On Mon 19-11-18 15:10:16, Michal Hocko wrote: [...] > In other words. Why cannot we do the following? Baoquan, this is certainly not the right fix but I would be really curious whether it makes the problem go away. > diff --git a/mm/migrate.c b/mm/migrate.c > index f7e4bfdc13b7..7ccab29bcf9a 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -324,19 +324,9 @@ void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, > goto out; > > page = migration_entry_to_page(entry); > - > - /* > - * Once page cache replacement of page migration started, page_count > - * *must* be zero. And, we don't want to call wait_on_page_locked() > - * against a page without get_page(). > - * So, we use get_page_unless_zero(), here. Even failed, page fault > - * will occur again. > - */ > - if (!get_page_unless_zero(page)) > - goto out; > pte_unmap_unlock(ptep, ptl); > - wait_on_page_locked(page); > - put_page(page); > + page_lock(page); > + page_unlock(page); > return; > out: > pte_unmap_unlock(ptep, ptl); -- Michal Hocko SUSE Labs
