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 09:24:49 -0400
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Cc: Jan Kara <jack@suse.cz>, 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: Surbhi Palande <surbhi.palande@ubuntu.com>
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On Mon, May 02, 2011 at 04:22:45PM +0300, Surbhi Palande wrote:
> This has another advantage, that it rightfully does not let you
> update the access time when the F.S is frozen (touch_atime called
> from a read path when the F.S is frozen) Otherwise we also need to
> fix this path.

In most filesystens atime updates aren't transactional.  They just
get written into inode->i_atime, and at some later point when the
VFS tries to clean the inode it gets writtent back, either through
a transaction or not.