linux-kernel - Re: [PATCH 1/1] mm/migrate: do not call prep_transhuge_page if !thp_migration

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Date:   Mon, 20 Nov 2017 17:07:09 +0000
From:   Andrea Reale <ar@...ux.vnet.ibm.com>
To:     Zi Yan <zi.yan@...rutgers.edu>
Cc:     linux-kernel@...r.kernel.org, n-horiguchi@...jp.nec.com,
        akpm@...ux-foundation.org, jglisse@...hat.com, realean2@...ibm.com
Subject: Re: [PATCH 1/1] mm/migrate: do not call prep_transhuge_page if
 !thp_migration_supported

Hi Yan Zi,

thanks for the feedback. Yes, it looks definitely less redundant :)

Regards,
Andrea

On Mon, Nov 20, 2017 at 11:33:06AM -0500, Zi Yan wrote:
> Hi Andrea,
> 
> Thanks for pointing this out.
> 
> I think the problem is that we should not prep_transhuge_page(new_page)
> unless new_page is allocated and PageTransHuge(). And several lines above,
> the allocation flags and the order is changed to make new_page a THP
> only if thp_migration_supported() is true.
> 
> Does the patch below look better?
> 
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 895ec0c..725eac5 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -54,7 +54,7 @@ static inline struct page *new_page_nodemask(struct page *page,
>  	new_page = __alloc_pages_nodemask(gfp_mask, order,
>  				preferred_nid, nodemask);
> 
> -	if (new_page && PageTransHuge(page))
> +	if (new_page && PageTransHuge(new_page))
>  		prep_transhuge_page(new_page);
> 
>  	return new_page;
> -- 
> 
> 
> --
> Best Regards
> Yan Zi
> 
> On 20 Nov 2017, at 11:17, Andrea Reale wrote:
> 
> > new_page_nodemask in linux/migrate.h should not call prep_transhuge_page
> > if thp_migration_support is false.
> >
> > Fixes commit 8135d8926c08 ("mm: memory_hotplug: memory hotremove supports
> > thp migration")
> >
> > Signed-off-by: Andrea Reale <ar@...ux.vnet.ibm.com>
> > ---
> >  include/linux/migrate.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> > index 895ec0c..725eac5 100644
> > --- a/include/linux/migrate.h
> > +++ b/include/linux/migrate.h
> > @@ -54,7 +54,7 @@ static inline struct page *new_page_nodemask(struct page *page,
> >  	new_page = __alloc_pages_nodemask(gfp_mask, order,
> >  				preferred_nid, nodemask);
> >
> > -	if (new_page && PageTransHuge(page))
> > +	if (thp_migration_supported() && new_page && PageTransHuge(page))
> >  		prep_transhuge_page(new_page);
> >
> >  	return new_page;
> > -- 
> > 2.7.4