, dnode is already dirty */
+	ASSERT(dn->dn_dirtyblksz[tx->tx_txg&TXG_MASK] != 0);
+	dn->dn_dirtyblksz[tx->tx_txg&TXG_MASK] = blocksize;
+	rw_exit(&dn->dn_struct_rwlock);
+
+	/* change type */
+	dn->dn_type = ot;
+
+	if (dn->dn_bonuslen != bonuslen) {
+		/* change bonus size */
+		if (bonuslen == 0)
+			bonuslen = 1; /* XXX */
+		db = dbuf_hold_bonus(dn, FTAG);
+		dbuf_read(db);
+		mutex_enter(&db->db_mtx);
+		ASSERT3U(db->db.db_size, ==, dn->dn_bonuslen);
+		ASSERT(db->db.db_data != NULL);
+		db->db.db_size = bonuslen;
+		mutex_exit(&db->db_mtx);
+		dbuf_dirty(db, tx);
+	}
+
+	/* change bonus size and type */
+	mutex_enter(&dn->dn_mtx);
+	dn->dn_bonustype = bonustype;
+	dn->dn_bonuslen = bonuslen;
+	dn->dn_nblkptr = 1 + ((DN_MAX_BONUSLEN - bonuslen) >> SPA_BLKPTRSHIFT);
+	dn->dn_checksum = ZIO_CHECKSUM_INHERIT;
+	dn->dn_compress = ZIO_COMPRESS_INHERIT;
+	ASSERT3U(dn->dn_nblkptr, <=, DN_MAX_NBLKPTR);
+
+	dn->dn_allocated_txg = tx->tx_txg;
+	mutex_exit(&dn->dn_mtx);
+
+	if (db)
+		dbuf_remove_ref(db, FTAG);
+}
+
+void
+dnode_special_close(dnode_t *dn)
+{
+	dnode_destroy(dn);
+}
+
+dnode_t *
+dnode_special_open(objset_impl_t *os, dnode_phys_t *dnp, uint64_t object)
+{
+	dnode_t *dn = dnode_create(os, dnp, NULL, object);
+	dnode_verify(dn);
+	return (dn);
+}
+
+static void
+dnode_buf_pageout(dmu_buf_t *db, void *arg)
+{
+	dnode_t **children_dnodes = arg;
+	int i;
+	int epb = db->db_size >> DNODE_SHIFT;
+
+	for (i = 0; i < epb; i++) {
+		dnode_t *dn = children_dnodes[i];
+		int n;
+
+		if (dn == NULL)
+			continue;
+#ifdef ZFS_DEBUG
+		/*
+		 * If there are holds on this dnode, then there should
+		 * be holds on the dnode's containing dbuf as well; thus
+		 * it wouldn't be eligable for eviction and this function
+		 * would not have been called.
+		 */
+		ASSERT(refcount_is_zero(&dn->dn_holds));
+		ASSERT(list_head(&dn->dn_dbufs) == NULL);
+		ASSERT(refcount_is_zero(&dn->dn_tx_holds));
+
+		for (n = 0; n < TXG_SIZE; n++)
+			ASSERT(dn->dn_dirtyblksz[n] == 0);
+#endif
+		children_dnodes[i] = NULL;
+		dnode_destroy(dn);
+	}
+	kmem_free(children_dnodes, epb * sizeof (dnode_t *));
+}
+
+/*
+ * Returns held dnode if the object number is valid, NULL if not.
+ * Note that this will succeed even for free dnodes.
+ */
+dnode_t *
+dnode_hold_impl(objset_impl_t *os, uint64_t object, int flag, void *ref)
+{
+	int epb, idx;
+	int drop_struct_lock = FALSE;
+	uint64_t blk;
+	dnode_t *mdn, *dn;
+	dmu_buf_impl_t *db;
+	dnode_t **children_dnodes;
+
+	if (object == 0 || object >= DN_MAX_OBJECT)
+		return (NULL);
+
+	mdn = os->os_meta_dnode;
+
+	dnode_verify(mdn);
+
+	if (!RW_WRITE_HELD(&mdn->dn_struct_rwlock)) {
+		rw_enter(&mdn->dn_struct_rwlock, RW_READER);
+		drop_struct_lock = TRUE;
+	}
+
+	blk = dbuf_whichblock(mdn, object * sizeof (dnode_phys_t));
+
+	db = dbuf_hold(mdn, blk);
+	if (drop_struct_lock)
+		rw_exit(&mdn->dn_struct_rwlock);
+	dbuf_read(db);
+
+	ASSERT3U(db->db.db_size, >=, 1<<DNODE_SHIFT);
+	epb = db->db.db_size >> DNODE_SHIFT;
+
+	idx = object & (epb-1);
+
+	children_dnodes = dmu_buf_get_user(&db->db);
+	if (children_dnodes == NULL) {
+		dnode_t **winner;
+		children_dnodes = kmem_zalloc(epb * sizeof (dnode_t *),
+		    KM_SLEEP);
+		if (winner = dmu_buf_set_user(&db->db, children_dnodes, NULL,
+		    dnode_buf_pageout)) {
+			kmem_free(children_dnodes, epb * sizeof (dnode_t *));
+			children_dnodes = winner;
+		}
+	}
+
+	if ((dn = children_dnodes[idx]) == NULL) {
+		dnode_t *winner;
+		dn = dnode_create(os, (dnode_phys_t *)db->db.db_data+idx,
+			db, object);
+		winner = atomic_cas_ptr(&children_dnodes[idx], NULL, dn);
+		if (winner != NULL) {
+			dnode_destroy(dn);
+			dn = winner;
+		}
+	}
+
+	mutex_enter(&dn->dn_mtx);
+	if (dn->dn_free_txg ||
+	    ((flag & DNODE_MUST_BE_ALLOCATED) && dn->dn_type == DMU_OT_NONE) ||
+	    ((flag & DNODE_MUST_BE_FREE) && dn->dn_type != DMU_OT_NONE)) {
+		mutex_exit(&dn->dn_mtx);
+		dbuf_rele(db);
+		return (NULL);
+	}
+	mutex_exit(&dn->dn_mtx);
+
+	if (refcount_add(&dn->dn_holds, ref) == 1)
+		dbuf_add_ref(db, dn);
+
+	dnode_verify(dn);
+	ASSERT3P(dn->dn_dbuf, ==, db);
+	ASSERT3U(dn->dn_object, ==, object);
+	dbuf_rele(db);
+
+	return (dn);
+}
+
+/*
+ * Return held dnode if the object is allocated, NULL if not.
+ */
+dnode_t *
+dnode_hold(objset_impl_t *os, uint64_t object, void *ref)
+{
+	return (dnode_hold_impl(os, object, DNODE_MUST_BE_ALLOCATED, ref));
+}
+
+void
+dnode_add_ref(dnode_t *dn, void *ref)
+{
+	ASSERT(refcount_count(&dn->dn_holds) > 0);
+	(void) refcount_add(&dn->dn_holds, ref);
+}
+
+void
+dnode_rele(dnode_t *dn, void *ref)
+{
+	uint64_t refs;
+
+	refs = refcount_remove(&dn->dn_holds, ref);
+	/* NOTE: the DNODE_DNODE does not have a dn_dbuf */
+	if (refs == 0 && dn->dn_dbuf)
+		dbuf_remove_ref(dn->dn_dbuf, dn);
+}
+
+void
+dnode_setdirty(dnode_t *dn, dmu_tx_t *tx)
+{
+	objset_impl_t *os = dn->dn_objset;
+	uint64_t txg = tx->tx_txg;
+
+	if (IS_DNODE_DNODE(dn->dn_object))
+		return;
+
+	dnode_verify(dn);
+
+#ifdef ZFS_DEBUG
+	mutex_enter(&dn->dn_mtx);
+	ASSERT(dn->dn_phys->dn_type || dn->dn_allocated_txg);
+	/* ASSERT(dn->dn_free_txg == 0 || dn->dn_free_txg >= txg); */
+	mutex_exit(&dn->dn_mtx);
+#endif
+
+	mutex_enter(&os->os_lock);
+
+	/*
+	 * If we are already marked dirty, we're done.
+	 */
+	if (dn->dn_dirtyblksz[txg&TXG_MASK] > 0) {
+		mutex_exit(&os->os_lock);
+		return;
+	}
+
+	ASSERT(!refcount_is_zero(&dn->dn_holds) || list_head(&dn->dn_dbufs));
+	ASSERT(dn->dn_datablksz != 0);
+	dn->dn_dirtyblksz[txg&TXG_MASK] = dn->dn_datablksz;
+
+	dprintf_ds(os->os_dsl_dataset, "obj=%llu txg=%llu\n",
+	    dn->dn_object, txg);
+
+	if (dn->dn_free_txg > 0 && dn->dn_free_txg <= txg) {
+		list_insert_tail(&os->os_free_dnodes[txg&TXG_MASK], dn);
+	} else {
+		list_insert_tail(&os->os_dirty_dnodes[txg&TXG_MASK], dn);
+	}
+
+	mutex_exit(&os->os_lock);
+
+	/*
+	 * The dnode maintains a hold on its containing dbuf as
+	 * long as there are holds on it.  Each instantiated child
+	 * dbuf maintaines a hold on the dnode.  When the last child
+	 * drops its hold, the dnode will drop its hold on the
+	 * containing dbuf. We add a "dirty hold" here so that the
+	 * dnode will hang around after we finish processing its
+	 * children.
+	 */
+	(void) refcount_add(&dn->dn_holds, (void *)(uintptr_t)tx->tx_txg);
+
+	dbuf_dirty(dn->dn_dbuf, tx);
+
+	dsl_dataset_dirty(os->os_dsl_dataset, tx);
+}
+
+void
+dnode_free(dnode_t *dn, dmu_tx_t *tx)
+{
+	dprintf("dn=%p txg=%llu\n", dn, tx->tx_txg);
+
+	/* we should be the only holder... hopefully */
+	/* ASSERT3U(refcount_count(&dn->dn_holds), ==, 1); */
+
+	mutex_enter(&dn->dn_mtx);
+	if (dn->dn_type == DMU_OT_NONE || dn->dn_free_txg) {
+		mutex_exit(&dn->dn_mtx);
+		return;
+	}
+	dn->dn_free_txg = tx->tx_txg;
+	mutex_exit(&dn->dn_mtx);
+
+	/*
+	 * If the dnode is already dirty, it needs to be moved from
+	 * the dirty list to the free list.
+	 */
+	mutex_enter(&dn->dn_objset->os_lock);
+	if (dn->dn_dirtyblksz[tx->tx_txg&TXG_MASK] > 0) {
+		list_remove(
+		    &dn->dn_objset->os_dirty_dnodes[tx->tx_txg&TXG_MASK], dn);
+		list_insert_tail(
+		    &dn->dn_objset->os_free_dnodes[tx->tx_txg&TXG_MASK], dn);
+		mutex_exit(&dn->dn_objset->os_lock);
+	} else {
+		mutex_exit(&dn->dn_objset->os_lock);
+		dnode_setdirty(dn, tx);
+	}
+}
+
+/*
+ * Try to change the block size for the indicated dnode.  This can only
+ * succeed if there are no blocks allocated or dirty beyond first block
+ */
+int
+dnode_set_blksz(dnode_t *dn, uint64_t size, int ibs, dmu_tx_t *tx)
+{
+	dmu_buf_impl_t *db, *db_next;
+	int have_db0 = FALSE;
+	int err = ENOTSUP;
+
+	if (size == 0)
+		size = SPA_MINBLOCKSIZE;
+	if (size > SPA_MAXBLOCKSIZE)
+		size = SPA_MAXBLOCKSIZE;
+	else
+		size = P2ROUNDUP(size, SPA_MINBLOCKSIZE);
+
+	if (ibs == 0)
+		ibs = dn->dn_indblkshift;
+
+	if (size >> SPA_MINBLOCKSHIFT == dn->dn_datablkszsec &&
+	    ibs == dn->dn_indblkshift)
+		return (0);
+
+	rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
+
+	/* Check for any allocated blocks beyond the first */
+	if (dn->dn_phys->dn_maxblkid != 0)
+		goto end;
+
+	/*
+	 * Any buffers allocated for blocks beyond the first
+	 * must be evictable/evicted, because they're the wrong size.
+	 */
+	mutex_enter(&dn->dn_dbufs_mtx);
+	/*
+	 * Since we have the dn_dbufs_mtx, nothing can be
+	 * removed from dn_dbufs.  Since we have dn_struct_rwlock/w,
+	 * nothing can be added to dn_dbufs.
+	 */
+	for (db = list_head(&dn->dn_dbufs); db; db = db_next) {
+		db_next = list_next(&dn->dn_dbufs, db);
+
+		if (db->db_blkid == 0) {
+			have_db0 = TRUE;
+		} else if (db->db_blkid != DB_BONUS_BLKID) {
+			mutex_exit(&dn->dn_dbufs_mtx);
+			goto end;
+		}
+	}
+	mutex_exit(&dn->dn_dbufs_mtx);
+
+	/* Fast-track if there is no data in the file */
+	if (BP_IS_HOLE(&dn->dn_phys->dn_blkptr[0]) && !have_db0) {
+		dnode_setdblksz(dn, size);
+		dn->dn_indblkshift = ibs;
+		dnode_setdirty(dn, tx);
+		/* don't need dd_dirty_mtx, dnode is already dirty */
+		dn->dn_dirtyblksz[tx->tx_txg&TXG_MASK] = size;
+		dn->dn_next_indblkshift[tx->tx_txg&TXG_MASK] = ibs;
+		rw_exit(&dn->dn_struct_rwlock);
+		return (0);
+	}
+
+	/* obtain the old block */
+	db = dbuf_hold(dn, 0);
+
+	/* Not allowed to decrease the size if there is data present */
+	if (size < db->db.db_size) {
+		dbuf_rele(db);
+		goto end;
+	}
+
+	dbuf_new_size(db, size, tx);
+
+	dnode_setdblksz(dn, size);
+	dn->dn_indblkshift = ibs;
+	/* don't need dd_dirty_mtx, dnode is already dirty */
+	dn->dn_dirtyblksz[tx->tx_txg&TXG_MASK] = size;
+	dn->dn_next_indblkshift[tx->tx_txg&TXG_MASK] = ibs;
+	dbuf_rele(db);
+
+	err = 0;
+end:
+	rw_exit(&dn->dn_struct_rwlock);
+	return (err);
+}
+
+uint64_t
+dnode_max_nonzero_offset(dnode_t *dn)
+{
+	if (dn->dn_phys->dn_maxblkid == 0 &&
+	    BP_IS_HOLE(&dn->dn_phys->dn_blkptr[0]))
+		return (0);
+	else
+		return ((dn->dn_phys->dn_maxblkid+1) * dn->dn_datablksz);
+}
+
+void
+dnode_new_blkid(dnode_t *dn, uint64_t blkid, dmu_tx_t *tx)
+{
+	uint64_t txgoff = tx->tx_txg & TXG_MASK;
+	int drop_struct_lock = FALSE;
+	int epbs, old_nlevels, new_nlevels;
+	uint64_t sz;
+
+	if (blkid == DB_BONUS_BLKID)
+		return;
+
+	if (!RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
+		rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
+		drop_struct_lock = TRUE;
+	}
+
+	if (blkid > dn->dn_maxblkid)
+		dn->dn_maxblkid = blkid;
+
+	/*
+	 * Compute the number of levels necessary to support the
+	 * new blkid.
+	 */
+	new_nlevels = 1;
+	epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
+
+	for (sz = dn->dn_nblkptr; sz <= blkid && sz >= dn->dn_nblkptr;
+	    sz <<= epbs)
+		new_nlevels++;
+	old_nlevels = dn->dn_nlevels;
+
+	if (new_nlevels > dn->dn_next_nlevels[txgoff])
+		dn->dn_next_nlevels[txgoff] = new_nlevels;
+
+	if (new_nlevels > old_nlevels) {
+		dprintf("dn %p increasing nlevels from %u to %u\n",
+		    dn, dn->dn_nlevels, new_nlevels);
+		dn->dn_nlevels = new_nlevels;
+	}
+
+	/*
+	 * Dirty the left indirects.
+	 * Note: the caller should have just dnode_use_space()'d one
+	 * data block's worth, so we could subtract that out of
+	 * dn_inflight_data to determine if there is any dirty data
+	 * besides this block.
+	 * We don't strictly need to dirty them unless there's
+	 * *something* in the object (eg. on disk or dirty)...
+	 */
+	if (new_nlevels > old_nlevels) {
+		dmu_buf_impl_t *db = dbuf_hold_level(dn, old_nlevels, 0, FTAG);
+		dprintf("dn %p dirtying left indirects\n", dn);
+		dbuf_dirty(db, tx);
+		dbuf_remove_ref(db, FTAG);
+	}
+#ifdef ZFS_DEBUG
+	else if (old_nlevels > 1 && new_nlevels > old_nlevels) {
+		dmu_buf_impl_t *db;
+		int i;
+
+		for (i = 0; i < dn->dn_nblkptr; i++) {
+			db = dbuf_hold_level(dn, old_nlevels-1, i, FTAG);
+			ASSERT(!
+			    list_link_active(&db->db_dirty_node[txgoff]));
+			dbuf_remove_ref(db, FTAG);
+		}
+	}
+#endif
+
+	dprintf("dn %p done\n", dn);
+
+out:
+	if (drop_struct_lock)
+		rw_exit(&dn->dn_struct_rwlock);
+}
+
+void
+dnode_clear_range(dnode_t *dn, uint64_t blkid, uint64_t nblks, dmu_tx_t *tx)
+{
+	avl_tree_t *tree = &dn->dn_ranges[tx->tx_txg&TXG_MASK];
+	avl_index_t where;
+	free_range_t *rp;
+	free_range_t rp_tofind;
+	uint64_t endblk = blkid + nblks;
+
+	ASSERT(MUTEX_HELD(&dn->dn_mtx));
+	ASSERT(nblks <= UINT64_MAX - blkid); /* no overflow */
+
+	dprintf_dnode(dn, "blkid=%llu nblks=%llu txg=%llu\n",
+	    blkid, nblks, tx->tx_txg);
+	rp_tofind.fr_blkid = blkid;
+	rp = avl_find(tree, &rp_tofind, &where);
+	if (rp == NULL)
+		rp = avl_nearest(tree, where, AVL_BEFORE);
+	if (rp == NULL)
+		rp = avl_nearest(tree, where, AVL_AFTER);
+
+	while (rp && (rp->fr_blkid <= blkid + nblks)) {
+		uint64_t fr_endblk = rp->fr_blkid + rp->fr_nblks;
+		free_range_t *nrp = AVL_NEXT(tree, rp);
+
+		if (blkid <= rp->fr_blkid && endblk >= fr_endblk) {
+			/* clear this entire range */
+			avl_remove(tree, rp);
+			kmem_free(rp, sizeof (free_range_t));
+		} else if (blkid <= rp->fr_blkid &&
+		    endblk > rp->fr_blkid && endblk < fr_endblk) {
+			/* clear the beginning of this range */
+			rp->fr_blkid = endblk;
+			rp->fr_nblks = fr_endblk - endblk;
+		} else if (blkid > rp->fr_blkid && blkid < fr_endblk &&
+		    endblk >= fr_endblk) {
+			/* clear the end of this range */
+			rp->fr_nblks = blkid - rp->fr_blkid;
+		} else if (blkid > rp->fr_blkid && endblk < fr_endblk) {
+			/* clear a chunk out of this range */
+			free_range_t *new_rp =
+			    kmem_alloc(sizeof (free_range_t), KM_SLEEP);
+
+			new_rp->fr_blkid = endblk;
+			new_rp->fr_nblks = fr_endblk - endblk;
+			avl_insert_here(tree, new_rp, rp, AVL_AFTER);
+			rp->fr_nblks = blkid - rp->fr_blkid;
+		}
+		/* there may be no overlap */
+		rp = nrp;
+	}
+}
+
+void
+dnode_free_range(dnode_t *dn, uint64_t off, uint64_t len, dmu_tx_t *tx)
+{
+	dmu_buf_impl_t *db;
+	uint64_t start, objsize, blkid, nblks;
+	int blkshift, blksz, tail, head, epbs;
+	int trunc = FALSE;
+
+	rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
+	blksz = dn->dn_datablksz;
+	blkshift = dn->dn_datablkshift;
+	epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
+
+	/* If the range is past the end of the file, this is a no-op */
+	objsize = blksz * (dn->dn_maxblkid+1);
+	if (off >= objsize)
+		goto out;
+	if (len == -1ULL) {
+		len = UINT64_MAX - off;
+		trunc = TRUE;
+	}
+
+	/*
+	 * First, block align the region to free:
+	 */
+	if (dn->dn_maxblkid == 0) {
+		if (off == 0) {
+			head = 0;
+		} else {
+			head = blksz - off;
+			ASSERT3U(head, >, 0);
+		}
+		start = off;
+	} else {
+		ASSERT(ISP2(blksz));
+		head = P2NPHASE(off, blksz);
+		start = P2PHASE(off, blksz);
+	}
+	/* zero out any partial block data at the start of the range */
+	if (head) {
+		ASSERT3U(start + head, ==, blksz);
+		if (len < head)
+			head = len;
+		if (dbuf_hold_impl(dn, 0, dbuf_whichblock(dn, off), TRUE,
+		    FTAG, &db) == 0) {
+			caddr_t data;
+
+			/* don't dirty if it isn't on disk and isn't dirty */
+			if (db->db_dirtied ||
+			    (db->db_blkptr && !BP_IS_HOLE(db->db_blkptr))) {
+				rw_exit(&dn->dn_struct_rwlock);
+				dbuf_will_dirty(db, tx);
+				rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
+				data = db->db.db_data;
+				bzero(data + start, head);
+			}
+			dbuf_remove_ref(db, FTAG);
+		}
+		off += head;
+		len -= head;
+	}
+	/* If the range was less than one block, we are done */
+	if (len == 0)
+		goto out;
+
+	/* If the remaining range is past the end of the file, we are done */
+	if (off > dn->dn_maxblkid << blkshift)
+		goto out;
+
+	if (off + len == UINT64_MAX)
+		tail = 0;
+	else
+		tail = P2PHASE(len, blksz);
+
+	ASSERT3U(P2PHASE(off, blksz), ==, 0);
+	/* zero out any partial block data at the end of the range */
+	if (tail) {
+		if (len < tail)
+			tail = len;
+		if (dbuf_hold_impl(dn, 0, dbuf_whichblock(dn, off+len),
+		    TRUE, FTAG, &db) == 0) {
+			/* don't dirty if it isn't on disk and isn't dirty */
+			if (db->db_dirtied ||
+			    (db->db_blkptr && !BP_IS_HOLE(db->db_blkptr))) {
+				rw_exit(&dn->dn_struct_rwlock);
+				dbuf_will_dirty(db, tx);
+				rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
+				bzero(db->db.db_data, tail);
+			}
+			dbuf_remove_ref(db, FTAG);
+		}
+		len -= tail;
+	}
+	/* If the range did not include a full block, we are done */
+	if (len == 0)
+		goto out;
+
+	/* dirty the left indirects */
+	if (dn->dn_nlevels > 1 && off != 0) {
+		db = dbuf_hold_level(dn, 1,
+		    (off - head) >> (blkshift + epbs), FTAG);
+		dbuf_will_dirty(db, tx);
+		dbuf_remove_ref(db, FTAG);
+	}
+
+	/* dirty the right indirects */
+	if (dn->dn_nlevels > 1 && !trunc) {
+		db = dbuf_hold_level(dn, 1,
+		    (off + len + tail - 1) >> (blkshift + epbs), FTAG);
+		dbuf_will_dirty(db, tx);
+		dbuf_remove_ref(db, FTAG);
+	}
+
+	/*
+	 * Finally, add this range to the dnode range list, we
+	 * will finish up this free operation in the syncing phase.
+	 */
+	ASSERT(IS_P2ALIGNED(off, 1<<blkshift));
+	ASSERT(off + len == UINT64_MAX || IS_P2ALIGNED(len, 1<<blkshift));
+	blkid = off >> blkshift;
+	nblks = len >> blkshift;
+
+	if (trunc)
+		dn->dn_maxblkid = (blkid ? blkid - 1 : 0);
+
+	mutex_enter(&dn->dn_mtx);
+	dnode_clear_range(dn, blkid, nblks, tx);
+	{
+		free_range_t *rp, *found;
+		avl_index_t where;
+		avl_tree_t *tree = &dn->dn_ranges[tx->tx_txg&TXG_MASK];
+
+		/* Add new range to dn_ranges */
+		rp = kmem_alloc(sizeof (free_range_t), KM_SLEEP);
+		rp->fr_blkid = blkid;
+		rp->fr_nblks = nblks;
+		found = avl_find(tree, rp, &where);
+		ASSERT(found == NULL);
+		avl_insert(tree, rp, where);
+		dprintf_dnode(dn, "blkid=%llu nblks=%llu txg=%llu\n",
+		    blkid, nblks, tx->tx_txg);
+	}
+	mutex_exit(&dn->dn_mtx);
+
+	dbuf_free_range(dn, blkid, nblks, tx);
+	dnode_setdirty(dn, tx);
+out:
+	rw_exit(&dn->dn_struct_rwlock);
+}
+
+/* return TRUE if this blkid was freed in a recent txg, or FALSE if it wasn't */
+uint64_t
+dnode_block_freed(dnode_t *dn, uint64_t blkid)
+{
+	free_range_t range_tofind;
+	void *dp = spa_get_dsl(dn->dn_objset->os_spa);
+	int i;
+
+	if (blkid == DB_BONUS_BLKID)
+		return (FALSE);
+
+	/*
+	 * If we're in the process of opening the pool, dp will not be
+	 * set yet, but there shouldn't be anything dirty.
+	 */
+	if (dp == NULL)
+		return (FALSE);
+
+	if (dn->dn_free_txg)
+		return (TRUE);
+
+	/*
+	 * If dn_datablkshift is not set, then there's only a single
+	 * block, in which case there will never be a free range so it
+	 * won't matter.
+	 */
+	range_tofind.fr_blkid = blkid;
+	mutex_enter(&dn->dn_mtx);
+	for (i = 0; i < TXG_SIZE; i++) {
+		free_range_t *range_found;
+		avl_index_t idx;
+
+		range_found = avl_find(&dn->dn_ranges[i], &range_tofind, &idx);
+		if (range_found) {
+			ASSERT(range_found->fr_nblks > 0);
+			break;
+		}
+		range_found = avl_nearest(&dn->dn_ranges[i], idx, AVL_BEFORE);
+		if (range_found &&
+		    range_found->fr_blkid + range_found->fr_nblks > blkid)
+			break;
+	}
+	mutex_exit(&dn->dn_mtx);
+	return (i < TXG_SIZE);
+}
+
+/* call from syncing context when we actually write/free space for this dnode */
+void
+dnode_diduse_space(dnode_t *dn, int64_t space)
+{
+	uint64_t sectors;
+
+	dprintf_dnode(dn, "dn=%p dnp=%p secphys=%llu space=%lld\n",
+	    dn, dn->dn_phys,
+	    (u_longlong_t)dn->dn_phys->dn_secphys,
+	    (longlong_t)space);
+
+	ASSERT(P2PHASE(space, 1<<DEV_BSHIFT) == 0);
+
+	mutex_enter(&dn->dn_mtx);
+	if (space > 0) {
+		sectors = space >> DEV_BSHIFT;
+		ASSERT3U(dn->dn_phys->dn_secphys + sectors, >=,
+		    dn->dn_phys->dn_secphys);
+		dn->dn_phys->dn_secphys += sectors;
+	} else {
+		sectors = -space >> DEV_BSHIFT;
+		ASSERT3U(dn->dn_phys->dn_secphys, >=, sectors);
+		dn->dn_phys->dn_secphys -= sectors;
+	}
+	mutex_exit(&dn->dn_mtx);
+}
+
+/*
+ * Call when we think we're going to write/free space in open context.
+ * Be conservative (ie. OK to write less than this or free more than
+ * this, but don't write more or free less).
+ */
+void
+dnode_willuse_space(dnode_t *dn, int64_t space, dmu_tx_t *tx)
+{
+	objset_impl_t *os = dn->dn_objset;
+	dsl_dataset_t *ds = os->os_dsl_dataset;
+
+	if (space > 0)
+		space = spa_get_asize(os->os_spa, space);
+
+	if (ds)
+		dsl_dir_willuse_space(ds->ds_dir, space, tx);
+
+	dmu_tx_willuse_space(tx, space);
+}
+
+static int
+dnode_next_offset_level(dnode_t *dn, boolean_t hole, uint64_t *offset,
+	int lvl, uint64_t blkfill)
+{
+	dmu_buf_impl_t *db = NULL;
+	void *data = NULL;
+	uint64_t epbs = dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;
+	uint64_t epb = 1ULL << epbs;
+	uint64_t minfill, maxfill;
+	int i, error, span;
+
+	dprintf("probing object %llu offset %llx level %d of %u\n",
+	    dn->dn_object, *offset, lvl, dn->dn_phys->dn_nlevels);
+
+	if (lvl == dn->dn_phys->dn_nlevels) {
+		error = 0;
+		epb = dn->dn_phys->dn_nblkptr;
+		data = dn->dn_phys->dn_blkptr;
+	} else {
+		uint64_t blkid = dbuf_whichblock(dn, *offset) >> (epbs * lvl);
+		error = dbuf_hold_impl(dn, lvl, blkid, TRUE, FTAG, &db);
+		if (error) {
+			if (error == ENOENT)
+				return (hole ? 0 : ESRCH);
+			return (error);
+		}
+		dbuf_read_havestruct(db);
+		data = db->db.db_data;
+	}
+
+	if (lvl == 0) {
+		dnode_phys_t *dnp = data;
+		span = DNODE_SHIFT;
+		ASSERT(dn->dn_type == DMU_OT_DNODE);
+
+		for (i = (*offset >> span) & (blkfill - 1); i < blkfill; i++) {
+			if (!dnp[i].dn_type == hole)
+				break;
+			*offset += 1ULL << span;
+		}
+		if (i == blkfill)
+			error = ESRCH;
+	} else {
+		blkptr_t *bp = data;
+		span = (lvl - 1) * epbs + dn->dn_datablkshift;
+		minfill = 0;
+		maxfill = blkfill << ((lvl - 1) * epbs);
+
+		if (hole)
+			maxfill--;
+		else
+			minfill++;
+
+		for (i = (*offset >> span) & ((1ULL << epbs) - 1);
+		    i < epb; i++) {
+			if (bp[i].blk_fill >= minfill &&
+			    bp[i].blk_fill <= maxfill)
+				break;
+			*offset += 1ULL << span;
+		}
+		if (i >= epb)
+			error = ESRCH;
+	}
+
+	if (db)
+		dbuf_remove_ref(db, FTAG);
+
+	return (error);
+}
+
+/*
+ * Find the next hole, data, or sparse region at or after *offset.
+ * The value 'blkfill' tells us how many items we expect to find
+ * in an L0 data block; this value is 1 for normal objects,
+ * DNODES_PER_BLOCK for the meta dnode, and some fraction of
+ * DNODES_PER_BLOCK when searching for sparse regions thereof.
+ * Examples:
+ *
+ * dnode_next_offset(dn, hole, offset, 1, 1);
+ *	Finds the next hole/data in a file.
+ *	Used in dmu_offset_next().
+ *
+ * dnode_next_offset(mdn, hole, offset, 0, DNODES_PER_BLOCK);
+ *	Finds the next free/allocated dnode an objset's meta-dnode.
+ *	Used in dmu_object_next().
+ *
+ * dnode_next_offset(mdn, TRUE, offset, 2, DNODES_PER_BLOCK >> 2);
+ *	Finds the next L2 meta-dnode bp that's at most 1/4 full.
+ *	Used in dmu_object_alloc().
+ */
+int
+dnode_next_offset(dnode_t *dn, boolean_t hole, uint64_t *offset,
+    int minlvl, uint64_t blkfill)
+{
+	int lvl, maxlvl;
+	int error = 0;
+	uint64_t initial_offset = *offset;
+
+	rw_enter(&dn->dn_struct_rwlock, RW_READER);
+
+	if (dn->dn_phys->dn_nlevels == 0) {
+		rw_exit(&dn->dn_struct_rwlock);
+		return (ESRCH);
+	}
+
+	if (dn->dn_datablkshift == 0) {
+		if (*offset < dn->dn_datablksz) {
+			if (hole)
+				*offset = dn->dn_datablksz;
+		} else {
+			error = ESRCH;
+		}
+		rw_exit(&dn->dn_struct_rwlock);
+		return (error);
+	}
+
+	maxlvl = dn->dn_phys->dn_nlevels;
+
+	for (lvl = minlvl; lvl <= maxlvl; lvl++) {
+		error = dnode_next_offset_level(dn, hole, offset, lvl, blkfill);
+		if (error == 0)
+			break;
+	}
+
+	while (--lvl >= minlvl && error == 0)
+		error = dnode_next_offset_level(dn, hole, offset, lvl, blkfill);
+
+	rw_exit(&dn->dn_struct_rwlock);
+
+	if (initial_offset > *offset)
+		return (ESRCH);
+
+	return (error);
+}