Esempio n. 1
0
int
dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
    objset_t **osp)
{
	objset_t *os;
	int i, err;

	ASSERT(ds == NULL || MUTEX_HELD(&ds->ds_opening_lock));

	os = kmem_zalloc(sizeof (objset_t), KM_SLEEP);
	os->os_dsl_dataset = ds;
	os->os_spa = spa;
	os->os_rootbp = bp;
	if (!BP_IS_HOLE(os->os_rootbp)) {
		arc_flags_t aflags = ARC_FLAG_WAIT;
		zbookmark_phys_t zb;
		SET_BOOKMARK(&zb, ds ? ds->ds_object : DMU_META_OBJSET,
		    ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);

		if (DMU_OS_IS_L2CACHEABLE(os))
			aflags |= ARC_FLAG_L2CACHE;
		if (DMU_OS_IS_L2COMPRESSIBLE(os))
			aflags |= ARC_FLAG_L2COMPRESS;

		dprintf_bp(os->os_rootbp, "reading %s", "");
		err = arc_read(NULL, spa, os->os_rootbp,
		    arc_getbuf_func, &os->os_phys_buf,
		    ZIO_PRIORITY_SYNC_READ, ZIO_FLAG_CANFAIL, &aflags, &zb);
		if (err != 0) {
			kmem_free(os, sizeof (objset_t));
			/* convert checksum errors into IO errors */
			if (err == ECKSUM)
				err = SET_ERROR(EIO);
			return (err);
		}

		/* Increase the blocksize if we are permitted. */
		if (spa_version(spa) >= SPA_VERSION_USERSPACE &&
		    arc_buf_size(os->os_phys_buf) < sizeof (objset_phys_t)) {
			arc_buf_t *buf = arc_buf_alloc(spa,
			    sizeof (objset_phys_t), &os->os_phys_buf,
			    ARC_BUFC_METADATA);
			bzero(buf->b_data, sizeof (objset_phys_t));
			bcopy(os->os_phys_buf->b_data, buf->b_data,
			    arc_buf_size(os->os_phys_buf));
			(void) arc_buf_remove_ref(os->os_phys_buf,
			    &os->os_phys_buf);
			os->os_phys_buf = buf;
		}

		os->os_phys = os->os_phys_buf->b_data;
		os->os_flags = os->os_phys->os_flags;
	} else {
		int size = spa_version(spa) >= SPA_VERSION_USERSPACE ?
		    sizeof (objset_phys_t) : OBJSET_OLD_PHYS_SIZE;
		os->os_phys_buf = arc_buf_alloc(spa, size,
		    &os->os_phys_buf, ARC_BUFC_METADATA);
		os->os_phys = os->os_phys_buf->b_data;
		bzero(os->os_phys, size);
	}

	/*
	 * Note: the changed_cb will be called once before the register
	 * func returns, thus changing the checksum/compression from the
	 * default (fletcher2/off).  Snapshots don't need to know about
	 * checksum/compression/copies.
	 */
	if (ds != NULL) {
		err = dsl_prop_register(ds,
		    zfs_prop_to_name(ZFS_PROP_PRIMARYCACHE),
		    primary_cache_changed_cb, os);
		if (err == 0) {
			err = dsl_prop_register(ds,
			    zfs_prop_to_name(ZFS_PROP_SECONDARYCACHE),
			    secondary_cache_changed_cb, os);
		}
		if (!ds->ds_is_snapshot) {
			if (err == 0) {
				err = dsl_prop_register(ds,
				    zfs_prop_to_name(ZFS_PROP_CHECKSUM),
				    checksum_changed_cb, os);
			}
			if (err == 0) {
				err = dsl_prop_register(ds,
				    zfs_prop_to_name(ZFS_PROP_COMPRESSION),
				    compression_changed_cb, os);
			}
			if (err == 0) {
				err = dsl_prop_register(ds,
				    zfs_prop_to_name(ZFS_PROP_COPIES),
				    copies_changed_cb, os);
			}
			if (err == 0) {
				err = dsl_prop_register(ds,
				    zfs_prop_to_name(ZFS_PROP_DEDUP),
				    dedup_changed_cb, os);
			}
			if (err == 0) {
				err = dsl_prop_register(ds,
				    zfs_prop_to_name(ZFS_PROP_LOGBIAS),
				    logbias_changed_cb, os);
			}
			if (err == 0) {
				err = dsl_prop_register(ds,
				    zfs_prop_to_name(ZFS_PROP_SYNC),
				    sync_changed_cb, os);
			}
			if (err == 0) {
				err = dsl_prop_register(ds,
				    zfs_prop_to_name(
				    ZFS_PROP_REDUNDANT_METADATA),
				    redundant_metadata_changed_cb, os);
			}
			if (err == 0) {
				err = dsl_prop_register(ds,
				    zfs_prop_to_name(ZFS_PROP_RECORDSIZE),
				    recordsize_changed_cb, os);
			}
		}
		if (err != 0) {
			VERIFY(arc_buf_remove_ref(os->os_phys_buf,
			    &os->os_phys_buf));
			kmem_free(os, sizeof (objset_t));
			return (err);
		}
	} else {
		/* It's the meta-objset. */
		os->os_checksum = ZIO_CHECKSUM_FLETCHER_4;
		os->os_compress = ZIO_COMPRESS_ON;
		os->os_copies = spa_max_replication(spa);
		os->os_dedup_checksum = ZIO_CHECKSUM_OFF;
		os->os_dedup_verify = B_FALSE;
		os->os_logbias = ZFS_LOGBIAS_LATENCY;
		os->os_sync = ZFS_SYNC_STANDARD;
		os->os_primary_cache = ZFS_CACHE_ALL;
		os->os_secondary_cache = ZFS_CACHE_ALL;
	}

	if (ds == NULL || !ds->ds_is_snapshot)
		os->os_zil_header = os->os_phys->os_zil_header;
	os->os_zil = zil_alloc(os, &os->os_zil_header);

	for (i = 0; i < TXG_SIZE; i++) {
		list_create(&os->os_dirty_dnodes[i], sizeof (dnode_t),
		    offsetof(dnode_t, dn_dirty_link[i]));
		list_create(&os->os_free_dnodes[i], sizeof (dnode_t),
		    offsetof(dnode_t, dn_dirty_link[i]));
	}
	list_create(&os->os_dnodes, sizeof (dnode_t),
	    offsetof(dnode_t, dn_link));
	list_create(&os->os_downgraded_dbufs, sizeof (dmu_buf_impl_t),
	    offsetof(dmu_buf_impl_t, db_link));

	mutex_init(&os->os_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&os->os_obj_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&os->os_user_ptr_lock, NULL, MUTEX_DEFAULT, NULL);

	dnode_special_open(os, &os->os_phys->os_meta_dnode,
	    DMU_META_DNODE_OBJECT, &os->os_meta_dnode);
	if (arc_buf_size(os->os_phys_buf) >= sizeof (objset_phys_t)) {
		dnode_special_open(os, &os->os_phys->os_userused_dnode,
		    DMU_USERUSED_OBJECT, &os->os_userused_dnode);
		dnode_special_open(os, &os->os_phys->os_groupused_dnode,
		    DMU_GROUPUSED_OBJECT, &os->os_groupused_dnode);
	}

	*osp = os;
	return (0);
}
Esempio n. 2
0
int
dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
    objset_t **osp)
{
	objset_t *os;
	int i, err = 0;

	ASSERT(ds == NULL || MUTEX_HELD(&ds->ds_opening_lock));

	os = kmem_zalloc(sizeof (objset_t), KM_PUSHPAGE);
	os->os_dsl_dataset = ds;
	os->os_spa = spa;
	os->os_rootbp = bp;
	if (!BP_IS_HOLE(os->os_rootbp)) {
		uint32_t aflags = ARC_WAIT;
		zbookmark_t zb;
		SET_BOOKMARK(&zb, ds ? ds->ds_object : DMU_META_OBJSET,
		    ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);

		if (DMU_OS_IS_L2CACHEABLE(os))
			aflags |= ARC_L2CACHE;

		dprintf_bp(os->os_rootbp, "reading %s", "");
		/*
		 * XXX when bprewrite scrub can change the bp,
		 * and this is called from dmu_objset_open_ds_os, the bp
		 * could change, and we'll need a lock.
		 */
		err = dsl_read_nolock(NULL, spa, os->os_rootbp,
		    arc_getbuf_func, &os->os_phys_buf,
		    ZIO_PRIORITY_SYNC_READ, ZIO_FLAG_CANFAIL, &aflags, &zb);
		if (err) {
			kmem_free(os, sizeof (objset_t));
			/* convert checksum errors into IO errors */
			if (err == ECKSUM)
				err = EIO;
			return (err);
		}

		/* Increase the blocksize if we are permitted. */
		if (spa_version(spa) >= SPA_VERSION_USERSPACE &&
		    arc_buf_size(os->os_phys_buf) < sizeof (objset_phys_t)) {
			arc_buf_t *buf = arc_buf_alloc(spa,
			    sizeof (objset_phys_t), &os->os_phys_buf,
			    ARC_BUFC_METADATA);
			bzero(buf->b_data, sizeof (objset_phys_t));
			bcopy(os->os_phys_buf->b_data, buf->b_data,
			    arc_buf_size(os->os_phys_buf));
			(void) arc_buf_remove_ref(os->os_phys_buf,
			    &os->os_phys_buf);
			os->os_phys_buf = buf;
		}

		os->os_phys = os->os_phys_buf->b_data;
		os->os_flags = os->os_phys->os_flags;
	} else {
		int size = spa_version(spa) >= SPA_VERSION_USERSPACE ?
		    sizeof (objset_phys_t) : OBJSET_OLD_PHYS_SIZE;
		os->os_phys_buf = arc_buf_alloc(spa, size,
		    &os->os_phys_buf, ARC_BUFC_METADATA);
		os->os_phys = os->os_phys_buf->b_data;
		bzero(os->os_phys, size);
	}

	/*
	 * Note: the changed_cb will be called once before the register
	 * func returns, thus changing the checksum/compression from the
	 * default (fletcher2/off).  Snapshots don't need to know about
	 * checksum/compression/copies.  But they do need to know about
	 * encryption so that clones from the snaphost inherit the
	 * same encryption property regardless of where in the namespace
	 * they get created.
	 */
	if (ds) {
		err = dsl_prop_register(ds, "primarycache",
		    primary_cache_changed_cb, os);
		if (err == 0)
			err = dsl_prop_register(ds, "secondarycache",
                                    secondary_cache_changed_cb, os);
		if (err == 0)
		  err = dsl_prop_register(ds, "encryption",
					  crypt_changed_cb, os);

		if (!dsl_dataset_is_snapshot(ds)) {
			if (err == 0)
				err = dsl_prop_register(ds, "checksum",
				    checksum_changed_cb, os);
			if (err == 0)
				err = dsl_prop_register(ds, "compression",
				    compression_changed_cb, os);
			if (err == 0)
				err = dsl_prop_register(ds, "copies",
				    copies_changed_cb, os);
			if (err == 0)
				err = dsl_prop_register(ds, "dedup",
				    dedup_changed_cb, os);
			if (err == 0)
				err = dsl_prop_register(ds, "logbias",
				    logbias_changed_cb, os);
			if (err == 0)
				err = dsl_prop_register(ds, "sync",
				    sync_changed_cb, os);
		}
		if (err) {
			VERIFY(arc_buf_remove_ref(os->os_phys_buf,
			    &os->os_phys_buf) == 1);
			kmem_free(os, sizeof (objset_t));
			return (err);
		}
	} else if (ds == NULL) {
        /*
         * It's the meta-objset.
         * Encryption is off for ZFS metadata but on for ZPL metadata
         * and file/zvol contents.
         */
		os->os_checksum = ZIO_CHECKSUM_FLETCHER_4;
		os->os_compress = ZIO_COMPRESS_LZJB;
		os->os_copies = spa_max_replication(spa);
		os->os_dedup_checksum = ZIO_CHECKSUM_OFF;
		os->os_dedup_verify = 0;
		os->os_logbias = 0;
		os->os_sync = 0;
		os->os_primary_cache = ZFS_CACHE_ALL;
		os->os_secondary_cache = ZFS_CACHE_ALL;
        os->os_crypt = ZIO_CRYPT_OFF;
	}

	if (ds == NULL || !dsl_dataset_is_snapshot(ds))
		os->os_zil_header = os->os_phys->os_zil_header;
	os->os_zil = zil_alloc(os, &os->os_zil_header);

	for (i = 0; i < TXG_SIZE; i++) {
		list_create(&os->os_dirty_dnodes[i], sizeof (dnode_t),
		    offsetof(dnode_t, dn_dirty_link[i]));
		list_create(&os->os_free_dnodes[i], sizeof (dnode_t),
		    offsetof(dnode_t, dn_dirty_link[i]));
	}
	list_create(&os->os_dnodes, sizeof (dnode_t),
	    offsetof(dnode_t, dn_link));
	list_create(&os->os_downgraded_dbufs, sizeof (dmu_buf_impl_t),
	    offsetof(dmu_buf_impl_t, db_link));

	mutex_init(&os->os_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&os->os_obj_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&os->os_user_ptr_lock, NULL, MUTEX_DEFAULT, NULL);

	DMU_META_DNODE(os) = dnode_special_open(os,
	    &os->os_phys->os_meta_dnode, DMU_META_DNODE_OBJECT,
	    &os->os_meta_dnode);
	if (arc_buf_size(os->os_phys_buf) >= sizeof (objset_phys_t)) {
		DMU_USERUSED_DNODE(os) = dnode_special_open(os,
		    &os->os_phys->os_userused_dnode, DMU_USERUSED_OBJECT,
		    &os->os_userused_dnode);
		DMU_GROUPUSED_DNODE(os) = dnode_special_open(os,
		    &os->os_phys->os_groupused_dnode, DMU_GROUPUSED_OBJECT,
		    &os->os_groupused_dnode);
	}

	/*
	 * We should be the only thread trying to do this because we
	 * have ds_opening_lock
	 */
	if (ds) {
		mutex_enter(&ds->ds_lock);
		ASSERT(ds->ds_objset == NULL);
		ds->ds_objset = os;
		mutex_exit(&ds->ds_lock);
	}

	*osp = os;

	return (0);
}
Esempio n. 3
0
int
dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
    objset_impl_t **osip)
{
	objset_impl_t *osi;
	int i, err;

	ASSERT(ds == NULL || MUTEX_HELD(&ds->ds_opening_lock));

	osi = kmem_zalloc(sizeof (objset_impl_t), KM_SLEEP);
	osi->os.os = osi;
	osi->os_dsl_dataset = ds;
	osi->os_spa = spa;
	osi->os_rootbp = bp;
	if (!BP_IS_HOLE(osi->os_rootbp)) {
		uint32_t aflags = ARC_WAIT;
		zbookmark_t zb;
		zb.zb_objset = ds ? ds->ds_object : 0;
		zb.zb_object = 0;
		zb.zb_level = -1;
		zb.zb_blkid = 0;

		dprintf_bp(osi->os_rootbp, "reading %s", "");
		/*
		 * NB: when bprewrite scrub can change the bp,
		 * and this is called from dmu_objset_open_ds_os, the bp
		 * could change, and we'll need a lock.
		 */
		err = arc_read_nolock(NULL, spa, osi->os_rootbp,
		    arc_getbuf_func, &osi->os_phys_buf,
		    ZIO_PRIORITY_SYNC_READ, ZIO_FLAG_CANFAIL, &aflags, &zb);
		if (err) {
			kmem_free(osi, sizeof (objset_impl_t));
			return (err);
		}
		osi->os_phys = osi->os_phys_buf->b_data;
	} else {
#ifdef __APPLE_KERNEL__
		osi->os_phys_buf = arc_buf_alloc(spa, sizeof (objset_phys_t),
		    &osi->os_phys_buf, ARC_BUFC_METADATA, TRUE/*alloc_buf*/);
#else
		osi->os_phys_buf = arc_buf_alloc(spa, sizeof (objset_phys_t),
		    &osi->os_phys_buf, ARC_BUFC_METADATA);
#endif
		osi->os_phys = osi->os_phys_buf->b_data;
		bzero(osi->os_phys, sizeof (objset_phys_t));
	}

	/*
	 * Note: the changed_cb will be called once before the register
	 * func returns, thus changing the checksum/compression from the
	 * default (fletcher2/off).  Snapshots don't need to know, and
	 * registering would complicate clone promotion.
	 */
	if (ds && ds->ds_phys->ds_num_children == 0) {
		err = dsl_prop_register(ds, "checksum",
		    checksum_changed_cb, osi);
		if (err == 0)
			err = dsl_prop_register(ds, "compression",
			    compression_changed_cb, osi);
		if (err == 0)
			err = dsl_prop_register(ds, "copies",
			    copies_changed_cb, osi);
		if (err) {
			VERIFY(arc_buf_remove_ref(osi->os_phys_buf,
			    &osi->os_phys_buf) == 1);
			kmem_free(osi, sizeof (objset_impl_t));
			return (err);
		}
	} else if (ds == NULL) {
		/* It's the meta-objset. */
		osi->os_checksum = ZIO_CHECKSUM_FLETCHER_4;
		osi->os_compress = ZIO_COMPRESS_LZJB;
		osi->os_copies = spa_max_replication(spa);
	}

	osi->os_zil_header = osi->os_phys->os_zil_header;
	osi->os_zil = zil_alloc(&osi->os, &osi->os_zil_header);

	for (i = 0; i < TXG_SIZE; i++) {
		list_create(&osi->os_dirty_dnodes[i], sizeof (dnode_t),
		    offsetof(dnode_t, dn_dirty_link[i]));
		list_create(&osi->os_free_dnodes[i], sizeof (dnode_t),
		    offsetof(dnode_t, dn_dirty_link[i]));
	}
	list_create(&osi->os_dnodes, sizeof (dnode_t),
	    offsetof(dnode_t, dn_link));
	list_create(&osi->os_downgraded_dbufs, sizeof (dmu_buf_impl_t),
	    offsetof(dmu_buf_impl_t, db_link));

	mutex_init(&osi->os_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&osi->os_obj_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&osi->os_user_ptr_lock, NULL, MUTEX_DEFAULT, NULL);

	osi->os_meta_dnode = dnode_special_open(osi,
	    &osi->os_phys->os_meta_dnode, DMU_META_DNODE_OBJECT);

	/*
	 * We should be the only thread trying to do this because we
	 * have ds_opening_lock
	 */
	if (ds) {
		VERIFY(NULL == dsl_dataset_set_user_ptr(ds, osi,
		    dmu_objset_evict));
	}

	*osip = osi;
	return (0);
}
int
dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
    objset_impl_t **osip)
{
	objset_impl_t *winner, *osi;
	int i, err, checksum;

	osi = kmem_zalloc(sizeof (objset_impl_t), KM_SLEEP);
	osi->os.os = osi;
	osi->os_dsl_dataset = ds;
	osi->os_spa = spa;
	osi->os_rootbp = bp;
	if (!BP_IS_HOLE(osi->os_rootbp)) {
		uint32_t aflags = ARC_WAIT;
		zbookmark_t zb;
		zb.zb_objset = ds ? ds->ds_object : 0;
		zb.zb_object = 0;
		zb.zb_level = -1;
		zb.zb_blkid = 0;

		dprintf_bp(osi->os_rootbp, "reading %s", "");
		err = arc_read(NULL, spa, osi->os_rootbp,
		    dmu_ot[DMU_OT_OBJSET].ot_byteswap,
		    arc_getbuf_func, &osi->os_phys_buf,
		    ZIO_PRIORITY_SYNC_READ, ZIO_FLAG_CANFAIL, &aflags, &zb);
		if (err) {
			kmem_free(osi, sizeof (objset_impl_t));
			return (err);
		}
		osi->os_phys = osi->os_phys_buf->b_data;
		arc_release(osi->os_phys_buf, &osi->os_phys_buf);
	} else {
		osi->os_phys_buf = arc_buf_alloc(spa, sizeof (objset_phys_t),
		    &osi->os_phys_buf, ARC_BUFC_METADATA);
		osi->os_phys = osi->os_phys_buf->b_data;
		bzero(osi->os_phys, sizeof (objset_phys_t));
	}

	/*
	 * Note: the changed_cb will be called once before the register
	 * func returns, thus changing the checksum/compression from the
	 * default (fletcher2/off).  Snapshots don't need to know, and
	 * registering would complicate clone promotion.
	 */
	if (ds && ds->ds_phys->ds_num_children == 0) {
		err = dsl_prop_register(ds, "checksum",
		    checksum_changed_cb, osi);
		if (err == 0)
			err = dsl_prop_register(ds, "compression",
			    compression_changed_cb, osi);
		if (err == 0)
			err = dsl_prop_register(ds, "copies",
			    copies_changed_cb, osi);
		if (err) {
			VERIFY(arc_buf_remove_ref(osi->os_phys_buf,
			    &osi->os_phys_buf) == 1);
			kmem_free(osi, sizeof (objset_impl_t));
			return (err);
		}
	} else if (ds == NULL) {
		/* It's the meta-objset. */
		osi->os_checksum = ZIO_CHECKSUM_FLETCHER_4;
		osi->os_compress = ZIO_COMPRESS_LZJB;
		osi->os_copies = spa_max_replication(spa);
	}

	osi->os_zil = zil_alloc(&osi->os, &osi->os_phys->os_zil_header);

	/*
	 * Metadata always gets compressed and 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.
	 */
	checksum = osi->os_checksum;

	if (zio_checksum_table[checksum].ci_correctable &&
	    !zio_checksum_table[checksum].ci_zbt)
		osi->os_md_checksum = checksum;
	else
		osi->os_md_checksum = ZIO_CHECKSUM_FLETCHER_4;
	osi->os_md_compress = ZIO_COMPRESS_LZJB;

	for (i = 0; i < TXG_SIZE; i++) {
		list_create(&osi->os_dirty_dnodes[i], sizeof (dnode_t),
		    offsetof(dnode_t, dn_dirty_link[i]));
		list_create(&osi->os_free_dnodes[i], sizeof (dnode_t),
		    offsetof(dnode_t, dn_dirty_link[i]));
	}
	list_create(&osi->os_dnodes, sizeof (dnode_t),
	    offsetof(dnode_t, dn_link));
	list_create(&osi->os_downgraded_dbufs, sizeof (dmu_buf_impl_t),
	    offsetof(dmu_buf_impl_t, db_link));

	mutex_init(&osi->os_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&osi->os_obj_lock, NULL, MUTEX_DEFAULT, NULL);

	osi->os_meta_dnode = dnode_special_open(osi,
	    &osi->os_phys->os_meta_dnode, DMU_META_DNODE_OBJECT);

	if (ds != NULL) {
		winner = dsl_dataset_set_user_ptr(ds, osi, dmu_objset_evict);
		if (winner) {
			dmu_objset_evict(ds, osi);
			osi = winner;
		}
	}

	*osip = osi;
	return (0);
}
Esempio n. 5
0
int
dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
    objset_impl_t **osip)
{
	objset_impl_t *osi;
	int i, err;

	ASSERT(ds == NULL || MUTEX_HELD(&ds->ds_opening_lock));

	osi = kmem_zalloc(sizeof (objset_impl_t), KM_SLEEP);
	osi->os.os = osi;
	osi->os_dsl_dataset = ds;
	osi->os_spa = spa;
	osi->os_rootbp = bp;
	if (!BP_IS_HOLE(osi->os_rootbp)) {
		uint32_t aflags = ARC_WAIT;
		zbookmark_t zb;
		zb.zb_objset = ds ? ds->ds_object : 0;
		zb.zb_object = 0;
		zb.zb_level = -1;
		zb.zb_blkid = 0;
		if (DMU_OS_IS_L2CACHEABLE(osi))
			aflags |= ARC_L2CACHE;

		dprintf_bp(osi->os_rootbp, "reading %s", "");
		/*
		 * NB: when bprewrite scrub can change the bp,
		 * and this is called from dmu_objset_open_ds_os, the bp
		 * could change, and we'll need a lock.
		 */
		err = arc_read_nolock(NULL, spa, osi->os_rootbp,
		    arc_getbuf_func, &osi->os_phys_buf,
		    ZIO_PRIORITY_SYNC_READ, ZIO_FLAG_CANFAIL, &aflags, &zb);
		if (err) {
			kmem_free(osi, sizeof (objset_impl_t));
			/* convert checksum errors into IO errors */
			if (err == ECKSUM)
				err = EIO;
			return (err);
		}

		/* Increase the blocksize if we are permitted. */
		if (spa_version(spa) >= SPA_VERSION_USERSPACE &&
		    arc_buf_size(osi->os_phys_buf) < sizeof (objset_phys_t)) {
			arc_buf_t *buf = arc_buf_alloc(spa,
			    sizeof (objset_phys_t), &osi->os_phys_buf,
			    ARC_BUFC_METADATA);
			bzero(buf->b_data, sizeof (objset_phys_t));
			bcopy(osi->os_phys_buf->b_data, buf->b_data,
			    arc_buf_size(osi->os_phys_buf));
			(void) arc_buf_remove_ref(osi->os_phys_buf,
			    &osi->os_phys_buf);
			osi->os_phys_buf = buf;
		}

		osi->os_phys = osi->os_phys_buf->b_data;
		osi->os_flags = osi->os_phys->os_flags;
	} else {
		int size = spa_version(spa) >= SPA_VERSION_USERSPACE ?
		    sizeof (objset_phys_t) : OBJSET_OLD_PHYS_SIZE;
		osi->os_phys_buf = arc_buf_alloc(spa, size,
		    &osi->os_phys_buf, ARC_BUFC_METADATA);
		osi->os_phys = osi->os_phys_buf->b_data;
		bzero(osi->os_phys, size);
	}

	/*
	 * Note: the changed_cb will be called once before the register
	 * func returns, thus changing the checksum/compression from the
	 * default (fletcher2/off).  Snapshots don't need to know about
	 * checksum/compression/copies.
	 */
	if (ds) {
		err = dsl_prop_register(ds, "primarycache",
		    primary_cache_changed_cb, osi);
		if (err == 0)
			err = dsl_prop_register(ds, "secondarycache",
			    secondary_cache_changed_cb, osi);
		if (!dsl_dataset_is_snapshot(ds)) {
			if (err == 0)
				err = dsl_prop_register(ds, "checksum",
				    checksum_changed_cb, osi);
			if (err == 0)
				err = dsl_prop_register(ds, "compression",
				    compression_changed_cb, osi);
			if (err == 0)
				err = dsl_prop_register(ds, "copies",
				    copies_changed_cb, osi);
		}
		if (err) {
			VERIFY(arc_buf_remove_ref(osi->os_phys_buf,
			    &osi->os_phys_buf) == 1);
			kmem_free(osi, sizeof (objset_impl_t));
			return (err);
		}
	} else if (ds == NULL) {
		/* It's the meta-objset. */
		osi->os_checksum = ZIO_CHECKSUM_FLETCHER_4;
		osi->os_compress = ZIO_COMPRESS_LZJB;
		osi->os_copies = spa_max_replication(spa);
		osi->os_primary_cache = ZFS_CACHE_ALL;
		osi->os_secondary_cache = ZFS_CACHE_ALL;
	}

	osi->os_zil_header = osi->os_phys->os_zil_header;
	osi->os_zil = zil_alloc(&osi->os, &osi->os_zil_header);

	for (i = 0; i < TXG_SIZE; i++) {
		list_create(&osi->os_dirty_dnodes[i], sizeof (dnode_t),
		    offsetof(dnode_t, dn_dirty_link[i]));
		list_create(&osi->os_free_dnodes[i], sizeof (dnode_t),
		    offsetof(dnode_t, dn_dirty_link[i]));
	}
	list_create(&osi->os_dnodes, sizeof (dnode_t),
	    offsetof(dnode_t, dn_link));
	list_create(&osi->os_downgraded_dbufs, sizeof (dmu_buf_impl_t),
	    offsetof(dmu_buf_impl_t, db_link));

	mutex_init(&osi->os_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&osi->os_obj_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&osi->os_user_ptr_lock, NULL, MUTEX_DEFAULT, NULL);

	osi->os_meta_dnode = dnode_special_open(osi,
	    &osi->os_phys->os_meta_dnode, DMU_META_DNODE_OBJECT);
	if (arc_buf_size(osi->os_phys_buf) >= sizeof (objset_phys_t)) {
		osi->os_userused_dnode = dnode_special_open(osi,
		    &osi->os_phys->os_userused_dnode, DMU_USERUSED_OBJECT);
		osi->os_groupused_dnode = dnode_special_open(osi,
		    &osi->os_phys->os_groupused_dnode, DMU_GROUPUSED_OBJECT);
	}

	/*
	 * We should be the only thread trying to do this because we
	 * have ds_opening_lock
	 */
	if (ds) {
		VERIFY(NULL == dsl_dataset_set_user_ptr(ds, osi,
		    dmu_objset_evict));
	}

	*osip = osi;
	return (0);
}