File truncation and extend fixes

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index 41a1790..b085cd1 100644
--- a/fio.h
+++ b/fio.h
@@ -214,6 +214,7 @@
 	FIO_SYNCIO	= 1 << 0,	/* io engine has synchronous ->queue */
 	FIO_RAWIO	= 1 << 1,	/* some sort of direct/raw io */
 	FIO_DISKLESSIO	= 1 << 2,	/* no disk involved */
+	FIO_NOEXTEND	= 1 << 3,	/* engine can't extend file */
 };
 
 /*