linux-kernel - Re: [PATCH v4 2/4] mm: Rename zap_skip_check_mapping() to should_zap

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Date:   Wed, 16 Feb 2022 19:18:03 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Peter Xu <peterx@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        Yang Shi <shy828301@...il.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Alistair Popple <apopple@...dia.com>,
        David Hildenbrand <david@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH v4 2/4] mm: Rename zap_skip_check_mapping() to
 should_zap_page()

On 2/16/22 1:48 AM, Peter Xu wrote:
> The previous name is against the natural way people think.  Invert the meaning

Definitely. 

> and also the return value.  No functional change intended.
> 
> Suggested-by: David Hildenbrand <david@...hat.com>
> Suggested-by: Hugh Dickins <hughd@...gle.com>
> Reviewed-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>  mm/memory.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)

Reviewed-by: John Hubbard <jhubbard@...dia.com>

thanks,
-- 
John Hubbard
NVIDIA

> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 4bfeaca7cbc7..14d8428ff4db 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1326,20 +1326,19 @@ static inline bool should_zap_cows(struct zap_details *details)
>  
>  /*
>   * We set details->zap_mapping when we want to unmap shared but keep private
> - * pages. Return true if skip zapping this page, false otherwise.
> + * pages. Return true if we should zap this page, false otherwise.
>   */
> -static inline bool
> -zap_skip_check_mapping(struct zap_details *details, struct page *page)
> +static inline bool should_zap_page(struct zap_details *details, struct page *page)
>  {
>  	/* If we can make a decision without *page.. */
>  	if (should_zap_cows(details))
> -		return false;
> +		return true;
>  
>  	/* E.g. zero page */
>  	if (!page)
> -		return false;
> +		return true;
>  
> -	return details->zap_mapping != page_rmapping(page);
> +	return details->zap_mapping == page_rmapping(page);
>  }
>  
>  static unsigned long zap_pte_range(struct mmu_gather *tlb,
> @@ -1374,7 +1373,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
>  			struct page *page;
>  
>  			page = vm_normal_page(vma, addr, ptent);
> -			if (unlikely(zap_skip_check_mapping(details, page)))
> +			if (unlikely(!should_zap_page(details, page)))
>  				continue;
>  			ptent = ptep_get_and_clear_full(mm, addr, pte,
>  							tlb->fullmm);
> @@ -1408,7 +1407,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
>  		    is_device_exclusive_entry(entry)) {
>  			struct page *page = pfn_swap_entry_to_page(entry);
>  
> -			if (unlikely(zap_skip_check_mapping(details, page)))
> +			if (unlikely(!should_zap_page(details, page)))
>  				continue;
>  			pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
>  			rss[mm_counter(page)]--;
> @@ -1433,7 +1432,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
>  			struct page *page;
>  
>  			page = pfn_swap_entry_to_page(entry);
> -			if (zap_skip_check_mapping(details, page))
> +			if (!should_zap_page(details, page))
>  				continue;
>  			rss[mm_counter(page)]--;
>  		} else if (is_hwpoison_entry(entry)) {