diff --git a/mm/swapfile.c b/mm/swapfile.c
index 8837b22c848d..52a9dd9dab8e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -296,13 +296,18 @@ static inline void unlock_cluster(struct swap_cluster_info *ci)
 		spin_unlock(&ci->lock);
 }
 
+/*
+ * Determine the locking method in use for this device.  Return
+ * swap_cluster_info if SSD-style cluster-based locking is in place.
+ */
 static inline struct swap_cluster_info *lock_cluster_or_swap_info(
-	struct swap_info_struct *si,
-	unsigned long offset)
+		struct swap_info_struct *si, unsigned long offset)
 {
 	struct swap_cluster_info *ci;
 
+	/* Try to use fine-grained SSD-style locking if available: */
 	ci = lock_cluster(si, offset);
+	/* Otherwise, fall back to traditional, coarse locking: */
 	if (!ci)
 		spin_lock(&si->lock);