6265 speed up mount/umount

@@ -201,10 +201,17 @@
 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 */