From a68b5b31cf846c0fc94c430bafd07a9bca369234 Mon Sep 17 00:00:00 2001
From: Kihwal Lee <kihwal@apache.org>
Date: Tue, 25 Jul 2017 11:03:09 -0500
Subject: [PATCH] HDFS-12171. Reduce IIP object allocations for inode lookup.
 Contributed by Daryn Sharp.

---
 .../namenode/EncryptionZoneManager.java       |  5 ++---
 .../server/namenode/FSDirErasureCodingOp.java |  5 ++---
 .../hdfs/server/namenode/INodesInPath.java    | 19 ++-----------------
 .../namenode/TestSnapshotPathINodes.java      |  5 ++---
 4 files changed, 8 insertions(+), 26 deletions(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EncryptionZoneManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EncryptionZoneManager.java
index 6dff62b97ee..96e189b91b5 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EncryptionZoneManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EncryptionZoneManager.java
@@ -209,9 +209,8 @@ public class EncryptionZoneManager {
     if (!hasCreatedEncryptionZone()) {
       return null;
     }
-    List<INode> inodes = iip.getReadOnlyINodes();
-    for (int i = inodes.size() - 1; i >= 0; i--) {
-      final INode inode = inodes.get(i);
+    for (int i = iip.length() - 1; i >= 0; i--) {
+      final INode inode = iip.getINode(i);
       if (inode != null) {
         final EncryptionZoneInt ezi = encryptionZones.get(inode.getId());
         if (ezi != null) {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirErasureCodingOp.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirErasureCodingOp.java
index 681f217d408..486503cbf7f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirErasureCodingOp.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirErasureCodingOp.java
@@ -355,9 +355,8 @@ final class FSDirErasureCodingOp {
     Preconditions.checkNotNull(iip, "INodes cannot be null");
     fsd.readLock();
     try {
-      List<INode> inodes = iip.getReadOnlyINodes();
-      for (int i = inodes.size() - 1; i >= 0; i--) {
-        final INode inode = inodes.get(i);
+      for (int i = iip.length() - 1; i >= 0; i--) {
+        final INode inode = iip.getINode(i);
         if (inode == null) {
           continue;
         }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodesInPath.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodesInPath.java
index abc8b6357f0..8235bf07d52 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodesInPath.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodesInPath.java
@@ -18,9 +18,6 @@
 package org.apache.hadoop.hdfs.server.namenode;
 
 import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
-import java.util.NoSuchElementException;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -336,17 +333,9 @@ public class INodesInPath {
    *         otherwise, i < 0, return the (length + i)-th inode.
    */
   public INode getINode(int i) {
-    if (inodes == null || inodes.length == 0) {
-      throw new NoSuchElementException("inodes is null or empty");
-    }
-    int index = i >= 0 ? i : inodes.length + i;
-    if (index < inodes.length && index >= 0) {
-      return inodes[index];
-    } else {
-      throw new NoSuchElementException("inodes.length == " + inodes.length);
-    }
+    return inodes[(i < 0) ? inodes.length + i : i];
   }
-  
+
   /** @return the last inode. */
   public INode getLastINode() {
     return getINode(-1);
@@ -384,10 +373,6 @@ public class INodesInPath {
     return inodes.length;
   }
 
-  public List<INode> getReadOnlyINodes() {
-    return Collections.unmodifiableList(Arrays.asList(inodes));
-  }
-
   public INode[] getINodesArray() {
     INode[] retArr = new INode[inodes.length];
     System.arraycopy(inodes, 0, retArr, 0, inodes.length);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestSnapshotPathINodes.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestSnapshotPathINodes.java
index d1d915e2ea4..b62a4180d43 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestSnapshotPathINodes.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestSnapshotPathINodes.java
@@ -310,9 +310,8 @@ public class TestSnapshotPathINodes {
   }
 
   private int getNumNonNull(INodesInPath iip) {
-    List<INode> inodes = iip.getReadOnlyINodes();
-    for (int i = inodes.size() - 1; i >= 0; i--) {
-      if (inodes.get(i) != null) {
+    for (int i = iip.length() - 1; i >= 0; i--) {
+      if (iip.getINode(i) != null) {
         return i+1;
       }
     }