Re: [PATCH 10/10] mm/migrate.c: call detach_page_private to cleanup code

[Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>]

On 5/23/20 1:53 AM, Andrew Morton wrote:
> On Fri, 22 May 2020 09:18:25 +0200 Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx> wrote:
>
> > > > -	ClearPagePrivate(page);
> > > > -	set_page_private(newpage, page_private(page));
> > > > -	set_page_private(page, 0);
> > > > -	put_page(page);
> > > > +	set_page_private(newpage, detach_page_private(page));
> > > attach_page_private(newpage, detach_page_private(page));
> > Mattew had suggested it as follows, but not sure if we can reorder of
> > the setup of
> > the bh and setting PagePrivate, so I didn't want to break the original
> > syntax.
> >
> > @@ -797,11 +797,7 @@ static int __buffer_migrate_page(struct address_space *mapping,
> >           if (rc != MIGRATEPAGE_SUCCESS)
> >                   goto unlock_buffers;
> >    
> > -       ClearPagePrivate(page);
> > -       set_page_private(newpage, page_private(page));
> > -       set_page_private(page, 0);
> > -       put_page(page);
> > -       get_page(newpage);
> > +       attach_page_private(newpage, detach_page_private(page));
> >    
> >           bh = head;
> >           do {
> > @@ -810,8 +806,6 @@ static int __buffer_migrate_page(struct address_space *mapping,
> >    
> >           } while (bh != head);
> >    
> > -       SetPagePrivate(newpage);
> > -
> >           if (mode != MIGRATE_SYNC_NO_COPY)
> This is OK - coherency between PG_private and the page's buffer
> ring is maintained by holding lock_page().

Appreciate for your explanation.

Thanks,
Guoqing

> I have (effectively) applied the above change.