superblock corruption, cannot obtain data
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How do you know it's a bad superblock? While I'm not a dev just a list regular, show-super looks reasonable from here, and find-root does find what appears to be a good root. From here the problem seems to be a bad ctree (of several), not a bad superblock.
yes i think you're right. i think that was just the initial thinking of #btrfs
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First thing to try is mounting with
nospace_cache. If that works, try mounting withclear_cacheand letting it work for a bit to rebuild.
nope, same error.
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If that doesn't work, it may simply be the log tree. btrfs-zero-log is used to fix that, but before you try that, read this entry in the FAQ and follow the instructions for making a filesystem image to turn in to the devs to help them fix such problems, and consider making a backup of the damaged filesystem using dd/ddrescue, since the warning about making it possibly more difficult to recover if this is NOT the problem applies:
tried this, btrfs-image complains about roughly the same error, btrfs-zero-log said the following: http://bpaste.net/show/328495
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Another thing to try is mounting recovery,ro. A number of people have reported that would work when simple recovery wouldn't, because when it was writable btrfs would immediately try to fix the problem and immediately fail.
nope, same error.
here's what happens when i run fsck http://cwillu.com:8080/74.84.235.22/3
"Critical roots corrupted, unable to fsck the FS" sounds like especially good news ;p
--
Shaun Reich,
KDE Software Developer (kde.org)
Tl;dr tried nearly everything, couldn't get it to recover, gave up and restored my old backup. I was running the newest Archlinux kernel release.
.. Extracting data with Btrfs restore was quite useless, Btrfs find root didn't list any object id's either, which I was unsure why. I guess I was just unlucky or the utility got changed since all the other people I've seen had used it.
Still have a full dd image of the disk that I'll keep for a week or so, and a Btrfs-image, if anyone is at all interested.