kern/41604: root-on-RAID set always dirty on startup

[Jukka Salmi <j+nbsd%salmi.ch@localhost>]

>Number:         41604
>Category:       kern
>Synopsis:       root-on-RAID set always dirty on startup
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jun 16 15:30:00 +0000 2009
>Originator:     Jukka Salmi
>Release:        NetBSD 5.99.12
>Organization:
>Environment:
System: NetBSD moray.salmi.ch 5.99.12 NetBSD 5.99.12 (MORAY) #0: Mon May 25 
17:09:01 CEST 2009 
root%moray.salmi.ch@localhost:/b/build/nbsd/c/i386/sys/arch/i386/compile/MORAY 
i386
Architecture: i386
Machine: i386
>Description:
Since upgrading from 5.99.11 to 5.99.12, the parity status of the RAID1 set
which contains the root file system (and /var and /usr) is always dirty on
system startup, even if the last shutdown was clean.  However, another RAID1
set (which is also auto-configured) in the same system is _not_ dirty on system
startup.
This regression seems to have been introduced with this change:
http://mail-index.netbsd.org/source-changes/2009/05/23/msg221612.html
At least a kernel from sources just before that commit
(`cvs up -D 2009.05.23.18.25.00') does not show the problem, while one from
sources just after it (`cvs up -D 2009.05.23.18.28.10') does show it.
>How-To-Repeat:
Run NetBSD 5.99.12 or later, configure the root file system to be on a RAID1
set (`raidctl -A root ...'), shut down the system, boot it and check parity
status of the RAID set in question.
>Fix:
Would be greatly appreciated...