diff --git a/mm/gup.c b/mm/gup.c
index c3014669988b..1d84291543fd 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1176,7 +1176,8 @@ static bool vma_permits_fault(struct vm_area_struct *vma,
  * @address:	user address
  * @fault_flags:flags to pass down to handle_mm_fault()
  * @unlocked:	did we unlock the mmap_sem while retrying, maybe NULL if caller
- *		does not allow retry
+ *		does not allow retry. If NULL, the caller must guarantee
+ *		that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY.
  *
  * This is meant to be called in the specific scenario where for locking reasons
  * we try to access user memory in atomic context (within a pagefault_disable()