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    SubjectRe: [PATCH] FRV: Fix mmap2 error handling
    On Thu, Nov 27, 2008 at 03:12:38PM +0000, David Howells wrote:
    > Fix the error handling in sys_mmap2(). Currently, if the pgoff check fails,
    > fput() might have to be called (which it isn't), so do the pgoff check first,
    > before fget() is called.

    *sigh*.

    My reaction was "Why do we have sys_mmap2 in every architecture?" So I
    started looking. Oh dear, oh dear oh dear.

    FRV:
    /* As with sparc32, make sure the shift for mmap2 is constant
    (12), no matter what PAGE_SIZE we have.... */
    ia64:
    Just uses PAGE_SIZE (currently supported values: 4k, 8k, 16k and 64k).

    So what is poor userspace to do? Check which architecture it's on and
    figure out what PAGE_SIZE to use for mmap2 based on that?


    How about we introduce a sys_mmap6() in common code which takes 'off'
    in multiples of 4k. Then FRV and other sane architectures can replace
    their sys_mmap2 entries in their syscall tables with sys_mmap6. ia64 has
    to keep its insane sys_mmap2 entry, but it can add a sys_mmap6 entry too.

    --
    Matthew Wilcox Intel Open Source Technology Centre
    "Bill, look, we understand that you're interested in selling us this
    operating system, but compare it to ours. We can't possibly take such
    a retrograde step."


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