Corrupt btrfs filesystem cannot be fixed by btrfs fsck or by mounting with -o restore

This is reported as bug https://bugzilla.kernel.org/show_bug.cgi?id=68951 since it causes a kernel panic - more details there.

The btrfs filesystem on my laptop became corrupted during a suspend / resume cycle. Afterwards, kernel 3.11 could no longer mount the filesystem and btrfs fsck crashed with abort() errors. Not having much time to deal with it, I took an image and re-installed the laptop from backups.

I've just tried to mount a copy of the image with 3.12, and the kernel successfully mounts, but a find . inside the fiesystem, segfaults. btrfs fsck dies with the error:

btrfsck: cmds-check.c:1320: walk_down_tree: Assertion `!(1)' failed.

I have a btrfs-image of the metadata, but it's 110Mb. I can probably make it available for download somewhere, meanwhile I'm happy to poke about if there's anything I can do to add more information.

Phil