iotune: don't coredump when directory fails to be created

The current file write code doesn't check if the directory was created
successfully because if it wasn't, writing the file itself will throw. However,
it is not always the case that creating a directory will return an error
message. It may throw, and if it does, the program will crash on an unhandled
exception. So let's change the code slightly so that everything related to file
creation falls within the try/catch block.

We do have to return an error code from this, which we currently don't do.

Fixes scylladb#129

Signed-off-by: Glauber Costa <[email protected]>

apps/iotune/iotune.cc

@@ -623,7 +623,7 @@ uint32_t io_queue_discovery(sstring dir, std::vector<unsigned> cpus, std::chrono
     return iotune_manager.finish_estimate();
 }
 
-void write_configuration_file(std::string conf_file, std::string format, unsigned max_io_requests, std::experimental::optional<unsigned> num_io_queues = {}) {
+int write_configuration_file(std::string conf_file, std::string format, unsigned max_io_requests, std::experimental::optional<unsigned> num_io_queues = {}) {
     std::cout << "Recommended --max-io-requests: " << max_io_requests << std::endl;
     if (num_io_queues) {
         std::cout << "Recommended --num-io-queues: " << *num_io_queues << std::endl;
@@ -637,10 +637,9 @@ void write_configuration_file(std::string conf_file, std::string format, unsigne
     boost::filesystem::path conf_path(k.we_wordv[0]);
     wordfree(&k);
 
-    // No need to test the return value here. If by any chance the directory was not created,
-    // writing the file itself will generate an exception.
-    boost::filesystem::create_directories(conf_path.parent_path());
+    auto error_msg = " when writing configuration file. Please add them to your seastar command line";
     try {
+        boost::filesystem::create_directories(conf_path.parent_path());
         std::ofstream ofs_io;
         ofs_io.exceptions(std::ofstream::failbit | std::ofstream::badbit);
         ofs_io.open(conf_path.string(), std::ofstream::trunc);
@@ -660,9 +659,14 @@ void write_configuration_file(std::string conf_file, std::string format, unsigne
         }
         ofs_io.close();
         std::cout << "Written the above values to " << conf_path.string() << std::endl;
+    } catch (boost::filesystem::filesystem_error &e) { // create directory may throw this
+        std::cout << e.what() << error_msg << std::endl;
+        return 1;
     } catch (std::ios_base::failure& e) {
-        std::cout << e.what() << " when writing configuration file. Please add them to your seastar command line" << std::endl;
+        std::cout << e.what() << error_msg << std::endl;
+        return 1;
     }
+    return 0;
 }
 
 int main(int ac, char** av) {
@@ -733,9 +737,9 @@ int main(int ac, char** av) {
 
         if (num_io_queues != cpuvec.size()) {
             iodepth = (iodepth / num_io_queues) * num_io_queues;
-            write_configuration_file(conf_file, format, iodepth, num_io_queues);
+            return write_configuration_file(conf_file, format, iodepth, num_io_queues);
         } else {
-            write_configuration_file(conf_file, format, iodepth);
+            return write_configuration_file(conf_file, format, iodepth);
         }
     } catch (iotune_timeout_exception &e) {
         // Otherwise we'll coredump on the exception, but this can happen