I have observed many crashes in fscache/cachefiles when accessing an automounted
NFS4 volume. I don't recall exactly what I was doing during this one.

I don't have a reproducer for this crash.

I'm runing:
kernel-2.6.18-8.1.1.el5
cachefilesd-0.7-6.el5
Backtrace from crash:
 #0 [f1d4edb4] crash_kexec at c0442bde
 #1 [f1d4edf8] die at c04054ae
 #2 [f1d4ee28] do_invalid_op at c0405bfe
 #3 [f1d4eed8] error_code (via invalid_op) at c0404a6f
    EAX: 00000027  EBX: 00000000  ECX: f8cb2388  EDX: f1d4ef14  EBP: 00000000 
    DS:  007b      ESI: f1b373d4  ES:  007b      EDI: 00000000 
    CS:  0060      EIP: f8cb108e  ERR: ffffffff  EFLAGS: 00010246 
 #4 [f1d4ef0c] __fscache_relinquish_cookie at f8cb108e
 #5 [f1d4ef2c] nfs_free_server at f8ed5aaf
 #6 [f1d4ef34] deactivate_super at c04702d4
 #7 [f1d4ef40] sys_umount at c0483160
 #8 [f1d4efac] sys_oldumount at c0483193
 #9 [f1d4efb8] system_call at c0403ef8
    EAX: ffffffda  EBX: 09f0b6d8  ECX: 00000000  EDX: 0037cd2c 
    DS:  007b      ESI: 09f0b748  ES:  007b      EDI: bfccddb8 
    SS:  007b      ESP: bfccdbe8  EBP: bfccdc38 
    CS:  0073      EIP: 00efb402  ERR: 00000016  EFLAGS: 00000246 

System data from crash:
      KERNEL: /usr/lib/debug/lib/modules/2.6.18-8.1.1.el5/vmlinux
    DUMPFILE: vmcore
        CPUS: 2
        DATE: Sun Mar 25 23:41:32 2007
      UPTIME: 00:14:10
LOAD AVERAGE: 0.04, 0.20, 0.29
       TASKS: 172
    NODENAME: mbooth.redhat.laptop
     RELEASE: 2.6.18-8.1.1.el5
     VERSION: #1 SMP Mon Feb 26 20:38:02 EST 2007
     MACHINE: i686  (1662 Mhz)
      MEMORY: 2 GB
       PANIC: "kernel BUG at fs/fscache/cookie.c:792!"

My reading of it suggests a bug in NFS4's usage of the netfs API, however
causing a kernel panic seems too severe a response.

I can provide a 2G core file directly to an individual developer on request.