Journaling patches

[Simon Burge <simonb%NetBSD.org@localhost>]

Folks,

Unfortunately none of the outstanding issues have been solved yet with
the journaling support.  However, I'd like to commit the patches to the
source tree in the new few days - this will hopefully make it easier for
more people to test and look at these issues.

In summary, the issues are:

 - Can't log the root filesystem (or any FS if /dev isn't an ffs).
 - Log must currently live at end of partition.
 - Some heavy workload performance issues on SMP machines.
 - Some stability issues on SMP machines.

There is one other behavioural change.  You now need to use the "-f"
option to mount a dirty filesystem.  I'm not sure of the original reason
for this, and am not sure if this behaviour is desirable or not.  Any
comments?

A patch against today's -current is at:

   http://www.NetBSD.org/~simonb/wapbl-current-20080422.diff

Cheers,
Simon.