Move the world out of /zfs/ and seperate out module build tree

1 files changed, 1068 insertions, 0 deletions

diff --git a/module/zfs/dmu_tx.c b/module/zfs/dmu_tx.c
new file mode 100644
index 000000000..bf560e565
--- /dev/null
+++ b/module/zfs/dmu_tx.c
@@ -0,0 +1,1068 @@
+/*
+ * 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.
+ */
+
+#include <sys/dmu.h>
+#include <sys/dmu_impl.h>
+#include <sys/dbuf.h>
+#include <sys/dmu_tx.h>
+#include <sys/dmu_objset.h>
+#include <sys/dsl_dataset.h> /* for dsl_dataset_block_freeable() */
+#include <sys/dsl_dir.h> /* for dsl_dir_tempreserve_*() */
+#include <sys/dsl_pool.h>
+#include <sys/zap_impl.h> /* for fzap_default_block_shift */
+#include <sys/spa.h>
+#include <sys/zfs_context.h>
+
+typedef void (*dmu_tx_hold_func_t)(dmu_tx_t *tx, struct dnode *dn,
+    uint64_t arg1, uint64_t arg2);
+
+
+dmu_tx_t *
+dmu_tx_create_dd(dsl_dir_t *dd)
+{
+	dmu_tx_t *tx = kmem_zalloc(sizeof (dmu_tx_t), KM_SLEEP);
+	tx->tx_dir = dd;
+	if (dd)
+		tx->tx_pool = dd->dd_pool;
+	list_create(&tx->tx_holds, sizeof (dmu_tx_hold_t),
+	    offsetof(dmu_tx_hold_t, txh_node));
+#ifdef ZFS_DEBUG
+	refcount_create(&tx->tx_space_written);
+	refcount_create(&tx->tx_space_freed);
+#endif
+	return (tx);
+}
+
+dmu_tx_t *
+dmu_tx_create(objset_t *os)
+{
+	dmu_tx_t *tx = dmu_tx_create_dd(os->os->os_dsl_dataset->ds_dir);
+	tx->tx_objset = os;
+	tx->tx_lastsnap_txg = dsl_dataset_prev_snap_txg(os->os->os_dsl_dataset);
+	return (tx);
+}
+
+dmu_tx_t *
+dmu_tx_create_assigned(struct dsl_pool *dp, uint64_t txg)
+{
+	dmu_tx_t *tx = dmu_tx_create_dd(NULL);
+
+	ASSERT3U(txg, <=, dp->dp_tx.tx_open_txg);
+	tx->tx_pool = dp;
+	tx->tx_txg = txg;
+	tx->tx_anyobj = TRUE;
+
+	return (tx);
+}
+
+int
+dmu_tx_is_syncing(dmu_tx_t *tx)
+{
+	return (tx->tx_anyobj);
+}
+
+int
+dmu_tx_private_ok(dmu_tx_t *tx)
+{
+	return (tx->tx_anyobj);
+}
+
+static dmu_tx_hold_t *
+dmu_tx_hold_object_impl(dmu_tx_t *tx, objset_t *os, uint64_t object,
+    enum dmu_tx_hold_type type, uint64_t arg1, uint64_t arg2)
+{
+	dmu_tx_hold_t *txh;
+	dnode_t *dn = NULL;
+	int err;
+
+	if (object != DMU_NEW_OBJECT) {
+		err = dnode_hold(os->os, object, tx, &dn);
+		if (err) {
+			tx->tx_err = err;
+			return (NULL);
+		}
+
+		if (err == 0 && tx->tx_txg != 0) {
+			mutex_enter(&dn->dn_mtx);
+			/*
+			 * dn->dn_assigned_txg == tx->tx_txg doesn't pose a
+			 * problem, but there's no way for it to happen (for
+			 * now, at least).
+			 */
+			ASSERT(dn->dn_assigned_txg == 0);
+			dn->dn_assigned_txg = tx->tx_txg;
+			(void) refcount_add(&dn->dn_tx_holds, tx);
+			mutex_exit(&dn->dn_mtx);
+		}
+	}
+
+	txh = kmem_zalloc(sizeof (dmu_tx_hold_t), KM_SLEEP);
+	txh->txh_tx = tx;
+	txh->txh_dnode = dn;
+#ifdef ZFS_DEBUG
+	txh->txh_type = type;
+	txh->txh_arg1 = arg1;
+	txh->txh_arg2 = arg2;
+#endif
+	list_insert_tail(&tx->tx_holds, txh);
+
+	return (txh);
+}
+
+void
+dmu_tx_add_new_object(dmu_tx_t *tx, objset_t *os, uint64_t object)
+{
+	/*
+	 * If we're syncing, they can manipulate any object anyhow, and
+	 * the hold on the dnode_t can cause problems.
+	 */
+	if (!dmu_tx_is_syncing(tx)) {
+		(void) dmu_tx_hold_object_impl(tx, os,
+		    object, THT_NEWOBJECT, 0, 0);
+	}
+}
+
+static int
+dmu_tx_check_ioerr(zio_t *zio, dnode_t *dn, int level, uint64_t blkid)
+{
+	int err;
+	dmu_buf_impl_t *db;
+
+	rw_enter(&dn->dn_struct_rwlock, RW_READER);
+	db = dbuf_hold_level(dn, level, blkid, FTAG);
+	rw_exit(&dn->dn_struct_rwlock);
+	if (db == NULL)
+		return (EIO);
+	err = dbuf_read(db, zio, DB_RF_CANFAIL | DB_RF_NOPREFETCH);
+	dbuf_rele(db, FTAG);
+	return (err);
+}
+
+/* ARGSUSED */
+static void
+dmu_tx_count_write(dmu_tx_hold_t *txh, uint64_t off, uint64_t len)
+{
+	dnode_t *dn = txh->txh_dnode;
+	uint64_t start, end, i;
+	int min_bs, max_bs, min_ibs, max_ibs, epbs, bits;
+	int err = 0;
+
+	if (len == 0)
+		return;
+
+	min_bs = SPA_MINBLOCKSHIFT;
+	max_bs = SPA_MAXBLOCKSHIFT;
+	min_ibs = DN_MIN_INDBLKSHIFT;
+	max_ibs = DN_MAX_INDBLKSHIFT;
+
+	/*
+	 * For i/o error checking, read the first and last level-0
+	 * blocks (if they are not aligned), and all the level-1 blocks.
+	 */
+
+	if (dn) {
+		if (dn->dn_maxblkid == 0) {
+			if ((off > 0 || len < dn->dn_datablksz) &&
+			    off < dn->dn_datablksz) {
+				err = dmu_tx_check_ioerr(NULL, dn, 0, 0);
+				if (err)
+					goto out;
+			}
+		} else {
+			zio_t *zio = zio_root(dn->dn_objset->os_spa,
+			    NULL, NULL, ZIO_FLAG_CANFAIL);
+
+			/* first level-0 block */
+			start = off >> dn->dn_datablkshift;
+			if (P2PHASE(off, dn->dn_datablksz) ||
+			    len < dn->dn_datablksz) {
+				err = dmu_tx_check_ioerr(zio, dn, 0, start);
+				if (err)
+					goto out;
+			}
+
+			/* last level-0 block */
+			end = (off+len-1) >> dn->dn_datablkshift;
+			if (end != start && end <= dn->dn_maxblkid &&
+			    P2PHASE(off+len, dn->dn_datablksz)) {
+				err = dmu_tx_check_ioerr(zio, dn, 0, end);
+				if (err)
+					goto out;
+			}
+
+			/* level-1 blocks */
+			if (dn->dn_nlevels > 1) {
+				start >>= dn->dn_indblkshift - SPA_BLKPTRSHIFT;
+				end >>= dn->dn_indblkshift - SPA_BLKPTRSHIFT;
+				for (i = start+1; i < end; i++) {
+					err = dmu_tx_check_ioerr(zio, dn, 1, i);
+					if (err)
+						goto out;
+				}
+			}
+
+			err = zio_wait(zio);
+			if (err)
+				goto out;
+		}
+	}
+
+	/*
+	 * If there's more than one block, the blocksize can't change,
+	 * so we can make a more precise estimate.  Alternatively,
+	 * if the dnode's ibs is larger than max_ibs, always use that.
+	 * This ensures that if we reduce DN_MAX_INDBLKSHIFT,
+	 * the code will still work correctly on existing pools.
+	 */
+	if (dn && (dn->dn_maxblkid != 0 || dn->dn_indblkshift > max_ibs)) {
+		min_ibs = max_ibs = dn->dn_indblkshift;
+		if (dn->dn_datablkshift != 0)
+			min_bs = max_bs = dn->dn_datablkshift;
+	}
+
+	/*
+	 * 'end' is the last thing we will access, not one past.
+	 * This way we won't overflow when accessing the last byte.
+	 */
+	start = P2ALIGN(off, 1ULL << max_bs);
+	end = P2ROUNDUP(off + len, 1ULL << max_bs) - 1;
+	txh->txh_space_towrite += end - start + 1;
+
+	start >>= min_bs;
+	end >>= min_bs;
+
+	epbs = min_ibs - SPA_BLKPTRSHIFT;
+
+	/*
+	 * The object contains at most 2^(64 - min_bs) blocks,
+	 * and each indirect level maps 2^epbs.
+	 */
+	for (bits = 64 - min_bs; bits >= 0; bits -= epbs) {
+		start >>= epbs;
+		end >>= epbs;
+		/*
+		 * If we increase the number of levels of indirection,
+		 * we'll need new blkid=0 indirect blocks.  If start == 0,
+		 * we're already accounting for that blocks; and if end == 0,
+		 * we can't increase the number of levels beyond that.
+		 */
+		if (start != 0 && end != 0)
+			txh->txh_space_towrite += 1ULL << max_ibs;
+		txh->txh_space_towrite += (end - start + 1) << max_ibs;
+	}
+
+	ASSERT(txh->txh_space_towrite < 2 * DMU_MAX_ACCESS);
+
+out:
+	if (err)
+		txh->txh_tx->tx_err = err;
+}
+
+static void
+dmu_tx_count_dnode(dmu_tx_hold_t *txh)
+{
+	dnode_t *dn = txh->txh_dnode;
+	dnode_t *mdn = txh->txh_tx->tx_objset->os->os_meta_dnode;
+	uint64_t space = mdn->dn_datablksz +
+	    ((mdn->dn_nlevels-1) << mdn->dn_indblkshift);
+
+	if (dn && dn->dn_dbuf->db_blkptr &&
+	    dsl_dataset_block_freeable(dn->dn_objset->os_dsl_dataset,
+	    dn->dn_dbuf->db_blkptr->blk_birth)) {
+		txh->txh_space_tooverwrite += space;
+	} else {
+		txh->txh_space_towrite += space;
+		if (dn && dn->dn_dbuf->db_blkptr)
+			txh->txh_space_tounref += space;
+	}
+}
+
+void
+dmu_tx_hold_write(dmu_tx_t *tx, uint64_t object, uint64_t off, int len)
+{
+	dmu_tx_hold_t *txh;
+
+	ASSERT(tx->tx_txg == 0);
+	ASSERT(len < DMU_MAX_ACCESS);
+	ASSERT(len == 0 || UINT64_MAX - off >= len - 1);
+
+	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
+	    object, THT_WRITE, off, len);
+	if (txh == NULL)
+		return;
+
+	dmu_tx_count_write(txh, off, len);
+	dmu_tx_count_dnode(txh);
+}
+
+static void
+dmu_tx_count_free(dmu_tx_hold_t *txh, uint64_t off, uint64_t len)
+{
+	uint64_t blkid, nblks, lastblk;
+	uint64_t space = 0, unref = 0, skipped = 0;
+	dnode_t *dn = txh->txh_dnode;
+	dsl_dataset_t *ds = dn->dn_objset->os_dsl_dataset;
+	spa_t *spa = txh->txh_tx->tx_pool->dp_spa;
+	int epbs;
+
+	if (dn->dn_nlevels == 0)
+		return;
+
+	/*
+	 * The struct_rwlock protects us against dn_nlevels
+	 * changing, in case (against all odds) we manage to dirty &
+	 * sync out the changes after we check for being dirty.
+	 * Also, dbuf_hold_level() wants us to have the struct_rwlock.
+	 */
+	rw_enter(&dn->dn_struct_rwlock, RW_READER);
+	epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
+	if (dn->dn_maxblkid == 0) {
+		if (off == 0 && len >= dn->dn_datablksz) {
+			blkid = 0;
+			nblks = 1;
+		} else {
+			rw_exit(&dn->dn_struct_rwlock);
+			return;
+		}
+	} else {
+		blkid = off >> dn->dn_datablkshift;
+		nblks = (len + dn->dn_datablksz - 1) >> dn->dn_datablkshift;
+
+		if (blkid >= dn->dn_maxblkid) {
+			rw_exit(&dn->dn_struct_rwlock);
+			return;
+		}
+		if (blkid + nblks > dn->dn_maxblkid)
+			nblks = dn->dn_maxblkid - blkid;
+
+	}
+	if (dn->dn_nlevels == 1) {
+		int i;
+		for (i = 0; i < nblks; i++) {
+			blkptr_t *bp = dn->dn_phys->dn_blkptr;
+			ASSERT3U(blkid + i, <, dn->dn_nblkptr);
+			bp += blkid + i;
+			if (dsl_dataset_block_freeable(ds, bp->blk_birth)) {
+				dprintf_bp(bp, "can free old%s", "");
+				space += bp_get_dasize(spa, bp);
+			}
+			unref += BP_GET_ASIZE(bp);
+		}
+		nblks = 0;
+	}
+
+	/*
+	 * Add in memory requirements of higher-level indirects.
+	 * This assumes a worst-possible scenario for dn_nlevels.
+	 */
+	{
+		uint64_t blkcnt = 1 + ((nblks >> epbs) >> epbs);
+		int level = (dn->dn_nlevels > 1) ? 2 : 1;
+
+		while (level++ < DN_MAX_LEVELS) {
+			txh->txh_memory_tohold += blkcnt << dn->dn_indblkshift;
+			blkcnt = 1 + (blkcnt >> epbs);
+		}
+		ASSERT(blkcnt <= dn->dn_nblkptr);
+	}
+
+	lastblk = blkid + nblks - 1;
+	while (nblks) {
+		dmu_buf_impl_t *dbuf;
+		uint64_t ibyte, new_blkid;
+		int epb = 1 << epbs;
+		int err, i, blkoff, tochk;
+		blkptr_t *bp;
+
+		ibyte = blkid << dn->dn_datablkshift;
+		err = dnode_next_offset(dn,
+		    DNODE_FIND_HAVELOCK, &ibyte, 2, 1, 0);
+		new_blkid = ibyte >> dn->dn_datablkshift;
+		if (err == ESRCH) {
+			skipped += (lastblk >> epbs) - (blkid >> epbs) + 1;
+			break;
+		}
+		if (err) {
+			txh->txh_tx->tx_err = err;
+			break;
+		}
+		if (new_blkid > lastblk) {
+			skipped += (lastblk >> epbs) - (blkid >> epbs) + 1;
+			break;
+		}
+
+		if (new_blkid > blkid) {
+			ASSERT((new_blkid >> epbs) > (blkid >> epbs));
+			skipped += (new_blkid >> epbs) - (blkid >> epbs) - 1;
+			nblks -= new_blkid - blkid;
+			blkid = new_blkid;
+		}
+		blkoff = P2PHASE(blkid, epb);
+		tochk = MIN(epb - blkoff, nblks);
+
+		dbuf = dbuf_hold_level(dn, 1, blkid >> epbs, FTAG);
+
+		txh->txh_memory_tohold += dbuf->db.db_size;
+		if (txh->txh_memory_tohold > DMU_MAX_ACCESS) {
+			txh->txh_tx->tx_err = E2BIG;
+			dbuf_rele(dbuf, FTAG);
+			break;
+		}
+		err = dbuf_read(dbuf, NULL, DB_RF_HAVESTRUCT | DB_RF_CANFAIL);
+		if (err != 0) {
+			txh->txh_tx->tx_err = err;
+			dbuf_rele(dbuf, FTAG);
+			break;
+		}
+
+		bp = dbuf->db.db_data;
+		bp += blkoff;
+
+		for (i = 0; i < tochk; i++) {
+			if (dsl_dataset_block_freeable(ds, bp[i].blk_birth)) {
+				dprintf_bp(&bp[i], "can free old%s", "");
+				space += bp_get_dasize(spa, &bp[i]);
+			}
+			unref += BP_GET_ASIZE(bp);
+		}
+		dbuf_rele(dbuf, FTAG);
+
+		blkid += tochk;
+		nblks -= tochk;
+	}
+	rw_exit(&dn->dn_struct_rwlock);
+
+	/* account for new level 1 indirect blocks that might show up */
+	if (skipped > 0) {
+		txh->txh_fudge += skipped << dn->dn_indblkshift;
+		skipped = MIN(skipped, DMU_MAX_DELETEBLKCNT >> epbs);
+		txh->txh_memory_tohold += skipped << dn->dn_indblkshift;
+	}
+	txh->txh_space_tofree += space;
+	txh->txh_space_tounref += unref;
+}
+
+void
+dmu_tx_hold_free(dmu_tx_t *tx, uint64_t object, uint64_t off, uint64_t len)
+{
+	dmu_tx_hold_t *txh;
+	dnode_t *dn;
+	uint64_t start, end, i;
+	int err, shift;
+	zio_t *zio;
+
+	ASSERT(tx->tx_txg == 0);
+
+	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
+	    object, THT_FREE, off, len);
+	if (txh == NULL)
+		return;
+	dn = txh->txh_dnode;
+
+	/* first block */
+	if (off != 0)
+		dmu_tx_count_write(txh, off, 1);
+	/* last block */
+	if (len != DMU_OBJECT_END)
+		dmu_tx_count_write(txh, off+len, 1);
+
+	if (off >= (dn->dn_maxblkid+1) * dn->dn_datablksz)
+		return;
+	if (len == DMU_OBJECT_END)
+		len = (dn->dn_maxblkid+1) * dn->dn_datablksz - off;
+
+	/*
+	 * For i/o error checking, read the first and last level-0
+	 * blocks, and all the level-1 blocks.  The above count_write's
+	 * have already taken care of the level-0 blocks.
+	 */
+	if (dn->dn_nlevels > 1) {
+		shift = dn->dn_datablkshift + dn->dn_indblkshift -
+		    SPA_BLKPTRSHIFT;
+		start = off >> shift;
+		end = dn->dn_datablkshift ? ((off+len) >> shift) : 0;
+
+		zio = zio_root(tx->tx_pool->dp_spa,
+		    NULL, NULL, ZIO_FLAG_CANFAIL);
+		for (i = start; i <= end; i++) {
+			uint64_t ibyte = i << shift;
+			err = dnode_next_offset(dn, 0, &ibyte, 2, 1, 0);
+			i = ibyte >> shift;
+			if (err == ESRCH)
+				break;
+			if (err) {
+				tx->tx_err = err;
+				return;
+			}
+
+			err = dmu_tx_check_ioerr(zio, dn, 1, i);
+			if (err) {
+				tx->tx_err = err;
+				return;
+			}
+		}
+		err = zio_wait(zio);
+		if (err) {
+			tx->tx_err = err;
+			return;
+		}
+	}
+
+	dmu_tx_count_dnode(txh);
+	dmu_tx_count_free(txh, off, len);
+}
+
+void
+dmu_tx_hold_zap(dmu_tx_t *tx, uint64_t object, int add, char *name)
+{
+	dmu_tx_hold_t *txh;
+	dnode_t *dn;
+	uint64_t nblocks;
+	int epbs, err;
+
+	ASSERT(tx->tx_txg == 0);
+
+	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
+	    object, THT_ZAP, add, (uintptr_t)name);
+	if (txh == NULL)
+		return;
+	dn = txh->txh_dnode;
+
+	dmu_tx_count_dnode(txh);
+
+	if (dn == NULL) {
+		/*
+		 * We will be able to fit a new object's entries into one leaf
+		 * block.  So there will be at most 2 blocks total,
+		 * including the header block.
+		 */
+		dmu_tx_count_write(txh, 0, 2 << fzap_default_block_shift);
+		return;
+	}
+
+	ASSERT3P(dmu_ot[dn->dn_type].ot_byteswap, ==, zap_byteswap);
+
+	if (dn->dn_maxblkid == 0 && !add) {
+		/*
+		 * If there is only one block  (i.e. this is a micro-zap)
+		 * and we are not adding anything, the accounting is simple.
+		 */
+		err = dmu_tx_check_ioerr(NULL, dn, 0, 0);
+		if (err) {
+			tx->tx_err = err;
+			return;
+		}
+
+		/*
+		 * Use max block size here, since we don't know how much
+		 * the size will change between now and the dbuf dirty call.
+		 */
+		if (dsl_dataset_block_freeable(dn->dn_objset->os_dsl_dataset,
+		    dn->dn_phys->dn_blkptr[0].blk_birth)) {
+			txh->txh_space_tooverwrite += SPA_MAXBLOCKSIZE;
+		} else {
+			txh->txh_space_towrite += SPA_MAXBLOCKSIZE;
+			txh->txh_space_tounref +=
+			    BP_GET_ASIZE(dn->dn_phys->dn_blkptr);
+		}
+		return;
+	}
+
+	if (dn->dn_maxblkid > 0 && name) {
+		/*
+		 * access the name in this fat-zap so that we'll check
+		 * for i/o errors to the leaf blocks, etc.
+		 */
+		err = zap_lookup(&dn->dn_objset->os, dn->dn_object, name,
+		    8, 0, NULL);
+		if (err == EIO) {
+			tx->tx_err = err;
+			return;
+		}
+	}
+
+	/*
+	 * 3 blocks overwritten: target leaf, ptrtbl block, header block
+	 * 3 new blocks written if adding: new split leaf, 2 grown ptrtbl blocks
+	 */
+	dmu_tx_count_write(txh, dn->dn_maxblkid * dn->dn_datablksz,
+	    (3 + (add ? 3 : 0)) << dn->dn_datablkshift);
+
+	/*
+	 * If the modified blocks are scattered to the four winds,
+	 * we'll have to modify an indirect twig for each.
+	 */
+	epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
+	for (nblocks = dn->dn_maxblkid >> epbs; nblocks != 0; nblocks >>= epbs)
+		txh->txh_space_towrite += 3 << dn->dn_indblkshift;
+}
+
+void
+dmu_tx_hold_bonus(dmu_tx_t *tx, uint64_t object)
+{
+	dmu_tx_hold_t *txh;
+
+	ASSERT(tx->tx_txg == 0);
+
+	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
+	    object, THT_BONUS, 0, 0);
+	if (txh)
+		dmu_tx_count_dnode(txh);
+}
+
+void
+dmu_tx_hold_space(dmu_tx_t *tx, uint64_t space)
+{
+	dmu_tx_hold_t *txh;
+	ASSERT(tx->tx_txg == 0);
+
+	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
+	    DMU_NEW_OBJECT, THT_SPACE, space, 0);
+
+	txh->txh_space_towrite += space;
+}
+
+int
+dmu_tx_holds(dmu_tx_t *tx, uint64_t object)
+{
+	dmu_tx_hold_t *txh;
+	int holds = 0;
+
+	/*
+	 * By asserting that the tx is assigned, we're counting the
+	 * number of dn_tx_holds, which is the same as the number of
+	 * dn_holds.  Otherwise, we'd be counting dn_holds, but
+	 * dn_tx_holds could be 0.
+	 */
+	ASSERT(tx->tx_txg != 0);
+
+	/* if (tx->tx_anyobj == TRUE) */
+		/* return (0); */
+
+	for (txh = list_head(&tx->tx_holds); txh;
+	    txh = list_next(&tx->tx_holds, txh)) {
+		if (txh->txh_dnode && txh->txh_dnode->dn_object == object)
+			holds++;
+	}
+
+	return (holds);
+}
+
+#ifdef ZFS_DEBUG
+void
+dmu_tx_dirty_buf(dmu_tx_t *tx, dmu_buf_impl_t *db)
+{
+	dmu_tx_hold_t *txh;
+	int match_object = FALSE, match_offset = FALSE;
+	dnode_t *dn = db->db_dnode;
+
+	ASSERT(tx->tx_txg != 0);
+	ASSERT(tx->tx_objset == NULL || dn->dn_objset == tx->tx_objset->os);
+	ASSERT3U(dn->dn_object, ==, db->db.db_object);
+
+	if (tx->tx_anyobj)
+		return;
+
+	/* XXX No checking on the meta dnode for now */
+	if (db->db.db_object == DMU_META_DNODE_OBJECT)
+		return;
+
+	for (txh = list_head(&tx->tx_holds); txh;
+	    txh = list_next(&tx->tx_holds, txh)) {
+		ASSERT(dn == NULL || dn->dn_assigned_txg == tx->tx_txg);
+		if (txh->txh_dnode == dn && txh->txh_type != THT_NEWOBJECT)
+			match_object = TRUE;
+		if (txh->txh_dnode == NULL || txh->txh_dnode == dn) {
+			int datablkshift = dn->dn_datablkshift ?
+			    dn->dn_datablkshift : SPA_MAXBLOCKSHIFT;
+			int epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
+			int shift = datablkshift + epbs * db->db_level;
+			uint64_t beginblk = shift >= 64 ? 0 :
+			    (txh->txh_arg1 >> shift);
+			uint64_t endblk = shift >= 64 ? 0 :
+			    ((txh->txh_arg1 + txh->txh_arg2 - 1) >> shift);
+			uint64_t blkid = db->db_blkid;
+
+			/* XXX txh_arg2 better not be zero... */
+
+			dprintf("found txh type %x beginblk=%llx endblk=%llx\n",
+			    txh->txh_type, beginblk, endblk);
+
+			switch (txh->txh_type) {
+			case THT_WRITE:
+				if (blkid >= beginblk && blkid <= endblk)
+					match_offset = TRUE;
+				/*
+				 * We will let this hold work for the bonus
+				 * buffer so that we don't need to hold it
+				 * when creating a new object.
+				 */
+				if (blkid == DB_BONUS_BLKID)
+					match_offset = TRUE;
+				/*
+				 * They might have to increase nlevels,
+				 * thus dirtying the new TLIBs.  Or the
+				 * might have to change the block size,
+				 * thus dirying the new lvl=0 blk=0.
+				 */
+				if (blkid == 0)
+					match_offset = TRUE;
+				break;
+			case THT_FREE:
+				/*
+				 * We will dirty all the level 1 blocks in
+				 * the free range and perhaps the first and
+				 * last level 0 block.
+				 */
+				if (blkid >= beginblk && (blkid <= endblk ||
+				    txh->txh_arg2 == DMU_OBJECT_END))
+					match_offset = TRUE;
+				break;
+			case THT_BONUS:
+				if (blkid == DB_BONUS_BLKID)
+					match_offset = TRUE;
+				break;
+			case THT_ZAP:
+				match_offset = TRUE;
+				break;
+			case THT_NEWOBJECT:
+				match_object = TRUE;
+				break;
+			default:
+				ASSERT(!"bad txh_type");
+			}
+		}
+		if (match_object && match_offset)
+			return;
+	}
+	panic("dirtying dbuf obj=%llx lvl=%u blkid=%llx but not tx_held\n",
+	    (u_longlong_t)db->db.db_object, db->db_level,
+	    (u_longlong_t)db->db_blkid);
+}
+#endif
+
+static int
+dmu_tx_try_assign(dmu_tx_t *tx, uint64_t txg_how)
+{
+	dmu_tx_hold_t *txh;
+	spa_t *spa = tx->tx_pool->dp_spa;
+	uint64_t memory, asize, fsize, usize;
+	uint64_t towrite, tofree, tooverwrite, tounref, tohold, fudge;
+
+	ASSERT3U(tx->tx_txg, ==, 0);
+
+	if (tx->tx_err)
+		return (tx->tx_err);
+
+	if (spa_suspended(spa)) {
+		/*
+		 * If the user has indicated a blocking failure mode
+		 * then return ERESTART which will block in dmu_tx_wait().
+		 * Otherwise, return EIO so that an error can get
+		 * propagated back to the VOP calls.
+		 *
+		 * Note that we always honor the txg_how flag regardless
+		 * of the failuremode setting.
+		 */
+		if (spa_get_failmode(spa) == ZIO_FAILURE_MODE_CONTINUE &&
+		    txg_how != TXG_WAIT)
+			return (EIO);
+
+		return (ERESTART);
+	}
+
+	tx->tx_txg = txg_hold_open(tx->tx_pool, &tx->tx_txgh);
+	tx->tx_needassign_txh = NULL;
+
+	/*
+	 * NB: No error returns are allowed after txg_hold_open, but
+	 * before processing the dnode holds, due to the
+	 * dmu_tx_unassign() logic.
+	 */
+
+	towrite = tofree = tooverwrite = tounref = tohold = fudge = 0;
+	for (txh = list_head(&tx->tx_holds); txh;
+	    txh = list_next(&tx->tx_holds, txh)) {
+		dnode_t *dn = txh->txh_dnode;
+		if (dn != NULL) {
+			mutex_enter(&dn->dn_mtx);
+			if (dn->dn_assigned_txg == tx->tx_txg - 1) {
+				mutex_exit(&dn->dn_mtx);
+				tx->tx_needassign_txh = txh;
+				return (ERESTART);
+			}
+			if (dn->dn_assigned_txg == 0)
+				dn->dn_assigned_txg = tx->tx_txg;
+			ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
+			(void) refcount_add(&dn->dn_tx_holds, tx);
+			mutex_exit(&dn->dn_mtx);
+		}
+		towrite += txh->txh_space_towrite;
+		tofree += txh->txh_space_tofree;
+		tooverwrite += txh->txh_space_tooverwrite;
+		tounref += txh->txh_space_tounref;
+		tohold += txh->txh_memory_tohold;
+		fudge += txh->txh_fudge;
+	}
+
+	/*
+	 * NB: This check must be after we've held the dnodes, so that
+	 * the dmu_tx_unassign() logic will work properly
+	 */
+	if (txg_how >= TXG_INITIAL && txg_how != tx->tx_txg)
+		return (ERESTART);
+
+	/*
+	 * If a snapshot has been taken since we made our estimates,
+	 * assume that we won't be able to free or overwrite anything.
+	 */
+	if (tx->tx_objset &&
+	    dsl_dataset_prev_snap_txg(tx->tx_objset->os->os_dsl_dataset) >
+	    tx->tx_lastsnap_txg) {
+		towrite += tooverwrite;
+		tooverwrite = tofree = 0;
+	}
+
+	/* needed allocation: worst-case estimate of write space */
+	asize = spa_get_asize(tx->tx_pool->dp_spa, towrite + tooverwrite);
+	/* freed space estimate: worst-case overwrite + free estimate */
+	fsize = spa_get_asize(tx->tx_pool->dp_spa, tooverwrite) + tofree;
+	/* convert unrefd space to worst-case estimate */
+	usize = spa_get_asize(tx->tx_pool->dp_spa, tounref);
+	/* calculate memory footprint estimate */
+	memory = towrite + tooverwrite + tohold;
+
+#ifdef ZFS_DEBUG
+	/*
+	 * Add in 'tohold' to account for our dirty holds on this memory
+	 * XXX - the "fudge" factor is to account for skipped blocks that
+	 * we missed because dnode_next_offset() misses in-core-only blocks.
+	 */
+	tx->tx_space_towrite = asize +
+	    spa_get_asize(tx->tx_pool->dp_spa, tohold + fudge);
+	tx->tx_space_tofree = tofree;
+	tx->tx_space_tooverwrite = tooverwrite;
+	tx->tx_space_tounref = tounref;
+#endif
+
+	if (tx->tx_dir && asize != 0) {
+		int err = dsl_dir_tempreserve_space(tx->tx_dir, memory,
+		    asize, fsize, usize, &tx->tx_tempreserve_cookie, tx);
+		if (err)
+			return (err);
+	}
+
+	return (0);
+}
+
+static void
+dmu_tx_unassign(dmu_tx_t *tx)
+{
+	dmu_tx_hold_t *txh;
+
+	if (tx->tx_txg == 0)
+		return;
+
+	txg_rele_to_quiesce(&tx->tx_txgh);
+
+	for (txh = list_head(&tx->tx_holds); txh != tx->tx_needassign_txh;
+	    txh = list_next(&tx->tx_holds, txh)) {
+		dnode_t *dn = txh->txh_dnode;
+
+		if (dn == NULL)
+			continue;
+		mutex_enter(&dn->dn_mtx);
+		ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
+
+		if (refcount_remove(&dn->dn_tx_holds, tx) == 0) {
+			dn->dn_assigned_txg = 0;
+			cv_broadcast(&dn->dn_notxholds);
+		}
+		mutex_exit(&dn->dn_mtx);
+	}
+
+	txg_rele_to_sync(&tx->tx_txgh);
+
+	tx->tx_lasttried_txg = tx->tx_txg;
+	tx->tx_txg = 0;
+}
+
+/*
+ * Assign tx to a transaction group.  txg_how can be one of:
+ *
+ * (1)	TXG_WAIT.  If the current open txg is full, waits until there's
+ *	a new one.  This should be used when you're not holding locks.
+ *	If will only fail if we're truly out of space (or over quota).
+ *
+ * (2)	TXG_NOWAIT.  If we can't assign into the current open txg without
+ *	blocking, returns immediately with ERESTART.  This should be used
+ *	whenever you're holding locks.  On an ERESTART error, the caller
+ *	should drop locks, do a dmu_tx_wait(tx), and try again.
+ *
+ * (3)	A specific txg.  Use this if you need to ensure that multiple
+ *	transactions all sync in the same txg.  Like TXG_NOWAIT, it
+ *	returns ERESTART if it can't assign you into the requested txg.
+ */
+int
+dmu_tx_assign(dmu_tx_t *tx, uint64_t txg_how)
+{
+	int err;
+
+	ASSERT(tx->tx_txg == 0);
+	ASSERT(txg_how != 0);
+	ASSERT(!dsl_pool_sync_context(tx->tx_pool));
+
+	while ((err = dmu_tx_try_assign(tx, txg_how)) != 0) {
+		dmu_tx_unassign(tx);
+
+		if (err != ERESTART || txg_how != TXG_WAIT)
+			return (err);
+
+		dmu_tx_wait(tx);
+	}
+
+	txg_rele_to_quiesce(&tx->tx_txgh);
+
+	return (0);
+}
+
+void
+dmu_tx_wait(dmu_tx_t *tx)
+{
+	spa_t *spa = tx->tx_pool->dp_spa;
+
+	ASSERT(tx->tx_txg == 0);
+
+	/*
+	 * It's possible that the pool has become active after this thread
+	 * has tried to obtain a tx. If that's the case then his
+	 * tx_lasttried_txg would not have been assigned.
+	 */
+	if (spa_suspended(spa) || tx->tx_lasttried_txg == 0) {
+		txg_wait_synced(tx->tx_pool, spa_last_synced_txg(spa) + 1);
+	} else if (tx->tx_needassign_txh) {
+		dnode_t *dn = tx->tx_needassign_txh->txh_dnode;
+
+		mutex_enter(&dn->dn_mtx);
+		while (dn->dn_assigned_txg == tx->tx_lasttried_txg - 1)
+			cv_wait(&dn->dn_notxholds, &dn->dn_mtx);
+		mutex_exit(&dn->dn_mtx);
+		tx->tx_needassign_txh = NULL;
+	} else {
+		txg_wait_open(tx->tx_pool, tx->tx_lasttried_txg + 1);
+	}
+}
+
+void
+dmu_tx_willuse_space(dmu_tx_t *tx, int64_t delta)
+{
+#ifdef ZFS_DEBUG
+	if (tx->tx_dir == NULL || delta == 0)
+		return;
+
+	if (delta > 0) {
+		ASSERT3U(refcount_count(&tx->tx_space_written) + delta, <=,
+		    tx->tx_space_towrite);
+		(void) refcount_add_many(&tx->tx_space_written, delta, NULL);
+	} else {
+		(void) refcount_add_many(&tx->tx_space_freed, -delta, NULL);
+	}
+#endif
+}
+
+void
+dmu_tx_commit(dmu_tx_t *tx)
+{
+	dmu_tx_hold_t *txh;
+
+	ASSERT(tx->tx_txg != 0);
+
+	while (txh = list_head(&tx->tx_holds)) {
+		dnode_t *dn = txh->txh_dnode;
+
+		list_remove(&tx->tx_holds, txh);
+		kmem_free(txh, sizeof (dmu_tx_hold_t));
+		if (dn == NULL)
+			continue;
+		mutex_enter(&dn->dn_mtx);
+		ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
+
+		if (refcount_remove(&dn->dn_tx_holds, tx) == 0) {
+			dn->dn_assigned_txg = 0;
+			cv_broadcast(&dn->dn_notxholds);
+		}
+		mutex_exit(&dn->dn_mtx);
+		dnode_rele(dn, tx);
+	}
+
+	if (tx->tx_tempreserve_cookie)
+		dsl_dir_tempreserve_clear(tx->tx_tempreserve_cookie, tx);
+
+	if (tx->tx_anyobj == FALSE)
+		txg_rele_to_sync(&tx->tx_txgh);
+	list_destroy(&tx->tx_holds);
+#ifdef ZFS_DEBUG
+	dprintf("towrite=%llu written=%llu tofree=%llu freed=%llu\n",
+	    tx->tx_space_towrite, refcount_count(&tx->tx_space_written),
+	    tx->tx_space_tofree, refcount_count(&tx->tx_space_freed));
+	refcount_destroy_many(&tx->tx_space_written,
+	    refcount_count(&tx->tx_space_written));
+	refcount_destroy_many(&tx->tx_space_freed,
+	    refcount_count(&tx->tx_space_freed));
+#endif
+	kmem_free(tx, sizeof (dmu_tx_t));
+}
+
+void
+dmu_tx_abort(dmu_tx_t *tx)
+{
+	dmu_tx_hold_t *txh;
+
+	ASSERT(tx->tx_txg == 0);
+
+	while (txh = list_head(&tx->tx_holds)) {
+		dnode_t *dn = txh->txh_dnode;
+
+		list_remove(&tx->tx_holds, txh);
+		kmem_free(txh, sizeof (dmu_tx_hold_t));
+		if (dn != NULL)
+			dnode_rele(dn, tx);
+	}
+	list_destroy(&tx->tx_holds);
+#ifdef ZFS_DEBUG
+	refcount_destroy_many(&tx->tx_space_written,
+	    refcount_count(&tx->tx_space_written));
+	refcount_destroy_many(&tx->tx_space_freed,
+	    refcount_count(&tx->tx_space_freed));
+#endif
+	kmem_free(tx, sizeof (dmu_tx_t));
+}
+
+uint64_t
+dmu_tx_get_txg(dmu_tx_t *tx)
+{
+	ASSERT(tx->tx_txg != 0);
+	return (tx->tx_txg);
+}