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unix friends,

a day or so ago my btrfs partition just stopped working, which means i can't mount it anymore which is why my Fedora Linux doesn't boot anymore. I don't really have much information, but Gparted outputs the following when i attempt to check the partition:

checking extents
checking fs root
checking root refs
btrfsck: extent_io.c:602:free_extent_buffer: Assertion `!(eb->refs < 0)` failed.

When I tried to mount the partition with a Fedora 18 Live DVD I got a SIGSEGV from the mount program and additionally an unknown kernel error which was also tainted.

Do you have any idea how to restore the data on this partition or it is lost for sure?

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2 Answers 2

Evidence is inconclusive. Since fsck is crashing, there may yet be hope, but not until fsck itself is fixed so that it can actually continue examining the filesystem.

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First of all, you should try with a very recent kernel. I think Fedora 18 comes with a 3.6 kernel, maybe find alive cd with a more recent kernel (3.8).

Then, you can try mounting your file system with one of the following options:

mount -o clear_cache /dev/sdX /your/mountpoint

(this will delete the freezspace cache, which is sometimes a cause for btrfs refusing to mount)

or:

mount -o recovery /dev/sdX /your/mountpoint

(will try to use an 'old but known as good' filesystem root.)

If it doesn't work, you may want to try btrfsck with the latest btrfs tools from git (you will have to download and compile them yourself)

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