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SubjectRe: [-mm][PATCH 8/10] fix shmem page migration incorrectness on memcgroup
On Fri, Jun 27, 2008 at 2:41 PM, KOSAKI Motohiro
<kosaki.motohiro@jp.fujitsu.com> wrote:
>> > mem_cgroup_uncharge() against old page is done after radix-tree-replacement.
>> > And there were special handling to ingore swap-cache page. But, shmem can
>> > be swap-cache and file-cache at the same time. Chekcing PageSwapCache() is
>> > not correct here. Check PageAnon() instead.
>>
>> When/How shmem can be both swap-cache and file-cache ?
>> I can't understand that situation.
>
> Hi
>
> see,
>
> shmem_writepage()
> -> add_to_swap_cache()
> -> SetPageSwapCache()
>
>
> BTW: his file-cache mean !Anon, not mean !SwapBacked.

Hi KOSAKI-san.
Thanks for explaining.

In the migrate_page_move_mapping, the page was already locked in unmap_and_move.
Also, we have a lock for that page for calling shmem_writepage.

So I think race problem between shmem_writepage and
migrate_page_move_mapping don't occur.
But I am not sure I am right.

If I am wrong, could you tell me when race problem happen ? :)


>
>



--
Kinds regards,
MinChan Kim


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