mount: create mount root on filer

fix https://github.com/seaweedfs/seaweedfs-csi-driver/issues/127

weed/command/mount_std.go

@@ -241,6 +241,14 @@ func RunMount(option *MountOptions, umask os.FileMode) bool {
 		DisableXAttr:       *option.disableXAttr,
 	})
 
+	// create mount root
+	mountRootPath := util.FullPath(mountRoot)
+	mountRootParent, mountDir := mountRootPath.DirAndName()
+	if err = filer_pb.Mkdir(seaweedFileSystem, mountRootParent, mountDir, nil); err != nil {
+		fmt.Printf("failed to create dir %s on filer %s: %v\n", mountRoot, filerAddresses, err)
+		return false
+	}
+
 	server, err := fuse.NewServer(seaweedFileSystem, dir, fuseMountOptions)
 	if err != nil {
 		glog.Fatalf("Mount fail: %v", err)