[*_restore] if things go wrong wipe the superblock.

So we don't leave the metadata device with partially restored metadata.

base/file_utils.cc

@@ -9,6 +9,7 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <string.h>
 
 //----------------------------------------------------------------
 
@@ -140,4 +141,16 @@ file_utils::get_file_length(string const &file) {
 	return nr_bytes;
 }
 
+void
+file_utils::zero_superblock(std::string const &path)
+{
+	unsigned const SUPERBLOCK_SIZE = 4096;
+	char buffer[SUPERBLOCK_SIZE];
+	int fd = open_block_file(path, SUPERBLOCK_SIZE, true, true);
+
+	memset(buffer, 0, SUPERBLOCK_SIZE);
+	if (::write(fd, buffer, SUPERBLOCK_SIZE) != SUPERBLOCK_SIZE)
+		throw runtime_error("couldn't zero superblock");
+}
+
 //----------------------------------------------------------------

base/file_utils.h

@@ -14,6 +14,7 @@ namespace file_utils {
 	int create_block_file(std::string const &path, off_t file_size);
 	int open_block_file(std::string const &path, off_t min_size, bool writeable, bool excl = true);
 	uint64_t get_file_length(std::string const &file);
+	void zero_superblock(std::string const &path);
 }
 
 //----------------------------------------------------------------

caching/cache_restore.cc

@@ -57,16 +57,20 @@ namespace {
 	}
 
 	int restore(flags const &fs) {
+		bool metadata_touched = false;
+
 		try {
 			block_manager<>::ptr bm = open_bm(*fs.output, block_manager<>::READ_WRITE);
+
+			check_file_exists(*fs.input);
+			ifstream in(fs.input->c_str(), ifstream::in);
+
+			metadata_touched = true;
 			metadata::ptr md(new metadata(bm, metadata::CREATE));
 			emitter::ptr restorer = create_restore_emitter(md,
 								       fs.metadata_version,
 								       fs.clean_shutdown ? CLEAN_SHUTDOWN : NO_CLEAN_SHUTDOWN);
 
-			check_file_exists(*fs.input);
-			ifstream in(fs.input->c_str(), ifstream::in);
-
 			unique_ptr<progress_monitor> monitor = create_monitor(fs.quiet);
 			parse_xml(in, restorer, get_file_length(*fs.input), *monitor);
 
@@ -74,6 +78,8 @@ namespace {
 				override_version(md, fs);
 
 		} catch (std::exception &e) {
+			if (metadata_touched)
+				zero_superblock(*fs.output);
 			cerr << e.what() << endl;
 			return 1;
 		}

era/era_restore.cc

@@ -1,5 +1,6 @@
 #include "version.h"
 
+#include "base/file_utils.h"
 #include "base/output_file_requirements.h"
 #include "era/commands.h"
 #include "era/metadata.h"
@@ -33,14 +34,19 @@ namespace {
 	};
 
 	int restore(flags const &fs, bool quiet) {
+		bool metadata_touched = false;
 		try {
 			block_manager<>::ptr bm = open_bm(*fs.output, block_manager<>::READ_WRITE);
+			file_utils::check_file_exists(*fs.output);
+			metadata_touched = true;
 			metadata::ptr md(new metadata(bm, metadata::CREATE));
 			emitter::ptr restorer = create_restore_emitter(*md);
 
 			parse_xml(*fs.input, restorer, fs.quiet);
 
 		} catch (std::exception &e) {
+			if (metadata_touched)
+				file_utils::zero_superblock(*fs.output);
 			cerr << e.what() << endl;
 			return 1;
 		}

thin-provisioning/thin_restore.cc

@@ -16,6 +16,7 @@
 // with thin-provisioning-tools.  If not, see
 // <http://www.gnu.org/licenses/>.
 
+#include "base/file_utils.h"
 #include "base/output_file_requirements.h"
 #include "persistent-data/file_utils.h"
 #include "thin-provisioning/commands.h"
@@ -44,15 +45,20 @@ using namespace thin_provisioning;
 
 namespace {
 	int restore(string const &backup_file, string const &dev, bool quiet) {
+		bool metadata_touched = false;
 		try {
 			// The block size gets updated by the restorer.
 			block_manager<>::ptr bm(open_bm(dev, block_manager<>::READ_WRITE));
+			file_utils::check_file_exists(backup_file);
+			metadata_touched = true;
 			metadata::ptr md(new metadata(bm, metadata::CREATE, 128, 0));
 			emitter::ptr restorer = create_restore_emitter(md);
 
 			parse_xml(backup_file, restorer, quiet);
 
 		} catch (std::exception &e) {
+			if (metadata_touched)
+				file_utils::zero_superblock(dev);
 			cerr << e.what() << endl;
 			return 1;
 		}