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

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Date:	Mon, 11 Jan 2010 15:06:58 -0500
From:	Ric Wheeler <rwheeler@...hat.com>
To:	Michal Novotny <minovotn@...hat.com>
CC:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] extend e2fsprogs functionality to add EXT2_FLAG_DIRECT
 option

On 01/08/2010 04:36 AM, Michal Novotny wrote:
> This patch extends functionality of e{2|4}fsprogs to add 
> EXT2_FLAG_DIRECT flag to be passed to ext2fs_open2() function. This 
> internally calls open() function with O_DIRECT and handles the memory 
> alignment for both read and write operations.
> In some cases direct access to devices is necessary and that was the 
> main reason for this patch to be done.
>
> The main reason why this was done is that pygrub (used by xen 
> virtualization user-space package, it's a python version of grub for 
> paravirtualized guests) sometimes uses outdated version of grub.conf 
> file. Modifications to xen package were *not* enough because e2fsprogs 
> doesn't open the files directly. That's why I added EXT2_FLAG_DIRECT 
> support to make read/write operations work directly when passed. It's 
> been tested with pygrub like mentioned above for read operation and 
> it's working fine.
>
> Signed-off-by: Michal Novotny <minovotn@...hat.com>

Can you add to this some kind of data flow overview?  Seems like a 
really odd way to update this file system...

ric

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