RE: [PATCH 1/1] mm/hugetlb: Set PTE as huge in hugetlb_change_protection

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>-----Original Message-----
>From: Michal Hocko [mailto:mhocko@xxxxxxx]
>Sent: Monday, January 21, 2013 6:04 PM
>To: Tony Lu
>Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; 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@xxxxxxxxxx>
>> 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@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
---
 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

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