[thin_check] Add support for --metadata-snap.

Not tested yet.

functional-tests/scenario-string-constants.scm

@@ -29,6 +29,7 @@ Options:
   {-q|--quiet}
   {-h|--help}
   {-V|--version}
+  {-m|--metadata-snap}
   {--override-mapping-root}
   {--clear-needs-check-flag}
   {--ignore-non-fatal-errors}

thin-provisioning/metadata_checker.cc

@@ -137,12 +137,13 @@ namespace {
 	//--------------------------------
 
 	error_state examine_superblock(block_manager::ptr bm,
+                                       block_address sb_location,
 				       nested_output &out) {
 		out << "examining superblock" << end_message();
 		nested_output::nest _ = out.push();
 
 		superblock_reporter sb_rep(out);
-		check_superblock(bm, sb_rep);
+		check_superblock(bm, sb_rep, sb_location);
 
 		return sb_rep.get_error();
 	}
@@ -307,18 +308,24 @@ namespace {
 
 		error_state check() {
 			error_state err = NO_ERROR;
+			auto sb_location = superblock_detail::SUPERBLOCK_LOCATION;
 
-			err << examine_superblock(bm_, out_);
-
+			if (options_.use_metadata_snap_) {
+				superblock_detail::superblock sb = read_superblock(bm_, sb_location);
+				sb_location = sb.metadata_snap_;
+				if (sb_location == superblock_detail::SUPERBLOCK_LOCATION)
+					throw runtime_error("No metadata snapshot found.");
+			}
+			
+			err << examine_superblock(bm_, sb_location, out_);
 			if (err == FATAL) {
 				if (check_for_xml(bm_))
 					out_ << "This looks like XML.  thin_check only checks the binary metadata format." << end_message();
 				return err;
 			}
 
-			superblock_detail::superblock sb = read_superblock(bm_);
-			transaction_manager::ptr tm =
-				open_tm(bm_, superblock_detail::SUPERBLOCK_LOCATION);
+			superblock_detail::superblock sb = read_superblock(bm_, sb_location);
+			transaction_manager::ptr tm = open_tm(bm_, sb_location);
 			sb.data_mapping_root_ = mapping_root(sb, options_);
 
 			print_info(tm, sb, info_out_);
@@ -412,6 +419,10 @@ void check_options::set_override_mapping_root(block_address b) {
 	override_mapping_root_ = b;
 }
 
+void check_options::set_metadata_snap() {
+	sm_opts_ = SPACE_MAP_NONE;
+}
+		
 base::error_state
 thin_provisioning::check_metadata(block_manager::ptr bm,
 				  check_options const &check_opts,

thin-provisioning/metadata_checker.h

@@ -43,11 +43,11 @@ namespace thin_provisioning {
 		void set_superblock_only();
 		void set_skip_mappings();
 		void set_override_mapping_root(bcache::block_address b);
+		void set_metadata_snap();
 
+		bool use_metadata_snap_;
 		data_mapping_options check_data_mappings_;
-
 		space_map_options sm_opts_;
-
 		boost::optional<bcache::block_address> override_mapping_root_;
 	};
 

thin-provisioning/superblock.cc

@@ -194,11 +194,12 @@ namespace thin_provisioning {
 
 	void
 	check_superblock(block_manager::ptr bm,
-			 superblock_detail::damage_visitor &visitor) {
+			 superblock_detail::damage_visitor &visitor,
+                         block_address sb_location) {
 		using namespace superblock_detail;
 
 		try {
-			bm->read_lock(SUPERBLOCK_LOCATION, superblock_validator());
+			bm->read_lock(sb_location, superblock_validator());
 
 		} catch (std::exception const &e) {
 			visitor.visit(superblock_corruption(e.what()));

thin-provisioning/superblock.h

@@ -139,7 +139,8 @@ namespace thin_provisioning {
 			      superblock_detail::superblock const &sb);
 
 	void check_superblock(persistent_data::block_manager::ptr bm,
-			      superblock_detail::damage_visitor &visitor);
+			      superblock_detail::damage_visitor &visitor,
+                              persistent_data::block_address sb_location = superblock_detail::SUPERBLOCK_LOCATION);
 }
 
 //----------------------------------------------------------------

thin-provisioning/thin_check.cc

@@ -109,15 +109,16 @@ thin_check_cmd::thin_check_cmd()
 void
 thin_check_cmd::usage(std::ostream &out) const
 {
-	out << "Usage: " << get_name() << " [options] {device|file}" << endl
-	    << "Options:" << endl
-	    << "  {-q|--quiet}" << endl
-	    << "  {-h|--help}" << endl
-	    << "  {-V|--version}" << endl
-	    << "  {--override-mapping-root}" << endl
-	    << "  {--clear-needs-check-flag}" << endl
-	    << "  {--ignore-non-fatal-errors}" << endl
-	    << "  {--skip-mappings}" << endl
+	out << "Usage: " << get_name() << " [options] {device|file}\n"
+	    << "Options:\n"
+	    << "  {-q|--quiet}\n"
+	    << "  {-h|--help}\n"
+	    << "  {-V|--version}\n"
+	    << "  {-m|--metadata-snap}\n"
+	    << "  {--override-mapping-root}\n"
+	    << "  {--clear-needs-check-flag}\n"
+	    << "  {--ignore-non-fatal-errors}\n"
+	    << "  {--skip-mappings}\n"
 	    << "  {--super-block-only}" << endl;
 }
 
@@ -132,6 +133,7 @@ thin_check_cmd::run(int argc, char **argv)
 		{ "quiet", no_argument, NULL, 'q'},
 		{ "help", no_argument, NULL, 'h'},
 		{ "version", no_argument, NULL, 'V'},
+		{ "metadata-snap", no_argument, NULL, 'm'},
 		{ "super-block-only", no_argument, NULL, 1},
 		{ "skip-mappings", no_argument, NULL, 2},
 		{ "ignore-non-fatal-errors", no_argument, NULL, 3},
@@ -154,6 +156,10 @@ thin_check_cmd::run(int argc, char **argv)
 			cout << THIN_PROVISIONING_TOOLS_VERSION << endl;
 			return 0;
 
+		case 'm':
+			fs.check_opts.set_metadata_snap();
+			break;
+
 		case 1:
 			// super-block-only
 			fs.check_opts.set_superblock_only();
@@ -185,6 +191,12 @@ thin_check_cmd::run(int argc, char **argv)
 		}
 	}
 
+	if (fs.clear_needs_check_flag_on_success && fs.check_opts.use_metadata_snap_) {
+		cerr << "--metadata-snap cannot be combined with --clear-needs-check-flag.";
+		usage(cerr);
+		exit(1);
+	}
+
 	if (argc == optind) {
 		if (!fs.quiet) {
 			cerr << "No input file provided." << endl;