On 01/12/2010 05:54 AM, Michal Novotny wrote:
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paravirtualized guests) sometimes uses outdated version of grub.conf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@xxxxxxxxxx>
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cached/outdated data so this was the first patch I did for file system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
Hi Michael,
What would be useful is where the data is written (guest/host) and the state of
the file system (mounted/unmounted). Which app it is that writes the data that
gets cached, who needs to read it and misses that cached data.
From the above, it is really not clear that you should not be able to use
existing interfaces to flush any cached data to disk....
ric
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