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    SubjectRe: [BUG] Kernel Bug at fs/btrfs/volumes.c:3638
    On Fri, 24 Feb 2012 16:11:29 +0530
    Nageswara R Sastry <rnsastry@linux.vnet.ibm.com> wrote:

    > Hello,
    >
    > While working with 'fsfuzz - file system fuzzing tool' on 'btrfs'
    > encountered the following kernel bug.

    I inquired about robustness a while ago and it seems it's at some point on the horizon, but not now.
    My concern was about hot-unplugged disk drives, but btrfs also doesn't appreciate meta-data corruption.
    btrfs-raid users could be concerned, because contrarily to on a real RAID, the btrfs meta-data is a potential weak link.

    At some point, I would appreciate some kind of thorough evaluation using a fuzzer on small disk images.
    The btrfs developers could for instance:
    - provide a script to create a filesystem image with a known layout (known corpus)
    - provide .config and reference to kernel sources to build the kernel
    - provide a minimal root filesystem to be run under qemu, it would run a procedure on the other disk image at boot
    crashes wouldn't affect the host, which is good.
    - provide a way to retrieve the test parameters and results for every test case
    in case of bug, the test can be reproduced by the developers since the configuration is known
    - expect volunteers to run the scenarios (I know I would)
    The tricky part is of course the potentially super-costly procedure...
    Simplest case: flipping every bit / writing blocks with pseudo-random data, even on meta-data only, as the outcome on data is supposed to be known.
    Smarter: flipping bits on every btrfs meta-data structure type at every possible logical location.

    The kind of stuff that would help all this could be something like Python bindings for a *btrfs library*.
    Helpful even for prototyping fsck stuff, making illustrations, etc.

    As of today, how are btrfs developers testing the filesystem implementation (except with xfstests) ?

    Best regards,

    --
    cJ

    PS: don't be mistaken, I'm not asking for all that, just suggesting.
    My time goes to something else, but I do have sleepy computers at home, and they could help.


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