linux-kernel - Re: [PATCH v2 05/16] mm/huge_memory: use helper touch_pmd in huge_pmd_set

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Message-ID: <YrsXygOe4dLaVn2t@FVFYT0MHHV2J.googleapis.com>
Date:   Tue, 28 Jun 2022 23:01:30 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     akpm@...ux-foundation.org, shy828301@...il.com,
        willy@...radead.org, zokeefe@...gle.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 05/16] mm/huge_memory: use helper touch_pmd in
 huge_pmd_set_accessed

On Tue, Jun 28, 2022 at 09:28:24PM +0800, Miaohe Lin wrote:
> Use helper touch_pmd to set pmd accessed to simplify the code and improve
> the readability. No functional change intended.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  mm/huge_memory.c | 18 +++++-------------
>  1 file changed, 5 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index d55d5efa06c8..d9fe9b034783 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1120,15 +1120,15 @@ EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot);
>  #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
>  
>  static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
> -		pmd_t *pmd, int flags)
> +		      pmd_t *pmd, bool write)

The same as comments as mentioned in previous thread. E.g. follow_devmap_pmd()
and follow_trans_huge_pmd().

Thanks.

>  {
>  	pmd_t _pmd;
>  
>  	_pmd = pmd_mkyoung(*pmd);
> -	if (flags & FOLL_WRITE)
> +	if (write)
>  		_pmd = pmd_mkdirty(_pmd);
>  	if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
> -				pmd, _pmd, flags & FOLL_WRITE))
> +				  pmd, _pmd, write))
>  		update_mmu_cache_pmd(vma, addr, pmd);
>  }
>  
> @@ -1398,21 +1398,13 @@ void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
>  
>  void huge_pmd_set_accessed(struct vm_fault *vmf)
>  {
> -	pmd_t entry;
> -	unsigned long haddr;
>  	bool write = vmf->flags & FAULT_FLAG_WRITE;
> -	pmd_t orig_pmd = vmf->orig_pmd;
>  
>  	vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
> -	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
> +	if (unlikely(!pmd_same(*vmf->pmd, vmf->orig_pmd)))
>  		goto unlock;
>  
> -	entry = pmd_mkyoung(orig_pmd);
> -	if (write)
> -		entry = pmd_mkdirty(entry);
> -	haddr = vmf->address & HPAGE_PMD_MASK;
> -	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
> -		update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
> +	touch_pmd(vmf->vma, vmf->address, vmf->pmd, write);
>  
>  unlock:
>  	spin_unlock(vmf->ptl);
> -- 
> 2.23.0
> 
>