HDFS-10875. Optimize du -x to cache intermediate result. Contributed by Xiao Chen.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeDirectory.java

@@ -630,14 +630,15 @@ public class INodeDirectory extends INodeWithAdditionalFields
       ContentSummaryComputationContext summary) {
     final DirectoryWithSnapshotFeature sf = getDirectoryWithSnapshotFeature();
     if (sf != null && snapshotId == Snapshot.CURRENT_STATE_ID) {
+      final ContentCounts counts = new ContentCounts.Builder().build();
       // if the getContentSummary call is against a non-snapshot path, the
       // computation should include all the deleted files/directories
       sf.computeContentSummary4Snapshot(summary.getBlockStoragePolicySuite(),
-          summary.getCounts());
-      // Also compute ContentSummary for snapshotCounts (So we can extract it
+          counts);
+      summary.getCounts().addContents(counts);
+      // Also add ContentSummary to snapshotCounts (So we can extract it
       // later from the ContentSummary of all).
-      sf.computeContentSummary4Snapshot(summary.getBlockStoragePolicySuite(),
-          summary.getSnapshotCounts());
+      summary.getSnapshotCounts().addContents(counts);
     }
     final DirectoryWithQuotaFeature q = getDirectoryWithQuotaFeature();
     if (q != null && snapshotId == Snapshot.CURRENT_STATE_ID) {