linux-kernel - Re: [PATCH] arm64/hugetlb: Fix building errors in huge_ptep_clear

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Date:   Fri, 27 May 2022 15:12:50 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>,
        torvalds@...ux-foundation.org
Cc:     catalin.marinas@....com, will@...nel.org,
        akpm@...ux-foundation.org, anshuman.khandual@....com,
        naresh.kamboju@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/hugetlb: Fix building errors in
 huge_ptep_clear_flush()

Hi Baolin,

On 5/27/22 12:51 PM, Baolin Wang wrote:
> Fix below building errors which was caused by commit ae07562909f3
> ("mm: change huge_ptep_clear_flush() to return the original pte")
> interacting with commit fb396bb459c1 ("arm64/hugetlb: Drop TLB flush
> from get_clear_flush()").
> 
> Due to the new get_clear_contig() has dropped TLB flush, we should
> add an explicit TLB flush in huge_ptep_clear_flush() to keep original
> semantics when changing to use new get_clear_contig().
> 
> "
> arch/arm64/mm/hugetlbpage.c: In function ‘huge_ptep_clear_flush’:
> arch/arm64/mm/hugetlbpage.c:515:9: error: implicit declaration of
> function ‘get_clear_flush’; did you mean ‘ptep_clear_flush’?
> [-Werror=implicit-function-declaration]
>    515 |  return get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
>        |         ^~~~~~~~~~~~~~~
>        |         ptep_clear_flush
> "
> 
> Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
> Suggested-by: Catalin Marinas <catalin.marinas@....com>
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Anshuman Khandual <anshuman.khandual@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> ---
>   arch/arm64/mm/hugetlbpage.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 

I ran to the compiling failure either and it would be caused by
commit fb396bb459c1 ("arm64/hugetlb: Drop TLB flush from get_clear_flush()").
It's worthy to have a "Fixes" tag. With those fixed:

Reviewed-by: Gavin Shan <gshan@...hat.com>


> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 0f0c17dfeb9c..e2a5ec9fdc0d 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -507,12 +507,15 @@ pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
>   {
>   	size_t pgsize;
>   	int ncontig;
> +	pte_t orig_pte;
>   
>   	if (!pte_cont(READ_ONCE(*ptep)))
>   		return ptep_clear_flush(vma, addr, ptep);
>   
>   	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
> -	return get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
> +	orig_pte = get_clear_contig(vma->vm_mm, addr, ptep, pgsize, ncontig);
> +	flush_tlb_range(vma, addr, addr + pgsize * ncontig);
> +	return orig_pte;
>   }
>   
>   static int __init hugetlbpage_init(void)
> 

Thanks,
Gavin