Re: [PATCHv2 1/5] mm/page_vma_mapped: Track if the page is mapped across page table boundary

[Shakeel Butt]

On Fri, Sep 19, 2025 at 01:40:32PM +0100, Kiryl Shutsemau wrote:
> From: Kiryl Shutsemau <kas@xxxxxxxxxx>
> 
> Add a PVMW_PGTABLE_CROSSSED flag that page_vma_mapped_walk() will set if
> the page is mapped across page table boundary. Unlike other PVMW_*
> flags, this one is result of page_vma_mapped_walk() and not set by the
> caller.
> 
> folio_referenced_one() will use it detect if it safe to mlock the folio.
> 
> Signed-off-by: Kiryl Shutsemau <kas@xxxxxxxxxx>

Reviewed-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>

> ---
>  include/linux/rmap.h | 5 +++++
>  mm/page_vma_mapped.c | 1 +
>  2 files changed, 6 insertions(+)
> 
> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
> index 6cd020eea37a..04797cea3205 100644
> --- a/include/linux/rmap.h
> +++ b/include/linux/rmap.h
> @@ -928,6 +928,11 @@ struct page *make_device_exclusive(struct mm_struct *mm, unsigned long addr,
>  /* Look for migration entries rather than present PTEs */
>  #define PVMW_MIGRATION		(1 << 1)
>  
> +/* Result flags */
> +
> +/* The page is mapped across page boundary */

I think you meant "page table boundary" in above comment.

> +#define PVMW_PGTABLE_CROSSSED	(1 << 16)
> +
>  struct page_vma_mapped_walk {
>  	unsigned long pfn;
>  	unsigned long nr_pages;
> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> index e981a1a292d2..a184b88743c3 100644
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -309,6 +309,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>  				}
>  				pte_unmap(pvmw->pte);
>  				pvmw->pte = NULL;
> +				pvmw->flags |= PVMW_PGTABLE_CROSSSED;
>  				goto restart;
>  			}
>  			pvmw->pte++;
> -- 
> 2.50.1
>