Merge patch series "pidfs: implement file handle support"

Merge patch series "pidfs: implement file handle support"

Christian Brauner <brauner@kernel.org> says:

Now that we have the preliminaries to lookup struct pid based on its
inode number alone we can implement file handle support.

This is based on custom export operation methods which allows pidfs to
implement permission checking and opening of pidfs file handles cleanly
without hacking around in the core file handle code too much.

* patches from https://lore.kernel.org/r/20241129-work-pidfs-file_handle-v1-0-87d803a42495@kernel.org:
  pidfs: implement file handle support
  exportfs: add permission method
  fhandle: pull CAP_DAC_READ_SEARCH check into may_decode_fh()
  exportfs: add open method
  fhandle: simplify error handling
  pseudofs: add support for export_ops

Link: https://lore.kernel.org/r/20241129-work-pidfs-file_handle-v1-0-87d803a42495@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>