linux-kernel - Re: [PATCH] mm/hmm: fix unused variable warning in hmm_vma_walk

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Date:   Wed, 6 Mar 2019 11:08:48 -0500
From:   Jerome Glisse <jglisse@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ralph Campbell <rcampbell@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/hmm: fix unused variable warning in hmm_vma_walk_pud

On Wed, Mar 06, 2019 at 12:00:55PM +0100, Arnd Bergmann wrote:
> Without CONFIG_HUGETLB_PAGE, the 'vma' variable is never referenced
> on x86, so we get this warning:
> 
> mm/hmm.c: In function 'hmm_vma_walk_pud':
> mm/hmm.c:764:25: error: unused variable 'vma' [-Werror=unused-variable]
> 
> Remove the local variable by open-coding walk-vma in the only
> place it is used.
> 
> Reported-by: John Hubbard <jhubbard@...dia.com>
> Suggested-by: John Hubbard <jhubbard@...dia.com>
> Fixes: 1bed8a07a556 ("mm/hmm: allow to mirror vma of a file on a DAX backed filesystem")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Jérôme Glisse <jglisse@...hat.com>

> ---
> Andrew, you already took a similar patch from me for a different
> warning in the same file. Feel free to fold both patches into
> one if you haven't already forwarded the first patch, or leave
> them separate. Note that the warnings were introduced by different
> patches from the same series originally.
> ---
>  mm/hmm.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index c4beb1628cad..c1cbe82d12b5 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -761,7 +761,6 @@ static int hmm_vma_walk_pud(pud_t *pudp,
>  {
>  	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>  	struct hmm_range *range = hmm_vma_walk->range;
> -	struct vm_area_struct *vma = walk->vma;
>  	unsigned long addr = start, next;
>  	pmd_t *pmdp;
>  	pud_t pud;
> @@ -807,7 +806,7 @@ static int hmm_vma_walk_pud(pud_t *pudp,
>  		return 0;
>  	}
>  
> -	split_huge_pud(vma, pudp, addr);
> +	split_huge_pud(walk->vma, pudp, addr);
>  	if (pud_none(*pudp))
>  		goto again;
>  
> -- 
> 2.20.0
>