[PATCH v8 07/15] mm/gup: migrate device coherent pages when pinning instead of failing

[David Hildenbrand]

On 11.07.22 16:00, Matthew Wilcox wrote:
> On Mon, Jul 11, 2022 at 03:35:42PM +0200, David Hildenbrand wrote:
>>> +		/*
>>> +		 * Device coherent pages are managed by a driver and should not
>>> +		 * be pinned indefinitely as it prevents the driver moving the
>>> +		 * page. So when trying to pin with FOLL_LONGTERM instead try
>>> +		 * to migrate the page out of device memory.
>>> +		 */
>>> +		if (folio_is_device_coherent(folio)) {
>>> +			WARN_ON_ONCE(PageCompound(&folio->page));
>>
>> Maybe that belongs into migrate_device_page()?
> 
> ... and should be simply WARN_ON_ONCE(folio_test_large(folio)).
> No need to go converting it back into a page in order to test things
> that can't possibly be true.
> 

Good point.

-- 
Thanks,

David / dhildenb