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    SubjectRe: vm_ops.page_mkwrite() fails with vmalloc on 2.6.23
    On 10/29/07, Peter Zijlstra <peterz@infradead.org> wrote:
    > On Mon, 2007-10-29 at 01:17 -0700, Jaya Kumar wrote:
    > > An aside, I just tested that deferred IO works fine on 2.6.22.10/pxa255.
    > >
    > > I understood from the thread that PeterZ is looking into page_mkclean
    > > changes which I guess went into 2.6.23. I'm also happy to help in any
    > > way if the way we're doing fb_defio needs to change.
    >
    > OK, seems I can't read. Or at least, I missed a large part of the
    > problem.
    >
    > page_mkclean() hasn't changed, it was ->page_mkwrite() that changed. And
    > looking at the fb_defio code, I'm not sure I understand how its
    > page_mkclean() use could ever have worked.
    >
    > The proposed patch [1] only fixes the issue of ->page_mkwrite() on
    > vmalloc()'ed memory. Not page_mkclean(), and that has never worked from
    > what I can make of it.
    >
    > Jaya, could you shed some light on this? I presume you had your display
    > working.
    >

    I thought I had it working. I saw the display update after each
    mmap/write sequence to the framebuffer. I need to check if there's an
    munmap or anything else going on in between write sequences that would
    cause it to behave like page_mkclean was working.

    Is it correct to assume that page_mkclean should mark the pages
    read-only so that the next write would again trigger mkwrite? Even if
    the page was from a vmalloc_to_page()?

    Thanks,
    jaya
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