linux-ext4 - Re: data corruption with ext4 (from 2.6.27.4) exposed by rtorrent

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Date:	Wed, 05 Nov 2008 10:16:49 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Cryptooctoploid <cryptooctoploid@...il.com>
CC:	Theodore Tso <tytso@....edu>, Roc Valles <vallesroc@...il.com>,
	linux-ext4@...r.kernel.org
Subject: Re: data corruption with ext4 (from 2.6.27.4) exposed by rtorrent

Cryptooctoploid wrote:
> On Mon, Nov 3, 2008 at 2:40 PM, Theodore Tso <tytso@....edu> wrote:
>> On Mon, Nov 03, 2008 at 12:42:11PM +0000, Roc Valles wrote:
>>> Some person already reported this. I'm having the same problem.
>>> http://marc.info/?l=linux-ext4&m=122557056518246&w=2
>>>
>>> rtorrent is a bittorrent client that makes heavy use of mmap instead
>>> of read/write to avoid needless duplication of data. It has exposed
>>> other bugs in the past (mmap bug in 2.6.19).
>>> http://libtorrent.rakshasa.no
>>> Downloading a big torrent (>2GB) with rtorrent triggers it more times
>>> than not. The bigger the torrent, the higher the likeliness of
>>> failure. When the torrent is finished, if a hash check is forced by
>>> pressing control-r on the torrent, some blocks will fail.
>> Can both of you send the output of "dumpe2fs -h /dev/<disk device>" of
>> the filesystem in question?  The thing which I'm most interested in is
>> whether the extents feature was enabled or not.  (i.e., was this a
>> freshly made ext4 filesystem, or a ext3 filesystem mounted under ext4,
>> and with which features eanbled?)
>>
> 
> I tested this further and it turned out that this bug is not extents
> related. I get the same hash failures on a partition formatted with:
> -O "^extent".

Thanks, that's good information.

> Besides the torrent failures,  ext4 also managed to corrupt two
> dspam sqlite3 databases on my system. (After the corruption I
> get the following error:
> *** glibc detected *** dspam: free(): invalid pointer: 0x0000000001e71c58 ***
> ======= Backtrace: =========
> /lib/libc.so.6[0x7fcd1f941af6]
> /lib/libc.so.6(cfree+0xbd)[0x7fcd1f942f3d]
> /usr/lib64/dspam/libsqlite3_drv.so(_ds_setall_spamrecords+0x395)[0x7fcd1ea03075]
> /usr/lib/libdspam.so.7(_ds_operate+0x400)[0x7fcd1fc3c710]
> /usr/lib/libdspam.so.7(dspam_process+0x1d9)[0x7fcd1fc3cf49]
> dspam(process_message+0xb49)[0x408579]
> dspam(process_users+0x57d)[0x40902d]
> dspam(main+0x2c2)[0x409832]
> /lib/libc.so.6(__libc_start_main+0xfd)[0x7fcd1f8e848d]
> dspam[0x402f79
> and the only solution is to restore the database from ext3 backup)

I think this would more likely indicate a userspace bug, though, not
something related to ext4.

-Eric

> My conclusion is that ext4 is not yet ready for prime time.
> I moved all my data back to ext3.
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