linux-ext4 - Re: What is status of metadata

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Date:	Fri, 17 Jan 2014 11:39:07 +0100
From:	Oleksij Rempel <linux@...pel-privat.de>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
CC:	linux-ext4@...r.kernel.org
Subject: Re: What is status of metadata_csum

Am 17.01.2014 09:18, schrieb Oleksij Rempel:
> Am 17.01.2014 03:00, schrieb Darrick J. Wong:
>> On Thu, Jan 16, 2014 at 11:57:20AM +0100, Oleksij Rempel wrote:
>>> What is metadata_csum status?
>>>
>>> i see there are benchmark updates on wiki page, but no updates for
>>> e2fsprogs. 1.43-WIP seems to be really old.
>>
>> Still waiting for 1.43.  I don't know if there are early adopters running
>> 1.43-WIP without complaint, or if simply nobody's using it at all. :/
> 
> I didn't tested current master.git - my bad. It is not outdated :)
> 
> Beside, the wiki should be corrected. If you enable 64bit, it will need
> extents too.
> 
> Are there any existing tools for error injection for file systems?
> Random read error from libata or silent data corruptions?
> 

I was playing with metadata_csum trying to kill my system and now i have
some questions:

first the test:
#find block number
sudo ./debugfs/debugfs -R "imap <3991825>" /dev/sdf1

#copy block
sudo dd if=/dev/sdf1 bs=4K count=1 skip=15958163 of=corrupt_block.bin

#change one byte
ghex corrupt_block.bin

#kill inode
sudo dd of=/dev/sdf1 bs=4K count=1 seek=15958163 if=corrupt_block.bin

sudo ./debugfs/debugfs -R "stat <3991825>" /dev/sdf1
#stat: Inode checksum does not match inode while reading inode 3991825

so, inode is corrupt:
- ext4 can detect inode corruption. Great work! I like it :)
- in this case file will not be shown by Nautilus.
- ls will show some thing like this:

4130898 drwx------  8 oleksij oleksij      4096 Jan 17 09:31 Bilder
      ? -?????????  ? ?       ?               ?            ?
ich-einfach_unverbesserlich_2.mkv
3991826 -rw-rw-r--  1 oleksij oleksij 622038707 Jan 17 11:12 igor.mkv
3989506 drwxr-xr-x 26 oleksij oleksij      4096 Okt  9 23:11 linux

it means, i know there is some thing wrong, but i do not know which inode

- If fs is not fixed, file is lost? are blocks still allocated to this
inode?
- debufs will not allow me to edit inode corrupt inode.
- If i run fsck -y file is lost. Most user wont be able to recover it.
- how can i sync it with back up software?





-- 
Regards,
Oleksij


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