diff --git a/fs/aio.c b/fs/aio.c
index 06d7d43..4f641ab 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -567,6 +567,10 @@
 	atomic_inc(&mm->mm_count);
 	tsk->mm = mm;
 	tsk->active_mm = mm;
+	/*
+	 * Note that on UML this *requires* PF_BORROWED_MM to be set, otherwise
+	 * it won't work. Update it accordingly if you change it here
+	 */
 	activate_mm(active_mm, mm);
 	task_unlock(tsk);