linux-kernel - Re: [PATCH] mm/smaps: Use vma->vm_pgoff directly when counting partial swap

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Date:   Fri, 17 Sep 2021 00:17:32 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH] mm/smaps: Use vma->vm_pgoff directly when counting
 partial swap

On 9/16/21 11:58 PM, Peter Xu wrote:
> linear_page_index(vma, vma->vm_start) of a shmem vma is exactly vm_pgoff.

Could you use "vma->vm_pgoff + vma_pages(vma)" instead of the other
linear_page_index() then?

But now I wonder, is smaps_pte_hole() broken? it calls
shmem_partial_swap_usage with addresses, not pgoffs?

> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>  mm/shmem.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 96ccf6e941aa..2aef5b8e17c9 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -856,8 +856,7 @@ unsigned long shmem_swap_usage(struct vm_area_struct *vma)
>  		return swapped << PAGE_SHIFT;
>  
>  	/* Here comes the more involved part */
> -	return shmem_partial_swap_usage(mapping,
> -			linear_page_index(vma, vma->vm_start),
> +	return shmem_partial_swap_usage(mapping, vma->vm_pgoff,
>  			linear_page_index(vma, vma->vm_end));
>  }
>  
>