On Thu, Aug 11, 2022 at 12:34:35PM +0200, David Hildenbrand wrote: > Reason is that uffd-wp doesn't clear the uffd-wp PTE bit when > unregistering and consequently keeps the PTE writeprotected. Reason for > this is to avoid the additional overhead when unregistering. Note > that this is the case also for !hugetlb and that we will end up with > writable PTEs that still have the uffd-wp PTE bit set once we return > from hugetlb_wp(). I'm not touching the uffd-wp PTE bit for now, because it > seems to be a generic thing -- wp_page_reuse() also doesn't clear it. This may justify that lazy reset of ptes may not really be a good idea, including anonymous. I'm indeed not aware of any app that do frequent reg/unreg at least. I'll prepare a patch to change it from uffd side too. Thanks again for finding this problem. -- Peter Xu
