Re: [PATCH v3 0/3] API for exporting connectable file handles to userspace

[Amir Goldstein <amir73il@gmail.com>]

On Tue, Oct 8, 2024 at 5:21 PM Amir Goldstein <amir73il@gmail.com> wrote:
>
> Jeff,
>
> These patches bring the NFS connectable file handles feature to
> userspace servers.
>
> They rely on Christian's and Aleksa's changes recently merged to v6.12.
>
> The API I chose for encoding conenctable file handles is pretty
> conventional (AT_HANDLE_CONNECTABLE).
>
> open_by_handle_at(2) does not have AT_ flags argument, but also, I find
> it more useful API that encoding a connectable file handle can mandate
> the resolving of a connected fd, without having to opt-in for a
> connected fd independently.
>
> I chose to implemnent this by using upper bits in the handle type field
> It may be valid (?) for filesystems to return a handle type with upper
> bits set, but AFAIK, no in-tree filesystem does that.
> I added some assertions just in case.

FYI, version with softened assertions at:
https://github.com/amir73il/linux/commits/connectable-fh/

fstest at:
https://github.com/amir73il/xfstests/commits/connectable-fh/

man-page at:
https://github.com/amir73il/man-pages/commits/connectable-fh/

>
> Thanks,
> Amir.
>
> Changes since v2 [2]:
> - Use bit arithmetics instead of bitfileds (Jeff)
> - Add assertions about use of high type bits
>
> Changes since v1 [1]:
> - Assert on encode for disconnected path (Jeff)
> - Don't allow AT_HANDLE_CONNECTABLE with AT_EMPTY_PATH
> - Drop the O_PATH mount_fd API hack (Jeff)
> - Encode an explicit "connectable" flag in handle type
>
> [1] https://lore.kernel.org/linux-fsdevel/20240919140611.1771651-1-amir73il@gmail.com/
> [2] https://lore.kernel.org/linux-fsdevel/20240923082829.1910210-1-amir73il@gmail.com/
>
> Amir Goldstein (3):
>   fs: prepare for "explicit connectable" file handles
>   fs: name_to_handle_at() support for "explicit connectable" file
>     handles
>   fs: open_by_handle_at() support for decoding "explicit connectable"
>     file handles
>
>  fs/exportfs/expfs.c        | 14 ++++++--
>  fs/fhandle.c               | 74 ++++++++++++++++++++++++++++++++++----
>  include/linux/exportfs.h   | 16 +++++++++
>  include/uapi/linux/fcntl.h |  1 +
>  4 files changed, 97 insertions(+), 8 deletions(-)
>
> --
> 2.34.1
>