Re: [PATCH v2 1/8] mm: migrate: remove PageTransHuge check in numamigrate_isolate_page()

[Kefeng Wang]

On 2023/8/21 20:52, Kefeng Wang wrote:
> On 2023/8/21 20:38, Matthew Wilcox wrote:
> > On Mon, Aug 21, 2023 at 07:56:17PM +0800, Kefeng Wang wrote:
> > > Since we begin to convert the numa migration code to use folio, which
> > > could let us to handle arbitrary sizes of folio, so drop assert that
> > > we only support PageTransHuge page(PMD size) when order > 0.
> >
> > Have you looked at the implementation of PageTransHuge()?  Your
> > description doesn't match what the code does.
>
> oops, not only PMD size...

Please ignore about reply, sorry，I misread， PageTransHuge return true
for head page, and BUG_ON for tail page, and compound_order(page) will
return 0 for tail page, so when begin to convert page to folio, we could
drop this line since it is not useful check for folio.

> > > Suggested-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> > > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> > > ---
> > >   mm/migrate.c | 2 --
> > >   1 file changed, 2 deletions(-)
> > >
> > > diff --git a/mm/migrate.c b/mm/migrate.c
> > > index b7fa020003f3..646d8ee7f102 100644
> > > --- a/mm/migrate.c
> > > +++ b/mm/migrate.c
> > > @@ -2483,8 +2483,6 @@ static int numamigrate_isolate_page(pg_data_t 
> > > *pgdat, struct page *page)
> > >       int nr_pages = thp_nr_pages(page);
> > >       int order = compound_order(page);
> > > -    VM_BUG_ON_PAGE(order && !PageTransHuge(page), page);
> > > -
> > >       /* Do not migrate THP mapped by multiple processes */
> > >       if (PageTransHuge(page) && total_mapcount(page) > 1)
> > >           return 0;
> > > --
> > > 2.41.0