Re: [PATCH 00/22][RFC] Unionfs: Stackable Namespace Unification Filesystem

Al Boldi
2006-09-05T04:45:44Z

Jörn Engel wrote:
> On Sun, 3 September 2006 11:05:08 +0000, Pavel Machek wrote:
> > > - Modifying a Unionfs branch directly, while the union is mounted, is
> > > currently unsupported. Any such change may cause Unionfs to oops
> > > and it can even result in data loss!
> >
> > I'm not sure if that is acceptable. Even root user should be unable to
> > oops the kernel using 'normal' actions.
>
> Direct modification of branches is similar to direct modification of
> block devices underneith a mounted filesystem. While I agree that
> such a thing _should_ not oops the kernel, I'd bet that you can easily
> run a stresstest on a filesystem while randomly flipping bits in the
> block device and get just that.

Not really a fair comparison. The block level is conceptionally totally
different than the fs level, while a stackable fs is within the realms of
the fs level.

> There are bigger problems in unionfs to worry about.

Agreed. Moving basic functionality abstractions into the VFS could easily
alleviate theses kinds of problems.

Thanks!

--
Al