Re: crash in btrfsck, btrfs-debug-tree, etc

["Vladimir G. Ivanovic" <vladimir@acm.org>]

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No help, eh? At the minimum, it would be nice if btrfsck were fixed...

Unfortunately, now btrfs will NOT mount the drive, so I am now
completely without data. The mount error is:

    kernel: device fsid c64b56bd1c869bb3-e85f95a29c7dd3ad devid 1
transid 21547 /dev/sdc1
    kernel: btrfs bad tree block start 14052438117991321731 20971520
    kernel: btrfs bad tree block start 14052438117991321731 20971520
    kernel: btrfs bad tree block start 8532476744452893537 20971520
    kernel: btrfs: failed to read chunk root on sdc1
    kernel: btrfs: open_ctree failed

--- Vladimir

Vladimir G. Ivanovic                            http://www.leonora.org
+1 650 450 4101                                       vladimir@acm.org


on 04/28/2010 01:03 PM Vladimir G. Ivanovic said the following:
> I overwrote some part of the first 195641856 bytes of a 1TB (nominal)
> btrfs volume (I CTRL-C'd out
> before dd finished.) OK, OK, you may stop laughing now. Surely something
> similar has happened to
> you. No? Then it will, someday.
>
> First things first: A huge congratulations to the btrfs team because the
> btrfs volume is still
> usable. I do get many errors similar to:
>
>     kernel: btrfs bad tree block start 3050544144921548175 12056985
>
> but for many of my files, I don't get errors.
>
> Now, onto my problems. My first thought was to btrfsck the unmount
> volume, but btrfsck crashes:
>
>     # btrfsck /dev/sdc1
>     btrfsck: disk-io.c:723: open_ctree_fd: Assertion
> `!(!chunk_root->node)' failed.
>     Aborted (core dumped)
>
> So does btrfs-debug-tree, and I suspect other utilities will as well. I
> tried the latest utilities
> from btrfs-progs-unstable, but they too crash with the same error. (I'm
> on a Athlon64-powered
> netbook running Fedora 12. btrfs's version is 0.19.) In particular, so
> does btrfs-image, so I can't
> share the volume's metadata.
>
> So, until the utilities are fixed, what are my options?
>
> * Can I create a snapshot of the root volume? Would I end up with
> everything that could be read in
>   the snapshot, or would it also have errors? If this is a good idea,
> would these commands work?
>
>       btrfsctl -s snapshot_of_root /mnt/chopin1
>       mount.btrfs -o subvol=snapshot_of_root /dev/sdc1 /mnt/snap
>
>   do the trick, assuming that btrfsctl doesn't also crash? Then what?
> Copy the snapshot to another
>   disk? Somehow make the new snapshot the new root, allowing me to
> delete the old root?
>
> * Should I just try and copy the data to another disk and reformat my
> current volume?
>
> * Is there a way of testing whether a particular file is good other than
> (slowly) going through
>   each and every file while watching syslog? cat, for example, doesn't
> return an error when the
>   file is bad, so I don't think I can write a shell script to copy good
> files to another volume.
>
> Are there other options that I haven't considered?
>
> Thanks for all help.
>
> --- Vladimir
>
>   


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