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

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Message-ID: <4B4C54DC.4040006@redhat.com>
Date:	Tue, 12 Jan 2010 11:54:20 +0100
From:	Michal Novotny <minovotn@...hat.com>
To:	Ric Wheeler <rwheeler@...hat.com>
CC:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] extend e2fsprogs functionality to add EXT2_FLAG_DIRECT
 option

On 01/11/2010 09:06 PM, Ric Wheeler wrote:
> 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 paravirtualized guests) sometimes uses outdated version of grub.conf 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
>
What do you mean by adding some kind of data flow overview? I am not 
working on file systems but I needed option  open files directly to be 
added to e2fsprogs to make pygrub working right with not using 
cached/outdated data so this was the first patch I did for file system 
so I don't realy know what do you mean by data flow overview ...

Thanks,
Michal
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