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    SubjectRe: [PATCH]fix VM_CAN_NONLINEAR check in sys_remap_file_pages
    Date
    On Tuesday 09 October 2007 03:04, Andrew Morton wrote:
    > On Mon, 8 Oct 2007 19:45:08 +0800 "Yan Zheng" <yanzheng@21cn.com> wrote:
    > > Hi all
    > >
    > > The test for VM_CAN_NONLINEAR always fails
    > >
    > > Signed-off-by: Yan Zheng<yanzheng@21cn.com>
    > > ----
    > > diff -ur linux-2.6.23-rc9/mm/fremap.c linux/mm/fremap.c
    > > --- linux-2.6.23-rc9/mm/fremap.c 2007-10-07 15:03:33.000000000 +0800
    > > +++ linux/mm/fremap.c 2007-10-08 19:33:44.000000000 +0800
    > > @@ -160,7 +160,7 @@
    > > if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
    > > goto out;
    > >
    > > - if (!vma->vm_flags & VM_CAN_NONLINEAR)
    > > + if (!(vma->vm_flags & VM_CAN_NONLINEAR))
    > > goto out;
    > >
    > > if (end <= start || start < vma->vm_start || end > vma->vm_end)
    >
    > Lovely. From this we can deduce that nobody has run remap_file_pages()
    > since 2.6.23-rc1 and that nobody (including the developer who made that
    > change) ran it while that change was in -mm.

    But you'd be wrong. remap_file_pages was tested both with my own tester
    and Ingo's test program.

    vm_flags != 0, !vm_flags = 0, 0 & x = 0, so the test always falls
    through. Of course, what I _should_ have done is also test a driver which
    does not have VM_CAN_NONLINEAR... but even I wouldn't rewrite half
    the nonlinear mapping code without once testing it ;)

    FWIW, Oracle (maybe the sole real user of this) has been testing it, which
    I'm very happy about (rather than testing after 2.6.23 is released).
    -
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