Merge commit 'refs/top-bases/gcc-unused' into gcc-unused

1 files changed, 627 insertions, 0 deletions

diff --git a/module/zfs/dnode_sync.c b/module/zfs/dnode_sync.c
new file mode 100644
index 000000000..3ead08de2
--- /dev/null
+++ b/module/zfs/dnode_sync.c
@@ -0,0 +1,627 @@
+/*
+ * 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 2008 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_tx.h>
+#include <sys/dmu_objset.h>
+#include <sys/dsl_dataset.h>
+#include <sys/spa.h>
+
+static void
+dnode_increase_indirection(dnode_t *dn, dmu_tx_t *tx)
+{
+	dmu_buf_impl_t *db;
+	int txgoff = tx->tx_txg & TXG_MASK;
+	int nblkptr = dn->dn_phys->dn_nblkptr;
+	int old_toplvl = dn->dn_phys->dn_nlevels - 1;
+	int new_level = dn->dn_next_nlevels[txgoff];
+	int i;
+
+	rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
+
+	/* this dnode can't be paged out because it's dirty */
+	ASSERT(dn->dn_phys->dn_type != DMU_OT_NONE);
+	ASSERT(RW_WRITE_HELD(&dn->dn_struct_rwlock));
+	ASSERT(new_level > 1 && dn->dn_phys->dn_nlevels > 0);
+
+	db = dbuf_hold_level(dn, dn->dn_phys->dn_nlevels, 0, FTAG);
+	ASSERT(db != NULL);
+
+	dn->dn_phys->dn_nlevels = new_level;
+	dprintf("os=%p obj=%llu, increase to %d\n", dn->dn_objset,
+	    dn->dn_object, dn->dn_phys->dn_nlevels);
+
+	/* check for existing blkptrs in the dnode */
+	for (i = 0; i < nblkptr; i++)
+		if (!BP_IS_HOLE(&dn->dn_phys->dn_blkptr[i]))
+			break;
+	if (i != nblkptr) {
+		/* transfer dnode's block pointers to new indirect block */
+		(void) dbuf_read(db, NULL, DB_RF_MUST_SUCCEED|DB_RF_HAVESTRUCT);
+		ASSERT(db->db.db_data);
+		ASSERT(arc_released(db->db_buf));
+		ASSERT3U(sizeof (blkptr_t) * nblkptr, <=, db->db.db_size);
+		bcopy(dn->dn_phys->dn_blkptr, db->db.db_data,
+		    sizeof (blkptr_t) * nblkptr);
+		arc_buf_freeze(db->db_buf);
+	}
+
+	/* set dbuf's parent pointers to new indirect buf */
+	for (i = 0; i < nblkptr; i++) {
+		dmu_buf_impl_t *child = dbuf_find(dn, old_toplvl, i);
+
+		if (child == NULL)
+			continue;
+		ASSERT3P(child->db_dnode, ==, dn);
+		if (child->db_parent && child->db_parent != dn->dn_dbuf) {
+			ASSERT(child->db_parent->db_level == db->db_level);
+			ASSERT(child->db_blkptr !=
+			    &dn->dn_phys->dn_blkptr[child->db_blkid]);
+			mutex_exit(&child->db_mtx);
+			continue;
+		}
+		ASSERT(child->db_parent == NULL ||
+		    child->db_parent == dn->dn_dbuf);
+
+		child->db_parent = db;
+		dbuf_add_ref(db, child);
+		if (db->db.db_data)
+			child->db_blkptr = (blkptr_t *)db->db.db_data + i;
+		else
+			child->db_blkptr = NULL;
+		dprintf_dbuf_bp(child, child->db_blkptr,
+		    "changed db_blkptr to new indirect %s", "");
+
+		mutex_exit(&child->db_mtx);
+	}
+
+	bzero(dn->dn_phys->dn_blkptr, sizeof (blkptr_t) * nblkptr);
+
+	dbuf_rele(db, FTAG);
+
+	rw_exit(&dn->dn_struct_rwlock);
+}
+
+static int
+free_blocks(dnode_t *dn, blkptr_t *bp, int num, dmu_tx_t *tx)
+{
+	dsl_dataset_t *ds = dn->dn_objset->os_dsl_dataset;
+	uint64_t bytesfreed = 0;
+	int i, blocks_freed = 0;
+
+	dprintf("ds=%p obj=%llx num=%d\n", ds, dn->dn_object, num);
+
+	for (i = 0; i < num; i++, bp++) {
+		if (BP_IS_HOLE(bp))
+			continue;
+
+		bytesfreed += dsl_dataset_block_kill(ds, bp, dn->dn_zio, tx);
+		ASSERT3U(bytesfreed, <=, DN_USED_BYTES(dn->dn_phys));
+		bzero(bp, sizeof (blkptr_t));
+		blocks_freed += 1;
+	}
+	dnode_diduse_space(dn, -bytesfreed);
+	return (blocks_freed);
+}
+
+#ifdef ZFS_DEBUG
+static void
+free_verify(dmu_buf_impl_t *db, uint64_t start, uint64_t end, dmu_tx_t *tx)
+{
+	int off, num;
+	int i, err, epbs;
+	uint64_t txg = tx->tx_txg;
+
+	epbs = db->db_dnode->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;
+	off = start - (db->db_blkid * 1<<epbs);
+	num = end - start + 1;
+
+	ASSERT3U(off, >=, 0);
+	ASSERT3U(num, >=, 0);
+	ASSERT3U(db->db_level, >, 0);
+	ASSERT3U(db->db.db_size, ==, 1<<db->db_dnode->dn_phys->dn_indblkshift);
+	ASSERT3U(off+num, <=, db->db.db_size >> SPA_BLKPTRSHIFT);
+	ASSERT(db->db_blkptr != NULL);
+
+	for (i = off; i < off+num; i++) {
+		uint64_t *buf;
+		dmu_buf_impl_t *child;
+		dbuf_dirty_record_t *dr;
+		int j;
+
+		ASSERT(db->db_level == 1);
+
+		rw_enter(&db->db_dnode->dn_struct_rwlock, RW_READER);
+		err = dbuf_hold_impl(db->db_dnode, db->db_level-1,
+		    (db->db_blkid << epbs) + i, TRUE, FTAG, &child);
+		rw_exit(&db->db_dnode->dn_struct_rwlock);
+		if (err == ENOENT)
+			continue;
+		ASSERT(err == 0);
+		ASSERT(child->db_level == 0);
+		dr = child->db_last_dirty;
+		while (dr && dr->dr_txg > txg)
+			dr = dr->dr_next;
+		ASSERT(dr == NULL || dr->dr_txg == txg);
+
+		/* data_old better be zeroed */
+		if (dr) {
+			buf = dr->dt.dl.dr_data->b_data;
+			for (j = 0; j < child->db.db_size >> 3; j++) {
+				if (buf[j] != 0) {
+					panic("freed data not zero: "
+					    "child=%p i=%d off=%d num=%d\n",
+					    (void *)child, i, off, num);
+				}
+			}
+		}
+
+		/*
+		 * db_data better be zeroed unless it's dirty in a
+		 * future txg.
+		 */
+		mutex_enter(&child->db_mtx);
+		buf = child->db.db_data;
+		if (buf != NULL && child->db_state != DB_FILL &&
+		    child->db_last_dirty == NULL) {
+			for (j = 0; j < child->db.db_size >> 3; j++) {
+				if (buf[j] != 0) {
+					panic("freed data not zero: "
+					    "child=%p i=%d off=%d num=%d\n",
+					    (void *)child, i, off, num);
+				}
+			}
+		}
+		mutex_exit(&child->db_mtx);
+
+		dbuf_rele(child, FTAG);
+	}
+}
+#endif
+
+#define	ALL -1
+
+static int
+free_children(dmu_buf_impl_t *db, uint64_t blkid, uint64_t nblks, int trunc,
+    dmu_tx_t *tx)
+{
+	dnode_t *dn = db->db_dnode;
+	blkptr_t *bp;
+	dmu_buf_impl_t *subdb;
+	uint64_t start, end, dbstart, dbend, i;
+	int epbs, shift, err;
+	int all = TRUE;
+	int blocks_freed = 0;
+
+	/*
+	 * There is a small possibility that this block will not be cached:
+	 *   1 - if level > 1 and there are no children with level <= 1
+	 *   2 - if we didn't get a dirty hold (because this block had just
+	 *	 finished being written -- and so had no holds), and then this
+	 *	 block got evicted before we got here.
+	 */
+	if (db->db_state != DB_CACHED)
+		(void) dbuf_read(db, NULL, DB_RF_MUST_SUCCEED);
+
+	arc_release(db->db_buf, db);
+	bp = (blkptr_t *)db->db.db_data;
+
+	epbs = db->db_dnode->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;
+	shift = (db->db_level - 1) * epbs;
+	dbstart = db->db_blkid << epbs;
+	start = blkid >> shift;
+	if (dbstart < start) {
+		bp += start - dbstart;
+		all = FALSE;
+	} else {
+		start = dbstart;
+	}
+	dbend = ((db->db_blkid + 1) << epbs) - 1;
+	end = (blkid + nblks - 1) >> shift;
+	if (dbend <= end)
+		end = dbend;
+	else if (all)
+		all = trunc;
+	ASSERT3U(start, <=, end);
+
+	if (db->db_level == 1) {
+		FREE_VERIFY(db, start, end, tx);
+		blocks_freed = free_blocks(dn, bp, end-start+1, tx);
+		arc_buf_freeze(db->db_buf);
+		ASSERT(all || blocks_freed == 0 || db->db_last_dirty);
+		return (all ? ALL : blocks_freed);
+	}
+
+	for (i = start; i <= end; i++, bp++) {
+		if (BP_IS_HOLE(bp))
+			continue;
+		rw_enter(&dn->dn_struct_rwlock, RW_READER);
+		err = dbuf_hold_impl(dn, db->db_level-1, i, TRUE, FTAG, &subdb);
+		ASSERT3U(err, ==, 0);
+		rw_exit(&dn->dn_struct_rwlock);
+
+		if (free_children(subdb, blkid, nblks, trunc, tx) == ALL) {
+			ASSERT3P(subdb->db_blkptr, ==, bp);
+			blocks_freed += free_blocks(dn, bp, 1, tx);
+		} else {
+			all = FALSE;
+		}
+		dbuf_rele(subdb, FTAG);
+	}
+	arc_buf_freeze(db->db_buf);
+#ifdef ZFS_DEBUG
+	bp -= (end-start)+1;
+	for (i = start; i <= end; i++, bp++) {
+		if (i == start && blkid != 0)
+			continue;
+		else if (i == end && !trunc)
+			continue;
+		ASSERT3U(bp->blk_birth, ==, 0);
+	}
+#endif
+	ASSERT(all || blocks_freed == 0 || db->db_last_dirty);
+	return (all ? ALL : blocks_freed);
+}
+
+/*
+ * free_range: Traverse the indicated range of the provided file
+ * and "free" all the blocks contained there.
+ */
+static void
+dnode_sync_free_range(dnode_t *dn, uint64_t blkid, uint64_t nblks, dmu_tx_t *tx)
+{
+	blkptr_t *bp = dn->dn_phys->dn_blkptr;
+	dmu_buf_impl_t *db;
+	int trunc, start, end, shift, i, err;
+	int dnlevel = dn->dn_phys->dn_nlevels;
+
+	if (blkid > dn->dn_phys->dn_maxblkid)
+		return;
+
+	ASSERT(dn->dn_phys->dn_maxblkid < UINT64_MAX);
+	trunc = blkid + nblks > dn->dn_phys->dn_maxblkid;
+	if (trunc)
+		nblks = dn->dn_phys->dn_maxblkid - blkid + 1;
+
+	/* There are no indirect blocks in the object */
+	if (dnlevel == 1) {
+		if (blkid >= dn->dn_phys->dn_nblkptr) {
+			/* this range was never made persistent */
+			return;
+		}
+		ASSERT3U(blkid + nblks, <=, dn->dn_phys->dn_nblkptr);
+		(void) free_blocks(dn, bp + blkid, nblks, tx);
+		if (trunc) {
+#ifndef NDEBUG
+			uint64_t off = (dn->dn_phys->dn_maxblkid + 1) *
+			    (dn->dn_phys->dn_datablkszsec << SPA_MINBLOCKSHIFT);
+#endif
+			dn->dn_phys->dn_maxblkid = (blkid ? blkid - 1 : 0);
+			ASSERT(off < dn->dn_phys->dn_maxblkid ||
+			    dn->dn_phys->dn_maxblkid == 0 ||
+			    dnode_next_offset(dn, 0, &off, 1, 1, 0) != 0);
+		}
+		return;
+	}
+
+	shift = (dnlevel - 1) * (dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT);
+	start = blkid >> shift;
+	ASSERT(start < dn->dn_phys->dn_nblkptr);
+	end = (blkid + nblks - 1) >> shift;
+	bp += start;
+	for (i = start; i <= end; i++, bp++) {
+		if (BP_IS_HOLE(bp))
+			continue;
+		rw_enter(&dn->dn_struct_rwlock, RW_READER);
+		err = dbuf_hold_impl(dn, dnlevel-1, i, TRUE, FTAG, &db);
+		ASSERT3U(err, ==, 0);
+		rw_exit(&dn->dn_struct_rwlock);
+
+		if (free_children(db, blkid, nblks, trunc, tx) == ALL) {
+			ASSERT3P(db->db_blkptr, ==, bp);
+			(void) free_blocks(dn, bp, 1, tx);
+		}
+		dbuf_rele(db, FTAG);
+	}
+	if (trunc) {
+#ifndef NDEBUG
+		uint64_t off = (dn->dn_phys->dn_maxblkid + 1) *
+		    (dn->dn_phys->dn_datablkszsec << SPA_MINBLOCKSHIFT);
+#endif
+		dn->dn_phys->dn_maxblkid = (blkid ? blkid - 1 : 0);
+		ASSERT(off < dn->dn_phys->dn_maxblkid ||
+		    dn->dn_phys->dn_maxblkid == 0 ||
+		    dnode_next_offset(dn, 0, &off, 1, 1, 0) != 0);
+	}
+}
+
+/*
+ * Try to kick all the dnodes dbufs out of the cache...
+ */
+void
+dnode_evict_dbufs(dnode_t *dn)
+{
+	int progress;
+	int pass = 0;
+
+	do {
+		dmu_buf_impl_t *db, marker;
+		int evicting = FALSE;
+
+		progress = FALSE;
+		mutex_enter(&dn->dn_dbufs_mtx);
+		list_insert_tail(&dn->dn_dbufs, &marker);
+		db = list_head(&dn->dn_dbufs);
+		for (; db != &marker; db = list_head(&dn->dn_dbufs)) {
+			list_remove(&dn->dn_dbufs, db);
+			list_insert_tail(&dn->dn_dbufs, db);
+			ASSERT3P(db->db_dnode, ==, dn);
+
+			mutex_enter(&db->db_mtx);
+			if (db->db_state == DB_EVICTING) {
+				progress = TRUE;
+				evicting = TRUE;
+				mutex_exit(&db->db_mtx);
+			} else if (refcount_is_zero(&db->db_holds)) {
+				progress = TRUE;
+				dbuf_clear(db); /* exits db_mtx for us */
+			} else {
+				mutex_exit(&db->db_mtx);
+			}
+
+		}
+		list_remove(&dn->dn_dbufs, &marker);
+		/*
+		 * NB: we need to drop dn_dbufs_mtx between passes so
+		 * that any DB_EVICTING dbufs can make progress.
+		 * Ideally, we would have some cv we could wait on, but
+		 * since we don't, just wait a bit to give the other
+		 * thread a chance to run.
+		 */
+		mutex_exit(&dn->dn_dbufs_mtx);
+		if (evicting)
+			delay(1);
+		pass++;
+		ASSERT(pass < 100); /* sanity check */
+	} while (progress);
+
+	rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
+	if (dn->dn_bonus && refcount_is_zero(&dn->dn_bonus->db_holds)) {
+		mutex_enter(&dn->dn_bonus->db_mtx);
+		dbuf_evict(dn->dn_bonus);
+		dn->dn_bonus = NULL;
+	}
+	rw_exit(&dn->dn_struct_rwlock);
+}
+
+static void
+dnode_undirty_dbufs(list_t *list)
+{
+	dbuf_dirty_record_t *dr;
+
+	while (dr = list_head(list)) {
+		dmu_buf_impl_t *db = dr->dr_dbuf;
+		uint64_t txg = dr->dr_txg;
+
+		mutex_enter(&db->db_mtx);
+		/* XXX - use dbuf_undirty()? */
+		list_remove(list, dr);
+		ASSERT(db->db_last_dirty == dr);
+		db->db_last_dirty = NULL;
+		db->db_dirtycnt -= 1;
+		if (db->db_level == 0) {
+			ASSERT(db->db_blkid == DB_BONUS_BLKID ||
+			    dr->dt.dl.dr_data == db->db_buf);
+			dbuf_unoverride(dr);
+			mutex_exit(&db->db_mtx);
+		} else {
+			mutex_exit(&db->db_mtx);
+			dnode_undirty_dbufs(&dr->dt.di.dr_children);
+		}
+		kmem_free(dr, sizeof (dbuf_dirty_record_t));
+		dbuf_rele(db, (void *)(uintptr_t)txg);
+	}
+}
+
+static void
+dnode_sync_free(dnode_t *dn, dmu_tx_t *tx)
+{
+	int txgoff = tx->tx_txg & TXG_MASK;
+
+	ASSERT(dmu_tx_is_syncing(tx));
+
+	/*
+	 * Our contents should have been freed in dnode_sync() by the
+	 * free range record inserted by the caller of dnode_free().
+	 */
+	ASSERT3U(DN_USED_BYTES(dn->dn_phys), ==, 0);
+	ASSERT(BP_IS_HOLE(dn->dn_phys->dn_blkptr));
+
+	dnode_undirty_dbufs(&dn->dn_dirty_records[txgoff]);
+	dnode_evict_dbufs(dn);
+	ASSERT3P(list_head(&dn->dn_dbufs), ==, NULL);
+
+	/*
+	 * XXX - It would be nice to assert this, but we may still
+	 * have residual holds from async evictions from the arc...
+	 *
+	 * zfs_obj_to_path() also depends on this being
+	 * commented out.
+	 *
+	 * ASSERT3U(refcount_count(&dn->dn_holds), ==, 1);
+	 */
+
+	/* Undirty next bits */
+	dn->dn_next_nlevels[txgoff] = 0;
+	dn->dn_next_indblkshift[txgoff] = 0;
+	dn->dn_next_blksz[txgoff] = 0;
+
+	/* ASSERT(blkptrs are zero); */
+	ASSERT(dn->dn_phys->dn_type != DMU_OT_NONE);
+	ASSERT(dn->dn_type != DMU_OT_NONE);
+
+	ASSERT(dn->dn_free_txg > 0);
+	if (dn->dn_allocated_txg != dn->dn_free_txg)
+		dbuf_will_dirty(dn->dn_dbuf, tx);
+	bzero(dn->dn_phys, sizeof (dnode_phys_t));
+
+	mutex_enter(&dn->dn_mtx);
+	dn->dn_type = DMU_OT_NONE;
+	dn->dn_maxblkid = 0;
+	dn->dn_allocated_txg = 0;
+	dn->dn_free_txg = 0;
+	mutex_exit(&dn->dn_mtx);
+
+	ASSERT(dn->dn_object != DMU_META_DNODE_OBJECT);
+
+	dnode_rele(dn, (void *)(uintptr_t)tx->tx_txg);
+	/*
+	 * Now that we've released our hold, the dnode may
+	 * be evicted, so we musn't access it.
+	 */
+}
+
+/*
+ * Write out the dnode's dirty buffers.
+ *
+ * NOTE: The dnode is kept in memory by being dirty.  Once the
+ * dirty bit is cleared, it may be evicted.  Beware of this!
+ */
+void
+dnode_sync(dnode_t *dn, dmu_tx_t *tx)
+{
+	free_range_t *rp;
+	dnode_phys_t *dnp = dn->dn_phys;
+	int txgoff = tx->tx_txg & TXG_MASK;
+	list_t *list = &dn->dn_dirty_records[txgoff];
+
+	ASSERT(dmu_tx_is_syncing(tx));
+	ASSERT(dnp->dn_type != DMU_OT_NONE || dn->dn_allocated_txg);
+	DNODE_VERIFY(dn);
+
+	ASSERT(dn->dn_dbuf == NULL || arc_released(dn->dn_dbuf->db_buf));
+
+	mutex_enter(&dn->dn_mtx);
+	if (dn->dn_allocated_txg == tx->tx_txg) {
+		/* The dnode is newly allocated or reallocated */
+		if (dnp->dn_type == DMU_OT_NONE) {
+			/* this is a first alloc, not a realloc */
+			/* XXX shouldn't the phys already be zeroed? */
+			bzero(dnp, DNODE_CORE_SIZE);
+			dnp->dn_nlevels = 1;
+		}
+
+		if (dn->dn_nblkptr > dnp->dn_nblkptr) {
+			/* zero the new blkptrs we are gaining */
+			bzero(dnp->dn_blkptr + dnp->dn_nblkptr,
+			    sizeof (blkptr_t) *
+			    (dn->dn_nblkptr - dnp->dn_nblkptr));
+		}
+		dnp->dn_type = dn->dn_type;
+		dnp->dn_bonustype = dn->dn_bonustype;
+		dnp->dn_bonuslen = dn->dn_bonuslen;
+		dnp->dn_nblkptr = dn->dn_nblkptr;
+	}
+
+	ASSERT(dnp->dn_nlevels > 1 ||
+	    BP_IS_HOLE(&dnp->dn_blkptr[0]) ||
+	    BP_GET_LSIZE(&dnp->dn_blkptr[0]) ==
+	    dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT);
+
+	if (dn->dn_next_blksz[txgoff]) {
+		ASSERT(P2PHASE(dn->dn_next_blksz[txgoff],
+		    SPA_MINBLOCKSIZE) == 0);
+		ASSERT(BP_IS_HOLE(&dnp->dn_blkptr[0]) ||
+		    dn->dn_maxblkid == 0 || list_head(list) != NULL ||
+		    dn->dn_next_blksz[txgoff] >> SPA_MINBLOCKSHIFT ==
+		    dnp->dn_datablkszsec);
+		dnp->dn_datablkszsec =
+		    dn->dn_next_blksz[txgoff] >> SPA_MINBLOCKSHIFT;
+		dn->dn_next_blksz[txgoff] = 0;
+	}
+
+	if (dn->dn_next_bonuslen[txgoff]) {
+		if (dn->dn_next_bonuslen[txgoff] == DN_ZERO_BONUSLEN)
+			dnp->dn_bonuslen = 0;
+		else
+			dnp->dn_bonuslen = dn->dn_next_bonuslen[txgoff];
+		ASSERT(dnp->dn_bonuslen <= DN_MAX_BONUSLEN);
+		dn->dn_next_bonuslen[txgoff] = 0;
+	}
+
+	if (dn->dn_next_indblkshift[txgoff]) {
+		ASSERT(dnp->dn_nlevels == 1);
+		dnp->dn_indblkshift = dn->dn_next_indblkshift[txgoff];
+		dn->dn_next_indblkshift[txgoff] = 0;
+	}
+
+	/*
+	 * Just take the live (open-context) values for checksum and compress.
+	 * Strictly speaking it's a future leak, but nothing bad happens if we
+	 * start using the new checksum or compress algorithm a little early.
+	 */
+	dnp->dn_checksum = dn->dn_checksum;
+	dnp->dn_compress = dn->dn_compress;
+
+	mutex_exit(&dn->dn_mtx);
+
+	/* process all the "freed" ranges in the file */
+	while (rp = avl_last(&dn->dn_ranges[txgoff])) {
+		dnode_sync_free_range(dn, rp->fr_blkid, rp->fr_nblks, tx);
+		/* grab the mutex so we don't race with dnode_block_freed() */
+		mutex_enter(&dn->dn_mtx);
+		avl_remove(&dn->dn_ranges[txgoff], rp);
+		mutex_exit(&dn->dn_mtx);
+		kmem_free(rp, sizeof (free_range_t));
+	}
+
+	if (dn->dn_free_txg > 0 && dn->dn_free_txg <= tx->tx_txg) {
+		dnode_sync_free(dn, tx);
+		return;
+	}
+
+	if (dn->dn_next_nlevels[txgoff]) {
+		dnode_increase_indirection(dn, tx);
+		dn->dn_next_nlevels[txgoff] = 0;
+	}
+
+	dbuf_sync_list(list, tx);
+
+	if (dn->dn_object != DMU_META_DNODE_OBJECT) {
+		ASSERT3P(list_head(list), ==, NULL);
+		dnode_rele(dn, (void *)(uintptr_t)tx->tx_txg);
+	}
+
+	/*
+	 * Although we have dropped our reference to the dnode, it
+	 * can't be evicted until its written, and we haven't yet
+	 * initiated the IO for the dnode's dbuf.
+	 */
+}