Re: [PATCH v2 00/12] mm: page migration enhancement for thp

[Hillf Danton]

On February 01, 2017 3:54 AM Zi Yan wrote: 
> 
> I am also doing some tests on THP migration and discover that there are
> some corner cases not handled in this patchset.
> 
> For example, in handle_mm_fault, without taking pmd_lock, the kernel may
> see pmd_none(*pmd) during THP migrations, which leads to
> handle_pte_fault or even deeper in the code path. At that moment,
> pmd_trans_unstable() will treat a pmd_migration_entry as pmd_bad and
> clear it. This leads to application crashing and page table leaks, since
> a deposited PTE page is not released when the application crashes.
> 
> Even after I add is_pmd_migration_entry() into pmd_trans_unstable(), I
> still see application data corruptions.
> 
> I hope someone can shed some light on how to debug this. Should I also
> look into pmd_trans_huge() call sites where pmd_migration_entry should
> be handled differently?
> 
Hm ... seems it helps more if you post your current works as RFC on
top of the mm tree, and the relevant tests as well.

Hillf
> 
> Anshuman Khandual wrote:
> > On 11/08/2016 05:01 AM, Naoya Horiguchi wrote:
> >> Hi everyone,
> >>
> >> I've updated thp migration patches for v4.9-rc2-mmotm-2016-10-27-18-27
> >> with feedbacks for ver.1.
> >
> > Hello Noaya,
> >
> > I have been working with Zi Yan on the parallel huge page migration series
> > (https://lkml.org/lkml/2016/11/22/457) and planning to post them on top of
> > this THP migration enhancement series. Hence we were wondering if you have
> > plans to post a new version of this series in near future ?
> >
> > Regards
> > Anshuman
> >
> 
> --
> Best Regards,
> Yan Zi