Re: [PATCH] mm/gup: don't check page lru flag before draining it

[David Hildenbrand]

On 04.06.24 12:48, yangge1116@xxxxxxx wrote:
> From: yangge <yangge1116@xxxxxxx>
>
> If a page is added in pagevec, its ref count increases one, remove
> the page from pagevec decreases one. Page migration requires the
> page is not referenced by others except page mapping. Before
> migrating a page, we should try to drain the page from pagevec in
> case the page is in it, however, folio_test_lru() is not sufficient
> to tell whether the page is in pagevec or not, if the page is in
> pagevec, the migration will fail.
>
> Remove the condition and drain lru once to ensure the page is not
> referenced by pagevec.

What you are saying is that we might have a page on which 
folio_test_lru() succeeds, that was added to one of the cpu_fbatches, 
correct?

Can you describe under which circumstances that happens?

--
Cheers,

David / dhildenb