Re: How to support directory opacity in a filesystem for overlayfs to use?

[David Howells]

Miklos Szeredi <miklos@xxxxxxxxxx> wrote:

> On Tue, 14 Jan 2025 at 16:15, David Howells <dhowells@xxxxxxxxxx> wrote:
> 
> > What's the best way for a network filesystem to make a native
> > directory-is-opaque flag available to the system?  Is it best to catch
> > setxattr/getxattr/removexattr("overlay.opaque") and translate these into the
> > RPCs to wrangle the flag?
> 
> I don't know.  Out of curiosity, which filesystem is it?

One of the varieties of AFS.  Unfortunately, xattrs aren't a thing and can't
easily be added because of the volume transfer and backup protocols and
formats.

> There's "trusted.overlay.opaque" and "user.overlay.opaque" and are
> used in different scenarios.   There was also talk of making the
> "trusted." namespace nest inside user namespaces, but apparently it's
> not so important.
> 
> Which one would you like to emulate?

Um - I don't know the difference to answer that question.

David