kern/48849: root mirror raid fails on shutdown

[prlw1%cam.ac.uk@localhost]

>Number:         48849
>Category:       kern
>Synopsis:       root mirror raid fails on shutdown
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu May 29 17:55:00 +0000 2014
>Originator:     Patrick Welche
>Release:        -current/amd64 6.99.43
>Organization:
>Environment:
-current/amd64 6.99.43
>Description:
The bootable root partition is a raidframe mirror made from dk wedge 
components, i.e., the disks were set up with gpt rather than disklabel.

The problem is that the raid appears to work perfectly, but on shutdown it is 
marked as failed with an "IO Error". On boot, rebuilding the failed component 
to itself is always successful, and appears to work correctly again until 
shutdown, when once again it is marked as failed.

wd0,1
          64    14680192      1  GPT part - NetBSD RAIDFrame component
raid
        :dt=RAID:se#512:ns#128:nt#8:sc#1024:nc#14336:\
        :pa#2097152:oa#0:ta=4.2BSD:ba#0:fa#0:\
        :pc#14680064:oc#0:\
        :pd#14680064:od#0:\
        :pe#12582912:oe#2097152:te=4.2BSD:be#0:fe#0:

It is just the root partition which exhibits the problem
   sectPerSU: 128, SUsPerPU: 1, SUsPerRU: 1
   Queue size: 100, blocksize: 512, numBlocks: 14680064
   RAID Level: 1
   Autoconfig: Yes
   Root partition: Force

The other raid partitions are fine.

>How-To-Repeat:
Boot a -current/amd64 box with root on raid 1 built from wedges.

Note: I have seen this on the other box with wedges (eg /dev/dk0 component), 
but not on -current/amd64 boxen with ordinary disklabel components eg /dev/wd0e.
>Fix: