Hi, Nadav & all, On Mon, Jan 31, 2022 at 02:39:01PM -0800, Nadav Amit wrote: > There are use-cases in which you do need to know the order between > user-initiated MADV_DONTNEED and page-faults. For instance, if you > build a userspace paging mechanism, you need to know whether the > page content is zero or whatever is held in the disk. When there's no uffd monitor, concurrent page faults with MADV_DONTNEED can already result in undefined behavior, right? Assuming the page fault is a write with non-zero data, then the page can either contain zero or non-zero data at last, IIUC. If above is true, I'm wondering whether it's already impossible to do it right when there is an uffd monitor? Thanks, -- Peter Xu
