How to rename files in hdfs from spark more efficiently?

I have 450K JSONs, and I want to rename them in hdfs based on certain rules. For the sake of simplicity I just add a suffix .finished to each of them. A managed to do this, with the following code:

import org.apache.hadoop.fs._

val hdfs = FileSystem.get(sc.hadoopConfiguration)
val files = hdfs.listStatus(new Path(pathToJson))
val originalPath = files.map(_.getPath())

for(i <- originalPath.indices)
{
   hdfs.rename(originalPath(i), originalPath(i).suffix(".finished"))
}

But it takes 12 minutes to rename all of them. Is there a way to make it faster? (Perhaps parallelize) I use spark 1.6.0.