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    SubjectRe: Checkin 7404ad3b6d04efbd918e9e2e776bf560fbedf47d breaks boot on KVM
    James Bottomley wrote:
    >> :040000 040000 98fc7ae95211b8d16e2e8ca46997be660ad9ba93
    >> 2d35d0a2b6232411b840a9ccf6a52b946172566e M drivers
    >> However, simply reverting this commit caused a panic on boot (not
    >> entirely surprising.)
    > Actually, it is surprising. That patch takes the default arithmetic for
    > calculating the disk size out of sd and uses a routine to do it more
    > efficiently in lib/string_helpers.c
    > So there are two problems: Why does it panic on revert (could you post
    > the oops) and what does kvm object to in string_get_size ... it's a
    > fairly innocuous routine as I read it ... your symptoms sound like the
    > for loop isn't terminating.

    Looks like it's trying to print a zero. I made a diff to print out the
    raw numbers, and did indeed get zero.

    Now, *why* it is printing a zero is another matter (as is why using
    ffz() instead of ilog2() there...). Some quick investigation showed
    that sdkp->capacity is a 32-bit quantity in this configuration, and
    shifting it left by 9 of course ends up with zero; being a virtual disk,
    it's an exact power of two.

    Still, it is bad that string_get_size() hangs on passing zero.

    The spinlock lockup is still happening, so I'm assuming it is an
    unrelated bug that was masked by the string_get_size issue.

    Patch series will follow shortly.


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      Last update: 2008-10-14 20:07    [W:0.021 / U:19.128 seconds]
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