Update text to reflect that:

- mount(8) now calls the nmount(2) system call directly, not mount(2)
- specifying a filesystem type with -t will not automatically
  invoke an external /sbin/mount_XXXX program....this only happens for
  certain file system types.  For all other file system types, nmount(2)
  is called directly.

sbin/mount/mount.8

@@ -52,7 +52,7 @@
 The
 .Nm
 utility calls the
-.Xr mount 2
+.Xr nmount 2
 system call to prepare and graft a
 .Ar "special device"
 or the remote node (rhost:path) on to the file system tree at the point
@@ -377,13 +377,39 @@ mounts all file systems except those of type
 and
 .Tn NULLFS .
 .Pp
-If the type is not one of the internally known types,
+The default behavior of
 .Nm
-will attempt to execute a program in
+is to pass the
+.Fl t
+option directly to the
+.Xr nmount 2
+system call in the
+.Li fstype
+option.
+.Pp
+However, for the following file system types:
+.Ar cd9660 ,
+.Ar mfs , 
+.Ar msdosfs ,
+.Ar nfs ,
+.Ar nfs4 ,
+.Ar ntfs ,
+.Ar nwfs ,
+.Ar nullfs ,
+.Ar portalfs ,
+.Ar smbfs ,
+.Ar udf ,
+.Ar umapfs ,
+and
+.Ar unionfs ,
+.Nm
+will not call
+.Xr nmount 2
+directly and will instead attempt to execute a program in
 .Pa /sbin/mount_ Ns Sy XXX
 where
 .Sy XXX
-is replaced by the type name.
+is replaced by the file system type name.
 For example, nfs file systems are mounted by the program
 .Pa /sbin/mount_nfs .
 .Pp
@@ -449,16 +475,13 @@ support for a particular file system might be provided either on a static
 .Sh SEE ALSO
 .Xr getfacl 1 ,
 .Xr setfacl 1 ,
-.Xr mount 2 ,
+.Xr nmount 2 ,
 .Xr acl 3 ,
 .Xr mac 4 ,
 .Xr fstab 5 ,
 .Xr kldload 8 ,
 .Xr mount_cd9660 8 ,
-.Xr mount_devfs 8 ,
 .Xr mount_ext2fs 8 ,
-.Xr mount_fdescfs 8 ,
-.Xr mount_linprocfs 8 ,
 .Xr mount_msdosfs 8 ,
 .Xr mount_nfs 8 ,
 .Xr mount_ntfs 8 ,
@@ -466,7 +489,6 @@ support for a particular file system might be provided either on a static
 .Xr mount_nwfs 8 ,
 .Xr mount_portalfs 8 ,
 .Xr mount_procfs 8 ,
-.Xr mount_reiserfs 8 ,
 .Xr mount_smbfs 8 ,
 .Xr mount_std 8 ,
 .Xr mount_udf 8 ,