Re: Quota limit question

[Dongsheng Yang <yangds.fnst@cn.fujitsu.com>]

Sorry about the late reply!!

On 03/10/2015 04:41 PM, Qu Wenruo wrote:
>
>
> -------- Original Message  --------
> Subject: Re: Quota limit question
> From: Christian Robottom Reis <kiko@canonical.com>
> To: Duncan <1i5t5.duncan@cox.net>
> Date: 2015年03月07日 05:44
>
>> Just as a follow-up, I upgraded btrfs-tools and the kernel again. I
>> currently have a filesystem which reports 1G exclusive use:
>>
>> root@riff# btrfs qg show -r -e /var -p -c
>> qgroupid         rfer         excl     max_rfer     max_excl parent 
>> child
>> --------         ----         ----     --------     -------- ------ 
>> -----
>> 0/261         1.52GiB      1.01GiB        0.00B    100.00GiB ---     ---
> It's recommended to sync the btrfs before 'qg show' command, since 
> quota tree is not updated until commit transaction.

Yes, sync is required be fore qg show now. There is no ioctl to get 
qgroup info from kernel space,
so we have to read the data from disk then we have to do a sync before 
we getting the correct information.
>>
>> This filesystem reports over quota, and removing the quota fixes that:
>>
>> root@riff# touch x
>> touch: cannot touch ‘x’: Disk quota exceeded
>> root@riff# btrfs qg limit -e
>> none 261 /var
>> root@riff# touch x
>> root@riff#
>>
>> So at the moment quotas are pretty much unusable in kernel 3.18.6/tools
>> 3.18.2, at least for my use case, and that's a bit surprising since
>> there isn't anything very interesting about it (other than it contains a
>> bunch of lxc-cloned rootfs).
> Yes, Btrfs really has some problems, from yours to other annoying 
> incorrect values.
>
> [Some guess]
> For your case, I'm afraid your reserved space in your qgroup takes too 
> much space, and it's definitely a bug. Maybe some 
> btrfs_qgroup_reserve() leaking?

Agreed, there must be a reserve leaking in your use case. And I have posted
some patches about qgroup.reserved. some of them is about reserved leaking.

Could you try the tree :

	btrfs:https://yangdongsheng@github.com/yangdongsheng/linux.git  qgroup_type
   btrfs-progs:https://yangdongsheng@github.com/yangdongsheng/btrfs-progs.git  qgroup_type

It could be working better but I can not guarantee your problem here 
will be solved by it.

>
> [Reproducer]
> Would you please describe your workload? Or some easy-to-reproduce 
> scripts?
>
> [Image dump/debug tree]
> Another one which may help is your btrfs-debug-tree output on your 
> quota tree.
> You can dump it by "btrfs-debug-tree -t 8 <DEVICE>".
> Or full disk metadata dump by "btrfs-image -c9 <DEVICE>"

A reproducer is great for investigation. "btrfs-debug-tree" is important 
to us.

Thanx
Yang
>
> Thanks,
> Qu
>>
>> I've proactively added Yang who has submitted a few patches on quota
>> checking recently just to let me know if he thinks that this should be
>> fixed with a trunk kernel, or if he'd like to investigate or consider
>> this further. Thanks!
>>
>> On Wed, Dec 24, 2014 at 03:52:41AM +0000, Duncan wrote:
>>> Christian Robottom Reis posted on Tue, 23 Dec 2014 18:36:02 -0200 as
>>> excerpted:
>>>
>>>> On Tue, Dec 16, 2014 at 11:15:37PM -0200, Christian Robottom Reis 
>>>> wrote:
>>>>>      # btrfs qgroup limit 2000m 0/261 . && touch x touch: cannot 
>>>>> touch
>>>>>      ‘x’: Disk quota exceeded
>>>>>
>>>>> The strange thing is that it doesn't seem to be actually out of 
>>>>> space:
>>>>>
>>>>>      # btrfs qgroup show -p -r -e /var | grep 261
>>>>>      0/261    1111810048  391114752   2097152000 0          ---
>>>>
>>>> Replying to myself as I had not yet been subscribed in time to 
>>>> receive a
>>>> reply; I just upgraded to 3.18.1 and am seeing the same issue on the
>>>> same subvolume (and on no others).
>>>
>>> Looking at the thread here on gmane.org (list2news and list2web 
>>> gateway),
>>> it appears my reply was the only reply in any case, and it was 
>>> general as
>>> I don't run quotas myself.
>>>
>>> Basically I suggested upgrading, as the quota code as some rather huge
>>> bugs in it (quotas could go seriously negative!) with the old versions
>>> you were running.  But you've upgraded at least the kernel now 
>>> (userspace
>>> you didn't say).
>>>
>>> Here's a link to the thread on the gmane web interface for 
>>> completeness,
>>> but the above about covers my reply, as I said the only one until your
>>> thread bump and my reply here, so there's not much new there unless
>>> someone posts further followups to this thread...
>>>
>>>
>>> http://comments.gmane.org/gmane.comp.file-systems.btrfs/41491
>>>
>>>
>>> -- 
>>> Duncan - List replies preferred.   No HTML msgs.
>>> "Every nonfree program has a lord, a master --
>>> and if you use the program, he is your master."  Richard Stallman
>>>
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> .
>