FS prob? df prob? or Infinite Improbability Drive?

[J.R. Oldroyd]

Anyone have any thoughts on what causes this?

Kernel, world are -current of 4/17.
After 13 days' uptime:

# df /home
/dev/ad2s1e  26908468 -54043195503950556 54043195528706348 -218305257630%    /home

# init 1

# umount /dev/ad2s1e
kernel: /home: unmount pending error: blocks 108086391056891904 files 0

# fsck /dev/ad2s1e
** /dev/ad2s1e
** Last Mounted on /home
** Phase 1 - Check Blocks and Sizes
** Phase 2 - Check Pathnames
** Phase 3 - Check Connectivity
** Phase 4 - Check Reference Counts
** Phase 5 - Check Cyl groups
120158 files, 12241320 used, 1212914 free (57666 frags, 144406 blocks, 0.4% fragmentation)

# mount /home

# df /home
/dev/ad2s1e  26908468  24254340   501452    98%    /home