On Mon, 1 May 2000, Richard Gooch wrote:
> Eric W. Biederman writes:
> > Richard Gooch <[EMAIL PROTECTED]> writes:
> >
> > > Hi, Al. You've previously stated that you consider the multiple
> > > mount feature of devfs broken. I agree that there are some races in
> > > there. However, I'm not clear on whether you're saying that the entire
> > > concept is broken, or that it can be fixed with appropriate loffcking.
> > > I've asked this before, but haven't had a response.
> >
> > Last I saw it was his complaint that you varied what you
> > showed at different mount points, and that doing that all in
> > one dcache tree was fundamentally broken.
>
> But it's not one dcache tree: there is a separate dcache tree for each
> mount of devfs. So I don't understand that complaint.
There is a lot of places where we do serialization using semaphores in
struct inode. You don't duplicate it all. Think what happens if two
instances operate on the same directory. You've got no locking here.
> > > If you feel that it's fundamentally impossible to mount a FS multiple
> > > times, please explain your reasoning.
> >
> > At this point it would make sense to just use the generic multiple
> > mount features in the VFS that Alexander has been putting in.
>
> The generic multi-mount patch is good, but it doesn't solve the
> particular problem of mounting with selective exposure.
There is one case when you can safely have multiple trees - when directories
in each tree are read-only. If you union-mount such trees you get some
selective exposure.
