Re: [PATCH 0/3 v5][RFC] ext3/4: enhance fsync performance when using CFQ

From: Jeff Moyer
Date: Tue Jun 29 2010 - 10:56:32 EST

Tao Ma <> writes:

> Hi Jeff,
> On 06/27/2010 09:48 PM, Jeff Moyer wrote:
>> Tao Ma<> writes:
>>> I am sorry to say that the patch make jbd2 locked up when I tested
>>> fs_mark using ocfs2.
>>> I have attached the log from my netconsole server. After I reverted
>>> the patch [3/3], the box works again.
>> I can't reproduce this, unfortunately. Also, when building with the
>> .config you sent me, the disassembly doesn't line up with the stack
>> trace you posted.
>> I'm not sure why yielding the queue would cause a deadlock. The only
>> explanation I can come up with is that I/O is not being issued. I'm
>> assuming that no other I/O will be completed to the file system in
>> question. Is that right? Could you send along the output from sysrq-t?
> yes, I just mounted it and begin the test, so there should be no
> outstanding I/O. So do you need me to setup another disk for test?
> I have attached the sysrq output in sysrq.log. please check.

Well, if it doesn't take long to reproduce, then it might be helpful to
see a blktrace of the run. However, it might also just be worth waiting
for the next version of the patch to see if that fixes your issue.

> btw, I also met with a NULL pointer deference in cfq_yield. I have
> attached the null.log also. This seems to be related to the previous
> deadlock and happens when I try to remount the same volume after
> reboot and ocfs2 try to do some recovery.

Pid: 4130, comm: ocfs2_wq Not tainted 2.6.35-rc3+ #5 0MM599/OptiPlex 745
RIP: 0010:[<ffffffff82161537>]
[<ffffffff82161537>] cfq_yield+0x5f/0x135
RSP: 0018:ffff880123061c60 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88012c2b5ea8 RCX: ffff88012c3a30d0

ffffffff82161528: e8 69 eb ff ff callq ffffffff82160096 <cfq_cic_lookup>
ffffffff8216152d: 49 89 c6 mov %rax,%r14
ffffffff82161530: 48 8b 85 00 06 00 00 mov 0x600(%rbp),%rax
ffffffff82161537: f0 48 ff 00 lock incq (%rax)

I'm pretty sure that's a NULL pointer deref of the tsk->iocontext that
was passed into the yield function. I've since fixed that, so your
recovery code should be safe in the newest version (which I've not yet

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at