From 09fa5296a40d01e014b4851def20b975feb98fd5 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Wed, 22 Feb 2017 15:42:46 -0800 Subject: [PATCH] userfaultfd: non-cooperative: wake userfaults after UFFDIO_UNREGISTER Userfaults may still happen after the userfaultfd monitor thread received a UFFD_EVENT_MADVDONTNEED until UFFDIO_UNREGISTER is run. Wake any pending userfault within UFFDIO_UNREGISTER protected by the mmap_sem for writing, so they will not be reported to userland leading to UFFDIO_COPY returning -EINVAL (as the range was already unregistered) and they will not hang permanently either. Link: http://lkml.kernel.org/r/20161216144821.5183-16-aarcange@redhat.com Signed-off-by: Andrea Arcangeli Cc: "Dr. David Alan Gilbert" Cc: Hillf Danton Cc: Michael Rapoport Cc: Mike Kravetz Cc: Mike Rapoport Cc: Pavel Emelyanov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index ea9008254df4..26e1ef00b63c 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1302,6 +1302,19 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, start = vma->vm_start; vma_end = min(end, vma->vm_end); + if (userfaultfd_missing(vma)) { + /* + * Wake any concurrent pending userfault while + * we unregister, so they will not hang + * permanently and it avoids userland to call + * UFFDIO_WAKE explicitly. + */ + struct userfaultfd_wake_range range; + range.start = start; + range.len = vma_end - start; + wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); + } + new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); prev = vma_merge(mm, prev, start, vma_end, new_flags, vma->anon_vma, vma->vm_file, vma->vm_pgoff, -- 2.30.2