[PATCH] Fix offset/size setting problem

Add ->real_file_size, as ->file_size is the io size. Otherwise we don't
know if an offset + size is valid. This fixes the bug of offset >= size,
if size is set smaller than the device/file size.
diff --git a/fio.h b/fio.h
index 3b4937d..bb5b8dd 100644
--- a/fio.h
+++ b/fio.h
@@ -133,6 +133,7 @@
 	unsigned int create_fsync;
 	unsigned int loops;
 	unsigned long long file_size;
+	unsigned long long real_file_size;
 	unsigned long long file_offset;
 	unsigned long long zone_size;
 	unsigned long long zone_skip;