problem with custom fs that utilizes ext3

Stephen Samuel samuel at
Tue Aug 24 20:32:45 UTC 2010

As far as I'm concerned, I consider the fact that you can extend the size of

the inode and get back old data to be the bug. (it's a data security

Also: Storing data in the slack space of files is dangerous because, if
someone else extends the same file, you're going to lose your data
Depending on an undocumented mis-feature of a filesystem is a rather
unsafe way to make a product.  If this is intended for production use, I'd
say that
you're better off to just bite the bullet and create a *real* file for
persistent strage.

On Mon, Jul 19, 2010 at 12:39 PM, Ryan O'Neill <ryan at> wrote:

> I have developed a file system, it is a virtual memory file system
> with persistence -- the persistence essentially works by storing the
> fs data (from memory) into the slack space
> of ext3 files (We are working on CentOS 5.3 -- old I know). The
> following details should be sufficient.
> I keep the inode size the same so that utilities don't see the hidden
> data -- it appears do_sync_read which ext3 uses and the function that
> it uses (such as generic_file_read) do not read past the size of the
> inode.
> .....

Stephen Samuel  Software, like love,
778-861-7641                              grows when you give it away
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