linux-kernel - Re: [PATCH RFC 01/10] mm/hugetlb: Let vma_offset

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Date:   Thu, 3 Nov 2022 08:25:49 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        James Houghton <jthoughton@...gle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        David Hildenbrand <david@...hat.com>,
        Muchun Song <songmuchun@...edance.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH RFC 01/10] mm/hugetlb: Let vma_offset_start() to return
 start

On 10/30/22 17:29, Peter Xu wrote:
> Even though vma_offset_start() is named like that, it's not returning "the
> start address of the range" but rather the offset we should use to offset
> the vma->vm_start address.
> 
> Make it return the real value of the start vaddr, and it also helps for all
> the callers because whenever the retval is used, it'll be ultimately added
> into the vma->vm_start anyway, so it's better.
> 
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>  fs/hugetlbfs/inode.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)

Thanks, nice cleanup/simplification.

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
-- 
Mike Kravetz

> 
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 3ee84604e36d..ac3a69fe29c3 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -412,10 +412,12 @@ static bool hugetlb_vma_maps_page(struct vm_area_struct *vma,
>   */
>  static unsigned long vma_offset_start(struct vm_area_struct *vma, pgoff_t start)
>  {
> +	unsigned long offset = 0;
> +
>  	if (vma->vm_pgoff < start)
> -		return (start - vma->vm_pgoff) << PAGE_SHIFT;
> -	else
> -		return 0;
> +		offset = (start - vma->vm_pgoff) << PAGE_SHIFT;
> +
> +	return vma->vm_start + offset;
>  }
>  
>  static unsigned long vma_offset_end(struct vm_area_struct *vma, pgoff_t end)
> @@ -457,7 +459,7 @@ static void hugetlb_unmap_file_folio(struct hstate *h,
>  		v_start = vma_offset_start(vma, start);
>  		v_end = vma_offset_end(vma, end);
>  
> -		if (!hugetlb_vma_maps_page(vma, vma->vm_start + v_start, page))
> +		if (!hugetlb_vma_maps_page(vma, v_start, page))
>  			continue;
>  
>  		if (!hugetlb_vma_trylock_write(vma)) {
> @@ -473,8 +475,8 @@ static void hugetlb_unmap_file_folio(struct hstate *h,
>  			break;
>  		}
>  
> -		unmap_hugepage_range(vma, vma->vm_start + v_start, v_end,
> -				NULL, ZAP_FLAG_DROP_MARKER);
> +		unmap_hugepage_range(vma, v_start, v_end, NULL,
> +				     ZAP_FLAG_DROP_MARKER);
>  		hugetlb_vma_unlock_write(vma);
>  	}
>  
> @@ -507,10 +509,9 @@ static void hugetlb_unmap_file_folio(struct hstate *h,
>  		 */
>  		v_start = vma_offset_start(vma, start);
>  		v_end = vma_offset_end(vma, end);
> -		if (hugetlb_vma_maps_page(vma, vma->vm_start + v_start, page))
> -			unmap_hugepage_range(vma, vma->vm_start + v_start,
> -						v_end, NULL,
> -						ZAP_FLAG_DROP_MARKER);
> +		if (hugetlb_vma_maps_page(vma, v_start, page))
> +			unmap_hugepage_range(vma, v_start, v_end, NULL,
> +					     ZAP_FLAG_DROP_MARKER);
>  
>  		kref_put(&vma_lock->refs, hugetlb_vma_lock_release);
>  		hugetlb_vma_unlock_write(vma);
> @@ -540,8 +541,7 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end,
>  		v_start = vma_offset_start(vma, start);
>  		v_end = vma_offset_end(vma, end);
>  
> -		unmap_hugepage_range(vma, vma->vm_start + v_start, v_end,
> -				     NULL, zap_flags);
> +		unmap_hugepage_range(vma, v_start, v_end, NULL, zap_flags);
>  
>  		/*
>  		 * Note that vma lock only exists for shared/non-private
> -- 
> 2.37.3
>