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

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:

quoted

On 11/08/2016 05:01 AM, Naoya Horiguchi wrote:

quoted

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

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