diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 5554ada..e61e0ef 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -863,9 +863,7 @@
 
 	/* We need 4 bits per page, rounded up to a multiple of sizeof(unsigned long) */
 	bitmap->filemap_attr = kzalloc(
-		(((num_pages*4/8)+sizeof(unsigned long)-1)
-		 /sizeof(unsigned long))
-		*sizeof(unsigned long),
+		roundup( DIV_ROUND_UP(num_pages*4, 8), sizeof(unsigned long)),
 		GFP_KERNEL);
 	if (!bitmap->filemap_attr)
 		goto out;