XFS defragmentation issue

[John Lister]

  Hi, using ubuntu 9.04, kernel version 2.6.28-18 and xfsprog v2.10.2-1 
I'm trying to defragment a drive. If I use xfs_db to check for 
fragmentation it shows for example that a file has 20k+ fragments:
inode 578505506 actual 23240 ideal 1

mapping the inode to the file and running xfs_frs states that the file 
is fully defragmented.

Also running xfs_frs says the drive is defragmented while xfs_db for 
example reports 300k fragments.

Which is right? and is it possible to defragment the file assuming it is 
fragmented so badly, if so how?

Thanks

John