Dump actual filename in failure to open

Helpful for debugging.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/filesetup.c b/filesetup.c
index 289db87..daae33f 100644
--- a/filesetup.c
+++ b/filesetup.c
@@ -384,9 +384,12 @@
 	}
 
 	if (f->fd == -1) {
+		char buf[FIO_VERROR_SIZE];
 		int __e = errno;
 
-		td_verror(td, __e, "open");
+		snprintf(buf, sizeof(buf) - 1, "open(%s)", f->file_name);
+
+		td_verror(td, __e, buf);
 		if (__e == EINVAL && td->o.odirect)
 			log_err("fio: destination does not support O_DIRECT\n");
 		if (__e == EMFILE)