linux-kernel - Re: notes on volatile write caches vs fdatasync

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Message-ID: <20090827184948.GA1367@lst.de>
Date:	Thu, 27 Aug 2009 20:49:48 +0200
From:	Christoph Hellwig <hch@....de>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	chris.mason@...cle.com, tytso@....edu, adilger@....com,
	swhiteho@...hat.com, konishi.ryusuke@....ntt.co.jp,
	mfasheh@...e.com, joel.becker@...cle.com
Subject: Re: notes on volatile write caches vs fdatasync

On Thu, Aug 27, 2009 at 03:02:52PM +0200, Jan Kara wrote:
>   I've noticed this as well when we were tracking some problems Pavel
> Machek found with his USB stick. I even wrote a patch at the time
>   http://osdir.com/ml/linux-ext4/2009-01/msg00015.html
> but it somehow died out. Now, the situation should be simpler with
> fsync paths cleaned up... BTW: People wanted this to be configurable per
> block device which probably makes sence...

Yeah, that patch is pretty ugly.  We need to do these cache flushes
in ->fsync (and ->sync_fs if any filesystem really doesn't guarantee to
issue  transaction there after data has been written).  Adding it
to simple_fsync too sounds good to me.
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