Re: btrfs qgroup assign -> "ERROR: bad relation requested"

[Arne Jansen <sensille@gmx.net>]

On 07/31/13 07:39, Tomasz Chmielewski wrote:
> On Wed, 31 Jul 2013 13:13:37 +0800
> Wang Shilong <wangsl.fnst@cn.fujitsu.com> wrote:
> 
>>> # git pull origin master
>>
>> Oops, i am sorry, here should:
>>
>> git pull origin qgroup
>>
>> would you please try it again
> 
> Excellent, it works:
> 
> # btrfs qgroup show -p /mnt/lxc2
> 0/260 154273873920 154273873920 ---
> 0/261 181260288 181260288 ---
> 0/262 155557888 983040 ---
> 0/377 180539392 26005504 ---
> 0/378 308607238144 308607238144 ---
> 0/535 572407808 417832960 ---
> 0/536 68085026816 68085026816 ---
> 0/642 247824384 93282304 ---
> 0/1276 636026880 4096 1/1
> 0/1277 38301687808 4096 1/1
> 0/1278 617164800 32768 1/1
> 0/1279 38297591808 4096 1/1
> 0/1284 38299160576 0 1/1
> 0/1285 38299160576 21364736 1/1
> 0/1286 620396544 0 1/1
> 0/1287 633090048 12722176 1/1
> 0/1293 38301687808 4096 1/1
> 0/1294 636026880 4096 1/1
> 1/1 38972137472 38972137472 ---
> 
> 
> Thanks a lot!
> 
> 
> Am I correct to think that I have to run quota rescan after
> assigning groups?
> 
> # btrfs qgroup assign 378 1/1 /mnt/lxc2  <<----- assigning volid 378, having 300+ GB
> 
> # btrfs qgroup show -p /mnt/lxc2 | grep 1/1
> 0/378 308607238144 308607238144 1/1
> 0/1276 636026880 4096 1/1
> 0/1277 38301687808 4096 1/1
> 0/1278 617164800 32768 1/1
> 0/1279 38297591808 4096 1/1
> 0/1284 38299160576 0 1/1
> 0/1285 38299160576 21364736 1/1
> 0/1286 620396544 0 1/1
> 0/1287 633090048 12722176 1/1
> 0/1293 38301687808 4096 1/1
> 0/1294 636026880 4096 1/1
> 1/1 38972137472 38972137472 ---  <<----- although we've added 300+ GB volume, the total numbers are unchanged
> 
> 
> That can be quite a bit of IO?

To avoid the rescan you can do the assignment atomically with
the creation of the subvol.
Basically if you lay out your future quota/subvol/snapshot when
you create your filesystem, you never have to do a rescan. The
commands are all there for that, but it's not really easy to do
if you have a complex setup. That part needs a better documentation
and more examples, and also probably a better UI.
Only if you change your mind later on you probably have to rescan.

-Arne

> 
>