oops jffs2_garbage_collect_live in 3.2.16

[Albrecht Dreß]

Hi all,

I'm running 3.2.16 on a Freescale MPC5200B (PPC) based board.  One MTD device with a jffs2 fs on it is a 512 kbyte NVRAM (/dev/mtd6), which is quite intensively used (syslogd writes to it).

I got an oops (a NULL pointer deref?) while I was running a test application which reads/writes a vfat-formatted CF card over the parallel ata interface of the '5200:

[105543.288910] Unable to handle kernel paging request for data at address 0x00000000
[105543.324759] Faulting instruction address: 0xc013a6c4
[105543.347657] Oops: Kernel access of bad area, sig: 11 [#1]
[105543.353293] PREEMPT test-cf
[105543.356611] Modules linked in:
[105543.359842] NIP: c013a6c4 LR: c0101fec CTR: 00000077
[105543.365026] REGS: cfabdd20 TRAP: 0300   Not tainted  (3.2.16)
[105543.371001] MSR: 00009032 <EE,ME,IR,DR>  CR: 48884022  XER: 00000000
[105543.377659] DAR: 00000000, DSISR: 20000000
[105543.381949] TASK = cfa28000[81] 'jffs2_gcd_mtd6' THREAD: cfabc000
[105543.388103] GPR00: 00000000 cfabddd0 cfa28000 fffffffc 00000000 00000002 00000000 54cc9384
[105543.396818] GPR08: c028e898 c0290000 00000000 ddd86af2 c028e548 df7fffff 0fff0000 cfabddfc
[105543.405530] GPR16: cfabddf8 cfabddf0 cfabddec cfabde00 cfabddf4 c0ad4000 00002000 00002000
[105543.414238] GPR24: 00001d07 00000006 00000000 c0ad4d07 4fbb3ec9 4fbb3ec9 cfa7f400 00000077
[105543.423160] NIP [c013a6c4] crc32_le+0xa4/0x150
[105543.427834] LR [c0101fec] jffs2_garbage_collect_live+0x624/0xf18
[105543.434076] Call Trace:
[105543.436679] [cfabddd0] [cf37b070] 0xcf37b070 (unreliable)
[105543.442329] [cfabdde0] [c0101f20] jffs2_garbage_collect_live+0x558/0xf18
[105543.449305] [cfabde90] [c0102fa8] jffs2_garbage_collect_pass+0x6c8/0x7c4
[105543.456284] [cfabdee0] [c01045f8] jffs2_garbage_collect_thread+0xa8/0x19c
[105543.463349] [cfabdf90] [c003d354] kthread+0x7c/0x80
[105543.468466] [cfabdff0] [c000e32c] kernel_thread+0x4c/0x68
[105543.474093] Instruction dump:
[105543.477230] 7c0a5a78 70800003 4240ffac 4082ffd0 54bff0bf 3864fffc 54a507be 41820068
[105543.485326] 3d20c029 7fe903a6 38c00000 3989e548 <7d26202e> 38c60004 7d494a78 552bd5ba

This happened exactly *once*, and I could not reproduce the issue.

Any idea what went wrong, and how I could fix the cause?

Thanks in advance,
Albrecht.
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