diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9ec7cff..e511f94 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -733,6 +733,9 @@
 	 * or node_spanned_pages stay constant.  Holding this will also
 	 * guarantee that any pfn_valid() stays that way.
 	 *
+	 * pgdat_resize_lock() and pgdat_resize_unlock() are provided to
+	 * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG.
+	 *
 	 * Nests above zone->lock and zone->span_seqlock
 	 */
 	spinlock_t node_size_lock;