ceph: drop redundant r_mds field

The r_mds field is redundant, since we can find the same information at
r_session->s_mds, and when r_session is NULL then r_mds is meaningless.

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/debugfs.c b/fs/ceph/debugfs.c
index 7ae1b3d..08f65fa 100644
--- a/fs/ceph/debugfs.c
+++ b/fs/ceph/debugfs.c
@@ -60,10 +60,13 @@
 	for (rp = rb_first(&mdsc->request_tree); rp; rp = rb_next(rp)) {
 		req = rb_entry(rp, struct ceph_mds_request, r_node);
 
-		if (req->r_request)
-			seq_printf(s, "%lld\tmds%d\t", req->r_tid, req->r_mds);
-		else
+		if (req->r_request && req->r_session)
+			seq_printf(s, "%lld\tmds%d\t", req->r_tid,
+				   req->r_session->s_mds);
+		else if (!req->r_request)
 			seq_printf(s, "%lld\t(no request)\t", req->r_tid);
+		else
+			seq_printf(s, "%lld\t(no session)\t", req->r_tid);
 
 		seq_printf(s, "%s", ceph_mds_op_name(req->r_op));