linux-kernel - Re: [PATCH v2 01/10] mm/hugetlb: Let vma_offset

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Date:   Wed, 7 Dec 2022 13:21:12 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Peter Xu <peterx@...hat.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
CC:     Muchun Song <songmuchun@...edance.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        James Houghton <jthoughton@...gle.com>,
        Jann Horn <jannh@...gle.com>, Rik van Riel <riel@...riel.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Mike Kravetz" <mike.kravetz@...cle.com>,
        David Hildenbrand <david@...hat.com>,
        Nadav Amit <nadav.amit@...il.com>
Subject: Re: [PATCH v2 01/10] mm/hugetlb: Let vma_offset_start() to return
 start

On 12/7/22 12:30, 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.
> 
> Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
> Reviewed-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>   fs/hugetlbfs/inode.c | 24 ++++++++++++------------
>   1 file changed, 12 insertions(+), 12 deletions(-)

This is a nice refinement.

Reviewed-by: John Hubbard <jhubbard@...dia.com>


thanks,
-- 
John Hubbard
NVIDIA

> 
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 790d2727141a..fdb16246f46e 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