6265 speed up mount/umount

*** 201,210 ****
--- 201,217 ----
  struct fem_head;        /* from fem.h */
  
  typedef struct vfs {
          struct vfs      *vfs_next;              /* next VFS in VFS list */
          struct vfs      *vfs_prev;              /* prev VFS in VFS list */
+         avl_node_t      vfs_avldev;             /* by dev index */
+         avl_node_t      vfs_avlmntpnt;          /* by mntpnt index */
+         /*
+          * global mount count to define an order on entries in
+          * the avl trees with same dev/mountpoint
+          */
+         uint64_t        vfs_mntix;
  
  /* vfs_op should not be used directly.  Accessor functions are provided */
          vfsops_t        *vfs_op;                /* operations on VFS */
  
          struct vnode    *vfs_vnodecovered;      /* vnode mounted on */