diff --git a/metadata.cc b/metadata.cc
index 82badbb..1032f44 100644
--- a/metadata.cc
+++ b/metadata.cc
@@ -65,7 +65,7 @@ namespace {
 		block_manager<>::read_ref r = bm->read_lock(SUPERBLOCK_LOCATION);
 		superblock_disk const *sbd = reinterpret_cast<superblock_disk const *>(&r.data());
 
-		crc32c sum(160774);
+		crc32c sum(160774); // FIXME: magic number
 		sum.append(&sbd->flags_, MD_BLOCK_SIZE - sizeof(uint32_t));
 		if (sum.get_sum() != to_cpu<uint32_t>(sbd->csum_)) {
 			ostringstream out;
@@ -87,10 +87,11 @@ metadata::metadata(std::string const &dev_path, open_type ot)
 	  sb_(read_superblock(tm_->get_bm())),
 	  metadata_sm_(open_metadata_sm(tm_, static_cast<void *>(&sb_.metadata_space_map_root_))),
 	  data_sm_(open_disk_sm(tm_, static_cast<void *>(&sb_.data_space_map_root_))),
-	  details_(tm_, sb_.device_details_root_, device_details_traits::ref_counter()),
-	  mappings_top_level_(tm_, sb_.data_mapping_root_, mtree_ref_counter(tm_)),
-	  mappings_(tm_, sb_.data_mapping_root_, block_time_ref_counter(data_sm_))
+	  details_(new detail_tree(tm_, sb_.device_details_root_, device_details_traits::ref_counter())),
+	  mappings_top_level_(new dev_tree(tm_, sb_.data_mapping_root_, mtree_ref_counter(tm_))),
+	  mappings_(new mapping_tree(tm_, sb_.data_mapping_root_, block_time_ref_counter(data_sm_)))
 {
+	tm_->set_sm(open_metadata_sm(tm_, sb_.metadata_space_map_root_));
 }
 
 #if 0
@@ -104,10 +105,10 @@ metadata::metadata(std::string const &dev_path, open_type ot)
 void
 metadata::commit()
 {
-	sb_.data_mapping_root_ = mappings_.get_root();
-	sb_.device_details_root_ = details_.get_root();
+	sb_.data_mapping_root_ = mappings_->get_root();
+	sb_.device_details_root_ = details_->get_root();
 
-	// FIXME: copy the space map roots
+	// FIXME: commit and copy the space map roots
 
 	write_ref superblock = tm_->get_bm()->superblock(SUPERBLOCK_LOCATION);
         superblock_disk *disk = reinterpret_cast<superblock_disk *>(superblock.data());
diff --git a/metadata.h b/metadata.h
index 39329d7..eebe006 100644
--- a/metadata.h
+++ b/metadata.h
@@ -142,9 +142,9 @@ namespace thin_provisioning {
 
 		checked_space_map::ptr metadata_sm_;
 		checked_space_map::ptr data_sm_;
-		detail_tree details_;
-		dev_tree mappings_top_level_;
-		mapping_tree mappings_;
+		detail_tree::ptr details_;
+		dev_tree::ptr mappings_top_level_;
+		mapping_tree::ptr mappings_;
 	};
 }
 
diff --git a/metadata_checker.cc b/metadata_checker.cc
index c212076..a826f5c 100644
--- a/metadata_checker.cc
+++ b/metadata_checker.cc
@@ -133,11 +133,11 @@ thin_provisioning::metadata_check(metadata::ptr md)
 
 	mapping_validator::ptr mv(new mapping_validator(metadata_counter,
 							data_counter));
-	md->mappings_.visit(mv);
+	md->mappings_->visit(mv);
 	set<uint64_t> const &mapped_devs = mv->get_devices();
 
 	details_validator::ptr dv(new details_validator(metadata_counter));
-	md->details_.visit(dv);
+	md->details_->visit(dv);
 	set<uint64_t> const &details_devs = dv->get_devices();
 
 	for (set<uint64_t>::const_iterator it = mapped_devs.begin(); it != mapped_devs.end(); ++it)
diff --git a/metadata_dumper.cc b/metadata_dumper.cc
index 851310d..d6598cc 100644
--- a/metadata_dumper.cc
+++ b/metadata_dumper.cc
@@ -133,7 +133,7 @@ thin_provisioning::metadata_dump(metadata::ptr md, emitter::ptr e)
 
 	details_extractor::ptr de(new details_extractor);
 
-	md->details_.visit(de);
+	md->details_->visit(de);
 	map<uint64_t, device_details> const &devs = de->get_devices();
 
 	map<uint64_t, device_details>::const_iterator it, end = devs.end();
@@ -148,7 +148,7 @@ thin_provisioning::metadata_dump(metadata::ptr md, emitter::ptr e)
 				dd.snapshotted_time_);
 
 		mappings_extractor::ptr me(new mappings_extractor(dev_id, e, md->metadata_sm_, md->data_sm_));
-		md->mappings_.visit(me);
+		md->mappings_->visit(me);
 
 		e->end_device();
 	}
diff --git a/restore_emitter.cc b/restore_emitter.cc
index 3fe2046..5a2a874 100644
--- a/restore_emitter.cc
+++ b/restore_emitter.cc
@@ -56,14 +56,14 @@ namespace {
 			// Add entry to the details tree
 			uint64_t key[1] = {dev};
 			device_details details = {mapped_blocks, trans_id, creation_time, snap_time};
-			md_->details_.insert(key, details);
+			md_->details_->insert(key, details);
 
 			// Insert an empty mapping tree
 			single_mapping_tree::ptr new_tree(
 				new single_mapping_tree(md_->tm_,
 							block_time_ref_counter(md_->data_sm_)));
-			md_->mappings_top_level_.insert(key, new_tree->get_root());
-			md_->mappings_.set_root(md_->mappings_top_level_.get_root()); // FIXME: ugly
+			md_->mappings_top_level_->insert(key, new_tree->get_root());
+			md_->mappings_->set_root(md_->mappings_top_level_->get_root()); // FIXME: ugly
 
 			current_device_ = optional<uint32_t>(dev);
 		}
@@ -97,14 +97,14 @@ namespace {
 			block_time bt;
 			bt.block_ = data_block;
 			bt.time_ = time;
-			md_->mappings_.insert(key, bt);
-			md_->mappings_top_level_.set_root(md_->mappings_.get_root());
+			md_->mappings_->insert(key, bt);
+			md_->mappings_top_level_->set_root(md_->mappings_->get_root());
 		}
 
 	private:
 		bool device_exists(thin_dev_t dev) const {
 			uint64_t key[1] = {dev};
-			return md_->details_.lookup(key);
+			return md_->details_->lookup(key);
 		}
 
 		metadata::ptr md_;
diff --git a/thin_pool.cc b/thin_pool.cc
index 0e5c9ce..fb6ef4c 100644
--- a/thin_pool.cc
+++ b/thin_pool.cc
@@ -31,7 +31,7 @@ thin::maybe_address
 thin::lookup(block_address thin_block)
 {
 	uint64_t key[2] = {dev_, thin_block};
-	return pool_->md_->mappings_.lookup(key);
+	return pool_->md_->mappings_->lookup(key);
 }
 
 void
@@ -41,33 +41,33 @@ thin::insert(block_address thin_block, block_address data_block)
 	block_time bt;
 	bt.block_ = data_block;
 	bt.time_ = 0;		// FIXME: use current time.
-	return pool_->md_->mappings_.insert(key, bt);
+	return pool_->md_->mappings_->insert(key, bt);
 }
 
 void
 thin::remove(block_address thin_block)
 {
 	uint64_t key[2] = {dev_, thin_block};
-	pool_->md_->mappings_.remove(key);
+	pool_->md_->mappings_->remove(key);
 }
 
 void
 thin::set_snapshot_time(uint32_t time)
 {
 	uint64_t key[1] = { dev_ };
-	optional<device_details> mdetail = pool_->md_->details_.lookup(key);
+	optional<device_details> mdetail = pool_->md_->details_->lookup(key);
 	if (!mdetail)
 		throw runtime_error("no such device");
 
 	mdetail->snapshotted_time_ = time;
-	pool_->md_->details_.insert(key, *mdetail);
+	pool_->md_->details_->insert(key, *mdetail);
 }
 
 block_address
 thin::get_mapped_blocks() const
 {
 	uint64_t key[1] = { dev_ };
-	optional<device_details> mdetail = pool_->md_->details_.lookup(key);
+	optional<device_details> mdetail = pool_->md_->details_->lookup(key);
 	if (!mdetail)
 		throw runtime_error("no such device");
 
@@ -78,12 +78,12 @@ void
 thin::set_mapped_blocks(block_address count)
 {
 	uint64_t key[1] = { dev_ };
-	optional<device_details> mdetail = pool_->md_->details_.lookup(key);
+	optional<device_details> mdetail = pool_->md_->details_->lookup(key);
 	if (!mdetail)
 		throw runtime_error("no such device");
 
 	mdetail->mapped_blocks_ = count;
-	pool_->md_->details_.insert(key, *mdetail);
+	pool_->md_->details_->insert(key, *mdetail);
 }
 
 //--------------------------------
@@ -107,8 +107,8 @@ thin_pool::create_thin(thin_dev_t dev)
 		throw std::runtime_error("Device already exists");
 
 	single_mapping_tree::ptr new_tree(new single_mapping_tree(md_->tm_, block_time_ref_counter(md_->data_sm_)));
-	md_->mappings_top_level_.insert(key, new_tree->get_root());
-	md_->mappings_.set_root(md_->mappings_top_level_.get_root()); // FIXME: ugly
+	md_->mappings_top_level_->insert(key, new_tree->get_root());
+	md_->mappings_->set_root(md_->mappings_top_level_->get_root()); // FIXME: ugly
 
 	// FIXME: doesn't set up the device details
 }
@@ -119,7 +119,7 @@ thin_pool::create_snap(thin_dev_t dev, thin_dev_t origin)
 	uint64_t snap_key[1] = {dev};
 	uint64_t origin_key[1] = {origin};
 
-	optional<uint64_t> mtree_root = md_->mappings_top_level_.lookup(origin_key);
+	optional<uint64_t> mtree_root = md_->mappings_top_level_->lookup(origin_key);
 	if (!mtree_root)
 		throw std::runtime_error("unknown origin");
 
@@ -127,8 +127,8 @@ thin_pool::create_snap(thin_dev_t dev, thin_dev_t origin)
 				  block_time_ref_counter(md_->data_sm_));
 
 	single_mapping_tree::ptr clone(otree.clone());
-	md_->mappings_top_level_.insert(snap_key, clone->get_root());
-	md_->mappings_.set_root(md_->mappings_top_level_.get_root()); // FIXME: ugly
+	md_->mappings_top_level_->insert(snap_key, clone->get_root());
+	md_->mappings_->set_root(md_->mappings_top_level_->get_root()); // FIXME: ugly
 
 	md_->sb_.time_++;
 
@@ -143,7 +143,7 @@ void
 thin_pool::del(thin_dev_t dev)
 {
 	uint64_t key[1] = {dev};
-	md_->mappings_top_level_.remove(key);
+	md_->mappings_top_level_->remove(key);
 }
 
 void
@@ -198,7 +198,7 @@ thin::ptr
 thin_pool::open_thin(thin_dev_t dev)
 {
 	uint64_t key[1] = {dev};
-	optional<device_details> mdetails = md_->details_.lookup(key);
+	optional<device_details> mdetails = md_->details_->lookup(key);
 	if (!mdetails)
 		throw runtime_error("no such device");
 
@@ -211,7 +211,7 @@ bool
 thin_pool::device_exists(thin_dev_t dev) const
 {
 	uint64_t key[1] = {dev};
-	return md_->details_.lookup(key);
+	return md_->details_->lookup(key);
 }
 
 //----------------------------------------------------------------
diff --git a/transaction_manager.h b/transaction_manager.h
index 353b38d..98045de 100644
--- a/transaction_manager.h
+++ b/transaction_manager.h
@@ -44,6 +44,10 @@ namespace persistent_data {
 			return sm_;
 		}
 
+		void set_sm(space_map::ptr sm) {
+			sm_ = sm;
+		}
+
 		block_manager<>::ptr get_bm() {
 			return bm_;
 		}