blktrace support: adjust largest io_u buffer size to match trace

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.c b/fio.c
index 75b448d..0c297f7 100644
--- a/fio.c
+++ b/fio.c
@@ -782,6 +782,13 @@
 	 */
 	fio_sem_remove(td->mutex);
 
+	/*
+	 * May alter parameters that init_io_u() will use, so we need to
+	 * do this first.
+	 */
+	if (init_iolog(td))
+		goto err;
+
 	if (init_io_u(td))
 		goto err;
 
@@ -790,9 +797,6 @@
 		goto err;
 	}
 
-	if (init_iolog(td))
-		goto err;
-
 	if (td->ioprio) {
 		if (ioprio_set(IOPRIO_WHO_PROCESS, 0, td->ioprio) == -1) {
 			td_verror(td, errno, "ioprio_set");