kern/41834: kernel diagnostic assertion "ncp->nc_dvp == NULL" failed

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

>Number:         41834
>Category:       kern
>Synopsis:       kernel diagnostic assertion "ncp->nc_dvp == NULL" failed
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Aug 06 19:55:00 +0000 2009
>Originator:     Manuel Bouyer
>Release:        NetBSD 5.0.1
>Organization:
>Environment:
System: NetBSD dhcp1.lip6.fr 5.0.1 NetBSD 5.0.1 (XEN3_DOMU) #0: Thu Jul 30 
01:37:42 UTC 2009  
builds%b8.netbsd.org@localhost:/home/builds/ab/netbsd-5-0-1-RELEASE/i386/200907292356Z-obj/home/builds/ab/netbsd-5-0-1-RELEASE/src/sys/arch/i386/compile/XEN3_DOMU
 i386

Architecture: i386
Machine: i386
plain ffs1, no softdep, log or quota
>Description:
        while running tar xpf as root on a full filesystem I got:
/: write failed, file system is full
tar: Failed write to file ./rescue/[ (No space left on device)
panic: kernel diagnostic assertion "ncp->nc_dvp == NULL" failed: file 
"/home/builds/ab/netbsd-5-0-1-RELEASE/src/sys/kern/vfs_cache.c", line 190
fatal breakpoint trap in supervisor mode
trap type 1 code 0 eip c0394c4c cs 9 eflags 246 cr2 bbae5000 ilevel 0
Stopped in pid 0.9 (system) at  netbsd:breakpoint+0x4:  popl    %ebp
db> tr
breakpoint(c044390b,c9ed1c88,c0459140,c02fdce3,c9b09c48,c9ed1cac,c0100168,c02d1a07,cb184eb0,0)
 at netbsd:breakpoint+0x4
panic(c044dcac,c0411fc4,c043c5c4,c043c6a8,be,cb183f6c,c9ed1cbc,c0339310,c0411fc4,c043c6a8)
 at netbsd:panic+0x1a6
__kernassert(c0411fc4,c043c6a8,be,c043c5c4,cb182068,cb182068,c9ed1d0c,c03395ea,0,cb183f6c)
 at netbsd:__kernassert+0x39
cache_disassociate(0,cb183f6c,ffffffff,0,c9b04f90,0,1998,0,0,c9ed1d08) at 
netbsd:cache_disassociate+0x100
cache_reclaim(c043c60b,0,64,c9b04f90,c0339b90,0,0,c01000a1,c9b0aa20,0) at 
netbsd:cache_reclaim+0x23a
cache_thread(c9b0aa20,0,c010006b,c0100063,c010006b,0,0,0,0,0) at 
netbsd:cache_thread+0x25
db> 
>How-To-Repeat:
        as root, tar xpf on a full filesystem ?
>Fix: