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List:       linux-ext4
Subject:    Re: ext4_da_release_space:1333: ext4_da_release_space: ino 12, to_free 1 with only 0 reserved data
From:       Jan Kara <jack () suse ! cz>
Date:       2013-07-31 18:32:00
Message-ID: 20130731183200.GA28018 () quack ! suse ! cz
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On Wed 31-07-13 12:39:01, Dave Jones wrote:
> On Wed, Jul 17, 2013 at 11:38:50PM +0200, Jan Kara wrote:
>  > On Wed 17-07-13 10:52:18, Dave Jones wrote:
>  > > On Wed, Jul 17, 2013 at 02:53:22PM +0200, Jan Kara wrote:
>  > >  > On Tue 16-07-13 16:25:33, Dave Jones wrote:
>  > >  > > I've seen this happen a few times this week..
>  > >  >   Thanks for report! Was this when fuzzing or just normal desktop load?
>  > >  > What is inode with inode number 12 on your filesystem sdb1? What IO happens
>  > >  > to it? Apparently some delalloc accounting went wrong somewhere and it's
>  > >  > searching for a needle in a haystack unless we have more details...
>  > > 
>  > > It was running this.. https://github.com/kernelslacker/io-tests/blob/master/setup.sh
>  > > in a loop. After about 6 hours, that fell out.  It made it all the way through
>  > > every test a few times, which is odd, as the test should be fairly deterministic.
>  > > Ah, I wasn't capturing the fsx seed. I'll do that on the next run.
>  >   So inode 12 was likely the file used by fsx. OK. Looking at the script
>  > link, fsx is run as:
>  >   /usr/local/bin/fsx -N 250000 -S0 foo &
>  > so the seed is always 0. So it is a deterministic test and there must be
>  > some race with writeback or something that is rarely triggered. Drat.
>  > 
>  > Umm, looking at the filesystems this tests, ext4 with 1 KB blocksize is
>  > likely the config which hits this (the accounting is more complex there) so
>  > it might be interesting to concentrace on this one.
> 
> I just retried these tests, and hit this again.
> I can confirm it happens on the 1k block filesystem.
  Great, thanks for confirmation. I've just managed to reproduce the
problem yesterday so I'm debugging it...

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR
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