Re: [PATCH 2/4] mm: teach release_pages() to take an array of encoded page pointers too

[David Hildenbrand]

On 09.11.22 21:30, Linus Torvalds wrote:
> release_pages() already could take either an array of page pointers, or
> an array of folio pointers.  Expand it to also accept an array of
> encoded page pointers, which is what both the existing mlock() use and
> the upcoming mmu_gather use of encoded page pointers wants.
>
> Note that release_pages() won't actually use, or react to, any extra
> encoded bits.  Instead, this is very much a case of "I have walked the
> array of encoded pages and done everything the extra bits tell me to do,
> now release it all".
>
> Also, while the "either page or folio pointers" dual use was handled
> with a cast of the pointer in "release_folios()", this takes a slightly
> different approach and uses the "transparent union" attribute to
> describe the set of arguments to the function:
>
>    https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html
>
> which has been supported by gcc forever, but the kernel hasn't used
> before.
>
> That allows us to avoid using various wrappers with casts, and just use
> the same function regardless of use.
>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> ---

Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>

--
Thanks,

David / dhildenb