Add create_only option

If this option is set, then fio will only run the preparation
phase of a job. This means it will create all the files it
needs, but exit after that.

Suggested-by: Georg Schönberger <gschoenberger@thomas-krenn.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/HOWTO b/HOWTO
index aa5a6f0..025443b 100644
--- a/HOWTO
+++ b/HOWTO
@@ -893,6 +893,11 @@
 create_on_open=bool	Don't pre-setup the files for IO, just create open()
 			when it's time to do IO to that file.
 
+create_only=bool	If true, fio will only run the setup phase of the job.
+			If files need to be laid out or updated on disk, only
+			that will be done. The actual job contents are not
+			executed.
+
 pre_read=bool	If this is given, files will be pre-read into memory before
 		starting the given IO operation. This will also clear
 		the 'invalidate' flag, since it is pointless to pre-read