And your point about >16TB filesystems is completely buggy. That was
*my* point. Most people - even on 64-bit - do *not* have 16TB
filesystems, and the high 32 bits are zero or contain very very little
information (ie even on a multi-terabyte filesystem, it's one or two
bits worth of information). So hash_32() is not only much more
reasonable on a 32-bit machine, the end result is basically as good
for 99.999% of all uses. Exactly *because* people don't have those big
filesystems.

I agree; that's why I suggested using hash_32() if the number of
blocks in the file system is less than 2**32.  I did look at hash_u64
and didn't think it was that bad, but that's probably because compared
to crypto checksums it's positively fast, and it's really easy to get
into the bad habit of thinking that all the world's an x86_64.  :-)

     	     	      	       	    	- Ted