Re: [RFC PATCH 4/6] mm: Implement folio_add_new_anon_rmap_range()

[Yin Fengwei <fengwei.yin@intel.com>]

On 3/17/23 18:58, Ryan Roberts wrote:
> Like folio_add_new_anon_rmap() but batch-rmaps all the pages belonging
> to a folio, for effciency savings.
> 
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
>   include/linux/rmap.h |  2 ++
>   mm/rmap.c            | 43 +++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 45 insertions(+)
> 
> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
> index b87d01660412..d1d731650ce8 100644
> --- a/include/linux/rmap.h
> +++ b/include/linux/rmap.h
> @@ -196,6 +196,8 @@ void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
>   		unsigned long address);
>   void folio_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
>   		unsigned long address);
> +void folio_add_new_anon_rmap_range(struct folio *folio,
> +		struct vm_area_struct *vma, unsigned long address);
>   void page_add_file_rmap(struct page *, struct vm_area_struct *,
>   		bool compound);
>   void page_remove_rmap(struct page *, struct vm_area_struct *,
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 8632e02661ac..05a0c0a700e7 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1302,6 +1302,49 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
>   	__page_set_anon_rmap(folio, &folio->page, vma, address, 1);
>   }
> 
> +/**
> + * folio_add_new_anon_rmap_range - Add mapping to a new anonymous potentially
> + * large but definitely non-THP folio.
> + * @folio:      The folio to add the mapping to.
> + * @vma:        the vm area in which the mapping is added
> + * @address:    the user virtual address of the first page in the folio
> + *
> + * Like folio_add_new_anon_rmap() but must only be called for new *non-THP*
> + * folios. Like folio_add_new_anon_rmap(), the inc-and-test is bypassed and the
> + * folio does not have to be locked. All pages in the folio are individually
> + * accounted.
> + *
> + * As the folio is new, it's assumed to be mapped exclusively by a single
> + * process.
> + */
> +void folio_add_new_anon_rmap_range(struct folio *folio,
> +			struct vm_area_struct *vma, unsigned long address)
> +{
> +	int i;
> +	int nr = folio_nr_pages(folio);
> +	struct page *page = &folio->page;
> +
> +	VM_BUG_ON_VMA(address < vma->vm_start ||
> +		      address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
> +	__folio_set_swapbacked(folio);
> +
> +	if (folio_test_large(folio)) {
> +		/* increment count (starts at 0) */
> +		atomic_set(&folio->_nr_pages_mapped, nr);
> +	}
> +
> +	for (i = 0; i < nr; i++) {
> +		/* increment count (starts at -1) */
> +		atomic_set(&page->_mapcount, 0);
> +		__page_set_anon_rmap(folio, page, vma, address, 1);
My bad. You did call it here.

Regards
Yin, Fengwei

> +		page++;
> +		address += PAGE_SIZE;
> +	}
> +
> +	__lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
> +
> +}
> +
>   /**
>    * page_add_file_rmap - add pte mapping to a file page
>    * @page:	the page to add the mapping to
> --
> 2.25.1
>