Re: [PATCH 0/4] various improvements to the GUP interface

[Arnd Bergmann]

On Sun, Oct 1, 2023, at 12:00, Lorenzo Stoakes wrote:
> A series of fixes to simplify and improve the GUP interface with an eye to
> providing groundwork to future improvements:-
>
> * __access_remote_vm() and access_remote_vm() are functionally identical,
>   so make the former static such that in future we can potentially change
>   the external-facing implementation details of this function.
>
> * Extend is_valid_gup_args() to cover the missing FOLL_TOUCH case, and
>   simplify things by defining INTERNAL_GUP_FLAGS to check against.
>
> * Adjust __get_user_pages_locked() to explicitly treat a failure to pin any
>   pages as an error in all circumstances other than FOLL_NOWAIT being
>   specified, bringing it in line with the nommu implementation of this
>   function.
>
> * (With many thanks to Arnd who suggested this in the first instance)
>   Update get_user_page_vma_remote() to explicitly only return a page or an
>   error, simplifying the interface and avoiding the questionable
>   IS_ERR_OR_NULL() pattern.
>
> Lorenzo Stoakes (4):
>   mm: make __access_remote_vm() static
>   mm/gup: explicitly define and check internal GUP flags, disallow
>     FOLL_TOUCH
>   mm/gup: make failure to pin an error if FOLL_NOWAIT not specified
>   mm/gup: adapt get_user_page_vma_remote() to never return NULL

I don't normally review mm patches, but I had a look since it was
started by my earlier feedback. It all looks good to me, very nice
cleanup!

Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>