Re: [PATCH V2 2/2] mm/khugepaged: map dirty/writeback pages failures to EAGAIN

[Dev Jain]

On 20/11/25 1:47 pm, Garg, Shivank wrote:
> On 11/20/2025 1:33 PM, Dev Jain wrote:
> > On 20/11/25 12:20 pm, Shivank Garg wrote:
> > SCAN_PAGE_NOT_CLEAN is confusing - NOT_CLEAN literally means dirty, so why not SCAN_PAGE_DIRTY?
> > Or SCAN_PAGE_DIRTY_OR_UNDER_WRITEBACK? Since folio_test_writeback() is true as a result of
> > the folio being dirty, maybe just SCAN_PAGE_DIRTY can do.
> >
> > Reviewed-by: Dev Jain <dev.jain@xxxxxxx>
> Thanks for the review.
>
> I chose not to use SCAN_PAGE_DIRTY because dirty and writeback have different meanings[1]:
>
>      Dirty: Memory that is waiting to be written back to disk
> Writeback: Memory that is actively being written back to disk
>
> [1] https://www.kernel.org/doc/Documentation/filesystems/proc.txt
>
> IIUC, a page under writeback is no longer dirty, so using SCAN_PAGE_DIRTY would be misleading
> for pages in the writeback state.
>
> I considered SCAN_PAGE_DIRTY_OR_WRITEBACK initially but felt it was too long.
>
> SCAN_PAGE_NOT_CLEAN covers both states that indicate the page is not in a clean/stable
> state suitable for collapse.
>
> [1] https://www.kernel.org/doc/Documentation/filesystems/proc.txt

Alright, makes sense.

> Thanks,
> Shivank