Re: [PATCH v5 01/11] mm: add PMD swap entry detection support

[Usama Arif <usama.arif@linux.dev>]

On 24/07/2026 07:10, Dev Jain wrote:
> [------]
> 
>> diff --git a/include/linux/leafops.h b/include/linux/leafops.h
>> index 4c1476ae3234..8397193ba399 100644
>> --- a/include/linux/leafops.h
>> +++ b/include/linux/leafops.h
>> @@ -102,6 +102,8 @@ static inline softleaf_t softleaf_from_pmd(pmd_t pmd)
>>  		pmd = pmd_swp_clear_soft_dirty(pmd);
>>  	if (pmd_swp_uffd(pmd))
>>  		pmd = pmd_swp_clear_uffd(pmd);
>> +	if (pmd_swp_exclusive(pmd))
>> +		pmd = pmd_swp_clear_exclusive(pmd);
>>  	arch_entry = __pmd_to_swp_entry(pmd);
>>  
>>  	/* Temporary until swp_entry_t eliminated. */
>> @@ -634,18 +636,30 @@ static inline bool pmd_is_migration_entry(pmd_t pmd)
>>   */
>>  static inline bool softleaf_is_valid_pmd_entry(softleaf_t entry)
>>  {
>> -	/* Only device private, migration entries valid for PMD. */
>> +	/* Device private, migration, and swap entries valid for PMD. */
>>  	return softleaf_is_device_private(entry) ||
>> -		softleaf_is_migration(entry);
>> +		softleaf_is_migration(entry) ||
>> +		softleaf_is_swap(entry);
>> +}
>> +
>> +/**
>> + * pmd_is_swap_entry() - Does this PMD entry encode an actual swap entry?
>> + * @pmd: PMD entry.
>> + *
>> + * Returns: true if the PMD encodes a swap entry, otherwise false.
>> + */
>> +static inline bool pmd_is_swap_entry(pmd_t pmd)
>> +{
>> +	return softleaf_is_swap(softleaf_from_pmd(pmd));
>>  }
>>  
>>  /**
>>   * pmd_is_valid_softleaf() - Is this PMD entry a valid softleaf entry?
>>   * @pmd: PMD entry.
>>   *
>> - * PMD leaf entries are valid only if they are device private or migration
>> - * entries. This function asserts that a PMD leaf entry is valid in this
>> - * respect.
>> + * PMD leaf entries are valid only if they are device private, migration,
>> + * or swap entries. This function asserts that a PMD leaf entry is valid
>> + * in this respect.
>>   *
>>   * Returns: true if the PMD entry is a valid leaf entry, otherwise false.
>>   */
>> @@ -673,6 +687,8 @@ static inline struct folio *pmd_to_softleaf_folio(pmd_t pmd)
> 
> Nit: This function really should have been named "softleaf_pmd_to_folio", or
> "pmd_softleaf_to_folio", perhaps throw in a patch to rename?
> 

Sounds good, will add a patch to rename. Lorenzo any preferences here for the name?> 
>>  		VM_WARN_ON_ONCE(true);
>>  		return NULL;
>>  	}
>> +	if (!softleaf_has_pfn(entry))
>> +		return NULL;
> 
> I am guessing that after the later patches add swp support, we should
> never reach pmd_to_softleaf_folio() with a swap entry, in which case,
> we could add a WARN_ON_ONCE() here. (didn't check if you have done that
> later, just writing this here)
> 

Will add a warn. This was one of things sashiko pointed out to add.

>>  	return softleaf_to_folio(entry);
>>  }
>>  
>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
>> index 8c093c119e5a..e10a7e91e426 100644
>> --- a/include/linux/pgtable.h
>> +++ b/include/linux/pgtable.h
>> @@ -1917,6 +1917,23 @@ static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
>>  }
>>  #endif
>>  
>> +#ifndef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
>> +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd)
>> +{
>> +	return pmd;
>> +}
>> +
>> +static inline bool pmd_swp_exclusive(pmd_t pmd)
>> +{
>> +	return false;
>> +}
>> +
>> +static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd)
>> +{
>> +	return pmd;
>> +}
>> +#endif
>> +
>>  #ifndef __HAVE_PFNMAP_TRACKING
>>  /*
>>   * Interfaces that can be used by architecture code to keep track of
>