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    SubjectRe: [PATCH, RFD]: Unbreak no-mmu mmap
    Date
    Bernd Schmidt <bernds_cb1@t-online.de> wrote:
    > 1. munmap can now unmap subparts of previously allocated blocks. This
    > makes behaviour more consistent with mmu Linux, and allows us to
    > simplify and speed up the uClibc malloc implementation.

    There's a problem with your alteration to do_munmap() to split VMAs. What
    happens if an area of a file is mmap'd twice in a process? Consider the
    situation where two independent parts of a process (say two different
    libraries) each map an area of the same file. do_mmap_pgoff() will attempt to
    share these regions if it can.

    This can lead to you splitting the wrong VMA when someone comes along later to
    do an apparent partial unmap.

    I'm currently working on something to give each NOMMU process its own list
    VMAs rather than holding them in common. This is so that I can add VMA
    reservation (and more to the point, unreservation) which'll make some stuff
    easier.

    David
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