From 180a26d9fb2b3f4a0632e1379f867020326c7702 Mon Sep 17 00:00:00 2001
From: Jing Zhao <jing9@apache.org>
Date: Wed, 3 Aug 2016 11:39:06 -0700
Subject: [PATCH] HDFS-10710. In
 BlockManager#rescanPostponedMisreplicatedBlocks(), postponed misreplicated
 block counts should be retrieved within the NN lock protection.Contributed by
 GAO Rui.

(cherry picked from commit f4ba5ff1d70ef92d59851c09c4bd4b43d6c04971)
---
 .../hadoop/hdfs/server/blockmanagement/BlockManager.java      | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
index 0f6d6dd09ea..703200be350 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
@@ -2073,9 +2073,9 @@ public class BlockManager implements BlockStatsMXBean {
       return;
     }
     long startTimeRescanPostponedMisReplicatedBlocks = Time.monotonicNow();
+    namesystem.writeLock();
     long startPostponedMisReplicatedBlocksCount =
         getPostponedMisreplicatedBlocksCount();
-    namesystem.writeLock();
     try {
       // blocksPerRescan is the configured number of blocks per rescan.
       // Randomly select blocksPerRescan consecutive blocks from the HashSet
@@ -2128,9 +2128,9 @@ public class BlockManager implements BlockStatsMXBean {
         }
       }
     } finally {
-      namesystem.writeUnlock();
       long endPostponedMisReplicatedBlocksCount =
           getPostponedMisreplicatedBlocksCount();
+      namesystem.writeUnlock();
       LOG.info("Rescan of postponedMisreplicatedBlocks completed in " +
           (Time.monotonicNow() - startTimeRescanPostponedMisReplicatedBlocks) +
           " msecs. " + endPostponedMisReplicatedBlocksCount +