[PATCH v2 bpf-next 1/4] namei: Introduce new helper function path_walk_parent()

[Al Viro]

On Mon, Jun 02, 2025 at 11:59:17PM -0700, Song Liu wrote:
> This helper walks an input path to its parent. Logic are added to handle
> walking across mount tree.
> 
> This will be used by landlock, and BPF LSM.

Unless I'm misreading that, it does *NOT* walk to parent - it treats
step into mountpoint as a separate step.  NAK in that form - it's
simply a wrong primitive.