oops with umount -lf of krb5 NFS mount.

[Vince Busam]

We've been able to reproduce an oops in 2.6.16.11 when forcing an unmount of a dead krb5 
(nfsv3) mount.

turn the nfs server off
cd /path/to/nfsmount/ (this will hang)
(in a different terminal) umount -lf /path/to/nfsmount/
(in previous terminal) ctrl+c, cd /

It doesn't always work, which is frustrating... but it happens fairly often.  Is this a 
known issue?

Thanks,
Vince

Here's the kernel output (we'll reproduce this with an untainted kernel):

Jul 17 16:44:04 return kernel: net/sunrpc/rpc_pipe.c: rpc_lookup_parent failed to find 
path /nfs/clnt62/krb5
Jul 17 16:44:04 return kernel: Unable to handle kernel NULL pointer dereference at virtual 
address 00000068
Jul 17 16:44:04 return kernel: printing eip:
Jul 17 16:44:04 return kernel: c02b6243
Jul 17 16:44:04 return kernel: *pde = 00000000
Jul 17 16:44:04 return kernel: Oops: 0002 [#1]
Jul 17 16:44:04 return kernel: SMP
Jul 17 16:44:04 return kernel: Modules linked in: isofs udf nls_iso8859_1 nls_cp437 vfat 
fat des binfmt_misc rfcomm l2cap bluetooth acpi_cpufreq cpufreq_userspace cpufreq_ondemand 
cpufreq_powersave nfsd exportfs autofs4 video button battery container ac nfs lockd 
af_packet floppy rtc hw_random snd_hda_intel snd_hda_codec snd_pcm_oss snd_mixer_oss 
snd_pcm snd_timer snd soundcore snd_page_alloc shpchp pci_hotplug dm_mod nvidia agpgart 
psmouse mousedev parport_pc lp parport ide_disk rpcsec_gss_krb5 auth_rpcgss sunrpc md_mod 
ext3 jbd mbcache thermal processor fan usb_storage usbhid tg3 ehci_hcd uhci_hcd usbcore 
sd_mod ide_cd cdrom ide_generic ata_piix libata scsi_mod piix generic ide_core unix
Jul 17 16:44:04 return kernel: CPU: 1
Jul 17 16:44:04 return kernel: EIP: 0060:[_spin_lock+3/32] Tainted: P VLI
Jul 17 16:44:04 return kernel: EFLAGS: 00010296 (2.6.16.11-gg1 #1)
Jul 17 16:44:04 return kernel: EIP is at _spin_lock+0x3/0x20
Jul 17 16:44:04 return kernel: eax: 00000068 ebx: c2b28900 ecx: dae1bda0 edx: 00000000
Jul 17 16:44:04 return kernel: esi: 00000000 edi: f8957724 ebp: dae1bd64 esp: dae1bd64
Jul 17 16:44:04 return kernel: ds: 007b es: 007b ss: 0068
Jul 17 16:44:04 return kernel: Process bash (pid: 23302, threadinfo=dae1a000 task=c4d20550)
Jul 17 16:44:04 return kernel: Stack: <0>dae1bd80 f894eb90 c2b28900 00000068 c2b28900 
c2b28a7c f8957724 dae1bdb4
Jul 17 16:44:04 return kernel: f8b8b65e c2b28900 dae1bda0 f894ebe0 ffffffe0 f744dae0 
c2b28974 dae1bda0
Jul 17 16:44:04 return kernel: dae1bda0 f744df00 f744db18 f744d324 dae1be14 f8b8bf5f 
c2b28900 f744d324
Jul 17 16:44:04 return kernel: Call Trace:
Jul 17 16:44:04 return kernel: [show_stack_log_lvl+170/224] show_stack_log_lvl+0xaa/0xe0
Jul 17 16:44:04 return kernel: [show_registers+411/528] show_registers+0x19b/0x210
Jul 17 16:44:04 return kernel: [die+265/416] die+0x109/0x1a0
Jul 17 16:44:04 return kernel: [do_page_fault+954/1457] do_page_fault+0x3ba/0x5b1
Jul 17 16:44:04 return kernel: [error_code+79/84] error_code+0x4f/0x54
Jul 17 16:44:04 return kernel: [pg0+945359760/1069810688] gss_pipe_release+0x20/0x70 
[auth_rpcgss]
Jul 17 16:44:04 return kernel: [pg0+947705438/1069810688] rpc_close_pipes+0x13e/0x140 [sunrpc]
Jul 17 16:44:04 return kernel: [pg0+947707743/1069810688] rpc_depopulate+0xaf/0x120 [sunrpc]
Jul 17 16:44:04 return kernel: [pg0+947709123/1069810688] rpc_rmdir+0x73/0xb0 [sunrpc]
Jul 17 16:44:04 return kernel: [pg0+947639885/1069810688] rpc_destroy_client+0x9d/0xf0 
[sunrpc]
Jul 17 16:44:04 return kernel: [pg0+947639856/1069810688] rpc_destroy_client+0x80/0xf0 
[sunrpc]
Jul 17 16:44:04 return kernel: [pg0+947639629/1069810688] rpc_shutdown_client+0xdd/0x140 
[sunrpc]
Jul 17 16:44:04 return kernel: [pg0+949308424/1069810688] nfs_kill_super+0x78/0xd0 [nfs]
Jul 17 16:44:04 return kernel: [deactivate_super+122/176] deactivate_super+0x7a/0xb0
Jul 17 16:44:04 return kernel: [mntput_no_expire+80/128] mntput_no_expire+0x50/0x80
Jul 17 16:44:04 return kernel: [do_exit+747/1024] do_exit+0x2eb/0x400
Jul 17 16:44:04 return kernel: [do_group_exit+55/160] do_group_exit+0x37/0xa0
Jul 17 16:44:04 return kernel: [sys_exit_group+21/32] sys_exit_group+0x15/0x20
Jul 17 16:44:04 return kernel: [sysenter_past_esp+84/117] sysenter_past_esp+0x54/0x75
Jul 17 16:44:04 return kernel: Code: 21 e2 81 42 14 00 01 00 00 f0 81 28 00 00 00 01 74 05 
e8 fd d9 ff ff 5d c3 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 90 55 89 e5 <f0> fe 08 79 
09 f3 90 80 38 00 7e f9 eb f2 5d c3 8d b6 00 00 00
Jul 17 16:44:04 return kernel: <1>Fixing recursive fault but reboot is needed!
Jul 17 16:44:52 return kernel: device eth0 left promiscuous mode