Re: [PATCH 09/15] mm/filemap: drop uncached pages when writeback completes

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Sun, Nov 10, 2024 at 08:28:01AM -0700, Jens Axboe wrote:
> If the folio is marked as uncached, drop pages when writeback completes.
> Intended to be used with RWF_UNCACHED, to avoid needing sync writes for
> uncached IO.
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>  mm/filemap.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index bd698340ef24..efd02b047541 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1600,6 +1600,23 @@ int folio_wait_private_2_killable(struct folio *folio)
>  }
>  EXPORT_SYMBOL(folio_wait_private_2_killable);
>  
> +/*
> + * If folio was marked as uncached, then pages should be dropped when writeback
> + * completes. Do that now. If we fail, it's likely because of a big folio -
> + * just reset uncached for that case and latter completions should invalidate.
> + */
> +static void folio_end_uncached(struct folio *folio)
> +{
> +	bool reset = true;
> +
> +	if (folio_trylock(folio)) {
> +		reset = !invalidate_complete_folio2(folio->mapping, folio, 0);
> +		folio_unlock(folio);

The same problem with folio_mapped() here.

> +	}
> +	if (reset)
> +		folio_set_uncached(folio);
> +}
> +
>  /**
>   * folio_end_writeback - End writeback against a folio.
>   * @folio: The folio.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov