journal size. This is the journal size. For journal on host device it must be gretter
than 512 blocks and lesser than count of blocks described by first bitmap block. In
other words, journal must be lesser or equals block_size * 8 journal offset - 1.
In the case given journal size not equals previous journal size tunefs.reiserfs will
perform journal resizing. For relocated journal it will be recreated with new params.
And for standard journal data blocks will be relocated first, then journal will be recreated
with new boundaries.
And for journal on separated device journal size may be as big as device length -
journal offset - 1.