Re: PROBLEM: Kernel panic and system crash during RAID disk failure

From: Darko
Date: Mon Oct 31 2011 - 00:55:21 EST

Hi Yongqiang,

I am using kernel version 3.0.8. Looking through the file super.c, the file already has the code mentioned on the web. I also noticed the date of the post ( is back from March of 2011. I think the bug I reported here was not fixed by that patch since the kernel version I am using is much newer than March 2011.

I am not sure if I understand what you mean by "commit 0449641130 ext4"?



On Mon, 31 Oct 2011, Yongqiang Yang wrote:

Date: Mon, 31 Oct 2011 12:25:18 +0800
From: Yongqiang Yang <xiaoqiangnk@xxxxxxxxx>
To: Darko <darko@xxxxxxxxxx>
Cc: NeilBrown <neilb@xxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>,
linux-kernel@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx
Subject: Re: PROBLEM: Kernel panic and system crash during RAID disk failure

Hi Darko,

The bug has been fixed by commit 0449641130 ext4: Init timer earlier
to avoid a kernel panic in __save_error_info.

I suspect you mounted ext2/3 partition using ext4 module.


On Mon, Oct 31, 2011 at 11:13 AM, Darko <darko@xxxxxxxxxx> wrote:
Thank you for your reply!

I wanted to add to this that I was able to replicate the problem with ext3
and ext2 file systems as well. They both hard lock the system, and the only
way to recovery is to push the reset button. I can see the trace error on
the screen, but I am unable to do anything with it, since it goes by so fast
that the portion which says "kernel BUG" is invisible. I assume they both
have similar issues with the code in kernel/timer.c

On the other hand, I tried using raiserfs 3.5 tonight, and I got
input/output error as expected. The system did not crash. Just another proof
that a bug is laying somewhere in the ext2/3/4 file system.

When someone comes up with a patch, I am willing to try it out and feed you
back with the report.

Hope this helps.

Thank You,

Darko Kraus

On Sun, 30 Oct 2011, NeilBrown wrote:

Date: Sun, 30 Oct 2011 19:05:48 +1100
From: NeilBrown <neilb@xxxxxxx>
To: Darko <darko@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx,
Subject: Re: PROBLEM: Kernel panic and system crash during RAID disk

On Sun, 30 Oct 2011 03:27:28 -0400 (EDT) Darko <darko@xxxxxxxxxx> wrote:


I have been doing some testing with the md RAID driver and I think I
discovered a problem with it.
Everything was performed on a system with a single hard drive using loop
devices as virtual raid devices.
So here is the setup:
/dev/sdc is my main drive that hold entire Linux OS and has one
in the /tmp I created 7 files, 100MB each and associated them with loop

losetup -a
/dev/loop0: [0821]:294820 (/var/tmp/raid-0)
/dev/loop1: [0821]:294857 (/var/tmp/raid-1)
/dev/loop2: [0821]:300120 (/var/tmp/raid-2)
/dev/loop3: [0821]:301073 (/var/tmp/raid-3)
/dev/loop4: [0821]:301074 (/var/tmp/raid-4)
/dev/loop5: [0821]:301075 (/var/tmp/raid-5)
/dev/loop6: [0821]:301076 (/var/tmp/raid-6)

The next step was, created an RAID6 array:
mdadm --create /dev/md10 --level=6 -raid-deviced=7 /dev/loop[0-6]

Here is how it looks so far:

cat /proc/mdstat
Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md10 : active raid6 loop6[6] loop5[5] loop4[4] loop3[3] loop2[2] loop1[1]
      499200 blocks super 1.2 level 6, 512k chunk, algorithm 2 [7/7]

Then the filesystem...
mkfs.ext4 -b 4096 -i 4096 -m 0 /dev/md10

Mounting the file system to a folder called 'A' right in the root of my

mount /dev/md10 /A

Then I copied a few files on that file system. So far everything is good.

Then I purposly failed 2 drives:
mdadm --manage /dev/md10 --fail /dev/loop0
mdadm --manage /dev/md10 --fail /dev/loop1

The array continues to run fine in degraded mode. I was wondering what
would happen if another drive fails. So while I was doing a write
operating right in that filesystem (/dev/md10) using:
dd if=/dev/zero of=testfile bs=1k count=360000  ...

...quickly switched to a different console and entered the command:
mdadm --manage /dev/md10 --fail /dev/loop2

...which made 3 failed drives and the array can no longer work...

Well I would be happy to see just the array not working, but kernel panic
in both versions and 3.0.8 made me worry that it is serious bug
and appears to be in older and newer kernels as well.
I repeated this several times, and mostly the machine gets locked up with
kernel panic. But once I was able to get it not to lock up all the way,
and that is how I have dmesg output.

The attached files include dmesg from the system startup until the bug
trace, and some additional information regarding my system that might be

For any additional question, please feel free to contact me!

I hope this info helps someone find and resolve the problem in the code.

The important part of your kernel log message is:

[ 1227.766202] ------------[ cut here ]------------
[ 1227.766259] kernel BUG at kernel/timer.c:681!
[ 1227.766311] invalid opcode: 0000 [#1] SMP
[ 1227.766365] last sysfs file: /sys/devices/virtual/block/md10/dev
[ 1227.766419] Modules linked in:
[ 1227.766471]
[ 1227.766520] Pid: 1507, comm: mount Not tainted #7
[ 1227.766633] EIP: 0060:[<c104f960>] EFLAGS: 00010246 CPU: 0
[ 1227.766690] EIP is at mod_timer+0x210/0x250
[ 1227.766742] EAX: 00000000 EBX: f5494e1c ECX: 00000000 EDX: 00000000
[ 1227.766796] ESI: 00000000 EDI: 05348416 EBP: f54a3c90 ESP: f54a3c74
[ 1227.766851]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
[ 1227.766904] Process mount (pid: 1507, ti=f54a2000 task=f2068880
[ 1227.767002] Stack:
[ 1227.767003]  f2068880 f54b159c 00000010 00000000 f1f8e400 f4efc57c
0000128d f54a3ca8
[ 1227.767003]  c11cb7ba c17d4e52 f4efc400 00000124 00000000 f54a3cb4
c11ce4e6 ecee6318
[ 1227.767003]  f54a3cdc c11cf7cc ecec7578 00000124 00000000 f4efc400
f54a3cd4 00000124
[ 1227.767003] Call Trace:
[ 1227.767003]  [<c11cb7ba>] ? __save_error_info.clone.61+0x7a/0xf0
[ 1227.767003]  [<c11ce4e6>] ? save_error_info+0x16/0x30
[ 1227.767003]  [<c11cf7cc>] ? ext4_error_inode+0x4c/0xf0
[ 1227.767003]  [<c11b57e1>] ? __ext4_get_inode_loc+0x201/0x410
[ 1227.767003]  [<c110b62a>] ? inode_init_always+0x1aa/0x1c0
[ 1227.767003]  [<c11b72f9>] ? ext4_iget+0x59/0x6f0
[ 1227.767003]  [<c11d2716>] ? ext4_fill_super+0x1ab6/0x2c70
[ 1227.767003]  [<c114896f>] ? disk_name+0xbf/0xd0
[ 1227.767003]  [<c10fa119>] ? mount_bdev+0x179/0x1c0
[ 1227.767003]  [<c11d0c60>] ? ext4_fill_super+0x0/0x2c70
[ 1227.767003]  [<c11ca17f>] ? ext4_mount+0x1f/0x30
[ 1227.767003]  [<c11d0c60>] ? ext4_fill_super+0x0/0x2c70
[ 1227.767003]  [<c10f9835>] ? vfs_kern_mount+0x75/0x250
[ 1227.767003]  [<c110df03>] ? get_fs_type+0x33/0xb0
[ 1227.767003]  [<c11ca160>] ? ext4_mount+0x0/0x30
[ 1227.767003]  [<c10f9a6e>] ? do_kern_mount+0x3e/0xe0
[ 1227.767003]  [<c111080f>] ? do_mount+0x35f/0x6b0
[ 1227.767003]  [<c10d47c9>] ? strndup_user+0x49/0x70
[ 1227.767003]  [<c1110e0b>] ? sys_mount+0x6b/0xa0
[ 1227.767003]  [<c17b550c>] ? syscall_call+0x7/0xb
[ 1227.767003] Code: fe ff ff 8b 0e 89 4d e4 8b 46 04 83 c6 08 89 f9 89 da
ff 55 e4 8b 06 85 c0 89 45 e4 75 ea e9 aa fe ff ff 8b 75 ec e9 ee fe ff ff
<0f> 0b 8b 55 04 89 d8 e8 34 f9 ff ff e9 2a fe ff ff 8b 35 30 b8
[ 1227.767003] EIP: [<c104f960>] mod_timer+0x210/0x250 SS:ESP
[ 1227.770073] ---[ end trace d7b3d7a67954d202 ]---

which happens after:

[ 1137.167043] Aborting journal on device md10-8.
[ 1137.167058] Buffer I/O error on device md10, logical block 139265
[ 1137.167060] lost page write due to I/O error on md10
[ 1137.167065] JBD2: I/O error detected when updating journal superblock
for md10-8.
[ 1137.660922] Buffer I/O error on device md10, logical block 1
[ 1137.660926] lost page write due to I/O error on md10
[ 1137.660932] EXT4-fs error (device md10): ext4_journal_start_sb:260:
Detected aborted journal
[ 1137.661046] EXT4-fs (md10): Remounting filesystem read-only
[ 1137.661103] EXT4-fs (md10): previous I/O error to superblock detected
[ 1137.661313] Buffer I/O error on device md10, logical block 1
[ 1137.661315] lost page write due to I/O error on md10
[ 1219.891363] EXT4-fs (md10): previous I/O error to superblock detected
[ 1220.050654] Buffer I/O error on device md10, logical block 1
[ 1220.050657] lost page write due to I/O error on md10
[ 1220.050663] EXT4-fs error (device md10): ext4_put_super:728: Couldn't
clean up the journal

and some more "Buffer I/O error"s.

So it looks like an ext4 issue.

I have Cc:ed the appropriate list.

Thanks for the report.


Darko Kraus
Enterprise Network Administrator

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Best Wishes
Yongqiang Yang

Darko Kraus
Enterprise Network Administrator