linux-kernel - Re: [PATCH 1/1] mm/hugetlb: Set PTE as huge in hugetlb_change

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Date:	Tue, 22 Jan 2013 11:21:34 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Tony Lu <zlu@...era.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Hillf Danton <dhillf@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Chris Metcalf <cmetcalf@...era.com>
Subject: Re: [PATCH 1/1] mm/hugetlb: Set PTE as huge in
 hugetlb_change_protection

On Tue 22-01-13 02:37:15, Tony Lu wrote:
> >-----Original Message-----
> >From: Michal Hocko [mailto:mhocko@...e.cz]
> >Sent: Monday, January 21, 2013 6:04 PM
> >To: Tony Lu
> >Cc: linux-kernel@...r.kernel.org; linux-mm@...ck.org; Andrew Morton; Aneesh
> >Kumar K.V; Hillf Danton; KAMEZAWA Hiroyuki; Chris Metcalf
> >Subject: Re: [PATCH 1/1] mm/hugetlb: Set PTE as huge in
> >hugetlb_change_protection
> >
> >On Mon 21-01-13 04:13:07, Tony Lu wrote:
> >> From da8432aafd231e7cdcda9d15484829def4663cb0 Mon Sep 17 00:00:00 2001
> >> From: Zhigang Lu <zlu@...era.com>
> >> Date: Mon, 21 Jan 2013 11:23:26 +0800
> >> Subject: [PATCH 1/1] mm/hugetlb: Set PTE as huge in hugetlb_change_protection
> >>
> >> When setting a huge PTE, besides calling pte_mkhuge(), we also need
> >> to call arch_make_huge_pte(), which we indeed do in make_huge_pte(),
> >> but we forget to do in hugetlb_change_protection().
> >
> >I guess you also need it in remove_migration_pte. This calls for a
> >helper which would do both pte_mkhuge() and arch_make_huge_pte.
> >
> >Besides that, tile seem to be the only arch which implements this arch
> >hook (introduced by 621b1955 in 3.5) so this should be considered for
> >stable.
> 
> Thank you. Yes, remove_migration_pte also needs it. Here is the updated patch.
> 
> From 44045d672aa72eb2e76be89f95ab720952b4b09c Mon Sep 17 00:00:00 2001
> From: Zhigang Lu <zlu@...era.com>
> Date: Tue, 22 Jan 2013 09:58:58 +0800
> Subject: [PATCH 1/1] mm/hugetlb: Set PTE as huge in hugetlb_change_protection
>  and remove_migration_pte
> 
> When setting a huge PTE, besides calling pte_mkhuge(), we also need
> to call arch_make_huge_pte(), which we indeed do in make_huge_pte(),
> but we forget to do in hugetlb_change_protection() and
> remove_migration_pte().
> 
> Signed-off-by: Zhigang Lu <zlu@...era.com>
> Signed-off-by: Chris Metcalf <cmetcalf@...era.com>

Reviewed-by: Michal Hocko <mhocko@...e.cz>

> ---
>  mm/hugetlb.c |    1 +
>  mm/migrate.c |    4 +++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 4f3ea0b..546db81 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3033,6 +3033,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
>                 if (!huge_pte_none(huge_ptep_get(ptep))) {
>                         pte = huge_ptep_get_and_clear(mm, address, ptep);
>                         pte = pte_mkhuge(pte_modify(pte, newprot));
> +                       pte = arch_make_huge_pte(pte, vma, NULL, 0);
>                         set_huge_pte_at(mm, address, ptep, pte);
>                         pages++;
>                 }
> diff --git a/mm/migrate.c b/mm/migrate.c
> index c387786..2fd8b4a 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -160,8 +160,10 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
>         if (is_write_migration_entry(entry))
>                 pte = pte_mkwrite(pte);
>  #ifdef CONFIG_HUGETLB_PAGE
> -       if (PageHuge(new))
> +       if (PageHuge(new)) {
>                 pte = pte_mkhuge(pte);
> +               pte = arch_make_huge_pte(pte, vma, new, 0);
> +       }
>  #endif
>         flush_cache_page(vma, addr, pte_pfn(pte));
>         set_pte_at(mm, addr, ptep, pte);
> -- 
> 1.7.10.3

-- 
Michal Hocko
SUSE Labs
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