Date: Mon, 14 Jun 2004 10:55:29 +0100
From: Christoph Hellwig <hch@infradead.org>
To: Cesar Eduardo Barros <cesarb@nitnet.com.br>
Cc: linux-kernel@vger.kernel.org, Alexander Viro <viro@math.psu.edu>
Subject: Re: [PATCH] O_NOATIME support
Message-ID: <20040614095529.GA11563@infradead.org>
Mail-Followup-To: Christoph Hellwig <hch@infradead.org>,
	Cesar Eduardo Barros <cesarb@nitnet.com.br>,
	linux-kernel@vger.kernel.org, Alexander Viro <viro@math.psu.edu>
References: <20040612011129.GD1967@flower.home.cesarb.net>
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On Fri, Jun 11, 2004 at 10:11:29PM -0300, Cesar Eduardo Barros wrote:
> (not subscribed to lkml, please CC: me on replies)
> 
> This patch adds support for the O_NOATIME open flag (GNU extension):
> 
> int O_NOATIME  	Macro
>   If this bit is set, read will not update the access time of the file.
>   See File Times. This is used by programs that do backups, so that
>   backing a file up does not count as reading it. Only the owner of the
>   file or the superuser may use this bit.
> 
> It is useful if you want to do something with the file atime (for
> instance, moving files that have not been accessed in a while to
> somewhere else, or something like Debian's popularity-contest) but you
> also want to read all files periodically (for instance, tripwire or
> debsums).
> 
> Currently, the program that reads all files periodically has to use
> utimes, which can race with the atime update:

Any chance we could change the flag to also not update mtime and ctime
for updates on a fd opened with it (and renaming it to O_INVISIBLE for
example).  That's needed for your above moving infrequently used files
away scenario (aka a HSM)

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