staging: lustre: osc: debug to match extent to brw RPC

Currently, it's difficult to match brw RPCs to objects and
extents from client logs.  This patch adds a D_RPCTRACE
debug message giving the necessary information.
Signed-off-by: Patrick Farrell <paf@cray.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5531
Reviewed-on: http://review.whamcloud.com/11548Reviewed-by: Alexey Lyashkov <alexey.lyashkov@seagate.com>
Reviewed-by: Ann Koehler <amk@cray.com>
Reviewed-by: Ryan Haasken <haasken@cray.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/osc/osc_request.c

@@ -1419,6 +1419,11 @@ static int osc_brw_prep_request(int cmd, struct client_obd *cli,
 	INIT_LIST_HEAD(&aa->aa_oaps);
 
 	*reqp = req;
+	niobuf = req_capsule_client_get(pill, &RMF_NIOBUF_REMOTE);
+	CDEBUG(D_RPCTRACE, "brw rpc %p - object " DOSTID " offset %lld<>%lld\n",
+	       req, POSTID(&oa->o_oi), niobuf[0].rnb_offset,
+	       niobuf[niocount - 1].rnb_offset + niobuf[niocount - 1].rnb_len);
+
 	return 0;
 
  out: