Index: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c
===================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c	(revision 294624)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c	(revision 294625)
@@ -1,2127 +1,2130 @@
 /*
  * 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) 2011, 2015 by Delphix. All rights reserved.
  */
 /* Copyright (c) 2013 by Saso Kiselkov. All rights reserved. */
 /* Copyright (c) 2013, Joyent, Inc. All rights reserved. */
 /* Copyright (c) 2014, Nexenta Systems, Inc. All rights reserved. */
 
 #include <sys/dmu.h>
 #include <sys/dmu_impl.h>
 #include <sys/dmu_tx.h>
 #include <sys/dbuf.h>
 #include <sys/dnode.h>
 #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/dsl_synctask.h>
 #include <sys/dsl_prop.h>
 #include <sys/dmu_zfetch.h>
 #include <sys/zfs_ioctl.h>
 #include <sys/zap.h>
 #include <sys/zio_checksum.h>
 #include <sys/zio_compress.h>
 #include <sys/sa.h>
 #include <sys/zfeature.h>
 #ifdef _KERNEL
 #include <sys/vm.h>
 #include <sys/zfs_znode.h>
 #endif
 
 /*
  * Enable/disable nopwrite feature.
  */
 int zfs_nopwrite_enabled = 1;
 SYSCTL_DECL(_vfs_zfs);
 SYSCTL_INT(_vfs_zfs, OID_AUTO, nopwrite_enabled, CTLFLAG_RDTUN,
     &zfs_nopwrite_enabled, 0, "Enable nopwrite feature");
 
 const dmu_object_type_info_t dmu_ot[DMU_OT_NUMTYPES] = {
 	{	DMU_BSWAP_UINT8,	TRUE,	"unallocated"		},
 	{	DMU_BSWAP_ZAP,		TRUE,	"object directory"	},
 	{	DMU_BSWAP_UINT64,	TRUE,	"object array"		},
 	{	DMU_BSWAP_UINT8,	TRUE,	"packed nvlist"		},
 	{	DMU_BSWAP_UINT64,	TRUE,	"packed nvlist size"	},
 	{	DMU_BSWAP_UINT64,	TRUE,	"bpobj"			},
 	{	DMU_BSWAP_UINT64,	TRUE,	"bpobj header"		},
 	{	DMU_BSWAP_UINT64,	TRUE,	"SPA space map header"	},
 	{	DMU_BSWAP_UINT64,	TRUE,	"SPA space map"		},
 	{	DMU_BSWAP_UINT64,	TRUE,	"ZIL intent log"	},
 	{	DMU_BSWAP_DNODE,	TRUE,	"DMU dnode"		},
 	{	DMU_BSWAP_OBJSET,	TRUE,	"DMU objset"		},
 	{	DMU_BSWAP_UINT64,	TRUE,	"DSL directory"		},
 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL directory child map"},
 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL dataset snap map"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL props"		},
 	{	DMU_BSWAP_UINT64,	TRUE,	"DSL dataset"		},
 	{	DMU_BSWAP_ZNODE,	TRUE,	"ZFS znode"		},
 	{	DMU_BSWAP_OLDACL,	TRUE,	"ZFS V0 ACL"		},
 	{	DMU_BSWAP_UINT8,	FALSE,	"ZFS plain file"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"ZFS directory"		},
 	{	DMU_BSWAP_ZAP,		TRUE,	"ZFS master node"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"ZFS delete queue"	},
 	{	DMU_BSWAP_UINT8,	FALSE,	"zvol object"		},
 	{	DMU_BSWAP_ZAP,		TRUE,	"zvol prop"		},
 	{	DMU_BSWAP_UINT8,	FALSE,	"other uint8[]"		},
 	{	DMU_BSWAP_UINT64,	FALSE,	"other uint64[]"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"other ZAP"		},
 	{	DMU_BSWAP_ZAP,		TRUE,	"persistent error log"	},
 	{	DMU_BSWAP_UINT8,	TRUE,	"SPA history"		},
 	{	DMU_BSWAP_UINT64,	TRUE,	"SPA history offsets"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"Pool properties"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL permissions"	},
 	{	DMU_BSWAP_ACL,		TRUE,	"ZFS ACL"		},
 	{	DMU_BSWAP_UINT8,	TRUE,	"ZFS SYSACL"		},
 	{	DMU_BSWAP_UINT8,	TRUE,	"FUID table"		},
 	{	DMU_BSWAP_UINT64,	TRUE,	"FUID table size"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL dataset next clones"},
 	{	DMU_BSWAP_ZAP,		TRUE,	"scan work queue"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"ZFS user/group used"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"ZFS user/group quota"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"snapshot refcount tags"},
 	{	DMU_BSWAP_ZAP,		TRUE,	"DDT ZAP algorithm"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"DDT statistics"	},
 	{	DMU_BSWAP_UINT8,	TRUE,	"System attributes"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"SA master node"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"SA attr registration"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"SA attr layouts"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"scan translations"	},
 	{	DMU_BSWAP_UINT8,	FALSE,	"deduplicated block"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL deadlist map"	},
 	{	DMU_BSWAP_UINT64,	TRUE,	"DSL deadlist map hdr"	},
 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL dir clones"	},
 	{	DMU_BSWAP_UINT64,	TRUE,	"bpobj subobj"		}
 };
 
 const dmu_object_byteswap_info_t dmu_ot_byteswap[DMU_BSWAP_NUMFUNCS] = {
 	{	byteswap_uint8_array,	"uint8"		},
 	{	byteswap_uint16_array,	"uint16"	},
 	{	byteswap_uint32_array,	"uint32"	},
 	{	byteswap_uint64_array,	"uint64"	},
 	{	zap_byteswap,		"zap"		},
 	{	dnode_buf_byteswap,	"dnode"		},
 	{	dmu_objset_byteswap,	"objset"	},
 	{	zfs_znode_byteswap,	"znode"		},
 	{	zfs_oldacl_byteswap,	"oldacl"	},
 	{	zfs_acl_byteswap,	"acl"		}
 };
 
 int
 dmu_buf_hold_noread(objset_t *os, uint64_t object, uint64_t offset,
     void *tag, dmu_buf_t **dbp)
 {
 	dnode_t *dn;
 	uint64_t blkid;
 	dmu_buf_impl_t *db;
 	int err;
 
 	err = dnode_hold(os, object, FTAG, &dn);
 	if (err)
 		return (err);
 	blkid = dbuf_whichblock(dn, 0, offset);
 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
 	db = dbuf_hold(dn, blkid, tag);
 	rw_exit(&dn->dn_struct_rwlock);
 	dnode_rele(dn, FTAG);
 
 	if (db == NULL) {
 		*dbp = NULL;
 		return (SET_ERROR(EIO));
 	}
 
 	*dbp = &db->db;
 	return (err);
 }
 
 int
 dmu_buf_hold(objset_t *os, uint64_t object, uint64_t offset,
     void *tag, dmu_buf_t **dbp, int flags)
 {
 	int err;
 	int db_flags = DB_RF_CANFAIL;
 
 	if (flags & DMU_READ_NO_PREFETCH)
 		db_flags |= DB_RF_NOPREFETCH;
 
 	err = dmu_buf_hold_noread(os, object, offset, tag, dbp);
 	if (err == 0) {
 		dmu_buf_impl_t *db = (dmu_buf_impl_t *)(*dbp);
 		err = dbuf_read(db, NULL, db_flags);
 		if (err != 0) {
 			dbuf_rele(db, tag);
 			*dbp = NULL;
 		}
 	}
 
 	return (err);
 }
 
 int
 dmu_bonus_max(void)
 {
 	return (DN_MAX_BONUSLEN);
 }
 
 int
 dmu_set_bonus(dmu_buf_t *db_fake, int newsize, dmu_tx_t *tx)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 	dnode_t *dn;
 	int error;
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 
 	if (dn->dn_bonus != db) {
 		error = SET_ERROR(EINVAL);
 	} else if (newsize < 0 || newsize > db_fake->db_size) {
 		error = SET_ERROR(EINVAL);
 	} else {
 		dnode_setbonuslen(dn, newsize, tx);
 		error = 0;
 	}
 
 	DB_DNODE_EXIT(db);
 	return (error);
 }
 
 int
 dmu_set_bonustype(dmu_buf_t *db_fake, dmu_object_type_t type, dmu_tx_t *tx)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 	dnode_t *dn;
 	int error;
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 
 	if (!DMU_OT_IS_VALID(type)) {
 		error = SET_ERROR(EINVAL);
 	} else if (dn->dn_bonus != db) {
 		error = SET_ERROR(EINVAL);
 	} else {
 		dnode_setbonus_type(dn, type, tx);
 		error = 0;
 	}
 
 	DB_DNODE_EXIT(db);
 	return (error);
 }
 
 dmu_object_type_t
 dmu_get_bonustype(dmu_buf_t *db_fake)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 	dnode_t *dn;
 	dmu_object_type_t type;
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 	type = dn->dn_bonustype;
 	DB_DNODE_EXIT(db);
 
 	return (type);
 }
 
 int
 dmu_rm_spill(objset_t *os, uint64_t object, dmu_tx_t *tx)
 {
 	dnode_t *dn;
 	int error;
 
 	error = dnode_hold(os, object, FTAG, &dn);
 	dbuf_rm_spill(dn, tx);
 	rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
 	dnode_rm_spill(dn, tx);
 	rw_exit(&dn->dn_struct_rwlock);
 	dnode_rele(dn, FTAG);
 	return (error);
 }
 
 /*
  * returns ENOENT, EIO, or 0.
  */
 int
 dmu_bonus_hold(objset_t *os, uint64_t object, void *tag, dmu_buf_t **dbp)
 {
 	dnode_t *dn;
 	dmu_buf_impl_t *db;
 	int error;
 
 	error = dnode_hold(os, object, FTAG, &dn);
 	if (error)
 		return (error);
 
 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
 	if (dn->dn_bonus == NULL) {
 		rw_exit(&dn->dn_struct_rwlock);
 		rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
 		if (dn->dn_bonus == NULL)
 			dbuf_create_bonus(dn);
 	}
 	db = dn->dn_bonus;
 
 	/* as long as the bonus buf is held, the dnode will be held */
 	if (refcount_add(&db->db_holds, tag) == 1) {
 		VERIFY(dnode_add_ref(dn, db));
 		atomic_inc_32(&dn->dn_dbufs_count);
 	}
 
 	/*
 	 * Wait to drop dn_struct_rwlock until after adding the bonus dbuf's
 	 * hold and incrementing the dbuf count to ensure that dnode_move() sees
 	 * a dnode hold for every dbuf.
 	 */
 	rw_exit(&dn->dn_struct_rwlock);
 
 	dnode_rele(dn, FTAG);
 
 	VERIFY(0 == dbuf_read(db, NULL, DB_RF_MUST_SUCCEED | DB_RF_NOPREFETCH));
 
 	*dbp = &db->db;
 	return (0);
 }
 
 /*
  * returns ENOENT, EIO, or 0.
  *
  * This interface will allocate a blank spill dbuf when a spill blk
  * doesn't already exist on the dnode.
  *
  * if you only want to find an already existing spill db, then
  * dmu_spill_hold_existing() should be used.
  */
 int
 dmu_spill_hold_by_dnode(dnode_t *dn, uint32_t flags, void *tag, dmu_buf_t **dbp)
 {
 	dmu_buf_impl_t *db = NULL;
 	int err;
 
 	if ((flags & DB_RF_HAVESTRUCT) == 0)
 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
 
 	db = dbuf_hold(dn, DMU_SPILL_BLKID, tag);
 
 	if ((flags & DB_RF_HAVESTRUCT) == 0)
 		rw_exit(&dn->dn_struct_rwlock);
 
 	ASSERT(db != NULL);
 	err = dbuf_read(db, NULL, flags);
 	if (err == 0)
 		*dbp = &db->db;
 	else
 		dbuf_rele(db, tag);
 	return (err);
 }
 
 int
 dmu_spill_hold_existing(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)bonus;
 	dnode_t *dn;
 	int err;
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 
 	if (spa_version(dn->dn_objset->os_spa) < SPA_VERSION_SA) {
 		err = SET_ERROR(EINVAL);
 	} else {
 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
 
 		if (!dn->dn_have_spill) {
 			err = SET_ERROR(ENOENT);
 		} else {
 			err = dmu_spill_hold_by_dnode(dn,
 			    DB_RF_HAVESTRUCT | DB_RF_CANFAIL, tag, dbp);
 		}
 
 		rw_exit(&dn->dn_struct_rwlock);
 	}
 
 	DB_DNODE_EXIT(db);
 	return (err);
 }
 
 int
 dmu_spill_hold_by_bonus(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)bonus;
 	dnode_t *dn;
 	int err;
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 	err = dmu_spill_hold_by_dnode(dn, DB_RF_CANFAIL, tag, dbp);
 	DB_DNODE_EXIT(db);
 
 	return (err);
 }
 
 /*
  * Note: longer-term, we should modify all of the dmu_buf_*() interfaces
  * to take a held dnode rather than <os, object> -- the lookup is wasteful,
  * and can induce severe lock contention when writing to several files
  * whose dnodes are in the same block.
  */
 static int
 dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset, uint64_t length,
     boolean_t read, void *tag, int *numbufsp, dmu_buf_t ***dbpp, uint32_t flags)
 {
 	dmu_buf_t **dbp;
 	uint64_t blkid, nblks, i;
 	uint32_t dbuf_flags;
 	int err;
 	zio_t *zio;
 
 	ASSERT(length <= DMU_MAX_ACCESS);
 
 	/*
 	 * Note: We directly notify the prefetch code of this read, so that
 	 * we can tell it about the multi-block read.  dbuf_read() only knows
 	 * about the one block it is accessing.
 	 */
 	dbuf_flags = DB_RF_CANFAIL | DB_RF_NEVERWAIT | DB_RF_HAVESTRUCT |
 	    DB_RF_NOPREFETCH;
 
 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
 	if (dn->dn_datablkshift) {
 		int blkshift = dn->dn_datablkshift;
 		nblks = (P2ROUNDUP(offset + length, 1ULL << blkshift) -
 		    P2ALIGN(offset, 1ULL << blkshift)) >> blkshift;
 	} else {
 		if (offset + length > dn->dn_datablksz) {
 			zfs_panic_recover("zfs: accessing past end of object "
 			    "%llx/%llx (size=%u access=%llu+%llu)",
 			    (longlong_t)dn->dn_objset->
 			    os_dsl_dataset->ds_object,
 			    (longlong_t)dn->dn_object, dn->dn_datablksz,
 			    (longlong_t)offset, (longlong_t)length);
 			rw_exit(&dn->dn_struct_rwlock);
 			return (SET_ERROR(EIO));
 		}
 		nblks = 1;
 	}
 	dbp = kmem_zalloc(sizeof (dmu_buf_t *) * nblks, KM_SLEEP);
 
 	zio = zio_root(dn->dn_objset->os_spa, NULL, NULL, ZIO_FLAG_CANFAIL);
 	blkid = dbuf_whichblock(dn, 0, offset);
 	for (i = 0; i < nblks; i++) {
 		dmu_buf_impl_t *db = dbuf_hold(dn, blkid + i, tag);
 		if (db == NULL) {
 			rw_exit(&dn->dn_struct_rwlock);
 			dmu_buf_rele_array(dbp, nblks, tag);
 			zio_nowait(zio);
 			return (SET_ERROR(EIO));
 		}
 
 		/* initiate async i/o */
 		if (read)
 			(void) dbuf_read(db, zio, dbuf_flags);
 #ifdef _KERNEL
 		else
 			curthread->td_ru.ru_oublock++;
 #endif
 		dbp[i] = &db->db;
 	}
 
 	if ((flags & DMU_READ_NO_PREFETCH) == 0 && read &&
 	    length <= zfetch_array_rd_sz) {
 		dmu_zfetch(&dn->dn_zfetch, blkid, nblks);
 	}
 	rw_exit(&dn->dn_struct_rwlock);
 
 	/* wait for async i/o */
 	err = zio_wait(zio);
 	if (err) {
 		dmu_buf_rele_array(dbp, nblks, tag);
 		return (err);
 	}
 
 	/* wait for other io to complete */
 	if (read) {
 		for (i = 0; i < nblks; i++) {
 			dmu_buf_impl_t *db = (dmu_buf_impl_t *)dbp[i];
 			mutex_enter(&db->db_mtx);
 			while (db->db_state == DB_READ ||
 			    db->db_state == DB_FILL)
 				cv_wait(&db->db_changed, &db->db_mtx);
 			if (db->db_state == DB_UNCACHED)
 				err = SET_ERROR(EIO);
 			mutex_exit(&db->db_mtx);
 			if (err) {
 				dmu_buf_rele_array(dbp, nblks, tag);
 				return (err);
 			}
 		}
 	}
 
 	*numbufsp = nblks;
 	*dbpp = dbp;
 	return (0);
 }
 
 static int
 dmu_buf_hold_array(objset_t *os, uint64_t object, uint64_t offset,
     uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
 {
 	dnode_t *dn;
 	int err;
 
 	err = dnode_hold(os, object, FTAG, &dn);
 	if (err)
 		return (err);
 
 	err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
 	    numbufsp, dbpp, DMU_READ_PREFETCH);
 
 	dnode_rele(dn, FTAG);
 
 	return (err);
 }
 
 int
 dmu_buf_hold_array_by_bonus(dmu_buf_t *db_fake, uint64_t offset,
     uint64_t length, boolean_t read, void *tag, int *numbufsp,
     dmu_buf_t ***dbpp)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 	dnode_t *dn;
 	int err;
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 	err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
 	    numbufsp, dbpp, DMU_READ_PREFETCH);
 	DB_DNODE_EXIT(db);
 
 	return (err);
 }
 
 void
 dmu_buf_rele_array(dmu_buf_t **dbp_fake, int numbufs, void *tag)
 {
 	int i;
 	dmu_buf_impl_t **dbp = (dmu_buf_impl_t **)dbp_fake;
 
 	if (numbufs == 0)
 		return;
 
 	for (i = 0; i < numbufs; i++) {
 		if (dbp[i])
 			dbuf_rele(dbp[i], tag);
 	}
 
 	kmem_free(dbp, sizeof (dmu_buf_t *) * numbufs);
 }
 
 /*
  * Issue prefetch i/os for the given blocks.  If level is greater than 0, the
  * indirect blocks prefeteched will be those that point to the blocks containing
  * the data starting at offset, and continuing to offset + len.
  *
  * Note that if the indirect blocks above the blocks being prefetched are not in
  * cache, they will be asychronously read in.
  */
 void
 dmu_prefetch(objset_t *os, uint64_t object, int64_t level, uint64_t offset,
     uint64_t len, zio_priority_t pri)
 {
 	dnode_t *dn;
 	uint64_t blkid;
 	int nblks, err;
 
 	if (len == 0) {  /* they're interested in the bonus buffer */
 		dn = DMU_META_DNODE(os);
 
 		if (object == 0 || object >= DN_MAX_OBJECT)
 			return;
 
 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
 		blkid = dbuf_whichblock(dn, level,
 		    object * sizeof (dnode_phys_t));
 		dbuf_prefetch(dn, level, blkid, pri, 0);
 		rw_exit(&dn->dn_struct_rwlock);
 		return;
 	}
 
 	/*
 	 * XXX - Note, if the dnode for the requested object is not
 	 * already cached, we will do a *synchronous* read in the
 	 * dnode_hold() call.  The same is true for any indirects.
 	 */
 	err = dnode_hold(os, object, FTAG, &dn);
 	if (err != 0)
 		return;
 
 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
 	/*
 	 * offset + len - 1 is the last byte we want to prefetch for, and offset
 	 * is the first.  Then dbuf_whichblk(dn, level, off + len - 1) is the
 	 * last block we want to prefetch, and dbuf_whichblock(dn, level,
 	 * offset)  is the first.  Then the number we need to prefetch is the
 	 * last - first + 1.
 	 */
 	if (level > 0 || dn->dn_datablkshift != 0) {
 		nblks = dbuf_whichblock(dn, level, offset + len - 1) -
 		    dbuf_whichblock(dn, level, offset) + 1;
 	} else {
 		nblks = (offset < dn->dn_datablksz);
 	}
 
 	if (nblks != 0) {
 		blkid = dbuf_whichblock(dn, level, offset);
 		for (int i = 0; i < nblks; i++)
 			dbuf_prefetch(dn, level, blkid + i, pri, 0);
 	}
 
 	rw_exit(&dn->dn_struct_rwlock);
 
 	dnode_rele(dn, FTAG);
 }
 
 /*
  * Get the next "chunk" of file data to free.  We traverse the file from
  * the end so that the file gets shorter over time (if we crashes in the
  * middle, this will leave us in a better state).  We find allocated file
  * data by simply searching the allocated level 1 indirects.
  *
  * On input, *start should be the first offset that does not need to be
  * freed (e.g. "offset + length").  On return, *start will be the first
  * offset that should be freed.
  */
 static int
 get_next_chunk(dnode_t *dn, uint64_t *start, uint64_t minimum)
 {
 	uint64_t maxblks = DMU_MAX_ACCESS >> (dn->dn_indblkshift + 1);
 	/* bytes of data covered by a level-1 indirect block */
 	uint64_t iblkrange =
 	    dn->dn_datablksz * EPB(dn->dn_indblkshift, SPA_BLKPTRSHIFT);
 
 	ASSERT3U(minimum, <=, *start);
 
 	if (*start - minimum <= iblkrange * maxblks) {
 		*start = minimum;
 		return (0);
 	}
 	ASSERT(ISP2(iblkrange));
 
 	for (uint64_t blks = 0; *start > minimum && blks < maxblks; blks++) {
 		int err;
 
 		/*
 		 * dnode_next_offset(BACKWARDS) will find an allocated L1
 		 * indirect block at or before the input offset.  We must
 		 * decrement *start so that it is at the end of the region
 		 * to search.
 		 */
 		(*start)--;
 		err = dnode_next_offset(dn,
 		    DNODE_FIND_BACKWARDS, start, 2, 1, 0);
 
 		/* if there are no indirect blocks before start, we are done */
 		if (err == ESRCH) {
 			*start = minimum;
 			break;
 		} else if (err != 0) {
 			return (err);
 		}
 
 		/* set start to the beginning of this L1 indirect */
 		*start = P2ALIGN(*start, iblkrange);
 	}
 	if (*start < minimum)
 		*start = minimum;
 	return (0);
 }
 
 static int
 dmu_free_long_range_impl(objset_t *os, dnode_t *dn, uint64_t offset,
     uint64_t length)
 {
 	uint64_t object_size = (dn->dn_maxblkid + 1) * dn->dn_datablksz;
 	int err;
 
 	if (offset >= object_size)
 		return (0);
 
 	if (length == DMU_OBJECT_END || offset + length > object_size)
 		length = object_size - offset;
 
 	while (length != 0) {
 		uint64_t chunk_end, chunk_begin;
 
 		chunk_end = chunk_begin = offset + length;
 
 		/* move chunk_begin backwards to the beginning of this chunk */
 		err = get_next_chunk(dn, &chunk_begin, offset);
 		if (err)
 			return (err);
 		ASSERT3U(chunk_begin, >=, offset);
 		ASSERT3U(chunk_begin, <=, chunk_end);
 
 		dmu_tx_t *tx = dmu_tx_create(os);
 		dmu_tx_hold_free(tx, dn->dn_object,
 		    chunk_begin, chunk_end - chunk_begin);
 
 		/*
 		 * Mark this transaction as typically resulting in a net
 		 * reduction in space used.
 		 */
 		dmu_tx_mark_netfree(tx);
 		err = dmu_tx_assign(tx, TXG_WAIT);
 		if (err) {
 			dmu_tx_abort(tx);
 			return (err);
 		}
 		dnode_free_range(dn, chunk_begin, chunk_end - chunk_begin, tx);
 		dmu_tx_commit(tx);
 
 		length -= chunk_end - chunk_begin;
 	}
 	return (0);
 }
 
 int
 dmu_free_long_range(objset_t *os, uint64_t object,
     uint64_t offset, uint64_t length)
 {
 	dnode_t *dn;
 	int err;
 
 	err = dnode_hold(os, object, FTAG, &dn);
 	if (err != 0)
 		return (err);
 	err = dmu_free_long_range_impl(os, dn, offset, length);
 
 	/*
 	 * It is important to zero out the maxblkid when freeing the entire
 	 * file, so that (a) subsequent calls to dmu_free_long_range_impl()
 	 * will take the fast path, and (b) dnode_reallocate() can verify
 	 * that the entire file has been freed.
 	 */
 	if (err == 0 && offset == 0 && length == DMU_OBJECT_END)
 		dn->dn_maxblkid = 0;
 
 	dnode_rele(dn, FTAG);
 	return (err);
 }
 
 int
 dmu_free_long_object(objset_t *os, uint64_t object)
 {
 	dmu_tx_t *tx;
 	int err;
 
 	err = dmu_free_long_range(os, object, 0, DMU_OBJECT_END);
 	if (err != 0)
 		return (err);
 
 	tx = dmu_tx_create(os);
 	dmu_tx_hold_bonus(tx, object);
 	dmu_tx_hold_free(tx, object, 0, DMU_OBJECT_END);
 	dmu_tx_mark_netfree(tx);
 	err = dmu_tx_assign(tx, TXG_WAIT);
 	if (err == 0) {
 		err = dmu_object_free(os, object, tx);
 		dmu_tx_commit(tx);
 	} else {
 		dmu_tx_abort(tx);
 	}
 
 	return (err);
 }
 
 int
 dmu_free_range(objset_t *os, uint64_t object, uint64_t offset,
     uint64_t size, dmu_tx_t *tx)
 {
 	dnode_t *dn;
 	int err = dnode_hold(os, object, FTAG, &dn);
 	if (err)
 		return (err);
 	ASSERT(offset < UINT64_MAX);
 	ASSERT(size == -1ULL || size <= UINT64_MAX - offset);
 	dnode_free_range(dn, offset, size, tx);
 	dnode_rele(dn, FTAG);
 	return (0);
 }
 
 int
 dmu_read(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
     void *buf, uint32_t flags)
 {
 	dnode_t *dn;
 	dmu_buf_t **dbp;
 	int numbufs, err;
 
 	err = dnode_hold(os, object, FTAG, &dn);
 	if (err)
 		return (err);
 
 	/*
 	 * Deal with odd block sizes, where there can't be data past the first
 	 * block.  If we ever do the tail block optimization, we will need to
 	 * handle that here as well.
 	 */
 	if (dn->dn_maxblkid == 0) {
 		int newsz = offset > dn->dn_datablksz ? 0 :
 		    MIN(size, dn->dn_datablksz - offset);
 		bzero((char *)buf + newsz, size - newsz);
 		size = newsz;
 	}
 
 	while (size > 0) {
 		uint64_t mylen = MIN(size, DMU_MAX_ACCESS / 2);
 		int i;
 
 		/*
 		 * NB: we could do this block-at-a-time, but it's nice
 		 * to be reading in parallel.
 		 */
 		err = dmu_buf_hold_array_by_dnode(dn, offset, mylen,
 		    TRUE, FTAG, &numbufs, &dbp, flags);
 		if (err)
 			break;
 
 		for (i = 0; i < numbufs; i++) {
 			int tocpy;
 			int bufoff;
 			dmu_buf_t *db = dbp[i];
 
 			ASSERT(size > 0);
 
 			bufoff = offset - db->db_offset;
 			tocpy = (int)MIN(db->db_size - bufoff, size);
 
 			bcopy((char *)db->db_data + bufoff, buf, tocpy);
 
 			offset += tocpy;
 			size -= tocpy;
 			buf = (char *)buf + tocpy;
 		}
 		dmu_buf_rele_array(dbp, numbufs, FTAG);
 	}
 	dnode_rele(dn, FTAG);
 	return (err);
 }
 
 void
 dmu_write(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
     const void *buf, dmu_tx_t *tx)
 {
 	dmu_buf_t **dbp;
 	int numbufs, i;
 
 	if (size == 0)
 		return;
 
 	VERIFY(0 == dmu_buf_hold_array(os, object, offset, size,
 	    FALSE, FTAG, &numbufs, &dbp));
 
 	for (i = 0; i < numbufs; i++) {
 		int tocpy;
 		int bufoff;
 		dmu_buf_t *db = dbp[i];
 
 		ASSERT(size > 0);
 
 		bufoff = offset - db->db_offset;
 		tocpy = (int)MIN(db->db_size - bufoff, size);
 
 		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
 
 		if (tocpy == db->db_size)
 			dmu_buf_will_fill(db, tx);
 		else
 			dmu_buf_will_dirty(db, tx);
 
 		bcopy(buf, (char *)db->db_data + bufoff, tocpy);
 
 		if (tocpy == db->db_size)
 			dmu_buf_fill_done(db, tx);
 
 		offset += tocpy;
 		size -= tocpy;
 		buf = (char *)buf + tocpy;
 	}
 	dmu_buf_rele_array(dbp, numbufs, FTAG);
 }
 
 void
 dmu_prealloc(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
     dmu_tx_t *tx)
 {
 	dmu_buf_t **dbp;
 	int numbufs, i;
 
 	if (size == 0)
 		return;
 
 	VERIFY(0 == dmu_buf_hold_array(os, object, offset, size,
 	    FALSE, FTAG, &numbufs, &dbp));
 
 	for (i = 0; i < numbufs; i++) {
 		dmu_buf_t *db = dbp[i];
 
 		dmu_buf_will_not_fill(db, tx);
 	}
 	dmu_buf_rele_array(dbp, numbufs, FTAG);
 }
 
 void
 dmu_write_embedded(objset_t *os, uint64_t object, uint64_t offset,
     void *data, uint8_t etype, uint8_t comp, int uncompressed_size,
     int compressed_size, int byteorder, dmu_tx_t *tx)
 {
 	dmu_buf_t *db;
 
 	ASSERT3U(etype, <, NUM_BP_EMBEDDED_TYPES);
 	ASSERT3U(comp, <, ZIO_COMPRESS_FUNCTIONS);
 	VERIFY0(dmu_buf_hold_noread(os, object, offset,
 	    FTAG, &db));
 
 	dmu_buf_write_embedded(db,
 	    data, (bp_embedded_type_t)etype, (enum zio_compress)comp,
 	    uncompressed_size, compressed_size, byteorder, tx);
 
 	dmu_buf_rele(db, FTAG);
 }
 
 /*
  * DMU support for xuio
  */
 kstat_t *xuio_ksp = NULL;
 
 int
 dmu_xuio_init(xuio_t *xuio, int nblk)
 {
 	dmu_xuio_t *priv;
 	uio_t *uio = &xuio->xu_uio;
 
 	uio->uio_iovcnt = nblk;
 	uio->uio_iov = kmem_zalloc(nblk * sizeof (iovec_t), KM_SLEEP);
 
 	priv = kmem_zalloc(sizeof (dmu_xuio_t), KM_SLEEP);
 	priv->cnt = nblk;
 	priv->bufs = kmem_zalloc(nblk * sizeof (arc_buf_t *), KM_SLEEP);
 	priv->iovp = uio->uio_iov;
 	XUIO_XUZC_PRIV(xuio) = priv;
 
 	if (XUIO_XUZC_RW(xuio) == UIO_READ)
 		XUIOSTAT_INCR(xuiostat_onloan_rbuf, nblk);
 	else
 		XUIOSTAT_INCR(xuiostat_onloan_wbuf, nblk);
 
 	return (0);
 }
 
 void
 dmu_xuio_fini(xuio_t *xuio)
 {
 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
 	int nblk = priv->cnt;
 
 	kmem_free(priv->iovp, nblk * sizeof (iovec_t));
 	kmem_free(priv->bufs, nblk * sizeof (arc_buf_t *));
 	kmem_free(priv, sizeof (dmu_xuio_t));
 
 	if (XUIO_XUZC_RW(xuio) == UIO_READ)
 		XUIOSTAT_INCR(xuiostat_onloan_rbuf, -nblk);
 	else
 		XUIOSTAT_INCR(xuiostat_onloan_wbuf, -nblk);
 }
 
 /*
  * Initialize iov[priv->next] and priv->bufs[priv->next] with { off, n, abuf }
  * and increase priv->next by 1.
  */
 int
 dmu_xuio_add(xuio_t *xuio, arc_buf_t *abuf, offset_t off, size_t n)
 {
 	struct iovec *iov;
 	uio_t *uio = &xuio->xu_uio;
 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
 	int i = priv->next++;
 
 	ASSERT(i < priv->cnt);
 	ASSERT(off + n <= arc_buf_size(abuf));
 	iov = uio->uio_iov + i;
 	iov->iov_base = (char *)abuf->b_data + off;
 	iov->iov_len = n;
 	priv->bufs[i] = abuf;
 	return (0);
 }
 
 int
 dmu_xuio_cnt(xuio_t *xuio)
 {
 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
 	return (priv->cnt);
 }
 
 arc_buf_t *
 dmu_xuio_arcbuf(xuio_t *xuio, int i)
 {
 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
 
 	ASSERT(i < priv->cnt);
 	return (priv->bufs[i]);
 }
 
 void
 dmu_xuio_clear(xuio_t *xuio, int i)
 {
 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
 
 	ASSERT(i < priv->cnt);
 	priv->bufs[i] = NULL;
 }
 
 static void
 xuio_stat_init(void)
 {
 	xuio_ksp = kstat_create("zfs", 0, "xuio_stats", "misc",
 	    KSTAT_TYPE_NAMED, sizeof (xuio_stats) / sizeof (kstat_named_t),
 	    KSTAT_FLAG_VIRTUAL);
 	if (xuio_ksp != NULL) {
 		xuio_ksp->ks_data = &xuio_stats;
 		kstat_install(xuio_ksp);
 	}
 }
 
 static void
 xuio_stat_fini(void)
 {
 	if (xuio_ksp != NULL) {
 		kstat_delete(xuio_ksp);
 		xuio_ksp = NULL;
 	}
 }
 
 void
 xuio_stat_wbuf_copied()
 {
 	XUIOSTAT_BUMP(xuiostat_wbuf_copied);
 }
 
 void
 xuio_stat_wbuf_nocopy()
 {
 	XUIOSTAT_BUMP(xuiostat_wbuf_nocopy);
 }
 
 #ifdef _KERNEL
 static int
 dmu_read_uio_dnode(dnode_t *dn, uio_t *uio, uint64_t size)
 {
 	dmu_buf_t **dbp;
 	int numbufs, i, err;
 	xuio_t *xuio = NULL;
 
 	/*
 	 * NB: we could do this block-at-a-time, but it's nice
 	 * to be reading in parallel.
 	 */
 	err = dmu_buf_hold_array_by_dnode(dn, uio->uio_loffset, size,
 	    TRUE, FTAG, &numbufs, &dbp, 0);
 	if (err)
 		return (err);
 
 #ifdef UIO_XUIO
 	if (uio->uio_extflg == UIO_XUIO)
 		xuio = (xuio_t *)uio;
 #endif
 
 	for (i = 0; i < numbufs; i++) {
 		int tocpy;
 		int bufoff;
 		dmu_buf_t *db = dbp[i];
 
 		ASSERT(size > 0);
 
 		bufoff = uio->uio_loffset - db->db_offset;
 		tocpy = (int)MIN(db->db_size - bufoff, size);
 
 		if (xuio) {
 			dmu_buf_impl_t *dbi = (dmu_buf_impl_t *)db;
 			arc_buf_t *dbuf_abuf = dbi->db_buf;
 			arc_buf_t *abuf = dbuf_loan_arcbuf(dbi);
 			err = dmu_xuio_add(xuio, abuf, bufoff, tocpy);
 			if (!err) {
 				uio->uio_resid -= tocpy;
 				uio->uio_loffset += tocpy;
 			}
 
 			if (abuf == dbuf_abuf)
 				XUIOSTAT_BUMP(xuiostat_rbuf_nocopy);
 			else
 				XUIOSTAT_BUMP(xuiostat_rbuf_copied);
 		} else {
 			err = uiomove((char *)db->db_data + bufoff, tocpy,
 			    UIO_READ, uio);
 		}
 		if (err)
 			break;
 
 		size -= tocpy;
 	}
 	dmu_buf_rele_array(dbp, numbufs, FTAG);
 
 	return (err);
 }
 
 /*
  * Read 'size' bytes into the uio buffer.
  * From object zdb->db_object.
  * Starting at offset uio->uio_loffset.
  *
  * If the caller already has a dbuf in the target object
  * (e.g. its bonus buffer), this routine is faster than dmu_read_uio(),
  * because we don't have to find the dnode_t for the object.
  */
 int
 dmu_read_uio_dbuf(dmu_buf_t *zdb, uio_t *uio, uint64_t size)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)zdb;
 	dnode_t *dn;
 	int err;
 
 	if (size == 0)
 		return (0);
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 	err = dmu_read_uio_dnode(dn, uio, size);
 	DB_DNODE_EXIT(db);
 
 	return (err);
 }
 
 /*
  * Read 'size' bytes into the uio buffer.
  * From the specified object
  * Starting at offset uio->uio_loffset.
  */
 int
 dmu_read_uio(objset_t *os, uint64_t object, uio_t *uio, uint64_t size)
 {
 	dnode_t *dn;
 	int err;
 
 	if (size == 0)
 		return (0);
 
 	err = dnode_hold(os, object, FTAG, &dn);
 	if (err)
 		return (err);
 
 	err = dmu_read_uio_dnode(dn, uio, size);
 
 	dnode_rele(dn, FTAG);
 
 	return (err);
 }
 
 static int
 dmu_write_uio_dnode(dnode_t *dn, uio_t *uio, uint64_t size, dmu_tx_t *tx)
 {
 	dmu_buf_t **dbp;
 	int numbufs;
 	int err = 0;
 	int i;
 
 	err = dmu_buf_hold_array_by_dnode(dn, uio->uio_loffset, size,
 	    FALSE, FTAG, &numbufs, &dbp, DMU_READ_PREFETCH);
 	if (err)
 		return (err);
 
 	for (i = 0; i < numbufs; i++) {
 		int tocpy;
 		int bufoff;
 		dmu_buf_t *db = dbp[i];
 
 		ASSERT(size > 0);
 
 		bufoff = uio->uio_loffset - db->db_offset;
 		tocpy = (int)MIN(db->db_size - bufoff, size);
 
 		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
 
 		if (tocpy == db->db_size)
 			dmu_buf_will_fill(db, tx);
 		else
 			dmu_buf_will_dirty(db, tx);
 
 		/*
 		 * XXX uiomove could block forever (eg. nfs-backed
 		 * pages).  There needs to be a uiolockdown() function
 		 * to lock the pages in memory, so that uiomove won't
 		 * block.
 		 */
 		err = uiomove((char *)db->db_data + bufoff, tocpy,
 		    UIO_WRITE, uio);
 
 		if (tocpy == db->db_size)
 			dmu_buf_fill_done(db, tx);
 
 		if (err)
 			break;
 
 		size -= tocpy;
 	}
 
 	dmu_buf_rele_array(dbp, numbufs, FTAG);
 	return (err);
 }
 
 /*
  * Write 'size' bytes from the uio buffer.
  * To object zdb->db_object.
  * Starting at offset uio->uio_loffset.
  *
  * If the caller already has a dbuf in the target object
  * (e.g. its bonus buffer), this routine is faster than dmu_write_uio(),
  * because we don't have to find the dnode_t for the object.
  */
 int
 dmu_write_uio_dbuf(dmu_buf_t *zdb, uio_t *uio, uint64_t size,
     dmu_tx_t *tx)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)zdb;
 	dnode_t *dn;
 	int err;
 
 	if (size == 0)
 		return (0);
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 	err = dmu_write_uio_dnode(dn, uio, size, tx);
 	DB_DNODE_EXIT(db);
 
 	return (err);
 }
 
 /*
  * Write 'size' bytes from the uio buffer.
  * To the specified object.
  * Starting at offset uio->uio_loffset.
  */
 int
 dmu_write_uio(objset_t *os, uint64_t object, uio_t *uio, uint64_t size,
     dmu_tx_t *tx)
 {
 	dnode_t *dn;
 	int err;
 
 	if (size == 0)
 		return (0);
 
 	err = dnode_hold(os, object, FTAG, &dn);
 	if (err)
 		return (err);
 
 	err = dmu_write_uio_dnode(dn, uio, size, tx);
 
 	dnode_rele(dn, FTAG);
 
 	return (err);
 }
 
 #ifdef illumos
 int
 dmu_write_pages(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
     page_t *pp, dmu_tx_t *tx)
 {
 	dmu_buf_t **dbp;
 	int numbufs, i;
 	int err;
 
 	if (size == 0)
 		return (0);
 
 	err = dmu_buf_hold_array(os, object, offset, size,
 	    FALSE, FTAG, &numbufs, &dbp);
 	if (err)
 		return (err);
 
 	for (i = 0; i < numbufs; i++) {
 		int tocpy, copied, thiscpy;
 		int bufoff;
 		dmu_buf_t *db = dbp[i];
 		caddr_t va;
 
 		ASSERT(size > 0);
 		ASSERT3U(db->db_size, >=, PAGESIZE);
 
 		bufoff = offset - db->db_offset;
 		tocpy = (int)MIN(db->db_size - bufoff, size);
 
 		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
 
 		if (tocpy == db->db_size)
 			dmu_buf_will_fill(db, tx);
 		else
 			dmu_buf_will_dirty(db, tx);
 
 		for (copied = 0; copied < tocpy; copied += PAGESIZE) {
 			ASSERT3U(pp->p_offset, ==, db->db_offset + bufoff);
 			thiscpy = MIN(PAGESIZE, tocpy - copied);
 			va = zfs_map_page(pp, S_READ);
 			bcopy(va, (char *)db->db_data + bufoff, thiscpy);
 			zfs_unmap_page(pp, va);
 			pp = pp->p_next;
 			bufoff += PAGESIZE;
 		}
 
 		if (tocpy == db->db_size)
 			dmu_buf_fill_done(db, tx);
 
 		offset += tocpy;
 		size -= tocpy;
 	}
 	dmu_buf_rele_array(dbp, numbufs, FTAG);
 	return (err);
 }
 
 #else	/* !illumos */
 
 int
 dmu_write_pages(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
     vm_page_t *ma, dmu_tx_t *tx)
 {
 	dmu_buf_t **dbp;
 	struct sf_buf *sf;
 	int numbufs, i;
 	int err;
 
 	if (size == 0)
 		return (0);
 
 	err = dmu_buf_hold_array(os, object, offset, size,
 	    FALSE, FTAG, &numbufs, &dbp);
 	if (err)
 		return (err);
 
 	for (i = 0; i < numbufs; i++) {
 		int tocpy, copied, thiscpy;
 		int bufoff;
 		dmu_buf_t *db = dbp[i];
 		caddr_t va;
 
 		ASSERT(size > 0);
 		ASSERT3U(db->db_size, >=, PAGESIZE);
 
 		bufoff = offset - db->db_offset;
 		tocpy = (int)MIN(db->db_size - bufoff, size);
 
 		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
 
 		if (tocpy == db->db_size)
 			dmu_buf_will_fill(db, tx);
 		else
 			dmu_buf_will_dirty(db, tx);
 
 		for (copied = 0; copied < tocpy; copied += PAGESIZE) {
 			ASSERT3U(ptoa((*ma)->pindex), ==, db->db_offset + bufoff);
 			thiscpy = MIN(PAGESIZE, tocpy - copied);
 			va = zfs_map_page(*ma, &sf);
 			bcopy(va, (char *)db->db_data + bufoff, thiscpy);
 			zfs_unmap_page(sf);
 			ma += 1;
 			bufoff += PAGESIZE;
 		}
 
 		if (tocpy == db->db_size)
 			dmu_buf_fill_done(db, tx);
 
 		offset += tocpy;
 		size -= tocpy;
 	}
 	dmu_buf_rele_array(dbp, numbufs, FTAG);
 	return (err);
 }
 #endif	/* illumos */
 #endif	/* _KERNEL */
 
 /*
  * Allocate a loaned anonymous arc buffer.
  */
 arc_buf_t *
 dmu_request_arcbuf(dmu_buf_t *handle, int size)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)handle;
 
 	return (arc_loan_buf(db->db_objset->os_spa, size));
 }
 
 /*
  * Free a loaned arc buffer.
  */
 void
 dmu_return_arcbuf(arc_buf_t *buf)
 {
 	arc_return_buf(buf, FTAG);
 	VERIFY(arc_buf_remove_ref(buf, FTAG));
 }
 
 /*
  * When possible directly assign passed loaned arc buffer to a dbuf.
  * If this is not possible copy the contents of passed arc buf via
  * dmu_write().
  */
 void
 dmu_assign_arcbuf(dmu_buf_t *handle, uint64_t offset, arc_buf_t *buf,
     dmu_tx_t *tx)
 {
 	dmu_buf_impl_t *dbuf = (dmu_buf_impl_t *)handle;
 	dnode_t *dn;
 	dmu_buf_impl_t *db;
 	uint32_t blksz = (uint32_t)arc_buf_size(buf);
 	uint64_t blkid;
 
 	DB_DNODE_ENTER(dbuf);
 	dn = DB_DNODE(dbuf);
 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
 	blkid = dbuf_whichblock(dn, 0, offset);
 	VERIFY((db = dbuf_hold(dn, blkid, FTAG)) != NULL);
 	rw_exit(&dn->dn_struct_rwlock);
 	DB_DNODE_EXIT(dbuf);
 
 	/*
 	 * We can only assign if the offset is aligned, the arc buf is the
 	 * same size as the dbuf, and the dbuf is not metadata.  It
 	 * can't be metadata because the loaned arc buf comes from the
 	 * user-data kmem arena.
 	 */
 	if (offset == db->db.db_offset && blksz == db->db.db_size &&
 	    DBUF_GET_BUFC_TYPE(db) == ARC_BUFC_DATA) {
+#ifdef _KERNEL
+		curthread->td_ru.ru_oublock++;
+#endif
 		dbuf_assign_arcbuf(db, buf, tx);
 		dbuf_rele(db, FTAG);
 	} else {
 		objset_t *os;
 		uint64_t object;
 
 		DB_DNODE_ENTER(dbuf);
 		dn = DB_DNODE(dbuf);
 		os = dn->dn_objset;
 		object = dn->dn_object;
 		DB_DNODE_EXIT(dbuf);
 
 		dbuf_rele(db, FTAG);
 		dmu_write(os, object, offset, blksz, buf->b_data, tx);
 		dmu_return_arcbuf(buf);
 		XUIOSTAT_BUMP(xuiostat_wbuf_copied);
 	}
 }
 
 typedef struct {
 	dbuf_dirty_record_t	*dsa_dr;
 	dmu_sync_cb_t		*dsa_done;
 	zgd_t			*dsa_zgd;
 	dmu_tx_t		*dsa_tx;
 } dmu_sync_arg_t;
 
 /* ARGSUSED */
 static void
 dmu_sync_ready(zio_t *zio, arc_buf_t *buf, void *varg)
 {
 	dmu_sync_arg_t *dsa = varg;
 	dmu_buf_t *db = dsa->dsa_zgd->zgd_db;
 	blkptr_t *bp = zio->io_bp;
 
 	if (zio->io_error == 0) {
 		if (BP_IS_HOLE(bp)) {
 			/*
 			 * A block of zeros may compress to a hole, but the
 			 * block size still needs to be known for replay.
 			 */
 			BP_SET_LSIZE(bp, db->db_size);
 		} else if (!BP_IS_EMBEDDED(bp)) {
 			ASSERT(BP_GET_LEVEL(bp) == 0);
 			bp->blk_fill = 1;
 		}
 	}
 }
 
 static void
 dmu_sync_late_arrival_ready(zio_t *zio)
 {
 	dmu_sync_ready(zio, NULL, zio->io_private);
 }
 
 /* ARGSUSED */
 static void
 dmu_sync_done(zio_t *zio, arc_buf_t *buf, void *varg)
 {
 	dmu_sync_arg_t *dsa = varg;
 	dbuf_dirty_record_t *dr = dsa->dsa_dr;
 	dmu_buf_impl_t *db = dr->dr_dbuf;
 
 	mutex_enter(&db->db_mtx);
 	ASSERT(dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC);
 	if (zio->io_error == 0) {
 		dr->dt.dl.dr_nopwrite = !!(zio->io_flags & ZIO_FLAG_NOPWRITE);
 		if (dr->dt.dl.dr_nopwrite) {
 			blkptr_t *bp = zio->io_bp;
 			blkptr_t *bp_orig = &zio->io_bp_orig;
 			uint8_t chksum = BP_GET_CHECKSUM(bp_orig);
 
 			ASSERT(BP_EQUAL(bp, bp_orig));
 			ASSERT(zio->io_prop.zp_compress != ZIO_COMPRESS_OFF);
 			ASSERT(zio_checksum_table[chksum].ci_flags &
 			    ZCHECKSUM_FLAG_NOPWRITE);
 		}
 		dr->dt.dl.dr_overridden_by = *zio->io_bp;
 		dr->dt.dl.dr_override_state = DR_OVERRIDDEN;
 		dr->dt.dl.dr_copies = zio->io_prop.zp_copies;
 
 		/*
 		 * Old style holes are filled with all zeros, whereas
 		 * new-style holes maintain their lsize, type, level,
 		 * and birth time (see zio_write_compress). While we
 		 * need to reset the BP_SET_LSIZE() call that happened
 		 * in dmu_sync_ready for old style holes, we do *not*
 		 * want to wipe out the information contained in new
 		 * style holes. Thus, only zero out the block pointer if
 		 * it's an old style hole.
 		 */
 		if (BP_IS_HOLE(&dr->dt.dl.dr_overridden_by) &&
 		    dr->dt.dl.dr_overridden_by.blk_birth == 0)
 			BP_ZERO(&dr->dt.dl.dr_overridden_by);
 	} else {
 		dr->dt.dl.dr_override_state = DR_NOT_OVERRIDDEN;
 	}
 	cv_broadcast(&db->db_changed);
 	mutex_exit(&db->db_mtx);
 
 	dsa->dsa_done(dsa->dsa_zgd, zio->io_error);
 
 	kmem_free(dsa, sizeof (*dsa));
 }
 
 static void
 dmu_sync_late_arrival_done(zio_t *zio)
 {
 	blkptr_t *bp = zio->io_bp;
 	dmu_sync_arg_t *dsa = zio->io_private;
 	blkptr_t *bp_orig = &zio->io_bp_orig;
 
 	if (zio->io_error == 0 && !BP_IS_HOLE(bp)) {
 		/*
 		 * If we didn't allocate a new block (i.e. ZIO_FLAG_NOPWRITE)
 		 * then there is nothing to do here. Otherwise, free the
 		 * newly allocated block in this txg.
 		 */
 		if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
 			ASSERT(BP_EQUAL(bp, bp_orig));
 		} else {
 			ASSERT(BP_IS_HOLE(bp_orig) || !BP_EQUAL(bp, bp_orig));
 			ASSERT(zio->io_bp->blk_birth == zio->io_txg);
 			ASSERT(zio->io_txg > spa_syncing_txg(zio->io_spa));
 			zio_free(zio->io_spa, zio->io_txg, zio->io_bp);
 		}
 	}
 
 	dmu_tx_commit(dsa->dsa_tx);
 
 	dsa->dsa_done(dsa->dsa_zgd, zio->io_error);
 
 	kmem_free(dsa, sizeof (*dsa));
 }
 
 static int
 dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sync_cb_t *done, zgd_t *zgd,
     zio_prop_t *zp, zbookmark_phys_t *zb)
 {
 	dmu_sync_arg_t *dsa;
 	dmu_tx_t *tx;
 
 	tx = dmu_tx_create(os);
 	dmu_tx_hold_space(tx, zgd->zgd_db->db_size);
 	if (dmu_tx_assign(tx, TXG_WAIT) != 0) {
 		dmu_tx_abort(tx);
 		/* Make zl_get_data do txg_waited_synced() */
 		return (SET_ERROR(EIO));
 	}
 
 	dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_SLEEP);
 	dsa->dsa_dr = NULL;
 	dsa->dsa_done = done;
 	dsa->dsa_zgd = zgd;
 	dsa->dsa_tx = tx;
 
 	zio_nowait(zio_write(pio, os->os_spa, dmu_tx_get_txg(tx), zgd->zgd_bp,
 	    zgd->zgd_db->db_data, zgd->zgd_db->db_size, zp,
 	    dmu_sync_late_arrival_ready, NULL, dmu_sync_late_arrival_done, dsa,
 	    ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, zb));
 
 	return (0);
 }
 
 /*
  * Intent log support: sync the block associated with db to disk.
  * N.B. and XXX: the caller is responsible for making sure that the
  * data isn't changing while dmu_sync() is writing it.
  *
  * Return values:
  *
  *	EEXIST: this txg has already been synced, so there's nothing to do.
  *		The caller should not log the write.
  *
  *	ENOENT: the block was dbuf_free_range()'d, so there's nothing to do.
  *		The caller should not log the write.
  *
  *	EALREADY: this block is already in the process of being synced.
  *		The caller should track its progress (somehow).
  *
  *	EIO: could not do the I/O.
  *		The caller should do a txg_wait_synced().
  *
  *	0: the I/O has been initiated.
  *		The caller should log this blkptr in the done callback.
  *		It is possible that the I/O will fail, in which case
  *		the error will be reported to the done callback and
  *		propagated to pio from zio_done().
  */
 int
 dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
 {
 	blkptr_t *bp = zgd->zgd_bp;
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)zgd->zgd_db;
 	objset_t *os = db->db_objset;
 	dsl_dataset_t *ds = os->os_dsl_dataset;
 	dbuf_dirty_record_t *dr;
 	dmu_sync_arg_t *dsa;
 	zbookmark_phys_t zb;
 	zio_prop_t zp;
 	dnode_t *dn;
 
 	ASSERT(pio != NULL);
 	ASSERT(txg != 0);
 
 	SET_BOOKMARK(&zb, ds->ds_object,
 	    db->db.db_object, db->db_level, db->db_blkid);
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 	dmu_write_policy(os, dn, db->db_level, WP_DMU_SYNC, &zp);
 	DB_DNODE_EXIT(db);
 
 	/*
 	 * If we're frozen (running ziltest), we always need to generate a bp.
 	 */
 	if (txg > spa_freeze_txg(os->os_spa))
 		return (dmu_sync_late_arrival(pio, os, done, zgd, &zp, &zb));
 
 	/*
 	 * Grabbing db_mtx now provides a barrier between dbuf_sync_leaf()
 	 * and us.  If we determine that this txg is not yet syncing,
 	 * but it begins to sync a moment later, that's OK because the
 	 * sync thread will block in dbuf_sync_leaf() until we drop db_mtx.
 	 */
 	mutex_enter(&db->db_mtx);
 
 	if (txg <= spa_last_synced_txg(os->os_spa)) {
 		/*
 		 * This txg has already synced.  There's nothing to do.
 		 */
 		mutex_exit(&db->db_mtx);
 		return (SET_ERROR(EEXIST));
 	}
 
 	if (txg <= spa_syncing_txg(os->os_spa)) {
 		/*
 		 * This txg is currently syncing, so we can't mess with
 		 * the dirty record anymore; just write a new log block.
 		 */
 		mutex_exit(&db->db_mtx);
 		return (dmu_sync_late_arrival(pio, os, done, zgd, &zp, &zb));
 	}
 
 	dr = db->db_last_dirty;
 	while (dr && dr->dr_txg != txg)
 		dr = dr->dr_next;
 
 	if (dr == NULL) {
 		/*
 		 * There's no dr for this dbuf, so it must have been freed.
 		 * There's no need to log writes to freed blocks, so we're done.
 		 */
 		mutex_exit(&db->db_mtx);
 		return (SET_ERROR(ENOENT));
 	}
 
 	ASSERT(dr->dr_next == NULL || dr->dr_next->dr_txg < txg);
 
 	/*
 	 * Assume the on-disk data is X, the current syncing data (in
 	 * txg - 1) is Y, and the current in-memory data is Z (currently
 	 * in dmu_sync).
 	 *
 	 * We usually want to perform a nopwrite if X and Z are the
 	 * same.  However, if Y is different (i.e. the BP is going to
 	 * change before this write takes effect), then a nopwrite will
 	 * be incorrect - we would override with X, which could have
 	 * been freed when Y was written.
 	 *
 	 * (Note that this is not a concern when we are nop-writing from
 	 * syncing context, because X and Y must be identical, because
 	 * all previous txgs have been synced.)
 	 *
 	 * Therefore, we disable nopwrite if the current BP could change
 	 * before this TXG.  There are two ways it could change: by
 	 * being dirty (dr_next is non-NULL), or by being freed
 	 * (dnode_block_freed()).  This behavior is verified by
 	 * zio_done(), which VERIFYs that the override BP is identical
 	 * to the on-disk BP.
 	 */
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 	if (dr->dr_next != NULL || dnode_block_freed(dn, db->db_blkid))
 		zp.zp_nopwrite = B_FALSE;
 	DB_DNODE_EXIT(db);
 
 	ASSERT(dr->dr_txg == txg);
 	if (dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC ||
 	    dr->dt.dl.dr_override_state == DR_OVERRIDDEN) {
 		/*
 		 * We have already issued a sync write for this buffer,
 		 * or this buffer has already been synced.  It could not
 		 * have been dirtied since, or we would have cleared the state.
 		 */
 		mutex_exit(&db->db_mtx);
 		return (SET_ERROR(EALREADY));
 	}
 
 	ASSERT(dr->dt.dl.dr_override_state == DR_NOT_OVERRIDDEN);
 	dr->dt.dl.dr_override_state = DR_IN_DMU_SYNC;
 	mutex_exit(&db->db_mtx);
 
 	dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_SLEEP);
 	dsa->dsa_dr = dr;
 	dsa->dsa_done = done;
 	dsa->dsa_zgd = zgd;
 	dsa->dsa_tx = NULL;
 
 	zio_nowait(arc_write(pio, os->os_spa, txg,
 	    bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db),
 	    DBUF_IS_L2COMPRESSIBLE(db), &zp, dmu_sync_ready,
 	    NULL, dmu_sync_done, dsa, ZIO_PRIORITY_SYNC_WRITE,
 	    ZIO_FLAG_CANFAIL, &zb));
 
 	return (0);
 }
 
 int
 dmu_object_set_blocksize(objset_t *os, uint64_t object, uint64_t size, int ibs,
     dmu_tx_t *tx)
 {
 	dnode_t *dn;
 	int err;
 
 	err = dnode_hold(os, object, FTAG, &dn);
 	if (err)
 		return (err);
 	err = dnode_set_blksz(dn, size, ibs, tx);
 	dnode_rele(dn, FTAG);
 	return (err);
 }
 
 void
 dmu_object_set_checksum(objset_t *os, uint64_t object, uint8_t checksum,
     dmu_tx_t *tx)
 {
 	dnode_t *dn;
 
 	/*
 	 * Send streams include each object's checksum function.  This
 	 * check ensures that the receiving system can understand the
 	 * checksum function transmitted.
 	 */
 	ASSERT3U(checksum, <, ZIO_CHECKSUM_LEGACY_FUNCTIONS);
 
 	VERIFY0(dnode_hold(os, object, FTAG, &dn));
 	ASSERT3U(checksum, <, ZIO_CHECKSUM_FUNCTIONS);
 	dn->dn_checksum = checksum;
 	dnode_setdirty(dn, tx);
 	dnode_rele(dn, FTAG);
 }
 
 void
 dmu_object_set_compress(objset_t *os, uint64_t object, uint8_t compress,
     dmu_tx_t *tx)
 {
 	dnode_t *dn;
 
 	/*
 	 * Send streams include each object's compression function.  This
 	 * check ensures that the receiving system can understand the
 	 * compression function transmitted.
 	 */
 	ASSERT3U(compress, <, ZIO_COMPRESS_LEGACY_FUNCTIONS);
 
 	VERIFY0(dnode_hold(os, object, FTAG, &dn));
 	dn->dn_compress = compress;
 	dnode_setdirty(dn, tx);
 	dnode_rele(dn, FTAG);
 }
 
 int zfs_mdcomp_disable = 0;
 SYSCTL_INT(_vfs_zfs, OID_AUTO, mdcomp_disable, CTLFLAG_RWTUN,
     &zfs_mdcomp_disable, 0, "Disable metadata compression");
 
 /*
  * When the "redundant_metadata" property is set to "most", only indirect
  * blocks of this level and higher will have an additional ditto block.
  */
 int zfs_redundant_metadata_most_ditto_level = 2;
 
 void
 dmu_write_policy(objset_t *os, dnode_t *dn, int level, int wp, zio_prop_t *zp)
 {
 	dmu_object_type_t type = dn ? dn->dn_type : DMU_OT_OBJSET;
 	boolean_t ismd = (level > 0 || DMU_OT_IS_METADATA(type) ||
 	    (wp & WP_SPILL));
 	enum zio_checksum checksum = os->os_checksum;
 	enum zio_compress compress = os->os_compress;
 	enum zio_checksum dedup_checksum = os->os_dedup_checksum;
 	boolean_t dedup = B_FALSE;
 	boolean_t nopwrite = B_FALSE;
 	boolean_t dedup_verify = os->os_dedup_verify;
 	int copies = os->os_copies;
 
 	/*
 	 * We maintain different write policies for each of the following
 	 * types of data:
 	 *	 1. metadata
 	 *	 2. preallocated blocks (i.e. level-0 blocks of a dump device)
 	 *	 3. all other level 0 blocks
 	 */
 	if (ismd) {
 		if (zfs_mdcomp_disable) {
 			compress = ZIO_COMPRESS_EMPTY;
 		} else {
 			/*
 			 * XXX -- we should design a compression algorithm
 			 * that specializes in arrays of bps.
 			 */
 			compress = zio_compress_select(os->os_spa,
 			    ZIO_COMPRESS_ON, ZIO_COMPRESS_ON);
 		}
 
 		/*
 		 * Metadata always gets checksummed.  If the data
 		 * checksum is multi-bit correctable, and it's not a
 		 * ZBT-style checksum, then it's suitable for metadata
 		 * as well.  Otherwise, the metadata checksum defaults
 		 * to fletcher4.
 		 */
 		if (!(zio_checksum_table[checksum].ci_flags &
 		    ZCHECKSUM_FLAG_METADATA) ||
 		    (zio_checksum_table[checksum].ci_flags &
 		    ZCHECKSUM_FLAG_EMBEDDED))
 			checksum = ZIO_CHECKSUM_FLETCHER_4;
 
 		if (os->os_redundant_metadata == ZFS_REDUNDANT_METADATA_ALL ||
 		    (os->os_redundant_metadata ==
 		    ZFS_REDUNDANT_METADATA_MOST &&
 		    (level >= zfs_redundant_metadata_most_ditto_level ||
 		    DMU_OT_IS_METADATA(type) || (wp & WP_SPILL))))
 			copies++;
 	} else if (wp & WP_NOFILL) {
 		ASSERT(level == 0);
 
 		/*
 		 * If we're writing preallocated blocks, we aren't actually
 		 * writing them so don't set any policy properties.  These
 		 * blocks are currently only used by an external subsystem
 		 * outside of zfs (i.e. dump) and not written by the zio
 		 * pipeline.
 		 */
 		compress = ZIO_COMPRESS_OFF;
 		checksum = ZIO_CHECKSUM_NOPARITY;
 	} else {
 		compress = zio_compress_select(os->os_spa, dn->dn_compress,
 		    compress);
 
 		checksum = (dedup_checksum == ZIO_CHECKSUM_OFF) ?
 		    zio_checksum_select(dn->dn_checksum, checksum) :
 		    dedup_checksum;
 
 		/*
 		 * Determine dedup setting.  If we are in dmu_sync(),
 		 * we won't actually dedup now because that's all
 		 * done in syncing context; but we do want to use the
 		 * dedup checkum.  If the checksum is not strong
 		 * enough to ensure unique signatures, force
 		 * dedup_verify.
 		 */
 		if (dedup_checksum != ZIO_CHECKSUM_OFF) {
 			dedup = (wp & WP_DMU_SYNC) ? B_FALSE : B_TRUE;
 			if (!(zio_checksum_table[checksum].ci_flags &
 			    ZCHECKSUM_FLAG_DEDUP))
 				dedup_verify = B_TRUE;
 		}
 
 		/*
 		 * Enable nopwrite if we have secure enough checksum
 		 * algorithm (see comment in zio_nop_write) and
 		 * compression is enabled.  We don't enable nopwrite if
 		 * dedup is enabled as the two features are mutually
 		 * exclusive.
 		 */
 		nopwrite = (!dedup && (zio_checksum_table[checksum].ci_flags &
 		    ZCHECKSUM_FLAG_NOPWRITE) &&
 		    compress != ZIO_COMPRESS_OFF && zfs_nopwrite_enabled);
 	}
 
 	zp->zp_checksum = checksum;
 	zp->zp_compress = compress;
 	zp->zp_type = (wp & WP_SPILL) ? dn->dn_bonustype : type;
 	zp->zp_level = level;
 	zp->zp_copies = MIN(copies, spa_max_replication(os->os_spa));
 	zp->zp_dedup = dedup;
 	zp->zp_dedup_verify = dedup && dedup_verify;
 	zp->zp_nopwrite = nopwrite;
 }
 
 int
 dmu_offset_next(objset_t *os, uint64_t object, boolean_t hole, uint64_t *off)
 {
 	dnode_t *dn;
 	int err;
 
 	/*
 	 * Sync any current changes before
 	 * we go trundling through the block pointers.
 	 */
 	err = dmu_object_wait_synced(os, object);
 	if (err) {
 		return (err);
 	}
 
 	err = dnode_hold(os, object, FTAG, &dn);
 	if (err) {
 		return (err);
 	}
 
 	err = dnode_next_offset(dn, (hole ? DNODE_FIND_HOLE : 0), off, 1, 1, 0);
 	dnode_rele(dn, FTAG);
 
 	return (err);
 }
 
 /*
  * Given the ZFS object, if it contains any dirty nodes
  * this function flushes all dirty blocks to disk. This
  * ensures the DMU object info is updated. A more efficient
  * future version might just find the TXG with the maximum
  * ID and wait for that to be synced.
  */
 int
 dmu_object_wait_synced(objset_t *os, uint64_t object)
 {
 	dnode_t *dn;
 	int error, i;
 
 	error = dnode_hold(os, object, FTAG, &dn);
 	if (error) {
 		return (error);
 	}
 
 	for (i = 0; i < TXG_SIZE; i++) {
 		if (list_link_active(&dn->dn_dirty_link[i])) {
 			break;
 		}
 	}
 	dnode_rele(dn, FTAG);
 	if (i != TXG_SIZE) {
 		txg_wait_synced(dmu_objset_pool(os), 0);
 	}
 
 	return (0);
 }
 
 void
 dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
 {
 	dnode_phys_t *dnp;
 
 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
 	mutex_enter(&dn->dn_mtx);
 
 	dnp = dn->dn_phys;
 
 	doi->doi_data_block_size = dn->dn_datablksz;
 	doi->doi_metadata_block_size = dn->dn_indblkshift ?
 	    1ULL << dn->dn_indblkshift : 0;
 	doi->doi_type = dn->dn_type;
 	doi->doi_bonus_type = dn->dn_bonustype;
 	doi->doi_bonus_size = dn->dn_bonuslen;
 	doi->doi_indirection = dn->dn_nlevels;
 	doi->doi_checksum = dn->dn_checksum;
 	doi->doi_compress = dn->dn_compress;
 	doi->doi_nblkptr = dn->dn_nblkptr;
 	doi->doi_physical_blocks_512 = (DN_USED_BYTES(dnp) + 256) >> 9;
 	doi->doi_max_offset = (dn->dn_maxblkid + 1) * dn->dn_datablksz;
 	doi->doi_fill_count = 0;
 	for (int i = 0; i < dnp->dn_nblkptr; i++)
 		doi->doi_fill_count += BP_GET_FILL(&dnp->dn_blkptr[i]);
 
 	mutex_exit(&dn->dn_mtx);
 	rw_exit(&dn->dn_struct_rwlock);
 }
 
 /*
  * Get information on a DMU object.
  * If doi is NULL, just indicates whether the object exists.
  */
 int
 dmu_object_info(objset_t *os, uint64_t object, dmu_object_info_t *doi)
 {
 	dnode_t *dn;
 	int err = dnode_hold(os, object, FTAG, &dn);
 
 	if (err)
 		return (err);
 
 	if (doi != NULL)
 		dmu_object_info_from_dnode(dn, doi);
 
 	dnode_rele(dn, FTAG);
 	return (0);
 }
 
 /*
  * As above, but faster; can be used when you have a held dbuf in hand.
  */
 void
 dmu_object_info_from_db(dmu_buf_t *db_fake, dmu_object_info_t *doi)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 
 	DB_DNODE_ENTER(db);
 	dmu_object_info_from_dnode(DB_DNODE(db), doi);
 	DB_DNODE_EXIT(db);
 }
 
 /*
  * Faster still when you only care about the size.
  * This is specifically optimized for zfs_getattr().
  */
 void
 dmu_object_size_from_db(dmu_buf_t *db_fake, uint32_t *blksize,
     u_longlong_t *nblk512)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 	dnode_t *dn;
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
 
 	*blksize = dn->dn_datablksz;
 	/* add 1 for dnode space */
 	*nblk512 = ((DN_USED_BYTES(dn->dn_phys) + SPA_MINBLOCKSIZE/2) >>
 	    SPA_MINBLOCKSHIFT) + 1;
 	DB_DNODE_EXIT(db);
 }
 
 void
 byteswap_uint64_array(void *vbuf, size_t size)
 {
 	uint64_t *buf = vbuf;
 	size_t count = size >> 3;
 	int i;
 
 	ASSERT((size & 7) == 0);
 
 	for (i = 0; i < count; i++)
 		buf[i] = BSWAP_64(buf[i]);
 }
 
 void
 byteswap_uint32_array(void *vbuf, size_t size)
 {
 	uint32_t *buf = vbuf;
 	size_t count = size >> 2;
 	int i;
 
 	ASSERT((size & 3) == 0);
 
 	for (i = 0; i < count; i++)
 		buf[i] = BSWAP_32(buf[i]);
 }
 
 void
 byteswap_uint16_array(void *vbuf, size_t size)
 {
 	uint16_t *buf = vbuf;
 	size_t count = size >> 1;
 	int i;
 
 	ASSERT((size & 1) == 0);
 
 	for (i = 0; i < count; i++)
 		buf[i] = BSWAP_16(buf[i]);
 }
 
 /* ARGSUSED */
 void
 byteswap_uint8_array(void *vbuf, size_t size)
 {
 }
 
 void
 dmu_init(void)
 {
 	zfs_dbgmsg_init();
 	sa_cache_init();
 	xuio_stat_init();
 	dmu_objset_init();
 	dnode_init();
 	dbuf_init();
 	zfetch_init();
 	zio_compress_init();
 	l2arc_init();
 	arc_init();
 }
 
 void
 dmu_fini(void)
 {
 	arc_fini(); /* arc depends on l2arc, so arc must go first */
 	l2arc_fini();
 	zfetch_fini();
 	zio_compress_fini();
 	dbuf_fini();
 	dnode_fini();
 	dmu_objset_fini();
 	xuio_stat_fini();
 	sa_cache_fini();
 	zfs_dbgmsg_fini();
 }