ceph: add global total_caps to count the mdsc's total caps number

This will help to reduce using the global mdsc->mutex lock in many
places.

Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/metric.c

@@ -22,6 +22,7 @@ int ceph_metric_init(struct ceph_client_metric *m)
 	if (ret)
 		goto err_d_lease_mis;
 
+	atomic64_set(&m->total_caps, 0);
 	ret = percpu_counter_init(&m->i_caps_hit, 0, GFP_KERNEL);
 	if (ret)
 		goto err_i_caps_hit;