linux-ext4 - Re: ext4 df regression introduced by commit 9d0be50

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Message-ID: <20100520161121.GB28963@atrey.karlin.mff.cuni.cz>
Date:	Thu, 20 May 2010 18:11:21 +0200
From:	Jan Kara <jack@...e.cz>
To:	linux-ext4@...r.kernel.org
Cc:	Bruce Guenter <bruce@...roubled.org>
Subject: Re: ext4 df regression introduced by commit 9d0be50

  Hi,

> I think I have found a regression introduced by commit 9d0be50 "ext4:
> Calculate metadata requirements more accurately".
  Thanks for report!

> I am using ext4 on a NFSv4 server running unpatched kernel 2.6.33.3.
> The client is currently running unpatch 2.6.33.3, although I also saw
> the problem with the client running 2.6.32.10.
> 
> The output from 'df' on the client varies wildly in the presence of
> certain writes.  I have not pinned down an exact write pattern that
> causes it, but I do have an application that causes it fairly reliably.
> When the bug happens, I see swings like this:
> 
> Sun May  9 23:04:58 2010 blocks=961173888 available=28183168
> Sun May  9 23:04:59 2010 blocks=961173888 available=12823424
> Sun May  9 23:05:00 2010 blocks=961173888 available=28183040
> 
> (produced by a script that checks statvfs output every second; units are
> kB, df output is effectively identical)
  Hmm, I'm not seeing anything obviously wrong with that patch but
apparently the number of blocks reserved for delayed allocation is
miscomputed by a lot...
  Is your ext4 filesystem create from scratch or converted from ext3? Is
your application using lots of different files or rather a couple of small
ones? Anyways a reproducing program would be the best in this case...

								Honza

-- 
Jan Kara <jack@...e.cz>
SuSE CR Labs
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