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DragonFly kernel List (threaded) for 2010-02
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Re: kernel work week of 3-Feb-2010 HEADS UP

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Fri, 5 Feb 2010 08:14:09 -0800 (PST)

:Could I implement moving the UNDO log by flushing everything to disk, so
:that the UNDO log gets empty and then simply switching the log to the
:new one? IIRC, writing an UNDO entry required the root volume to be
:updated in HAMMER versions <= 3, which is no longer true as of V4.
:  Michael

    I think it can be done by acquiring the appropriate lock inside
    HAMMER to prevent anyone else from messing with the UNDO area,
    then copying the contents to new blocks.  Then flush, then
    reassign the blocks.  The block assignments for the UNDO log are
    in the volume header I believe.  Then flush the volume header
    and you are done.

    I haven't looked at it closely but I think that's all there is
    to it.

					Matthew Dillon 

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