HAMMER fs space problem

[lhmwzy]

I mount a HAMMER file system called /www
$df -h
Filesystem    Size   Used  Avail Capacity  Mounted on
/dev/da0s1a   252M    88M   144M    38%    /
/dev/da0s1d   252M    25M   207M    11%    /var
/dev/da0s1e   252M    14K   232M     0%    /tmp
/dev/da0s1f   7.9G   2.1G   5.1G    30%    /usr
/dev/da0s1g    29G   169M    26G     1%    /home
procfs        4.0K   4.0K     0B   100%    /proc
www            19G   0M    19G     0%    /www


I create a php file which content is <? phpinfo(); ?>

Then after days,run df -h again:
$df -h
Filesystem    Size   Used  Avail Capacity  Mounted on
/dev/da0s1a   252M    88M   144M    38%    /
/dev/da0s1d   252M    25M   207M    11%    /var
/dev/da0s1e   252M    14K   232M     0%    /tmp
/dev/da0s1f   7.9G   2.1G   5.1G    30%    /usr
/dev/da0s1g    29G   169M    26G     1%    /home
procfs        4.0K   4.0K     0B   100%    /proc
www            19G   8.0M    19G     0%    /www

I am not run a cron to reblock /www
which file(s)  consume the 8m space?

Or run a cron like
     15 2 * * * hammer -c /var/run/www -t 300 reblock /www >/dev/null 2>&1
would make it better?

I run      15 2 * * * hammer -c /var/run/Home -t 300 reblock /home
>/dev/null 2>&1 manually,

$hammer -c /var/run/www -t 300 reblock /www
reblock free level 0
Reblock /www succeeded
Reblocked:
    1/1 btree nodes
    9/9 data elements
    909/909 data bytes
$df -h
Filesystem    Size   Used  Avail Capacity  Mounted on
/dev/da0s1a   252M    88M   144M    38%    /
/dev/da0s1d   252M    25M   207M    11%    /var
/dev/da0s1e   252M    14K   232M     0%    /tmp
/dev/da0s1f   7.9G   2.1G   5.1G    30%    /usr
/dev/da0s1g    29G   169M    26G     1%    /home
procfs        4.0K   4.0K     0B   100%    /proc
www            19G   8.0M    19G     0%    /www

the 8M space is not released.