ref: e82f565015fd0b75085d8d2a4f1aaca53e875f64
dir: /decisions/
make /adm/frees dynamic? what value does it add? debug extents? there are test cases to debug extents already. that code should be bug free(?) and, even then, /adm/frees would be too slow to debug extents. disk/reconcile is good enough for debugging extents. /adm/ctl can show the free blocks and used blocks anyway.