Add 'filesize' option

Allows the user to define the range of file sizes generated.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/HOWTO b/HOWTO
index e54b37b..a2070d6 100644
--- a/HOWTO
+++ b/HOWTO
@@ -237,6 +237,11 @@
 		size if larger than the current file size. If this parameter
 		is not given and the file exists, the file size will be used.
 
+filesize=siint	Individual file sizes. May be a range, in which case fio
+		will select sizes for files at random within the given range
+		and limited to 'size' in total (if that is given). If not
+		given, each created file is the same size.
+
 bs=siint	The block size used for the io units. Defaults to 4k. Values
 		can be given for both read and writes. If a single siint is
 		given, it will apply to both. If a second siint is specified