git: hammer2 - freemap and data check code

Michael Neumann mneumann at
Mon Aug 4 05:01:13 PDT 2014

Am 04.08.2014 um 10:20 schrieb Matthew Dillon:
 > commit a71db85d9ad6015dbdba1b15106e08ea69fdd67d
 > Author: Matthew Dillon <dillon at>
 > Date:   Mon Aug 4 01:11:46 2014 -0700
 >      hammer2 - freemap and data check code
 >      * Change the freemap to use 8 sets = ~32 reserved blocks instead 
of 14 sets.
 >        Use a straight iterator.  (TODO - must invalidate newer 
volumes if an older
 >        volume backup is mounted RW because freemap will become 
 >      * Update the freemap documentation.  Requires more work.

I think a little error creeped into the documentation.

You write:

   Level 1 - (radix 10 + 21) 16KB blockmap representing 2GB

Shouldn't it be

   64KB blockmap?

Also, is it still true that HAMMER2 is always sized in multiples of 8MB?
What is the reason behind? To make sure that we have a least one volume
header backup?



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