On 2017/5/24 19:52, Vlastimil Babka wrote:
> On 05/24/2017 01:38 PM, Xishi Qiu wrote:
>>>
>>> Race condition with what? Who else would isolate our pages?
>>>
>>
>> Hi Vlastimil,
>>
>> I find the root cause, if the page was not cached on the current cpu,
>> lru_add_drain() will not push it to LRU. So we should handle fail
>> case in mlock_vma_page().
>
> Yeah that would explain it.
>
>> follow_page_pte()
>> ...
>> if (page->mapping && trylock_page(page)) {
>> lru_add_drain(); /* push cached pages to LRU */
>> /*
>> * Because we lock page here, and migration is
>> * blocked by the pte's page reference, and we
>> * know the page is still mapped, we don't even
>> * need to check for file-cache page truncation.
>> */
>> mlock_vma_page(page);
>> unlock_page(page);
>> }
>> ...
>>
>> I think we should add yisheng's patch, also we should add the following change.
>> I think it is better than use lru_add_drain_all().
>
> I agree about yisheng's fix (but v2 didn't address my comments). I don't
> think we should add the hunk below, as that deviates from the rest of
> the design.
Hi Vlastimil,
The rest of the design is that mlock should always success here, right?
If we don't handle the fail case, the page will be in anon/file lru list
later when call __pagevec_lru_add(), but NR_MLOCK increased,
this is wrong, right?
Thanks,
Xishi Qiu
>
> Thanks,
> Vlastimil
>
>> diff --git a/mm/mlock.c b/mm/mlock.c
>> index 3d3ee6c..ca2aeb9 100644
>> --- a/mm/mlock.c
>> +++ b/mm/mlock.c
>> @@ -88,6 +88,11 @@ void mlock_vma_page(struct page *page)
>> count_vm_event(UNEVICTABLE_PGMLOCKED);
>> if (!isolate_lru_page(page))
>> putback_lru_page(page);
>> + else {
>> + ClearPageMlocked(page);
>> + mod_zone_page_state(page_zone(page), NR_MLOCK,
>> + -hpage_nr_pages(page));
>> + }
>> }
>> }
>>
>> Thanks,
>> Xishi Qiu
>>
>
>
> .
>
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