Re: BTRFS constantly reports "No space left on device" even with a huge unallocated space

["Austin S. Hemmelgarn" <ahferroin7@gmail.com>]

On 2016-09-01 08:57, Ronan Arraes Jardim Chagas wrote:
> Hi!
>
> Em Qua, 2016-08-31 às 17:09 -0600, Chris Murphy escreveu:
>> OK so Ronan, I'm gonna guess the simplest work around for your
>> problem
>> is to disable quota support, and see if the problem happens again.
>>
>
> Look at the output of the command proposed by Jeff:
>
> btrfs qgroup show /
> qgroupid         rfer         excl
> --------         ----         ----
> 0/5          16.00KiB     16.00KiB
> 0/257        16.00KiB     16.00KiB
> 0/258        16.30MiB     16.30MiB
> 0/259        11.65GiB    309.67MiB
> 0/260         2.34MiB      2.34MiB
> 0/261        16.00KiB     16.00KiB
> 0/262        13.19GiB     13.19GiB
> 0/263        16.00KiB     16.00KiB
> 0/264        60.00KiB     60.00KiB
> 0/265       480.00KiB    480.00KiB
> 0/266        16.00KiB     16.00KiB
> 0/267         2.00GiB      2.00GiB
> 0/268        16.00KiB     16.00KiB
> 0/269        16.00KiB     16.00KiB
> 0/270        16.00KiB     16.00KiB
> 0/271        16.00KiB     16.00KiB
> 0/272        16.00KiB     16.00KiB
> 0/273        16.00KiB     16.00KiB
> 0/274        16.00KiB     16.00KiB
> 0/275       205.78MiB    205.78MiB
> 0/276        16.00KiB     16.00KiB
> 0/277        48.00KiB     48.00KiB
> 0/278       328.41MiB    328.41MiB
> 0/283         3.92GiB     26.63MiB
> 0/285         3.93GiB      4.10MiB
> 0/294         7.84GiB    100.59MiB
> 0/330         7.98GiB      6.61MiB
> 0/332         8.32GiB     69.17MiB
> 0/353         9.53GiB     49.46MiB
> 0/355        10.51GiB    235.39MiB
> 0/415        11.54GiB      3.38MiB
> 0/416        11.54GiB    896.00KiB
> 0/417        11.57GiB      2.68MiB
> 0/418        11.57GiB    160.00KiB
> 0/419        11.54GiB      2.40MiB
> 0/420        11.54GiB    192.00KiB
> 0/421        11.62GiB      4.61MiB
> 0/422        11.83GiB    212.93MiB
> 0/427        11.64GiB      1.27MiB
> 0/428        11.65GiB      4.25MiB
> 1/0          16.11GiB      4.77GiB
> 255/262      13.19GiB     13.19GiB
>
> This system was installed with Tumbleweed ISO and I did not change
> anything in btrfs options. Hence, it seems that openSUSE is enabling
> quotas by default. Now, I need to disable it and avoid triggering the
> problem. What is the best way I can do this? Is it OK to do just:
>
> btrfs quota disable /
>
> ? Or do I need to format and recreate btrfs without quotas?
Yes, you can just run `btrfs quota disable /` and it should work.  This 
ironically reiterates that one of the bigger problems with BTRFS is that 
distros are enabling unstable and known broken features by default on 
install.  I was pretty much dumbfounded when I first learned that 
OpenSUSE is enabling BTRFS qgroups by default since they are known to 
not work reliably and cause all kinds of issues.
>
>> If it doesn't happen again then it sounds like the reproduce steps
>> are:
>>
>> a. enable quota support
>> b. do something metadata heavy workload that's also maybe hitting
>> fsync; from opensuse list the example that sometimes causes it:
>>
>>
>>   osc co home:Ronis_BR/julia
>>   cd home:Ronis_BR/julia
>>   osc build --root=`pwd`/jail openSUSE_Tumbleweed x86_64
>>
>> I wonder if it's easier to hit it on a hard drive, slower fsyncs?
>
> This sounds good! Actually, I'm using a 7200RPM hard driver.