What does this Linux kernel trace mean?

Question

I’m running a linux server at home which is mostly a file and e-mail server and a digital video recorder. All the data goes on an ext4 partition on a software raid-6.

Every now and then (sometimes twice a day, sometimes twice a month) the whole server locks up. Sometimes I have a kernel report in the syslog which I cannot understand:

------------[ cut here ]------------
kernel BUG at fs/ext4/inode.c:2118!
invalid opcode: 0000 [#1] SMP
last sysfs file: /sys/devices/virtual/net/ppp0/uevent
CPU 0
Modules linked in: ppp_async crc_ccitt nvidia(P) fcpci(P) scsi_wait_scan

Pid: 27841, comm: mythbackend Tainted: P            2.6.39-gentoo-r3 #2 System manufacturer System Product Name/M2N-E
RIP: 0010:[<ffffffff8116f580>]  [<ffffffff8116f580>] mpage_da_submit_io+0x268/0x3bf
RSP: 0018:ffff88004262bba8  EFLAGS: 00010286
RAX: ffffea000048b650 RBX: ffffea000051d118 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff880000826890 RDI: 0000000000005d38
RBP: ffff88004262bcf8 R08: 000000000d654538 R09: 0100000000002820
R10: 0000000000005d0d R11: 0000000000000000 R12: ffff88004262bde8
R13: ffff88004262bd28 R14: ffff88005ef46150 R15: 0000000000005d37
FS:  00007fbeb053f700(0000) GS:ffff88007fc00000(0000) knlGS:00000000f74aa8e0
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007fdcb7a36000 CR3: 000000006b721000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process mythbackend (pid: 27841, threadinfo ffff88004262a000, task ffff88007fb83330)
Stack:
 ffff88007b193b88 ffff88004262bc98 ffff88004741c138 000004ac00001424
 ffff88004262bc28 0000000000005d70 ffff88005ef46298 00000000811a337f
 0000000000005d70 000000010000000e ffff88004262bc30 0000100000000000
Call Trace:
 [<ffffffff811731df>] mpage_da_map_and_submit+0x2c6/0x2dc
 [<ffffffff8117390a>] ext4_da_writepages+0x2d4/0x465
 [<ffffffff810aafd6>] do_writepages+0x1c/0x26
 [<ffffffff810a3bc0>] __filemap_fdatawrite_range+0x4b/0x4d
 [<ffffffff810a3bea>] filemap_write_and_wait_range+0x28/0x51
 [<ffffffff810fcba1>] vfs_fsync_range+0x30/0x75
 [<ffffffff810fcc3b>] vfs_fsync+0x17/0x19
 [<ffffffff810fcc66>] do_fsync+0x29/0x3e
 [<ffffffff810fcc89>] sys_fdatasync+0xe/0x12
 [<ffffffff8155f4fb>] system_call_fastpath+0x16/0x1b
Code: c1 00 02 00 00 74 09 f0 80 60 01 fd 4c 89 40 18 4c 8b 08 41 f7 c1 00 10 00 00 75 09 4c 8b 08 41 80 e1 20 74 0a 4c 39 40 18 74 04 <0f> 0b eb fe 41 f6 45 12 80 74 05 f0 80 48 02 80 f0 80 60 01 ef
RIP  [<ffffffff8116f580>] mpage_da_submit_io+0x268/0x3bf
 RSP <ffff88004262bba8>
---[ end trace c228cd85b8ef2f99 ]---

Answer 1

Looking at your trace it seems that the kernel oops during writing in the ext4 file system. If you have not prepared for linux crash, then I am afraid there is nothing much that you could do.

You can read this :

http://magazine.redhat.com/2007/08/15/a-quick-overview-of-linux-kernel-crash-dump-analysis/

This will tell you how to setup your system so that you can check your system, next time it crashes. And if you think it's a bug in kernel (either in ext4 or raid6), raise a bug at the appropriate forum. Or, you can try to solve the bug yourself.