filesetup: limit rand map to the actual IO size, if needed

No need allocating a larger map than we need.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/filesetup.c b/filesetup.c
index ab5cc48..478bda8 100644
--- a/filesetup.c
+++ b/filesetup.c
@@ -956,7 +956,9 @@
 		return 0;
 
 	for_each_file(td, f, i) {
-		blocks = (f->real_file_size + td->o.rw_min_bs - 1) /
+		uint64_t file_size = min(f->real_file_size, f->io_size);
+
+		blocks = (file_size + td->o.rw_min_bs - 1) /
 				(unsigned long long) td->o.rw_min_bs;
 		if (td->o.random_generator == FIO_RAND_GEN_LFSR) {
 			unsigned long seed;