linux-ext4 - Re: EXT4 ENOSPC Bug

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Date:	Tue, 17 Feb 2009 17:21:15 +0000
From:	Alex Buell <alex.buell@...ted.org.uk>
To:	Theodore Tso <tytso@....edu>
Cc:	Andres Freund <andres@...razel.de>, adilger@....com,
	LKML <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org,
	Jonathan Bastien-Filiatrault <joe@....org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: EXT4 ENOSPC Bug

On Mon, 16 Feb 2009 14:00:01 -0500, I waved a wand and this message
magically appears in front of Theodore Tso:

> On Mon, Feb 16, 2009 at 04:27:03PM +0100, Andres Freund wrote:
> >
> > So, yes, seems to be an inode allocation problem.
> 
> Andres, Alex, others,
> 
> I'm pretty sure the ENOSPC problem which you both found is an inode
> allocation problem.  Some of you seem to have an easier time
> reproducing it than others; could you try this patch, and periodically
> scan your system logs for the message "ext4: find_group_flex failed,
> fallback succeeded"?  If the problem goes away for you, and you find
> the occasional aforemention message in your system log, that will
> confirm what I suspect, which is the bug is in fs/ext4/inode.c's
> find_group_flex() function.  (If I'm wrong, the fallback code will
> activate only when the filesystem is genuinely out of inodes, which
> should be very rare.)

OK, I had to go look through the archives on linux-ext4 mailing list to
see what the context was. For myself, this used to happen at least once
a week with 2.6.26, and less frequently with 2.6.27. I think that 2.6.28
with your patch should get rid of that problem altogether. I will of
course get in touch should I see any more of these find_group_flex
failures as that would mean your patch worked. 

Thanks for your work on tracking this one down!
-- 
http://www.munted.org.uk

Fearsome grindings.
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