Re: [PATCH 3.11 54/66] mm: migration: do not lose soft dirty bit if page is in migration state

William Dauchy
2013-11-27T11:38:34Z

Hi Greg,

I was wondering if v3.10.x stable branch was also concerned by this
patch since I did not found it in this later branch.
Maybe too hard to backport? (I saw that it requires new functions like
pte_swp_soft_dirty which is not present in v3.10.x)
Maybe it was planned in the future?

Thanks,

On Fri, Nov 1, 2013 at 11:07 PM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> 3.11-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Cyrill Gorcunov <gorcunov@gmail.com>
>
> commit c3d16e16522fe3fe8759735850a0676da18f4b1d upstream.
>
> If page migration is turned on in config and the page is migrating, we
> may lose the soft dirty bit. If fork and mprotect are called on
> migrating pages (once migration is complete) pages do not obtain the
> soft dirty bit in the correspond pte entries. Fix it adding an
> appropriate test on swap entries.
>
> Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
> Cc: Pavel Emelyanov <xemul@parallels.com>
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: Matt Mackall <mpm@selenic.com>
> Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: Mel Gorman <mel@csn.ul.ie>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> ---
> mm/memory.c | 2 ++
> mm/migrate.c | 2 ++
> mm/mprotect.c | 7 +++++--
> 3 files changed, 9 insertions(+), 2 deletions(-)
>
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -861,6 +861,8 @@ 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);
> }
> }
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -157,6 +157,8 @@ 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
> --- a/mm/mprotect.c
> +++ b/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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--
William