From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [RFC][PATCH] Re: [BUG] ext4: cannot unfreeze a filesystem due to
 a deadlock
Date: Mon, 2 May 2011 09:22:04 -0400
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Cc: Surbhi Palande <surbhi.palande@ubuntu.com>,
	Dave Chinner <david@fromorbit.com>,
	Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>,
	Ted Ts'o <tytso@mit.edu>,
	Masayoshi MIZUMA <m.mizuma@jp.fujitsu.com>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Christoph Hellwig <hch@infradead.org>
To: Jan Kara <jack@suse.cz>
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On Mon, May 02, 2011 at 03:16:19PM +0200, Jan Kara wrote:
> Dave, Christoph, any opinions on this?

The busyloop in xfs_quiesce_attr which waits for all active transactions
to finish is supposed to fix this issue.

Note that XFS traditionally expects a two stage freeze process where
we first freeze new VFS-level writes, then flush the caches and then
stop transactions, wait for them to finish and do the remainder of
the freeze process, but I really messed that process up when moving
the sequence to generic code.  Funnily enough it seems to work
neverless.