Re: [PATCH 0/4] exportfs: add flag to allow marking export operations as only supporting file handles

[Jeff Layton <jlayton@kernel.org>]

On Sun, 2024-12-01 at 14:12 +0100, Christian Brauner wrote:
> Hey,
> 
> Some filesystems like kernfs and pidfs support file handles as a
> convenience to enable the use of name_to_handle_at(2) and
> open_by_handle_at(2) but don't want to and cannot be reliably exported.
> Add a flag that allows them to mark their export operations accordingly
> and make NFS check for its presence.
> 
> @Amir, I'll reorder the patches such that this series comes prior to the
> pidfs file handle series. Doing it that way will mean that there's never
> a state where pidfs supports file handles while also being exportable.
> It's probably not a big deal but it's definitely cleaner. It also means
> the last patch in this series to mark pidfs as non-exportable can be
> dropped. Instead pidfs export operations will be marked as
> non-exportable in the patch that they are added in.
> 
> Thanks!
> Christian
> 
> ---
> Christian Brauner (4):
>       exportfs: add flag to indicate local file handles
>       kernfs: restrict to local file handles
>       ovl: restrict to exportable file handles
>       pidfs: restrict to local file handles
> 
>  fs/kernfs/mount.c        | 1 +
>  fs/nfsd/export.c         | 8 +++++++-
>  fs/overlayfs/util.c      | 7 ++++++-
>  fs/pidfs.c               | 1 +
>  include/linux/exportfs.h | 1 +
>  5 files changed, 16 insertions(+), 2 deletions(-)
> ---
> base-commit: 74e20c5946ab3f8ad959ea34f63f21e157d3ebae
> change-id: 20241201-work-exportfs-cd49bee773c5
> 

I've been following the pidfs filehandle discussion and this is exactly
what I was thinking we needed: a way to explicitly label certain
fstypes as unexportable via nfsd.

Reviewed-by: Jeff Layton <jlayton@kernel.org>