Re: [PATCH 15/16] mm/migration: fix possible do_pages_stat_array racing with memory offline

[Miaohe Lin]

On 2022/3/7 15:42, Huang, Ying wrote:
> Muchun Song <songmuchun@xxxxxxxxxxxxx> writes:
> 
>> On Mon, Mar 7, 2022 at 1:22 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>>>
>>> Miaohe Lin <linmiaohe@xxxxxxxxxx> writes:
>>>
>>>> When follow_page peeks a page, the page could be reclaimed under heavy
>>>> memory pressure
>>>
>>> I don't think that memory pressure and reclaiming will be an issue.
>>
>> I think he means a page first to be reclaimed then to be offline
>> could encounter this issue and reclaiming is a precondition.
> 
> I don't think reclaiming is a precondition.  It seems possible that the
> virtual page is migrated, then the physical page is offlined.
> 

What I indeed mean is a page could first be reclaimed, migrated and so on.
And then be offlined. Sorry for confusing.

Thanks both of you.

> Best Regards,
> Huang, Ying
> 
>> Thanks.
>>
>>>
>>>> and thus be offlined while it's still being used by the
>>>> do_pages_stat_array().
>>>
>>> "offline" seems a possible problem.
> .
>