page 8

segment usage bitmaps.  1 bit for each block
block = 1024 bytes

1024 blocks per segment

segment block
-------------
	0:	header: - sb
			- offset of usage changes
			- num of usages
			- offset of inode mapping changes
			- num of inode changes
	1:	every 8th segment gets SB


256 bits: 1 byte
1024 bits: 4 bytes: int


NEED to store info in addressable buffers.  CHECK kernel source.

---------

can I *remove* a buffer from cache, change data, then re-insert it?
		Yes->

			remove_from_queues(bh)
			insert_into_queues(bh)
			refile_buffer(bh)