From: tytso@mit.edu
Subject: Re: [PATCH 4/4] ext4: Wait for proper transaction commit on fsync
Date: Tue, 8 Dec 2009 22:51:20 -0500
Message-ID: <20091209035120.GA27692@thunk.org>
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Cc: linux-ext4@vger.kernel.org
To: Jan Kara <jack@suse.cz>
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On Mon, Nov 16, 2009 at 11:43:31AM +0100, Jan Kara wrote:
> > Why do we need an atomic_t here at all?  It's not clear it's
> > necessary.  What specific race are you worried about?
>   Well, i_[data]sync_tid are set and read from several places which aren't
> currently synchronized against each other and I din't want to introduce any
> synchronization. So atomic_t seemed like a clean way of making clear that
> loads / stores from those fields are atomic, regardless of architecture,
> memory alignment or whatever insanity that might make us see just half
> overwritten field.  On all archs where this means just plain stores / loads
> (such as x86), there's no performance hit since the operations are
> implemented as such.

Sorry for not responding to this one sooner, but see this URL:

http://digitalvampire.org/blog/index.php/2007/05/13/atomic-cargo-cults/

							- Ted