:>     Try using null mounts.  The warning is in there because making the
:>     null mount code work is a real hack and the authors aren't entirely
:>     sure that everything's gotten covered.  That said, use of a null mount
:>     is certainly a lot safer if the stuff behind the mount is mostly
:>     static.
:
:The problem is in the VM object alias code.  Specifically, the
:getpages/putpages have to be implemented in terms of read/write,
:so that there are not two vm_object_t's that refer to the same
:data, since there is no "upcall" to notify of changes in a lower
:layer, and therefore guarantee coherency.

    I'm fairly sure the VM issues were fixed when VOP_GETVOBJECT was
    added.  A file accessed via a null mount will have the same VM object
    as the file in the original filesystem.  I'm not 100% sure about
    that, I wasn't the one who did it, but I seem to recall it being
    discussed.

                                                -Matt


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