Re: Vnode API cleanup pass 2a

[Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost>]

   Date: Mon, 30 Dec 2013 11:35:48 +0100
   From: "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>

   The layered file systems hashlists currently have to work on locked
   vnodes as the vnode operations returning vnodes return them locked.

   This leads to some very dirty hacks -- see layer_node_find() from
   sys/miscfs/genfs/layer_subr.c for example.

   The best solution is to change these vnode operations to return
   unlocked (and referenced) vnodes.

   The attached diff implements this change for operations create, mknod,
   mkdir and symlink.  It passes the atf test suite and some file system
   stress tests I use here.

This seems to largely add code to file systems to mess with locking
further, rather than reducing that code.  Can you explain how this
change helps to clean up those dirty hacks?  Are you planning to make
lookup return the node unlocked too or something first?