From 524de134a4468b8adab1c9a94a87cec5ac2e45e6 Mon Sep 17 00:00:00 2001
From: Ming-Hung Tsai <mtsai@redhat.com>
Date: Tue, 2 Jun 2020 19:07:13 +0800
Subject: [PATCH] [thin_pool] Support creating metadadata snapshot

---
 thin-provisioning/thin_pool.cc | 46 ++++++++++++++++++++++++++++++++++
 thin-provisioning/thin_pool.h  |  3 +++
 2 files changed, 49 insertions(+)

diff --git a/thin-provisioning/thin_pool.cc b/thin-provisioning/thin_pool.cc
index d9d9684..2b58e4d 100644
--- a/thin-provisioning/thin_pool.cc
+++ b/thin-provisioning/thin_pool.cc
@@ -227,6 +227,52 @@ thin_pool::get_transaction_id() const
 	return md_->sb_.trans_id_;
 }
 
+void
+thin_pool::reserve_metadata_snap()
+{
+	if (md_->sb_.metadata_snap_)
+		throw std::runtime_error("pool metadata snapshot already exists.");
+
+	commit();
+
+	md_->metadata_sm_->inc(superblock_detail::SUPERBLOCK_LOCATION);
+	transaction_manager::write_ref wr = md_->tm_->shadow(
+			superblock_detail::SUPERBLOCK_LOCATION,
+			superblock_validator()).first;
+
+	superblock_detail::superblock sb;
+	superblock_detail::superblock_disk *sbd = reinterpret_cast<superblock_detail::superblock_disk *>(wr.data());
+	superblock_detail::superblock_traits::unpack(*sbd, sb);
+
+	memset(sb.data_space_map_root_, 0, superblock_detail::SPACE_MAP_ROOT_SIZE);
+	memset(sb.metadata_space_map_root_, 0, superblock_detail::SPACE_MAP_ROOT_SIZE);
+	md_->metadata_sm_->inc(sb.data_mapping_root_);
+	md_->metadata_sm_->inc(sb.device_details_root_);
+
+	superblock_detail::superblock_traits::pack(sb, *sbd);
+
+	md_->sb_.metadata_snap_ = wr.get_location();
+}
+
+void
+thin_pool::release_metadata_snap()
+{
+	if (!md_->sb_.metadata_snap_)
+		throw std::runtime_error("No pool metadata snapshot found");
+
+	superblock_detail::superblock sb = read_superblock(md_->tm_->get_bm(),
+							   md_->sb_.metadata_snap_);
+	device_tree dtree(*md_->tm_, sb.device_details_root_,
+			  device_tree_detail::device_details_traits::ref_counter());
+	dtree.destroy();
+	mapping_tree mtree(*md_->tm_, sb.data_mapping_root_,
+			   mapping_tree_detail::block_traits::ref_counter(md_->tm_->get_sm()));
+	mtree.destroy();
+	md_->metadata_sm_->dec(md_->sb_.metadata_snap_);
+
+	md_->sb_.metadata_snap_ = 0;
+}
+
 block_address
 thin_pool::get_metadata_snap() const
 {
diff --git a/thin-provisioning/thin_pool.h b/thin-provisioning/thin_pool.h
index 4dffc7b..62f6945 100644
--- a/thin-provisioning/thin_pool.h
+++ b/thin-provisioning/thin_pool.h
@@ -82,6 +82,9 @@ namespace thin_provisioning {
 		void set_transaction_id(uint64_t id);
 		uint64_t get_transaction_id() const;
 
+		// handling metadata snapshot
+		void reserve_metadata_snap();
+		void release_metadata_snap();
 		block_address get_metadata_snap() const;
 
 		block_address alloc_data_block();