linux-ext4 - Re: [PATCH] extend e2fsprogs functionality to add EXT2_FLAG

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Date:	Tue, 12 Jan 2010 07:23:19 -0500
From:	Christoph Hellwig <hch@...radead.org>
To:	Michal Novotny <minovotn@...hat.com>
Cc:	Ric Wheeler <rwheeler@...hat.com>, linux-ext4@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH] extend e2fsprogs functionality to add EXT2_FLAG_DIRECT
	option

On Tue, Jan 12, 2010 at 01:15:49PM +0100, Michal Novotny wrote:
> I don't really know if I see your point but the thing here is that there  
> was no way to open a file directly (ie. using O_DIRECT). The direct  
> write support has been added only to make it possible to use both read  
> and write directly. The main reason to create this patch was to add  
> direct read support and flush capability won't help me at all. I am  
> working in Red Hat, Virtualization team on Xen so I am really not that  
> much familiar with file systems but what I needed was an option to read  
> the data directly (using O_DIRECT) in e2fsprogs. One bug was about  
> pygrub (Python version of GRUB of Xen PV guests that is internally using  
> e2fsprogs functionality to access data on ext2/3/4 partition to boot the  
> PV guests) uses outdated/cached data so some modifications were  
> necessary to open everything directly...

So to get things staigt:  you're using e2fsprogs to manipulate a life
filesystem and thing using O_DIRECT saves your ass?  I think you need to
rething your model of operation fundamentally in that case. 

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