diff --git a/lib/flex_array.c b/lib/flex_array.c
index c0ea40b..0c33b24 100644
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -232,10 +232,10 @@
 
 /**
  * flex_array_prealloc - guarantee that array space exists
- * @fa:		the flex array for which to preallocate parts
- * @start:	index of first array element for which space is allocated
- * @end:	index of last (inclusive) element for which space is allocated
- * @flags:	page allocation flags
+ * @fa:			the flex array for which to preallocate parts
+ * @start:		index of first array element for which space is allocated
+ * @nr_elements:	number of elements for which space is allocated
+ * @flags:		page allocation flags
  *
  * This will guarantee that no future calls to flex_array_put()
  * will allocate memory.  It can be used if you are expecting to
@@ -245,13 +245,16 @@
  * Locking must be provided by the caller.
  */
 int flex_array_prealloc(struct flex_array *fa, unsigned int start,
-			unsigned int end, gfp_t flags)
+			unsigned int nr_elements, gfp_t flags)
 {
 	int start_part;
 	int end_part;
 	int part_nr;
+	unsigned int end;
 	struct flex_array_part *part;
 
+	end = start + nr_elements - 1;
+
 	if (start >= fa->total_nr_elements || end >= fa->total_nr_elements)
 		return -ENOSPC;
 	if (elements_fit_in_base(fa))