On Sun, Jul 01, 2018 at 09:10:57AM -0700, Dan Williams wrote: > I think we also need the following clue bat for people like me in the future: > > diff --git a/mm/gup.c b/mm/gup.c > index b70d7ba7cc13..388a5c799fa5 100644 > +++ b/mm/gup.c > @@ -873,6 +873,8 @@ static __always_inline long > __get_user_pages_locked(struct task_struct *ts > long ret, pages_done; > bool lock_dropped; > > + lockdep_assert_held_read(&mm->mmap_sem); > + > if (locked) { > /* if VM_FAULT_RETRY can be returned, vmas become invalid */ > BUG_ON(vmas); Yes please, I had the same thought.. Dan, can you make this happen? Jason