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Date: Mon, 29 Dec 2008 14:54:06 -0500
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: safe writing in applications (was: Re: massively truncated
	files with XFS with sudden power loss on 2.6.27 and 2.6.28)
Message-ID: <20081229195406.GA7613@infradead.org>
References: <200812291920.34123.Martin@Lichtvoll.de>
	<200812292048.41193.Martin@lichtvoll.de>
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To: Martin Steigerwald <Martin@lichtvoll.de>
Cc: xfs@oss.sgi.com

On Mon, Dec 29, 2008 at 08:48:40PM +0100, Martin Steigerwald wrote:
> It might be wise however to file enhancement requests for the KDE 
> applications where I observed this behavior if safer writing within the 
> applications is possible. Any hints on what application developers should 
> keep in mind when writing out config files?

Preferably use O_SYNC.  Never truncate and then rewrite, in doubt write
a new file and rename it to the right place after it was fsync'ed (the
mailserver trick)

in the meantime a nice way to hack around this is do chattr +S for all
these files which forces synchronous writes.  Doesn't help if they
actually use the rename trick above sometimes.

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