Date: Wed, 13 Oct 2004 14:01:36 -0500
To: Oliver Neukum <oliver@neukum.org>
Cc: James Bruce <bruce@andrew.cmu.edu>, bert hubert <ahu@ds9a.nl>,
       Greg KH <greg@kroah.com>, linux-hotplug-devel@lists.sourceforge.net,
       linux-kernel@vger.kernel.org
Subject: Re: [2.6.9-rc4] USB && mass-storage && disconnect broken semantics
Message-ID: <20041013190136.GD12237@austin.ibm.com>
References: <20041011120701.GA824@outpost.ds9a.nl> <416B9436.3010902@andrew.cmu.edu> <200410121224.44910.oliver@neukum.org>
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From: Linas Vepstas <linas@austin.ibm.com>
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On Tue, Oct 12, 2004 at 12:24:44PM +0200, Oliver Neukum was heard to remark:
>  
> > With *nix, most data only gets written at unmount, so the only way this 
> > can "sanely" work is for mounts you haven't written to.  That case is of 
> 
> This is not a law of nature. You can mount sync as well. That, of course,
> sucks in terms of performance and wear. A reasonable compromise
> would be to do sync on close.
> Supermount did this years ago.

As a practical matter, sync-on-file-close should solve most 
of the practical problem of data corruption if the device is 
yanked before being onmounted.  However, when I read 
'man 2 open' there is no O_SYNC_ON_CLOSE.  

Similarly 'man 8 mount' doesn't list any option -o synconclose

It sure would be nice to be able to set up a sync-on-file-close
in the hotplug equiv of /etc/fstab for USB devices ... 

(When I think of sync-on-file-close, I don't mean 'global sync 
when the file is closed', I mean 'sync only that file's data and 
metadata only when the file is closed'.  That way, you don't slow 
down systems doing a lot of i/o on other, unrelated files)

--linas
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