linux-kernel - Re: [PATCH 1/2] mm/page_vma_mapped: use PMD

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Date:   Thu, 28 Nov 2019 11:32:55 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Wei Yang <richardw.yang@...ux.intel.com>
Cc:     akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm/page_vma_mapped: use PMD_SIZE instead of
 calculating it

On Thu, Nov 28, 2019 at 09:03:20AM +0800, Wei Yang wrote:
> At this point, we are sure page is PageTransHuge, which means
> hpage_nr_pages is HPAGE_PMD_NR.
> 
> This is safe to use PMD_SIZE instead of calculating it.
> 
> Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
> ---
>  mm/page_vma_mapped.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> index eff4b4520c8d..76e03650a3ab 100644
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -223,7 +223,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>  			if (pvmw->address >= pvmw->vma->vm_end ||
>  			    pvmw->address >=
>  					__vma_address(pvmw->page, pvmw->vma) +
> -					hpage_nr_pages(pvmw->page) * PAGE_SIZE)
> +					PMD_SIZE)
>  				return not_found(pvmw);
>  			/* Did we cross page table boundary? */
>  			if (pvmw->address % PMD_SIZE == 0) {

It is dubious cleanup. Maybe page_size(pvmw->page) instead? It will not
break if we ever get PUD THP pages.

-- 
 Kirill A. Shutemov