[fpc-pascal] XML files and the ext4 bug

Michael Van Canneyt michael at freepascal.org
Thu Mar 12 09:25:38 CET 2009

On Wed, 11 Mar 2009, Gustavo Enrique Jimenez wrote:

> Hi
> Seems like the ext4 file system has a bug or some issue with files
> updated often :
> https://bugs.edge.launchpad.net/ubuntu/+source/linux/+bug/317781
> I use XML files heavily. It is great, XML units save me a lot of work
> ! My programs update de xml files quite often.
> I am concerned about this particular ext4 bug. Could you say if
> freepascal's XML units are affected by this bug ? ext4 developers
> recomend this :

Well, there is no 'bug', there is a misunderstanding of how things work.
That said, XML algorithms use method 1.

You can do method 3 yourself (it's just renaming files and syncing), but 
I wouldn't recommend it as standard practice, as it uses 3 times more 
diskspace and is quite slow.

And if methods 1 & 2 are "unsafe", then I think that there is a fundamental 
bug in the filesystem (I never believed "journaling" filesystems can work
100% correctly in the first place), despite what Theodore T'so says.

The filesystem should just work. The standard application programmer should 
never have to take into account the eventualities described there.


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