Re: [PATCH] mm : fix pte _PAGE_DIRTY bit when fallback migrate page

[Kirill A. Shutemov]

On Tue, Jul 14, 2020 at 11:46:12AM +0200, Vlastimil Babka wrote:
> On 7/13/20 3:57 AM, Robbie Ko wrote:
> > 
> > Vlastimil Babka æ 2020/7/10 äå11:31 åé:
> >> On 7/9/20 4:48 AM, robbieko wrote:
> >>> From: Robbie Ko <robbieko@xxxxxxxxxxxx>
> >>>
> >>> When a migrate page occurs, we first create a migration entry
> >>> to replace the original pte, and then go to fallback_migrate_page
> >>> to execute a writeout if the migratepage is not supported.
> >>>
> >>> In the writeout, we will clear the dirty bit of the page and use
> >>> page_mkclean to clear the dirty bit along with the corresponding pte,
> >>> but page_mkclean does not support migration entry.

I don't follow the scenario.

When we establish migration entries with try_to_unmap(), it transfers
dirty bit from PTE to the page.

-- 
 Kirill A. Shutemov