Add support for replaying blktrace trim/discard

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/io_ddir.h b/io_ddir.h
index f83fc9b..b234256 100644
--- a/io_ddir.h
+++ b/io_ddir.h
@@ -34,4 +34,9 @@
 	       ddir == DDIR_SYNC_FILE_RANGE;
 }
 
+static inline int ddir_rw(enum fio_ddir ddir)
+{
+	return ddir == DDIR_READ || ddir == DDIR_WRITE;
+}
+
 #endif