On Mon, Jun 26, 2023 at 03:04:21PM -0400, Peter Xu wrote: > On Mon, Jun 26, 2023 at 03:18:48PM -0300, Jason Gunthorpe wrote: > > On Mon, Jun 26, 2023 at 08:14:27PM +0200, David Hildenbrand wrote: > > > > > So we might have to implement the same page migration as gup does on > > > FOLL_LONGTERM here ... maybe there are more such cases/drivers that actually > > > require that handling when simply taking pages out of the memfd, believing > > > they can hold on to them forever. > > > > In general I would like to see an interface to FOLL_LONGTERM pin pages > > from a memfd. I would quite happily use that in iommufd as well. > > > > It solves some problems we have there with fork/exec/etc if the pages > > are not linked to a mm_struct. > > Afaiu any fd based approach should mean it'll never work with private > memories, while mm-based should be able to work on any kind. Is there a significant use case to open a memfd and then use MAP_PRIVATE? Why would anyone want to do that instead of just using normal mmap anonymous memory? Jason
