On Oct 2, 2006, at 2:53 PM, Jochen Kunz wrote:

> On Mon, 2 Oct 2006 13:45:07 -0700
> Jason Thorpe <thorpej@shagadelic.org> wrote:
>
>> Doing journaling as a mount option is not as feasible as it sounds.
>> You actually need to record "journal enabled" in the superblock
>> because it changes how recovery is performed.
> Sure. I should have written: Ability to switch jornaling on or off
> without affecting data stored on the file system. (Maybe via tunefs 
> (8).)

This is where it all gets exciting :-)

So, tunefs would need:

1- Journal reply (for "turn journal off").

2- A way to allocate space for the journal in the file system  
(presumably contiguous space, this this avoids having to do bmap to  
write to the journal) (for "turn journal on").

-- thorpej