Sometimes we allocated too little memory for buffers

Fix it by adding page_mask to the allocation size, then the
alignment is guarenteed to fit.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.c b/fio.c
index 3c01156..92cb657 100644
--- a/fio.c
+++ b/fio.c
@@ -599,7 +599,7 @@
 		max_units = td->o.iodepth;
 
 	max_bs = max(td->o.max_bs[DDIR_READ], td->o.max_bs[DDIR_WRITE]);
-	td->orig_buffer_size = max_bs * max_units;
+	td->orig_buffer_size = page_mask + (max_bs * max_units);
 
 	if (td->o.mem_type == MEM_SHMHUGE || td->o.mem_type == MEM_MMAPHUGE)
 		td->orig_buffer_size = (td->orig_buffer_size + td->o.hugepage_size - 1) & ~(td->o.hugepage_size - 1);