linux-kernel - Re: [RFC] ext4: Don't send extra barrier during fsync if there are no dirty pages.

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Message-ID: <20100805203928.GM2901@thunk.org>
Date:	Thu, 5 Aug 2010 16:39:28 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	Avi Kivity <avi@...hat.com>, Christoph Hellwig <hch@...radead.org>,
	Ric Wheeler <rwheeler@...hat.com>,
	Mingming Cao <cmm@...ibm.com>, djwong@...ibm.com,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Keith Mannthey <kmannth@...ibm.com>,
	Mingming Cao <mcao@...ibm.com>
Subject: Re: [RFC] ext4: Don't send extra barrier during fsync if there are
 no dirty pages.

On Thu, Aug 05, 2010 at 03:13:44PM -0400, Jeff Moyer wrote:
> > IO_CMD_FSYNC doesn't exist right now, but sure, it means we don't have
> 
> Well, there's IOCB_CMD_FSYNC.  But still, this isn't the same thing as
> what's requested.  If I understand correctly, what is requested is a
> mechanism to flush out all data for multiple file descriptors and follow
> that with a single barrier/flush (and yes, Ted did give a summary of the
> commands that would be required to accomplish that).
> 
> There still remains the question of why this should be tied to the AIO
> submission interface.

I don't think it should, personally.  The only excuse might be if
someone wanted to do an asynchronous fsync(), but I don't think that
makes sense in most cases.

					- Ted
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