Re: [v1 resend 07/12] mm/memremap: add folio_split support

[Balbir Singh]

On 7/4/25 21:14, Mika Penttilä wrote:
> 
> On 7/4/25 02:35, Balbir Singh wrote:
>>  
>> +			if (folio_is_device_private(origin_folio) &&
>> +					origin_folio->pgmap->ops->folio_split)
>> +				origin_folio->pgmap->ops->folio_split(
>> +					origin_folio, release);
> 
> Should folio split fail if pgmap->ops->folio_split() is not defined? If not then at least the >pgmap pointer copy should be in the common code.
> 

We could change the code can check ->folio_split callback is not NULL when MIGRATE_VMA_SELECT_COMPOUND is used and cause migrate_vma to fail

Providing a default implementation might surprise drivers about the split

Balbir Singh