kern/50159: "panic: ifree: freeing free inode" mounting root fs

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         50159
>Category:       kern
>Synopsis:       "panic: ifree: freeing free inode" mounting root fs
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Aug 21 07:50:00 +0000 2015
>Originator:     Andreas Gustafsson
>Release:        NetBSD 6.1.4
>Organization:

>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

One of my NetBSD/amd64 machines is failing to reboot after a crash.
When remounting the root file system read/write after fsck, it panics
with "panic: ifree: freeing free inode", apparently while replaying
the wapbl log.

Backtrace:

  http://www.gson.org/netbsd/bugs/ifree/ifree2.jpg

If I power cycle the machine, I just end up in the same situation
again.

This looks somewhat similar to kern/49419, but there the panic
occurred during an unlink() syscall, not mount().

Any hints how to recover from this situation would be appreciated.
Since this machine hosts my automated NetBSD test runs and most of my
other NetBSD related work, my ability to contribute to the project is
somewhat limited until I can get it to boot.

>How-To-Repeat:

>Fix:

>Unformatted: