Re: [PATCH] mm/vmscan: drop checking if _deferred_list is empty before using TTU_SYNC

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 1 Jul 2024 21:35:41 +1200 Barry Song <21cnbao@gmail.com> wrote:

> > > +++ b/mm/vmscan.c
> > > @@ -1291,7 +1291,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
> > >                        * try_to_unmap acquire PTL from the first PTE,
> > >                        * eliminating the influence of temporary PTE values.
> > >                        */
> > > -                     if (folio_test_large(folio) && list_empty(&folio->_deferred_list))
> > > +                     if (folio_test_large(folio))
> >
> > As it stands, the list_empty() technically needs a data_race() annotation. I
> > think your original patch went into v6.10-rc1? If so, perhaps it makes sense to
> > try to get this into the next rc?
> 
> Either way is fine. Hi Andrew, if you include it for the next RC, could you
> please add this tag?
> 
> Fixes: 73bc32875ee9 ("mm: hold PTL from the first PTE while reclaiming
> a large folio")

Nope!  That invites people to backport this change into kernels which
don't contain Ryan's 5ed890ce5147 ("mm: vmscan: avoid split during
shrink_folio_list()").

I'll simply queue this in the normal fashion.

> And an additional changelog:
> 
> Additionally, the list_empty() technically requires a data_race() annotation.

Done, thanks.