[PATCH v3 09/25] fs: add is_userns_visible() helper

[Christian Brauner]

On Tue, Feb 18, 2020 at 08:42:33PM -0600, Serge Hallyn wrote:
> On Tue, Feb 18, 2020 at 03:33:55PM +0100, Christian Brauner wrote:
> > Introduce a helper which makes it possible to detect fileystems whose
> > superblock is visible in multiple user namespace. This currently only
> > means proc and sys. Such filesystems usually have special semantics so their
> > behavior will not be changed with the introduction of fsid mappings.
> 
> Hi,
> 
> I'm afraid I've got a bit of a hangup about the terminology here.  I
> *think* what you mean is that SB_I_USERNS_VISIBLE is an fs whose uids are
> always translated per the id mappings, not fsid mappings.  But when I see

Correct!

> the name it seems to imply that !SB_I_USERNS_VISIBLE filesystems can't
> be seen by other namespaces at all.
> 
> Am I right in my first interpretation?  If so, can we talk about the
> naming?

Yep, your first interpretation is right. What about: wants_idmaps()