On Tue, 2023-04-25 at 16:01 +0300, Amir Goldstein wrote:

Jan,

Following up on the FAN_REPORT_ANY_FID proposal [1], here is a shot at an
alternative proposal to seamlessly support more filesystems.

While fanotify relaxes the requirements for filesystems to support
reporting fid to require only the ->encode_fh() operation, there are
currently no new filesystems that meet the relaxed requirements.

I will shortly post patches that allow overlayfs to meet the new
requirements with default overlay configurations.

The overlay and vfs/fanotify patch sets are completely independent.
The are both available on my github branch [2] and there is a simple
LTP test variant that tests reporting fid from overlayfs [3], which
also demonstrates the minor UAPI change of name_to_handle_at(2) for
requesting a non-decodeable file handle by userspace.

Thanks,
Amir.

[1] https://lore.kernel.org/linux-fsdevel/20230417162721.ouzs33oh6mb7vtft@quack3/ (local)
[2] https://github.com/amir73il/linux/commits/exportfs_encode_fid
[3] https://github.com/amir73il/ltp/commits/exportfs_encode_fid

Amir Goldstein (4):
  exportfs: change connectable argument to bit flags
  exportfs: add explicit flag to request non-decodeable file handles
  exportfs: allow exporting non-decodeable file handles to userspace
  fanotify: support reporting non-decodeable file handles

 Documentation/filesystems/nfs/exporting.rst |  4 +--
 fs/exportfs/expfs.c                         | 29 ++++++++++++++++++---
 fs/fhandle.c                                | 20 ++++++++------
 fs/nfsd/nfsfh.c                             |  5 ++--
 fs/notify/fanotify/fanotify.c               |  4 +--
 fs/notify/fanotify/fanotify_user.c          |  6 ++---
 fs/notify/fdinfo.c                          |  2 +-
 include/linux/exportfs.h                    | 18 ++++++++++---
 include/uapi/linux/fcntl.h                  |  5 ++++
 9 files changed, 67 insertions(+), 26 deletions(-)

This set looks fairly benign to me, so ACK on the general concept.

I am starting to dislike how the AT_* flags are turning into a bunch of
flags that only have meanings on certain syscalls. I don't see a cleaner
way to handle it though.
-- 
Jeff Layton [off-list ref]