-extern int td_io_init(struct thread_data *);
-extern int td_io_prep(struct thread_data *, struct io_u *);
-extern int td_io_queue(struct thread_data *, struct io_u *);
-extern int td_io_sync(struct thread_data *, struct fio_file *);
-extern int td_io_getevents(struct thread_data *, int, int, struct timespec *);
-extern int td_io_commit(struct thread_data *);
+extern int __must_check td_io_init(struct thread_data *);
+extern int __must_check td_io_prep(struct thread_data *, struct io_u *);
+extern int __must_check td_io_queue(struct thread_data *, struct io_u *);
+extern int __must_check td_io_sync(struct thread_data *, struct fio_file *);
+extern int __must_check td_io_getevents(struct thread_data *, int, int, struct timespec *);
+extern int __must_check td_io_commit(struct thread_data *);