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    SubjectRe: [ANNOUNCE] ddtree: A git kernel tree for storage servers
    Date
    On Wednesday 19 March 2008 13:23, Mike Snitzer wrote:
    > > * Block layer deadlock fixes (Status: production)
    >
    > Do you happen to have a pointer to where these block layer deadlock
    > fixes are? Or will you be committing them shortly?

    Hi Mike,

    OK, this is committed now, but caveat: improved, untested except for
    booting. But what could possibly go wrong? :-/

    http://phunq.net/ddtree?p=ddtree/.git;a=blob;f=patches/bio-throttle

    The production version is sitting in the code.google.com svn repository
    in ddsnap/patches/2.6.23.8. That one has a known bug that has somehow
    escaped being stomped with a new commit, since it only manifests if you
    stack one stacking block device on top of another one. I will post here
    when we have an official, torture tested version of the patch.

    The patch above is improved from the most recently posted version by
    using using the ->bi_max_vecs field for throttle accounting instead of
    calling out to a per-driver metric. This works nicely because the
    max_vecs field cannot change during the life of the bio, and it gives
    a decent upper bound on the resource consumption of the bio, better
    than simply counting bios in flight. The queue->metric() method is
    still in there as a stub, some more cleanup to do there (and further
    shrinking of the patch). It does no harm.

    This improvement shrinks the throttled version of struct bio by 4
    bytes.

    Regards,

    Daniel


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