linux-kernel - Re: [PATCH 02/11] mm: page_vma_mapped

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Message-ID: <YMIe/mn9TKpK3n4K@t490s>
Date:   Thu, 10 Jun 2021 10:17:34 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>,
        Wang Yugui <wangyugui@...-tech.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>, Zi Yan <ziy@...dia.com>,
        Will Deacon <will@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/11] mm: page_vma_mapped_walk(): settle PageHuge on
 entry

On Wed, Jun 09, 2021 at 11:36:36PM -0700, Hugh Dickins wrote:
> page_vma_mapped_walk() cleanup: get the hugetlbfs PageHuge case
> out of the way at the start, so no need to worry about it later.
> 
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> Cc: <stable@...r.kernel.org>
> ---
>  mm/page_vma_mapped.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> index a6dbf714ca15..7c0504641fb8 100644
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -153,10 +153,11 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>  	if (pvmw->pmd && !pvmw->pte)
>  		return not_found(pvmw);
>  
> -	if (pvmw->pte)
> -		goto next_pte;
> -
>  	if (unlikely(PageHuge(page))) {
> +		/* The only possible mapping was handled on last iteration */
> +		if (pvmw->pte)
> +			return not_found(pvmw);
> +
>  		/* when pud is not present, pte will be NULL */
>  		pvmw->pte = huge_pte_offset(mm, pvmw->address, page_size(page));
>  		if (!pvmw->pte)

Would it be even nicer to move the initial check to be after PageHuge() too?

	if (pvmw->pmd && !pvmw->pte)
		return not_found(pvmw);

It looks already better, so no strong opinion.

Reviewed-by: Peter Xu <peterx@...hat.com>

Thanks,

-- 
Peter Xu