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    SubjectRe: still nfs problems [Was: Linux 2.6.37-rc8]
    On Wed, Jan 5, 2011 at 11:05 AM, James Bottomley
    <> wrote:
    > I think the solution for the kernel direct mapping problem is to take
    > the expected flushes and invalidates into kmap/kunmap[_atomic].

    No, we really can't do that. Most of the time, the kmap() is the only
    way we access the page anyway, so flushing things would just be
    stupid. Why waste time and energy on doing something pointless?

    In fact, kmap() here is a total non-issue. It's not the kmap() that
    introduces any virtual aliases, and never has been. It's the
    "vm_map_ram()" that is the problem. Unlike the kmap(), that really
    _does_ introduce a virtual alias, and is a problem for any virtual

    So don't blame kmap(). It's innocent and irrelevant - the bug could
    happen entirely without it (think a 64-bit address space that doesn't
    even _have_ kmap, but has software that mixes vm_map_ram() with
    non-mapped accesses).


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