From: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH 1/2] ext4: avoid hangs in
 ext4_da_should_update_i_disksize()
Date: Mon, 12 Dec 2011 17:57:59 +0100
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Cc: linux-ext4@vger.kernel.org, Theodore Tso <tytso@mit.edu>,
	Jan Kara <jack@suse.cz>
To: Yongqiang Yang <xiaoqiangnk@gmail.com>
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On Mon, Dec 12, 2011 at 11:28:21AM +0800, Yongqiang Yang wrote:
> Hi Andrea,
> 
> I can not figure out why ext4 hangs.  Could you explain more on hanging?

Well I tried to explain it in the changeset comment.

If "copied" is zero, end/offset/idx becomes -1, and this loops:

	for (i = 0; i < idx; i++)

definitely a bug and checking ext4 git I don't see anything fixing it.