Re: [PATCH 01/13] mm: add softleaf_to_pmd() and convert existing callers

[Dev Jain]

On 27/04/26 3:31 pm, Usama Arif wrote:
> Add softleaf_to_pmd() as the PMD counterpart to softleaf_to_pte(),
> completing the symmetry of the softleaf abstraction for page table
> leaf entries.
> 
> The upcoming PMD swap entry support needs to construct PMD entries
> from swap entries. Converting existing swp_entry_to_pmd() callers
> to softleaf_to_pmd() in a prep patch keeps the feature patches
> focused on new functionality rather than mixing refactoring with
> new code.
> 
> Signed-off-by: Usama Arif <usama.arif@xxxxxxxxx>
> ---

Any reason why you have left out the conversion in migrate_device.c?


>  include/linux/leafops.h | 20 ++++++++++++++++++++
>  mm/huge_memory.c        | 12 ++++++------
>  2 files changed, 26 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/leafops.h b/include/linux/leafops.h
> index 992cd8bd8ed0..803d312437df 100644
> --- a/include/linux/leafops.h
> +++ b/include/linux/leafops.h
> @@ -108,6 +108,21 @@ static inline softleaf_t softleaf_from_pmd(pmd_t pmd)
>  	return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
>  }
>  
> +/**
> + * softleaf_to_pmd() - Obtain a PMD entry from a leaf entry.
> + * @entry: Leaf entry.
> + *
> + * This generates an architecture-specific PMD entry that can be utilised to
> + * encode the metadata the leaf entry encodes.
> + *
> + * Returns: Architecture-specific PMD entry encoding leaf entry.
> + */
> +static inline pmd_t softleaf_to_pmd(softleaf_t entry)
> +{
> +	/* Temporary until swp_entry_t eliminated. */
> +	return swp_entry_to_pmd(entry);
> +}
> +
>  #else
>  
>  static inline softleaf_t softleaf_from_pmd(pmd_t pmd)
> @@ -115,6 +130,11 @@ static inline softleaf_t softleaf_from_pmd(pmd_t pmd)
>  	return softleaf_mk_none();
>  }
>  
> +static inline pmd_t softleaf_to_pmd(softleaf_t entry)
> +{
> +	return __pmd(0);
> +}
> +
>  #endif
>  
>  /**
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 970e077019b7..49da0746b8ca 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1881,7 +1881,7 @@ static void copy_huge_non_present_pmd(
>  	if (softleaf_is_migration_write(entry) ||
>  	    softleaf_is_migration_read_exclusive(entry)) {
>  		entry = make_readable_migration_entry(swp_offset(entry));
> -		pmd = swp_entry_to_pmd(entry);
> +		pmd = softleaf_to_pmd(entry);
>  		if (pmd_swp_soft_dirty(*src_pmd))
>  			pmd = pmd_swp_mksoft_dirty(pmd);
>  		if (pmd_swp_uffd_wp(*src_pmd))
> @@ -1894,7 +1894,7 @@ static void copy_huge_non_present_pmd(
>  		 */
>  		if (softleaf_is_device_private_write(entry)) {
>  			entry = make_readable_device_private_entry(swp_offset(entry));
> -			pmd = swp_entry_to_pmd(entry);
> +			pmd = softleaf_to_pmd(entry);
>  
>  			if (pmd_swp_soft_dirty(*src_pmd))
>  				pmd = pmd_swp_mksoft_dirty(pmd);
> @@ -2632,12 +2632,12 @@ static void change_non_present_huge_pmd(struct mm_struct *mm,
>  			entry = make_readable_exclusive_migration_entry(swp_offset(entry));
>  		else
>  			entry = make_readable_migration_entry(swp_offset(entry));
> -		newpmd = swp_entry_to_pmd(entry);
> +		newpmd = softleaf_to_pmd(entry);
>  		if (pmd_swp_soft_dirty(*pmd))
>  			newpmd = pmd_swp_mksoft_dirty(newpmd);
>  	} else if (softleaf_is_device_private_write(entry)) {
>  		entry = make_readable_device_private_entry(swp_offset(entry));
> -		newpmd = swp_entry_to_pmd(entry);
> +		newpmd = softleaf_to_pmd(entry);
>  	} else {
>  		newpmd = *pmd;
>  	}
> @@ -5014,7 +5014,7 @@ int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
>  		entry = make_migration_entry_young(entry);
>  	if (pmd_dirty(pmdval))
>  		entry = make_migration_entry_dirty(entry);
> -	pmdswp = swp_entry_to_pmd(entry);
> +	pmdswp = softleaf_to_pmd(entry);
>  	if (pmd_soft_dirty(pmdval))
>  		pmdswp = pmd_swp_mksoft_dirty(pmdswp);
>  	if (pmd_uffd_wp(pmdval))
> @@ -5065,7 +5065,7 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
>  		else
>  			entry = make_readable_device_private_entry(
>  							page_to_pfn(new));
> -		pmde = swp_entry_to_pmd(entry);
> +		pmde = softleaf_to_pmd(entry);
>  
>  		if (pmd_swp_soft_dirty(*pvmw->pmd))
>  			pmde = pmd_swp_mksoft_dirty(pmde);