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authorAndrea Arcangeli <aarcange@redhat.com>2017-02-22 15:42:46 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-22 16:41:28 -0800
commit09fa5296a40d01e014b4851def20b975feb98fd5 (patch)
tree4b937777549f85e69134d5a1af48b849f174ddb0 /fs/userfaultfd.c
parent0594f58dbd954f7747553c041d7cbbf9b6ef1947 (diff)
downloadlinux-09fa5296a40d01e014b4851def20b975feb98fd5.tar.bz2
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 <aarcange@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Michael Rapoport <RAPOPORT@il.ibm.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/userfaultfd.c')
-rw-r--r--fs/userfaultfd.c13
1 files changed, 13 insertions, 0 deletions
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,