linux-kernel - Re: [PATCH v3 15/16] mm: eliminate further swapops predicates

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Message-ID: <2a1c9796-c55a-4a4d-99d2-3095fdec6ec0@suse.cz>
Date: Thu, 27 Nov 2025 18:42:47 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>
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Subject: Re: [PATCH v3 15/16] mm: eliminate further swapops predicates

On 11/10/25 23:21, Lorenzo Stoakes wrote:
> Having converted so much of the code base to software leaf entries, we can
> mop up some remaining cases.
> 
> We replace is_pfn_swap_entry(), pfn_swap_entry_to_page(),
> is_writable_device_private_entry(), is_device_exclusive_entry(),
> is_migration_entry(), is_writable_migration_entry(),
> is_readable_migration_entry(), swp_offset_pfn() and pfn_swap_entry_folio()
> with softleaf equivalents.
> 
> No functional change intended.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

Two completely non-urgent nits below.

> ---
>  16 files changed, 75 insertions(+), 176 deletions(-)

Nice.

> index f5ea9b0385ff..d282fab866a1 100644
> --- a/include/linux/leafops.h
> +++ b/include/linux/leafops.h
> @@ -355,7 +355,7 @@ static inline unsigned long softleaf_to_pfn(softleaf_t entry)
>  	VM_WARN_ON_ONCE(!softleaf_has_pfn(entry));
>  
>  	/* Temporary until swp_entry_t eliminated. */
> -	return swp_offset_pfn(entry);
> +	return swp_offset(entry) & SWP_PFN_MASK;
>  }
>  
>  /**
> @@ -366,10 +366,16 @@ static inline unsigned long softleaf_to_pfn(softleaf_t entry)
>   */
>  static inline struct page *softleaf_to_page(softleaf_t entry)
>  {
> +	struct page *page = pfn_to_page(softleaf_to_pfn(entry));
> +
>  	VM_WARN_ON_ONCE(!softleaf_has_pfn(entry));

Nit: the warning is already in softleaf_to_pfn()

> +	/*
> +	 * Any use of migration entries may only occur while the
> +	 * corresponding page is locked
> +	 */
> +	VM_WARN_ON_ONCE(softleaf_is_migration(entry) && !PageLocked(page));
>  
> -	/* Temporary until swp_entry_t eliminated. */
> -	return pfn_swap_entry_to_page(entry);
> +	return page;
>  }
>  
>  /**
> @@ -380,10 +386,17 @@ static inline struct page *softleaf_to_page(softleaf_t entry)
>   */
>  static inline struct folio *softleaf_to_folio(softleaf_t entry)
>  {
> -	VM_WARN_ON_ONCE(!softleaf_has_pfn(entry));
> +	struct folio *folio = pfn_folio(softleaf_to_pfn(entry));
>  
> -	/* Temporary until swp_entry_t eliminated. */
> -	return pfn_swap_entry_folio(entry);
> +	VM_WARN_ON_ONCE(!softleaf_has_pfn(entry));

Ditto.

> +	/*
> +	 * Any use of migration entries may only occur while the
> +	 * corresponding folio is locked.
> +	 */
> +	VM_WARN_ON_ONCE(softleaf_is_migration(entry) &&
> +			!folio_test_locked(folio));
> +
> +	return folio;
>  }
>  
>  /**