On Tue, Oct 08, 2013 at 01:00:20PM +0400, Cyrill Gorcunov wrote:
> If page migration is turne on in the config and the page is migrating,
> we may loose soft dirty bit. If fork and mprotect if called on migrating
> pages (once migration is complete) pages do not obtain soft dirty bit
> in correspond pte entries. Fix it adding appropriate test on swap
> entries.
>
> Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Matt Mackall <mpm@xxxxxxxxxxx>
> Cc: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
> Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx>
> Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> ---
> mm/memory.c | 2 ++
> mm/migrate.c | 2 ++
> mm/mprotect.c | 7 +++++--
> 3 files changed, 9 insertions(+), 2 deletions(-)
>
> Index: linux-2.6.git/mm/memory.c
> ===================================================================
> --- linux-2.6.git.orig/mm/memory.c
> +++ linux-2.6.git/mm/memory.c
> @@ -837,6 +837,8 @@ copy_one_pte(struct mm_struct *dst_mm, s
> */
> make_migration_entry_read(&entry);
> pte = swp_entry_to_pte(entry);
> + if (pte_swp_soft_dirty(*src_pte))
> + pte = pte_swp_mksoft_dirty(pte);
> set_pte_at(src_mm, addr, src_pte, pte);
> }
> }
When we convert pte to swap_entry, we convert soft-dirty bit in
pte_to_swp_entry(). So I think that it's better to convert it back
in swp_entry_to_pte() when we do swap_entry-to-pte conversion.
Thanks,
Naoya Horiguchi
> Index: linux-2.6.git/mm/migrate.c
> ===================================================================
> --- linux-2.6.git.orig/mm/migrate.c
> +++ linux-2.6.git/mm/migrate.c
> @@ -161,6 +161,8 @@ static int remove_migration_pte(struct p
>
> get_page(new);
> pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
> + if (pte_swp_soft_dirty(*ptep))
> + pte = pte_mksoft_dirty(pte);
> if (is_write_migration_entry(entry))
> pte = pte_mkwrite(pte);
> #ifdef CONFIG_HUGETLB_PAGE
> Index: linux-2.6.git/mm/mprotect.c
> ===================================================================
> --- linux-2.6.git.orig/mm/mprotect.c
> +++ linux-2.6.git/mm/mprotect.c
> @@ -94,13 +94,16 @@ static unsigned long change_pte_range(st
> swp_entry_t entry = pte_to_swp_entry(oldpte);
>
> if (is_write_migration_entry(entry)) {
> + pte_t newpte;
> /*
> * A protection check is difficult so
> * just be safe and disable write
> */
> make_migration_entry_read(&entry);
> - set_pte_at(mm, addr, pte,
> - swp_entry_to_pte(entry));
> + newpte = swp_entry_to_pte(entry);
> + if (pte_swp_soft_dirty(oldpte))
> + newpte = pte_swp_mksoft_dirty(newpte);
> + set_pte_at(mm, addr, pte, newpte);
> }
> pages++;
> }
>
> --
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