nfsd, v4: oops in find_acceptable_alias, ppc32 Linux, post-2.6.27-rc1

[Paul Collins]

I just got the oops below on a ppc32 NFS4 server.  I was cross-compiling
Linux with an amd64 client at the time.  The server is running Linus's
tree as of 94ad374a0751f40d25e22e036c37f7263569d24c, the client is
running 2.6.26.

The server's kernel was cross-compiled with gcc 4.2.4-3 and binutils
2.18.50.20080610-1, both built from the Debian sources following their
toolchain-building procedures.

Annoyingly, I can't kill two of the client processes:

    1 11634 11634   977 ?           -1 D     1000   0:00 make ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu- oldconfig vmlinux modules
    1 23887 11634   977 ?           -1 D     1000   0:00 [powerpc-linux-g]

Here's the oops.  The instruction dump really was all Xes.

  Unable to handle kernel paging request for instruction fetch
  Faulting instruction address: 0x00000000
  Oops: Kernel access of bad area, sig: 11 [#1]
  PowerMac
  Modules linked in: snd_aoa_codec_tas snd_aoa_fabric_layout snd_aoa snd_aoa_i2sbus snd_aoa_soundbus radeon drm b43 mac80211 cfg80211 pcmcia snd_pcm_oss snd_pcm snd_page_alloc yenta_socket rsrc_nonstatic pcmcia_core ssb uninorth_agp agpgart ehci_hcd ohci_hcd [last unloaded: snd_aoa_soundbus]
  NIP: 00000000 LR: c0159a44 CTR: 00000000
  REGS: c1d81c70 TRAP: 0400   Not tainted  (2.6.27-rc1-00158-g643fbd8)
  MSR: 40009032 <EE,ME,IR,DR>  CR: 82002024  XER: 20000000
  TASK = c1c7b210[2306] 'nfsd' THREAD: c1d80000
  GPR00: c0159bcc c1d81d20 c1c7b210 82002044 c2e538d4 82002044 002e499d f92d835f
  GPR08: 00000000 c2e55ac4 c2e55adc c1d81d50 82002024 00000000 018985fc 01898404
  GPR16: 01898710 018c7894 c04b03f4 c04b03e0 c0173da0 c05f4e84 fffff000 00000001
  GPR24: c00c05dc 00000000 82002044 00000000 c2e538d4 c2e538d4 c0437120 c1d81d20
  NIP [00000000] 0x0
  LR [c0159a44] find_acceptable_alias+0x44/0x108
  Call Trace:
  [c1d81d20] [c00cbab8] exportfs_d_alloc+0x40/0x70 (unreliable)
  [c1d81d50] [c0159bcc] exportfs_decode_fh+0xc4/0x200
  [c1d81e80] [c015d568] fh_verify+0x2e8/0x578
  [c1d81ed0] [c016b1ec] nfsd4_putfh+0x60/0x78
  [c1d81ef0] [c016afd0] nfsd4_proc_compound+0x1e4/0x34c
  [c1d81f30] [c015a060] nfsd_dispatch+0xfc/0x220
  [c1d81f50] [c0400c70] svc_process+0x3e4/0x6e8
  [c1d81f90] [c015a8bc] nfsd+0x1c4/0x294
  [c1d81fd0] [c0049e48] kthread+0x5c/0x9c
  [c1d81ff0] [c00125c0] kernel_thread+0x44/0x60
  Instruction dump:
  XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
  XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
  ---[ end trace 88de9451d0d3e759 ]---

-- 
Paul Collins
Wellington, New Zealand

Dag vijandelijk luchtschip de huismeester is dood