Re: [PATCH v4 18/25] gup: Don't allow FOLL_LONGTERM pinning of FS DAX pages

[David Hildenbrand]

On 17.12.24 06:13, Alistair Popple wrote:
> Longterm pinning of FS DAX pages should already be disallowed by
> various pXX_devmap checks. However a future change will cause these
> checks to be invalid for FS DAX pages so make
> folio_is_longterm_pinnable() return false for FS DAX pages.

Nit: I'd consistently use "mm/gup:" as prefix for GUP-related patches. 
(similarly, mm/huge_memory and mm/rmap in the other patches)

> Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
> Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
> ---
>   include/linux/mm.h | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index f267b06..01edca9 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2078,6 +2078,10 @@ static inline bool folio_is_longterm_pinnable(struct folio *folio)
>   	if (folio_is_device_coherent(folio))
>   		return false;
>   
> +	/* DAX must also always allow eviction. */
> +	if (folio_is_fsdax(folio))
> +		return false;
> +
>   	/* Otherwise, non-movable zone folios can be pinned. */
>   	return !folio_is_zone_movable(folio);
>   

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers,

David / dhildenb