[SCSI] libfc: fix rport event race between READY and LOGO

When a remote port becomes ready and a LOGO is received before
the READY event is in rport_work waiting on the mutex, the
event is changed to LOGO and the work queued, so both the
calls to rport_work see the LOGO event, and both try to do
the list_del(), causing a crash.

Don't change the event if it is already set.
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_rport.c

@@ -1267,9 +1267,7 @@ static void fc_rport_recv_logo_req(struct fc_rport_priv *rdata,
 		return;
 	}
 
-	rdata->event = RPORT_EV_LOGO;
-	fc_rport_state_enter(rdata, RPORT_ST_DELETE);
-	queue_work(rport_event_queue, &rdata->event_work);
+	fc_rport_enter_delete(rdata, RPORT_EV_LOGO);
 
 	lport->tt.seq_els_rsp_send(sp, ELS_LS_ACC, NULL);
 	fc_frame_free(fp);