* mount options
  */
 enum {
+       Opt_mds_namespace,
        Opt_wsize,
        Opt_rsize,
        Opt_rasize,
 };
 
 static match_table_t fsopt_tokens = {
+       {Opt_mds_namespace, "mds_namespace=%d"},
        {Opt_wsize, "wsize=%d"},
        {Opt_rsize, "rsize=%d"},
        {Opt_rasize, "rasize=%d"},
                break;
 
                /* misc */
+       case Opt_mds_namespace:
+               fsopt->mds_namespace = intval;
+               break;
        case Opt_wsize:
                fsopt->wsize = intval;
                break;
        fsopt->max_readdir = CEPH_MAX_READDIR_DEFAULT;
        fsopt->max_readdir_bytes = CEPH_MAX_READDIR_BYTES_DEFAULT;
        fsopt->congestion_kb = default_congestion_kb();
+       fsopt->mds_namespace = CEPH_FS_CLUSTER_ID_NONE;
 
        /*
         * Distinguish the server list from the path in "dev_name".
                seq_puts(m, ",noacl");
 #endif
 
+       if (fsopt->mds_namespace != CEPH_FS_CLUSTER_ID_NONE)
+               seq_printf(m, ",mds_namespace=%d", fsopt->mds_namespace);
        if (fsopt->wsize)
                seq_printf(m, ",wsize=%d", fsopt->wsize);
        if (fsopt->rsize != CEPH_RSIZE_DEFAULT)
                goto fail;
        }
        fsc->client->extra_mon_dispatch = extra_mon_dispatch;
+       fsc->client->monc.fs_cluster_id = fsopt->mds_namespace;
        ceph_monc_want_map(&fsc->client->monc, CEPH_SUB_MDSMAP, 0, true);
 
        fsc->mount_options = fsopt;