Re: silent semantic changes with reiser4

Linus Torvalds
2004-08-31T20:59:45Z

On Tue, 31 Aug 2004, Pavel Machek wrote:
> >
> > However, that said, user space can trivially cache things in the
> > filesystem, so while this may be a convenient feature, I think you should
> > look at perhaps doing it in the _shell_ instead..
>
> That cache should disappear as soon as I need disk
> space. I.e. userspace should never see -ENOSPC because of this kind of
> caching. This need some kernel support. Ouch and cached file should
> atomically go away as soon as main file changes, otherwise I do not
> see how multiple processes could cooperate on caching...

Well, what other projects have done is to just reserve a certain amount of
disk for caching. See "ccache", which solves both of the above problems
(it doesn't shrink the cache on ENOSPC, but reserving diskspace is
accepted practice for things like this..)

Linus