Merge branch 'link_path_walk'

Merge branch 'link_path_walk'

This is the last - for now - of the "look, we generated some
questionable code for basic pathname lookup operations" set of
branches.

This is mainly just re-organizing the name hashing code in
link_path_walk(), mostly by improving the calling conventions to
the inlined helper functions and moving some of the code around
to allow for more straightforward code generation.

The profiles - and the generated code - look much more palatable
to me now.

* link_path_walk:
  vfs: link_path_walk: move more of the name hashing into hash_name()
  vfs: link_path_walk: improve may_lookup() code generation
  vfs: link_path_walk: do '.' and '..' detection while hashing
  vfs: link_path_walk: clarify and improve name hashing interface
  vfs: link_path_walk: simplify name hash flow