MADV_DONTNEED must be notified to userland before the pages are zapped. This allows userland to immediately stop adding pages to the userfaultfd ranges before the pages are actually zapped or there could be non-zeropage leftovers as result of concurrent UFFDIO_COPY run in between zap_page_range and madvise_userfault_dontneed (both MADV_DONTNEED and UFFDIO_COPY runs under the mmap_sem for reading, so they can run concurrently). Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> --- mm/madvise.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/madvise.c b/mm/madvise.c index 06ffb5a..ca75b8a 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -477,8 +477,8 @@ static long madvise_dontneed(struct vm_area_struct *vma, if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP)) return -EINVAL; - zap_page_range(vma, start, end - start, NULL); madvise_userfault_dontneed(vma, prev, start, end); + zap_page_range(vma, start, end - start, NULL); return 0; } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>