linux-kernel - Re: [PATCH 04/10] mm/mmap/vma_merge: use the proper vma pointer in case 4

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Message-ID: <3052d4e5-fcb5-479e-8691-b218a31b6243@lucifer.local>
Date:   Wed, 15 Mar 2023 19:54:21 +0000
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        maple-tree@...ts.infradead.org
Subject: Re: [PATCH 04/10] mm/mmap/vma_merge: use the proper vma pointer in
 case 4

On Thu, Mar 09, 2023 at 12:12:52PM +0100, Vlastimil Babka wrote:
> Almost all cases now use the 'next' pointer for the vma following
> the merged area, and the cases diagram shows it as XXXX. Case 4 is
> different as it uses 'mid' and NNNN, so change it for consistency. No
> functional change.
>
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>  mm/mmap.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index c33237b283c9..420d6847c94c 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -851,9 +851,9 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
>   * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
>   *
>   *     AAAA             AAAA                   AAAA
> - *    PPPPPPNNNNNN    PPPPPPNNNNNN       PPPPPPNNNNNN
> + *    PPPPPPNNNNNN    PPPPPPXXXXXX       PPPPPPNNNNNN
>   *    cannot merge    might become       might become
> - *                    PPNNNNNNNNNN       PPPPPPPPPPNN
> + *                    PPXXXXXXXXXX       PPPPPPPPPPNN
>   *    mmap, brk or    case 4 below       case 5 below
>   *    mremap move:
>   *                        AAAA               AAAA
> @@ -972,9 +972,9 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
>  		res = next;
>  		if (prev && addr < prev->vm_end) {	/* case 4 */
>  			vma_end = addr;
> -			adjust = mid;
> +			adjust = next;
>  			adj_next = -(prev->vm_end - addr);
> -			err = dup_anon_vma(mid, prev);
> +			err = dup_anon_vma(next, prev);
>  		} else {
>  			vma = next;			/* case 3 */
>  			vma_start = addr;
> --
> 2.39.2
>

Reviewed-By: Lorenzo Stoakes <lstoakes@...il.com>