LFS-PFS control block integrity

To preserve the vnode-inode relationship, the LFS guarantees the following:

On every operation, the inode, represented by the PFS's token in Token_structure, has not been inactivated.
When the PFS is called to break the relationship (via vn_inactive at the time that a vnode is being freed), the LFS ensures that there are no other operations in progress against this vnode and, by extension, against the inode.
There are, in fact, no operations in progress against any file that is in the same mounted file system as the file that is being inactivated. This is so that no other operation may be attempting to find or recreate the inode while it is being deleted.
After a vn_inactive, the PFS does not receive any additional vn_ calls for that inode until the PFS creates a new vnode-inode binding for this same object as a result of a vn_lookup or vfs_vget call.