Re: reproducable oops in btrfs/130 with latests mainline

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2017年10月20日 17:25, Po-Hsu Lin wrote:
> Thanks for the info.
> 
> I have checked the comment inside the test case, which state that:
> # And unfortunately, btrfs send is one of these operations, and will cause
> # softlock or OOM on systems with small memory(<4G).
> 
> To my experience, this will stuck on a system with 32G memory too.

Sorry for the confusion, I mean softlock if you have enough memory.
And if you don't have enough memory, you will get an OOM.

> 
> And in the end of the script, it says:
> # send out the subvolume, and it will either:
> # 1) OOM since memory is allocated inside a O(n^3) loop
> # 2) Softlock since time consuming backref walk is called without scheduling.
> 
> I can see the soft lockup behaviour (I guess this is the second result
> listed above?) from dmesg as described in
> https://bugs.launchpad.net/bugs/1718925
> 
> So I'm curious that does anyone know how long it might take if this test works?

Just skip it, or make it dangerous.
(Which I should do it in the very beginning)

Thanks,
Qu

> Tried 8 hours as a timeout limit but no luck. Or maybe this test is
> totally broken?
> 
> Thanks!
> 
> On Tue, Oct 17, 2017 at 9:03 PM, Jeff Mahoney <jeffm@suse.com> wrote:
>> On 10/17/17 8:46 AM, Qu Wenruo wrote:
>>>
>>>
>>> On 2017年10月17日 19:11, Po-Hsu Lin wrote:
>>>> Hello Chris,
>>>>
>>>> I can reproduce this on my side too, with Ubuntu 16.04 + 4.4.0-97 kernel.
>>>
>>> Btrfs/130 is a known bug.
>>>
>>> I submitted it to raise the concern about such situation and purposed
>>> one possible solution (just disable deduped file detection).
>>>
>>> But the solution doesn't get accepted.
>>
>> It also works very well as a performance test for qgroup runtime
>> improvements. :)
>>
>> -Jeff
>>
>>> Thanks,
>>> Qu
>>>>
>>>> PREEMPT config:
>>>> $ cat config-4.4.0-97-generic | grep PREEMPT
>>>> CONFIG_PREEMPT_NOTIFIERS=y
>>>> # CONFIG_PREEMPT_NONE is not set
>>>> CONFIG_PREEMPT_VOLUNTARY=y
>>>> # CONFIG_PREEMPT is not set
>>>>
>>>> Bug reports on launchpad:
>>>> https://bugs.launchpad.net/bugs/1718925
>>>> https://bugs.launchpad.net/bugs/1717443
>>>> --
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>>>
>>
>>
>> --
>> Jeff Mahoney
>> SUSE Labs
>>
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