From: Thierry Vignaud <tvignaud@mandriva.com>
Subject: Re: More ext4 acl/xattr corruption - 4th occurence now
Date: Tue, 19 May 2009 12:00:56 +0200
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Cc: Kevin Shanahan <kmshanah@ucwb.org.au>,
	Andreas Dilger <adilger@sun.com>, Alex Tomas <bzzz@sun.com>,
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To: Theodore Tso <tytso@mit.edu>
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Theodore Tso <tytso@mit.edu> writes:

> So here's the final fix (it replaces the short circuit i_cached_extent
> patch) which I plan to push to Linus.  It should be much less of a
> performance hit than simply short-circuiting i_cached_extent...
> 
> Thanks so much for helping to find track this down!!!  If ever someone
> deserved an "Ext4 Baker Street Irregulars" T-shirt, it would be
> you....
> 
>        	       	   	      	   	      - Ted
> 
> commit 039ed7a483fdcb2dbbc29f00cd0d74c101ab14c5
> Author: Theodore Ts'o <tytso@mit.edu>
> Date:   Thu May 14 17:09:37 2009 -0400
> 
>     ext4: Fix race in ext4_inode_info.i_cached_extent
>     
>     If one CPU is reading from a file while another CPU is writing to the
>     same file different locations, there is nothing protecting the
>     i_cached_extent structure from being used and updated at the same
>     time.  This could potentially cause the wrong location on disk to be
>     read or written to, including potentially causing the corruption of
>     the block group descriptors and/or inode table.
>     
>     Many thanks to Ken Shannah for helping to track down this problem.
>     
>     Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

I wonder if that would explain the corruption I reported a couple weeks
ago.

Now I remember I wrongly got 2 parallel cp from the same source
directory to the same target directory.
Could this be the cause?