From what I can tell, it has never been used.

Mimi: This was introduced prior to Rusty's decision to use appended
signatures for kernel modules.
Signed-off-by: NThiago Jung Bauermann <bauerman@linux.ibm.com>
Acked-by: NMimi Zohar <zohar@linux.ibm.com>
Signed-off-by: NJames Morris <james.morris@microsoft.com>