Re: [PATCH v16 19/22] mm/lru: introduce the relock_page_lruvec function

Alex Shi
2020-07-18T14:01:40Z

在 2020/7/18 上午6:03, Alexander Duyck 写道:
>> index 129c532357a4..9fb906fbaed5 100644
>> --- a/mm/swap.c
>> +++ b/mm/swap.c
>> @@ -209,19 +209,12 @@ static void pagevec_lru_move_fn(struct pagevec *pvec,
>>
>> for (i = 0; i < pagevec_count(pvec); i++) {
>> struct page *page = pvec->pages[i];
>> - struct lruvec *new_lruvec;
>> -
>> - new_lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
>> - if (lruvec != new_lruvec) {
>> - if (lruvec)
>> - unlock_page_lruvec_irqrestore(lruvec, flags);
>> - lruvec = lock_page_lruvec_irqsave(page, &flags);
>> - }
>>
>> /* block memcg migration during page moving between lru */
>> if (!TestClearPageLRU(page))
>> continue;
>>
>> + lruvec = relock_page_lruvec_irqsave(page, lruvec, &flags);
>> (*move_fn)(page, lruvec);
>>
>> SetPageLRU(page);
> So looking at this I realize that patch 18 probably should have
> ordered this the same way with the TestClearPageLRU happening before
> you fetched the new_lruvec. Otherwise I think you are potentially
> exposed to the original issue you were fixing the the previous patch
> that added the call to TestClearPageLRU.

Good catch. It's better to be aligned in next version.
Thanks!

>
>> @@ -866,17 +859,12 @@ void release_pages(struct page **pages, int nr)
>> }
>>
>> if (PageLRU(page)) {
>> - struct lruvec *new_lruvec;
>> -
>> - new_lruvec = mem_cgroup_page_lruvec(page,
>> - page_pgdat(page));
>> - if (new_lruvec != lruvec) {
>> - if (lruvec)
>> - unlock_page_lruvec_irqrestore(lruvec,
>> - flags);
>> + struct lruvec *pre_lruvec = lruvec;
>> +
>> + lruvec = relock_page_lruvec_irqsave(page, lruvec,
>> + &flags);
>> + if (pre_lruvec != lruvec)
> So this doesn't really read right. I suppose "pre_lruvec" should
> probably be "prev_lruvec" since I assume you mean "previous" not
> "before".

yes, it's previous, I will rename it.
Thanks
Alex
>