[PATCH] userfaultfd: exit event: add comment about lockless vma walk

[Mike Rapoport]

Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
---
 fs/userfaultfd.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 6587f40..3c421d0 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -778,6 +778,10 @@ void userfaultfd_exit(struct mm_struct *mm)
 {
 	struct vm_area_struct *vma = mm->mmap;
 
+	/*
+	 * We can do the vma walk without locking because the caller
+	 * (exit_mm) knows it now has exclusive access
+	 */
 	while (vma) {
 		struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
 
-- 
1.9.1