Re: [RFC] FUSE permission modell (Was: fuse review bits)

[Jamie Lokier]

> > > A nice implemention of it in FUSE could push it along a bit :)
> > 
> > Aren't there some assumptions in VFS that currently make this
> > impossible?
> 
> I believe it's OK with VFS, but applications would be confused to death.
> Well, there really is one issue -- dentries have exactly one parent, so
> what do you do when opening a file with hardlinks as a directory? (In
> fact IIRC that is what lead to all the funny talk about mountpoints,
> since they don't have this limitation)

Hardlinks aren't a problem when entering a file as if it's a
directory, provided the directory does not contain any hard links to a
parent in the hierarchy.  In other words, as long as it's a directed
acyclic graph.

This is trivially always true for virtual directories such as entering
an archive file.  And detachable/movable mountpoints are a nice and
sensible way to implement it.  Some work has actually been done on this.

Experiments with the reiserfs file-as-directory extension showed that
applications are generally ok with it.  It looks like a file, but you
can cd into it or follow a path lookup into it.

Linus had some good ideas on the exact semantics to implement when
doing path lookup on these objects.

-- Jamie
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