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    SubjectRe: [PATCH 00/14] Pramfs: Persistent and protected ram filesystem
    From
    2009/6/24 Jamie Lokier <jamie@shareable.org>:
    > Pavel Machek wrote:
    >> On Tue 2009-06-23 20:07:23, Marco wrote:
    >> > You are talked about journaling. This schema works well for a disk, but
    >> > what about a piece of ram? What about a crazy kernel that write in that
    >> > area for a bug? Do you remember for example the e1000e bug? It's not
    >>
    >> I believe you need both journaling *and* write protection. How do you
    >> handle power fault while writing data?
    >
    > I think this is basically right.
    >
    > write protection for the crazy kernels, and journalling for
    > powerfail/crash during updates.
    >
    > Journalling can be extremely simple.  It can be just one memory block
    > at a fixed location, double-buffering all writes.
    >
    > Pramfs already has checksums, which makes that easier.  You just write
    > to the buffer area first, with checksum, then write to the final area.
    > Mount looks at the buffer area, and if the checksum is fine, copies
    > the contents to the destination block.
    >
    > That's all it takes to be resistant against power failures and crashes
    > during writes.  Probably <100 lines of code.
    >
    > -- Jamie
    >

    It seems a reasonable request.

    Marco
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