Re: kernel BUG at linux-4.2.0/fs/btrfs/extent-tree.c:1833 on rebalance

["Stéphane Lesimple" <stephane_btrfs@lesimple.fr>]

Le 2015-09-17 08:42, Qu Wenruo a écrit :
> Stéphane Lesimple wrote on 2015/09/17 08:11 +0200:
>> Le 2015-09-17 05:03, Qu Wenruo a écrit :
>>> Stéphane Lesimple wrote on 2015/09/16 22:41 +0200:
>>>> Le 2015-09-16 22:18, Duncan a écrit :
>>>>> Stéphane Lesimple posted on Wed, 16 Sep 2015 15:04:20 +0200 as
>>>>> excerpted:
>>>>> 
>>>> 
>>>> Well actually it's the (d) option ;)
>>>> I activate the quota feature for only one reason : being able to 
>>>> track
>>>> down how much space my snapshots are taking.
>>> 
>>> Yeah, that's completely one of the ideal use case of btrfs qgroup.
>>> 
>>> But I'm quite curious about the btrfsck error report on qgroup.
>>> 
>>> If btrfsck report such error, it means either I'm too confident about
>>> the recent qgroup accounting rework, or btrfsck has some bug which I
>>> didn't take much consideration during the kernel rework.
>>> 
>>> Would you please provide the full result of previous btrfsck with
>>> qgroup error?
>> 
>> Sure, I've saved the log somewhere just in case, here your are :
>> 
>> [...]
> Thanks for your log, pretty interesting result.
> 
> BTW, did you enabled qgroup from old kernel earlier than 4.2-rc1?
> If so, I would be much relaxed as they can be the problem of old 
> kernels.

The mkfs.btrfs was done under 3.19, but I'm almost sure I enabled quota 
under 4.2.0 precisely. My kern.log tends to confirm that (looking for 
'qgroup scan completed').

> If it's OK for you, would you please enable quota after reproducing
> the bug and use for sometime and recheck it?

Sure, I've just reproduced the bug twice as I wanted, and posted the 
info, so now I've cancelled the balance and I can reenable quota. Will 
do it under 4.3.0-rc1. I'll keep you posted if btrfsck complains about 
it in the following days.

Regards,

-- 
Stéphane.