Re: [PATCH 1/5] mm: Add vma_alloc_zeroed_movable_folio()

[Mike Rapoport <rppt@kernel.org>]

On Mon, Jan 16, 2023 at 07:18:09PM +0000, Matthew Wilcox (Oracle) wrote:
> Replace alloc_zeroed_user_highpage_movable().  The main difference is
> returning a folio containing a single page instead of returning the
> page, but take the opportunity to rename the function to match other
> allocation functions a little better and rewrite the documentation
> to place more emphasis on the zeroing rather than the highmem aspect.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  arch/alpha/include/asm/page.h   |  5 ++---
>  arch/arm64/include/asm/page.h   |  4 ++--
>  arch/arm64/mm/fault.c           |  4 ++--
>  arch/ia64/include/asm/page.h    | 14 ++++++--------
>  arch/m68k/include/asm/page_no.h |  5 ++---
>  arch/s390/include/asm/page.h    |  5 ++---
>  arch/x86/include/asm/page.h     |  5 ++---
>  include/linux/highmem.h         | 33 ++++++++++++++++-----------------
>  mm/memory.c                     | 16 ++++++++++------
>  9 files changed, 44 insertions(+), 47 deletions(-)

...

> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> index 56703082f803..9fa462561e05 100644
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
> @@ -208,31 +208,30 @@ static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
>  }
>  #endif
>  
> -#ifndef __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE
> +#ifndef vma_alloc_zeroed_movable_folio
>  /**
> - * alloc_zeroed_user_highpage_movable - Allocate a zeroed HIGHMEM page for a VMA that the caller knows can move
> - * @vma: The VMA the page is to be allocated for
> - * @vaddr: The virtual address the page will be inserted into
> + * vma_alloc_zeroed_movable_folio - Allocate a zeroed page for a VMA.
> + * @vma: The VMA the page is to be allocated for.
> + * @vaddr: The virtual address the page will be inserted into.
>   *
> - * Returns: The allocated and zeroed HIGHMEM page
> + * This function will allocate a page suitable for inserting into this
> + * VMA at this virtual address.  It may be allocated from highmem or
> + * the movable zone.  An architecture may provide its own implementation.
>   *
> - * This function will allocate a page for a VMA that the caller knows will
> - * be able to migrate in the future using move_pages() or reclaimed
> - *
> - * An architecture may override this function by defining
> - * __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE and providing their own
> - * implementation.
> + * Return: A folio containing one allocated and zeroed page or NULL if
> + * we are out of memory.
>   */
> -static inline struct page *
> -alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
> +static inline
> +struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma,
>  				   unsigned long vaddr)
>  {
> -	struct page *page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
> +	struct folio *folio;
>  
> -	if (page)
> -		clear_user_highpage(page, vaddr);
> +	folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr, false);

Add __GFP_ZERO and simply return vma_alloc_folio(...)?

> +	if (folio)
> +		clear_user_highpage(&folio->page, vaddr);
>  
> -	return page;
> +	return folio;
>  }
>  #endif

-- 
Sincerely yours,
Mike.