linux-ext4 - Re: EXT4 ENOSPC Bug

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Date:	Tue, 17 Feb 2009 12:13:06 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Theodore Tso <tytso@....edu>, Andres Freund <andres@...razel.de>,
	Alex Buell <alex.buell@...ted.org.uk>, 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

Theodore Tso wrote:
> 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.)
> 
> More comments are in the patch header.  My current long-term plan for
> dealing with this is to enhance find_group_orlov() to and
> find_group_other() to understand about flex_bg's.

Ok, I finally got to where I can reliably hit this.  Just as I was about
to install an ext4 with this patch in place, and the bug was preventing
the new initrd creation ;)  But worked around that, and:

ext4: find_group_flex failed, fallback succeeded dir 258402
ext4: find_group_flex failed, fallback succeeded dir 258402
ext4: find_group_flex failed, fallback succeeded dir 258402
ext4: find_group_flex failed, fallback succeeded dir 258402
....

I'll see if I can dig a bit more as to why the find_group_flex failed,
if you think it's worth it, Ted.

-Eric
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