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

Jörn Engel
2006-09-05T07:01:27Z

On Tue, 5 September 2006 07:46:44 +0300, Al Boldi wrote:
> Jörn Engel wrote:
> >
> > 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.

Well, I didn't realize that unionfs required its backing filesystems
to be mounted. That's more like having the block device open in a
text editor while mounting ext3. In the presence of such a design, an
oops clearly is not acceptable. And this sort of design is just what
I was talking about when I said:

> > There are bigger problems in unionfs to worry about.

Jörn

--
You can't tell where a program is going to spend its time. Bottlenecks
occur in surprising places, so don't try to second guess and put in a
speed hack until you've proven that's where the bottleneck is.
-- Rob Pike