Re: [BUG] "Quota Ignored On write" problem still exist with 3.16-rc5

[Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>]

Hi Wang,

(2014/07/18 19:29), Wang Shilong wrote:
> On 07/18/2014 04:45 PM, Satoru Takeuchi wrote:
>> Hi Josef, Chris,
>>
>> I found "Quota Ignored On write" problem still exist with 3.16-rc5,
>> which Kevin reported before.
>>
>> Kevin's report:
>> https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg35292.html
>>
>> The result of bisect:
>> https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg35304.html
> I guess this is because Josef's patch delayed qgroup accounting, it will
> cause @refer and @excl updating very late...
> 
> The patch maybe optimize to merge some delayed refs(for example), but
> it updates qgroup accounting when commiting transaction which will be
> very late,
> we may have accumulated many data..

Thank you for your comment. I know of the code logic which caused
this problem. However, what I want to say here is that this
problem should be fixed as soon as possible. It is a important
regression problem and we've already know the root cause.

If it's impossible to fix it by releasing 3.16, I consider this
patch should be reverted.

Thanks,
Satoru

> 
> Thanks,
> Wang
>>
>>> I bisected and found the bad commit is the following patch.
>>>
>>> ===============================================================================
>>> commit fcebe4562dec83b3f8d3088d77584727b09130b2
>>> Author: Josef Bacik <jba...@fb.com>
>>> Date:   Tue May 13 17:30:47 2014 -0700
>>>
>>>      Btrfs: rework qgroup accounting
>>> ===============================================================================
>>>
>>> Josef, please take a look at this patch.
>> Reproducer:
>> https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg35299.html
>>
>> Could you tell me the progress of fixing this bug?
>> In addition, could you fix it by 3.16?
>>
>> command log:
>> ===============================================================================
>> # ./test.sh
>> + uname -a
>> Linux luna.soft.fujitsu.com 3.16.0-rc5 #2 SMP Tue Jul 15 13:39:46 JST 2014 x86_64 x86_64 x86_64 GNU/Linux
>> + df -T /test7
>> Filesystem     Type  1K-blocks  Used Available Use% Mounted on
>> /dev/sdc7      btrfs  29296640  1536  27169536   1% /test7
>> + btrfs quota ena /test7
>> + cd /test7
>> + btrfs sub cre test
>> Create subvolume './test'
>> + btrfs sub l -a /test7
>> ID 270 gen 66 top level 5 path test
>> + btrfs qg lim 1G test                          # limit test subvol to 1GB
>> + btrfs qg show -pcre /test7
>> qgroupid rfer  excl  max_rfer   max_excl parent  child
>> -------- ----  ----  --------   -------- ------  -----
>> 0/5      16384 16384 0          0        ---     ---
>> 0/270    16384 16384 1073741824 0        ---     ---
>> + dd if=/dev/zero of=test/file0 bs=1M count=2000
>> 2000+0 records in
>> 2000+0 records out
>> 2097152000 bytes (2.1 GB) copied, 9.67876 s, 217 MB/s   # write 2GB. It's a bug!
>> + sync
>> + ls -lisaR /test7
>> /test7:
>> total 20
>> 256 16 drwxr-xr-x   1 root root    8 Jul 18 15:12 .
>>    2  4 drwxr-xr-x. 43 root root 4096 Jul 16 08:34 ..
>> 256  0 drwxr-xr-x   1 root root   10 Jul 18 15:17 test
>>
>> /test7/test:
>> total 2048016
>> 256       0 drwxr-xr-x 1 root root         10 Jul 18 15:17 .
>> 256      16 drwxr-xr-x 1 root root          8 Jul 18 15:12 ..
>> 257 2048000 -rw-r--r-- 1 root root 2097152000 Jul 18 15:17 file0
>> + btrfs qg show -pcre /test7
>> qgroupid rfer       excl       max_rfer   max_excl parent  child
>> -------- ----       ----       --------   -------- ------  -----
>> 0/5      16384      16384      0          0        ---     ---
>> 0/270    2097168384 2097168384 1073741824 0        ---     ---
>> + btrfs quota dis /test7
>> + btrfs sub del test
>> Transaction commit: none (default)
>> Delete subvolume '/test7/test'
>> + set +x
>> #
>> ===============================================================================
>>
>>    NOTE:
>>    The reproducer here (./test.sh) is a bit different from above-mentioned
>>    one because of some reason.
>>
>> Thanks,
>> Satoru
>>
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