linux-kernel - Re: [PATCH v3 10/16] mm: replace pmd_to_swp_entry() with softleaf_from

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Message-ID: <68f18daf-cc45-479f-ac6f-0b4dce153ea7@suse.cz>
Date: Fri, 21 Nov 2025 19:42:50 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>,
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Subject: Re: [PATCH v3 10/16] mm: replace pmd_to_swp_entry() with
 softleaf_from_pmd()

On 11/10/25 23:21, Lorenzo Stoakes wrote:
> Introduce softleaf_from_pmd() to do the equivalent operation for PMDs that
> softleaf_from_pte() fulfils, and cascade changes through code base
> accordingly, introducing helpers as necessary.

Some of that is adding new pte stuff too, so it could have been separate
patch, but it's not a big deal.

> We are then able to eliminate pmd_to_swp_entry(), is_pmd_migration_entry(),
> is_pmd_device_private_entry() and is_pmd_non_present_folio_entry().
> 
> This further establishes the use of leaf operations throughout the code
> base and further establishes the foundations for eliminating is_swap_pmd().
> 
> No functional change intended.
> 
> Reviewed-by: SeongJae Park <sj@...nel.org>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

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

Assuming the below is fixed. Glad I could demonstrate I'm not just rubber
stamping all this ;P
(probably missed stuff anyway, as usual)

> --- a/mm/page_table_check.c
> +++ b/mm/page_table_check.c
> @@ -8,7 +8,7 @@
>  #include <linux/mm.h>
>  #include <linux/page_table_check.h>
>  #include <linux/swap.h>
> -#include <linux/swapops.h>
> +#include <linux/leafops.h>
>  
>  #undef pr_fmt
>  #define pr_fmt(fmt)	"page_table_check: " fmt
> @@ -179,10 +179,10 @@ void __page_table_check_pud_clear(struct mm_struct *mm, pud_t pud)
>  EXPORT_SYMBOL(__page_table_check_pud_clear);
>  
>  /* Whether the swap entry cached writable information */
> -static inline bool swap_cached_writable(swp_entry_t entry)
> +static inline bool softleaf_cached_writable(softleaf_t entry)
>  {
> -	return is_writable_device_private_entry(entry) ||
> -	       is_writable_migration_entry(entry);
> +	return softleaf_is_device_private(entry) ||

Shouldn't there be softleaf_is_device_private_write(entry) ?

> +		softleaf_is_migration_write(entry);
>  }
>  
>  static void page_table_check_pte_flags(pte_t pte)
> @@ -190,9 +190,9 @@ static void page_table_check_pte_flags(pte_t pte)
>  	if (pte_present(pte)) {
>  		WARN_ON_ONCE(pte_uffd_wp(pte) && pte_write(pte));
>  	} else if (pte_swp_uffd_wp(pte)) {
> -		const swp_entry_t entry = pte_to_swp_entry(pte);
> +		const softleaf_t entry = softleaf_from_pte(pte);
>  
> -		WARN_ON_ONCE(swap_cached_writable(entry));
> +		WARN_ON_ONCE(softleaf_cached_writable(entry));
>  	}
>  }
>  
> @@ -219,9 +219,9 @@ static inline void page_table_check_pmd_flags(pmd_t pmd)
>  		if (pmd_uffd_wp(pmd))
>  			WARN_ON_ONCE(pmd_write(pmd));
>  	} else if (pmd_swp_uffd_wp(pmd)) {
> -		swp_entry_t entry = pmd_to_swp_entry(pmd);
> +		const softleaf_t entry = softleaf_from_pmd(pmd);
>  
> -		WARN_ON_ONCE(swap_cached_writable(entry));
> +		WARN_ON_ONCE(softleaf_cached_writable(entry));
>  	}
>  }
>