Re: [PATCH -mm] mm, pagemap: Fix soft dirty marking for PMD migration entry

[Huang\, Ying]

Zi Yan <zi.yan@xxxxxxxxxxxxxx> writes:

> Huang, Ying wrote:
>> "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> writes:
>> 
>>> On Tue, Oct 17, 2017 at 04:18:18PM +0800, Huang, Ying wrote:
>>>> From: Huang Ying <ying.huang@xxxxxxxxx>
>>>>
>>>> Now, when the page table is walked in the implementation of
>>>> /proc/<pid>/pagemap, pmd_soft_dirty() is used for both the PMD huge
>>>> page map and the PMD migration entries.  That is wrong,
>>>> pmd_swp_soft_dirty() should be used for the PMD migration entries
>>>> instead because the different page table entry flag is used.
>>>>
>>>> Cc: Michal Hocko <mhocko@xxxxxxxx>
>>>> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
>>>> Cc: David Rientjes <rientjes@xxxxxxxxxx>
>>>> Cc: Arnd Bergmann <arnd@xxxxxxxx>
>>>> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
>>>> Cc: "J.r.me Glisse" <jglisse@xxxxxxxxxx>
>>>> Cc: Daniel Colascione <dancol@xxxxxxxxxx>
>>>> Cc: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
>>>> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
>>>> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
>>> What is effect of the misbehaviour? pagemap reports garbage?
>> 
>> Yes.  pagemap may report incorrect soft dirty information for PMD
>> migration entries.
>
> Thanks for fixing it.
>
>> 
>>> Shoudn't it be in stable@? And maybe add Fixes: <sha1>.
>> 
>> Yes.  Will do that in the next version.
>
> PMD migration is merged in 4.14, which is not final yet. Do we need to
> split the patch, so that first hunk(for present PMD entries) goes into
> stable and second hunk(for PMD migration entries) goes into 4.14?

Oh, if so, I think we don't need to back port it to stable kernel.  But
we still need Fixes: tag.

Best Regards,
Huang, Ying