free block bitmap

[Eno Thereska]

Hi,

I am using FreeBSD4.4 with FFS as the underlying file system.
I need to examine which blocks in the file system
are currently in use. These blocks can be metadata or data blocks.

I have looked at the FFS code and it seems the only way to get
the list of free blocks (or busy blocks) is by querying
each cylinder group's (cg) bitmap of free blocks.

Is there a global bitmap that keeps track of busy/free blocks
over the entire file system or is the only option
the cg-by-cg lookup?

Thanks a lot
Eno