linux-kernel - Re: atomically swap two files

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Message-ID: <4CEF9E68.9080200@draigBrady.com>
Date:	Fri, 26 Nov 2010 11:47:52 +0000
From:	Pádraig Brady <P@...igBrady.com>
To:	"Frank A. Kingswood" <frank@...gswood-consulting.co.uk>
CC:	linux-kernel@...r.kernel.org
Subject: Re: atomically swap two files

On 25/11/10 20:11, Frank A. Kingswood wrote:
> Hi!
> 
> Is it possible to swap two files in an atomic way, so that after the
> syscall either the two files have exchanged names or neither has been
> modified?
> 
> I suspect that btrfs could do it, but I'm wondering about ext3/4.

I don't think there is anything equivalent to exchangedata() on Linux
http://developer.apple.com/library/mac/#DOCUMENTATION/Darwin/Reference/ManPages/man2/exchangedata.2.html

I've written some notes on atomically replacing
file contents with standard tools here:
http://www.pixelbeat.org/docs/unix_file_replacement.html

cheers,
Pádraig.
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