On Mon, Oct 02, 2023 at 10:00:03AM +0200, David Hildenbrand wrote: > In case we cannot simply remap the page, the fallback sequence (from the > cover letter) would be triggered. > > 1) UFFDIO_COPY > 2) MADV_DONTNEED > > So we would just handle the operation internally without a fallback. Note that I think there will be a slight difference on whole remap atomicity, on what happens if the page is modified after UFFDIO_COPY but before DONTNEED. UFFDIO_REMAP guarantees full atomicity when moving the page, IOW, threads can be updating the pages when ioctl(UFFDIO_REMAP), data won't get lost during movement, and it will generate a missing event after moved, with latest data showing up on dest. I'm not sure that means such a fallback is a problem, Suren may know better with the use case. Thanks, -- Peter Xu
