Inode Usage

[Doug Hardie]

I am building a tool to identify the file that has a specific LBA.   
The approach I am using is to search through each inode from number 2  
up.  This approach works well with UFS1 file systems as then  
preinitialize all the inodes.  However, UFS2 does lazy inode  
initialization so there are always some that are basically garbage.   
I have not found any relaiable way to determine from the inode  
contents if it is in use or not.  I suspect that information is in  
the inode bit map.  However, I haven't found any way to access that.   
Nothing in ffs.h seems to fit the need.  Is there a way to tell if  
inode x is initialized or in use?