While running "xfs_repair -n /dev/vg0/data" I got the following output
followed by a segfault:
---snip---
# xfs_repair -n /dev/vg0/data
Phase 1 - find and verify superblock...
Phase 2 - using internal log
        - scan filesystem freespace and inode maps...
        - found root inode chunk
Phase 3 - for each AG...
        - scan (but don't clear) agi unlinked lists...
        - process known inodes and perform inode discovery...
        - agno = 0
        - agno = 1
        - agno = 2
[…]
        - agno = 68
        - agno = 69
        - agno = 70
42804950: Badness in key lookup (length)
bp=(bno 356324224, len 16384 bytes) key=(bno 356324224, len 8192 bytes)
        - agno = 71
        - agno = 72
bad nblocks 113 for inode 1209889624, would reset to 61
bad nextents 60 for inode 1209889624, would reset to 35
        - agno = 74
        - agno = 75
        - agno = 76
[…]
        - agno = 108
        - agno = 109
        - agno = 110
42804950: Badness in key lookup (length)
bp=(bno 550873824, len 16384 bytes) key=(bno 550873824, len 8192 bytes)
        - agno = 111
        - agno = 112
        - agno = 113
[…]
        - agno = 176
        - agno = 177
        - agno = 178
bad nblocks 63 for inode 2986423625, would reset to 78
bad nextents 20 for inode 2986423625, would reset to 26
        - agno = 179
        - agno = 180
        - agno = 181
[…]
        - agno = 554
        - agno = 555
        - agno = 556
        - process newly discovered inodes...
Phase 4 - check for duplicate blocks...
        - setting up duplicate extent list...
        - check for inodes claiming duplicate blocks...
        - agno = 0
        - agno = 1
        - agno = 2
[…]
        - agno = 71
        - agno = 72
        - agno = 73
bad nblocks 113 for inode 1209889624, would reset to 61
bad nextents 60 for inode 1209889624, would reset to 35
        - agno = 74
        - agno = 75
        - agno = 76
[…]
        - agno = 177
        - agno = 178
        - agno = 179
bad nblocks 63 for inode 2986423625, would reset to 78
bad nextents 20 for inode 2986423625, would reset to 26
        - agno = 180
        - agno = 181
        - agno = 182
[…]
        - agno = 554
        - agno = 555
        - agno = 556
No modify flag set, skipping phase 5
Phase 6 - check inode connectivity...
        - traversing filesystem ...
Access to block zero: fs: <(null)> inode: 1209889624 start_block : 0 start_off : 0 blkcnt : 0 extent-state : 0

Access to block zero: fs: <(null)> inode: 1209889624 start_block : 0 start_off : 0 blkcnt : 0 extent-state : 0

bad hash table for directory inode 1209889624 (no leaf entry): would rebuild
corrupt dinode 2986423625, (btree extents).  This is a bug.
Please capture the filesystem metadata with xfs_metadump and
report it to xfs@oss.sgi.com.
corrupt dinode 2986423625, (btree extents).  This is a bug.
Please capture the filesystem metadata with xfs_metadump and
report it to xfs@oss.sgi.com.
corrupt dinode 2986423625, (btree extents).  This is a bug.
Please capture the filesystem metadata with xfs_metadump and
report it to xfs@oss.sgi.com.
Segmentation fault
---snap---

I do have the mentioned meta data file, but it's about 800 MB big and
still about 100 MB if I compress it with LZMA. I can put the
compressed file on a web server or upload it to some FTP server if
it's of interest.

severity 584256 minor
kthxbye

Despite the nasty looking errors in dmesg (attached) the filesystem
seems to have been fixed by solely mounting it again. Lowering the
severity since this bug only happened during a dry run…

		Kind regards, Axel Beckert

Alex,

can you please upload xfs_metadump of filesystem in question, if possible?

Thanks.