Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed

[Kuan-Ying Lee (李冠穎)]

On Tue, 2023-01-31 at 15:17 -0800, Andrew Morton wrote:
> On Tue, 31 Jan 2023 14:32:06 +0800 Kuan-Ying Lee <
> Kuan-Ying.Lee@xxxxxxxxxxxx> wrote:
> 
> > If we call folio_isolate_lru() successfully, we will get
> > return value 0. We need to add this folio to the
> > movable_pages_list.
> > 
> > Fixes: 67e139b02d99 ("mm/gup.c: refactor
> > check_and_migrate_movable_pages()")
> > Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@xxxxxxxxxxxx>
> > 
> > ...
> > 
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -1914,7 +1914,7 @@ static unsigned long
> > collect_longterm_unpinnable_pages(
> >  			drain_allow = false;
> >  		}
> >  
> > -		if (!folio_isolate_lru(folio))
> > +		if (folio_isolate_lru(folio))
> >  			continue;
> >  
> >  		list_add_tail(&folio->lru, movable_page_list);
> 
> Thanks.  What are the user-visible effects of this bug?

Hi Andrew,

I didn't hit bug on real devices. I observe this issue
by tracing get_user_pages() call flow.

Thanks.