>Number:         32986
>Category:       kern
>Synopsis:       unmounting a union filesystem causes panic
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Mar 04 11:25:00 +0000 2006
>Originator:     Kouichirou Hiratsuka
>Release:        NetBSD 3.99.16, NetBSD 3.0_STABLE
>Organization:
>Environment:
System: NetBSD firefly.localdomain 3.99.16 NetBSD 3.99.16 (X32) #1: Fri Mar 3 07:39:54 JST 2006 root@firefly.localdomain:/work/obj/usr/src/sys/arch/i386/compile/X32 i386
Architecture: i386
Machine: i386
>Description:
	Unmounting a union filesystem causes panic, if it's busy.
	This happens with -current and 3.0_STABLE.

# mkdir /foo /bar
# mount -t union -o -b /foo /bar
# cd /bar
# umount /bar
panic: unmount: dangling vnode
Stopped in pid 79.1 (umount) at netbsd:cpu_Debugger+0x4:        leave
db> 

	NetBSD 3.0 doesn't panic.

# umount /bar
umount: /bar: Device busy
# uname -a
NetBSD  3.0 NetBSD 3.0 (GENERIC) #0: Mon Dec 19 01:04:02 UTC 2005  builds@works.netbsd.org:/home/builds/ab/netbsd-3-0-RELEASE/i386/200512182024Z-obj/home/builds/ab/netbsd-3-0-RELEASE/src/sys/arch/i386/compile/GENERIC i386

>How-To-Repeat:
	see above

>Fix:
	Sorry, I don't know.