[SCSI] libfc: fix: empty zone causes endless discovery retries.

On some switches, an empty zone causes GPN_FT to be rejected
with reason 9 (unable) explanation 7 (FC-4 types not registered),
which causes discovery to be retried endlessly.  Treat this as
just an empty response and consider discovery complete.
Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/libfc/fc_disc.c

@@ -617,6 +617,9 @@ static void fc_disc_gpn_ft_resp(struct fc_seq *sp, struct fc_frame *fp,
 				    "(check zoning)\n", cp->ct_reason,
 				    cp->ct_explan);
 			event = DISC_EV_FAILED;
+			if (cp->ct_reason == FC_FS_RJT_UNABL &&
+			    cp->ct_explan == FC_FS_EXP_FTNR)
+				event = DISC_EV_SUCCESS;
 		} else {
 			FC_DISC_DBG(disc, "GPN_FT unexpected response code "
 				    "%x\n", ntohs(cp->ct_cmd));

include/scsi/fc/fc_gs.h

@@ -87,6 +87,7 @@ enum fc_ct_explan {
 	FC_FS_EXP_PNAM =	0x02,	/* port name not registered */
 	FC_FS_EXP_NNAM =	0x03,	/* node name not registered */
 	FC_FS_EXP_COS =		0x04,	/* class of service not registered */
+	FC_FS_EXP_FTNR =	0x07,	/* FC-4 types not registered */
 	/* definitions not complete */
 };