On Tue, Jul 18, 2023 at 01:28:56AM -0700, Vivek Kasireddy wrote: > Currently, there does not appear to be any mechanism for letting > drivers or other kernel entities know about updates made in a > mapping particularly when a new page is faulted in. Providing > notifications for such situations is really useful when using > memfds backed by ram-based filesystems such as shmem or hugetlbfs > that also allow FALLOC_FL_PUNCH_HOLE. Huh? You get an invalidate when this happens and the address becomes non-present. > More specifically, when a hole is punched in a memfd (that is > backed by shmem or hugetlbfs), a driver can register for > notifications associated with range invalidations. However, it > would also be useful to have notifications when new pages are > faulted in as a result of writes made to the mapping region that > overlaps with a previously punched hole. If there is no change to the PTEs then it is hard to see why this would be part of a mmu_notifier. Jason
