linux-ext4 - Re: bugs of Online Defragmentation

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Message-ID: <492DEA24.2040002@cn.fujitsu.com>
Date:	Thu, 27 Nov 2008 08:30:28 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Akira Fujita <a-fujita@...jp.nec.com>
CC:	linux-ext4@...r.kernel.org
Subject: Re: bugs of Online Defragmentation

Akira Fujita wrote:
> Hi Li,
> 
> Thank you for testing and sorry for delay reply.
> I am looking into this problem now,
> It seems to take a little time to fix.
> 
> (In my look, s_dirty_blocks goes wrong so that free blocks
> on memory decreases.  Maybe delalloc handling isn't good)
> 

Take your time. I'll test it once new version of online defrag
is released. :)

> Thanks,
> Akira Fujita
> 
> Li Zefan wrote:
>> I tested Online Defrag, and seems this feature is still
>> very unstable.
>>
>> 1)
>>
>> # mkfs.ext4 -m 0 -b 1024 -O ^flex_bg /dev/sdb7
>> # mount -t ext4 -o nodelalloc /dev/sdb7 mnt_point
>> # (age /dev/sdb7 using ffsb)
>> ...
>> # df
>> Filesystem           1K-blocks      Used Available Use% Mounted on
>> ...
>> /dev/sdb7              5159829   5118866     40963 100% ...
>>
>> sdb7 has 40M free space left. And I ran e4defrag on a directory full
>> of small files (most < 1M), but all failed, and dmesg didn't tell
>> me the reasion.
>>
>> # e4defrag mnt_point/data0/
>> ...
>> [62/1562]/../mnt_point/data0/fillfile1420:        0%    [ NG ]
>> [63/1562]/../mnt_point/data0/fillfile188:         0%    [ NG ]
>> ...
>>         Success:                        [ 0/1562 ]
>>         Failure:                        [ 1562/1562 ]
>>
>> # df
>> Filesystem           1K-blocks      Used Available Use% Mounted on
>> ...
>> /dev/sdb7              5159829   5159807        22 100% ...
>>
>> Though all failed, but now the 40M free space was occupied, why?
>>
>> If delalloc is turned on, things are somewhat different, most files can
>> be defraged, and dmesg told me not enough free blocks for the failure
>> cases.
>>
>> 2)
>>
>> I sometimes got panic after defrag a directory:
>>
>> Dirty block accounting went wrong -8977
>> Dirty block accounting went wrong -9279
>> Dirty block accounting went wrong -9718
>> Dirty block accounting went wrong -10258
>> ...
>> ...
>> Dirty block accounting went wrong -157352
>> Dirty block accounting went wrong -157700
>> EXT4-fs error(device sdb7): ext_mb_free_metadata: Double free of
>> blocks 985 (984 2)
>>
> 
> 
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