userfaultfd: non-cooperative: add madvise() event for MADV_REMOVE request

When a page is removed from a shared mapping, the uffd reader should be
notified, so that it won't attempt to handle #PF events for the removed
pages.

We can reuse the UFFD_EVENT_REMOVE because from the uffd monitor point
of view, the semantices of madvise(MADV_DONTNEED) and
madvise(MADV_REMOVE) is exactly the same.

Link: http://lkml.kernel.org/r/1484814154-1557-3-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/madvise.c b/mm/madvise.c
index ab5ef141cc9b382f9d874f7e7e465db621e3f156..0012071a6e502e30001cff587ce0069a1d9d2342 100644 (file)
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -520,6 +520,7 @@ static long madvise_remove(struct vm_area_struct *vma,
         * mmap_sem.
         */
        get_file(f);
+       userfaultfd_remove(vma, prev, start, end);
        up_read(&current->mm->mmap_sem);
        error = vfs_fallocate(f,
                                FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,