In some email I received from Jason Thorpe, sie wrote:
> 
> /* dia_flags */
> #define	DIAF_NEXT_VALID	0x00000001	/* dia_next is valid */

I don't think this is needed.  That field should not be controlled by
a user and as such, it's either going to be 0 (no next) or point to
something useful.  But, other flags might be useful..

> There should be a set of functions that:
> 
> 	* allocate a fs block for a dinode_aux

Hmmm...I'd prefer to use inodes rather than disk blocks.  Disk blocks
are quite large...