Re: Vnode API change: mnt_vnodelist traversal

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

   Date: Mon, 3 Mar 2014 15:55:16 +0100
   From: "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>

   On Mar 3, 2014, at 3:28 PM, Taylor R Campbell 
<campbell+netbsd-tech-kern%mumble.net@localhost> wrote:

   > /* mount.h */
   > struct vnode_iterator; /* opaque */
   > 
   > void vfs_vnode_iterator_init(struct mount *mp, struct vnode_iterator 
**vip);
   > void vfs_vnode_iterator_destroy(struct vnode_iterator *vi);
   > bool vfs_vnode_iterator_next(struct vnode_iterator *vi, struct vnode 
**vpp);
   > 
   > /* vfs_mount.c */
   > struct vnode_iterator {
   >    struct vnode vi_vnode;
   > };

   No.  I want to keep the state opaque to the caller.  There is no need for
   the calling party to know anything about state internals.

That is exactly what I was going for, except with a typed pointer
instead of a void pointer.  The definition of struct vnode_iterator
would be internal to vfs_mount.c; mount.h would only expose a forward
declaration.  Callers would be unable to dereference it or pass it
around anywhere else without casts or compiler warnings.

You don't even need to define struct vnode_iterator: leaving it as
`struct vnode_iterator;' and just casting inside vfs_vnode_iterator_*
instead of using &vi->vi_vnode would do just as well.