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    SubjectRe: [RFC] block integrity: Fix write after checksum calculation problem
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    >>>>> "Andreas" == Andreas Dilger <adilger@dilger.ca> writes:

    Andreas> I don't like adding a data copy in the IO path at all.

    No thanks!


    Andreas> I'd definitely prefer that the filesystem be in charge of
    Andreas> deciding whether this is needed or not.

    Absolutely. At the block layer we obviously have no idea whether the
    filesystem is safe or not. So in my current tree the protection is only
    generated if the relevant bio flag is set (unless the application
    already added it, obviously).


    Andreas> If the use of the data copy can be constrained to only the
    Andreas> minimum required cases (e.g. if fs checks for rewrite on page
    Andreas> that is marked as Writeback and either copies or blocks until
    Andreas> writeback is complete, as a mount option) that would be
    Andreas> better. At that point we can compare on different hardware
    Andreas> whether copying or blocking should be the default.

    Agreed.

    As Chris mentioned we've got somebody on our team working through the
    filesystem issues now. I'm hoping we can provide a status update at
    LSF2011.

    --
    Martin K. Petersen Oracle Linux Engineering


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