linux-ext4 - Re: Fw: ext3 dir_index causes an error

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Date:	Fri, 14 Sep 2007 12:14:12 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Eric Sandeen <sandeen@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"Theodore Ts'o" <tytso@....edu>, hooanon05@...oo.co.jp,
	sct@...hat.com, adilger@...sterfs.com,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: Fw: ext3 dir_index causes an error

Eric Sandeen wrote:
> Andrew Morton wrote:

>> Ted is dir_index maintainer ;)

...

>> [1.] One line summary of the problem:
>> ext3 dir_index causes an error
> 
> I'm looking at this now, FWIW... pretty easy to reproduce on ppc64,
> though I've not yet hit it on x86.

The issue here is that do_split() splits a leaf node at the entry with
the median hash value, after sorting by hash... but it pays no attention
to the resulting size of the records in the old & new blocks.

If you're unlucky, and your split is lopsided size-wise, you may not
have space in the block chosen for the new entry.  This is not checked,
however, and things go bad quickly.

Talked with Andreas a little about this, looking into the best way to
fix it up.

-Eric
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