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.
