Actually avoid calling open() :)

Author: JoshRosen

core/src/main/java/org/apache/spark/shuffle/sort/BypassMergeSortShuffleWriter.java

@@ -116,7 +116,7 @@ public void insertAll(Iterator<Product2<K, V>> records) throws IOException {
       // result in slower out-of-the-box performance due to these constant-factor overheads. This
       // optimization speeds up local microbenchmarking and SQL unit tests.
       partitionWriters[i] =
-        blockManager.getDiskWriter(blockId, file, serInstance, fileBufferSize, writeMetrics).open();
+        blockManager.getDiskWriter(blockId, file, serInstance, fileBufferSize, writeMetrics);
     }
     // Creating the file to write to and creating a disk writer both involve interacting with
     // the disk, and can take a long time in aggregate when we open many files, so should be