From 6a76250b39f33466bdc8dabab33070c90aa1a389 Mon Sep 17 00:00:00 2001
From: Xiaoyu Yao <xyao@apache.org>
Date: Tue, 16 Jun 2015 13:52:50 -0700
Subject: [PATCH] HDFS-8548. Minicluster throws NPE on shutdown. Contributed by
 surendra singh lilhore.

---
 hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt                 | 3 +++
 .../hadoop/hdfs/server/blockmanagement/BlocksMap.java       | 6 +++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index b921f2c916..c8c36e6440 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -900,6 +900,9 @@ Release 2.8.0 - UNRELEASED
 
     HDFS-8592. SafeModeException never get unwrapped. (wheat9)
 
+    HDFS-8548. Minicluster throws NPE on shutdown.
+    (surendra singh lilhore via xyao)
+
 Release 2.7.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlocksMap.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlocksMap.java
index 9eb1059b3a..0dbf4858b7 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlocksMap.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlocksMap.java
@@ -198,7 +198,11 @@ boolean removeNode(Block b, DatanodeDescriptor node) {
   }
 
   int size() {
-    return blocks.size();
+    if (blocks != null) {
+      return blocks.size();
+    } else {
+      return 0;
+    }
   }
 
   Iterable<BlockInfo> getBlocks() {