+what lock is current, and what lock desired. <<struct-ldlm-request>>
+
+.LDLM_GL_CALLBACK Reply Packet Structure
+image::ldlm-gl-callback-reply.png["LDLM_GL_CALLBACK Reply Packet Structure",height=50]
+
+//////////////////////////////////////////////////////////////////////
+The ldlm-gl-callback-reply.png diagram resembles this text
+art:
+
+ LDLM_GL_CALLBACK:
+ --reply------------------
+ | ptlrpc_body | ost_lvb |
+ -------------------------
+//////////////////////////////////////////////////////////////////////
+
+The reply updates the attributes on the requester.
+
+'ptlrpc_body'::
+RPC descriptor. <<struct-ptlrpc-body>>