HDFS-5215. dfs.datanode.du.reserved is not considered while computing

available space ( Brahma Reddy Battula via Yongjun Zhang)

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -421,6 +421,9 @@ Release 2.8.0 - UNRELEASED
  HDFS-7916. 'reportBadBlocks' from datanodes to standby Node BPServiceActor
  goes for infinite loop (vinayakumarb)
 
+ HDFS-5215. dfs.datanode.du.reserved is not considered while computing
+ available space ( Brahma Reddy Battula via Yongjun Zhang)
+
 Release 2.7.0 - UNRELEASED
 
  INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java

@@ -2494,9 +2494,9 @@ public synchronized void shutdownBlockPool(String bpid) {
  */
  private static class VolumeInfo {
  final String directory;
- final long usedSpace;
- final long freeSpace;
- final long reservedSpace;
+ final long usedSpace; // size of space used by HDFS
+ final long freeSpace; // size of free space excluding reserved space
+ final long reservedSpace; // size of space reserved for non-HDFS and RBW
 
  VolumeInfo(FsVolumeImpl v, long usedSpace, long freeSpace) {
  this.directory = v.toString();

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java

@@ -305,9 +305,11 @@ long getBlockPoolUsed(String bpid) throws IOException {
  }
 
  /**
- * Calculate the capacity of the filesystem, after removing any
- * reserved capacity.
- * @return the unreserved number of bytes left in this filesystem. May be zero.
+ * Return either the configured capacity of the file system if configured; or
+ * the capacity of the file system excluding space reserved for non-HDFS.
+ * 
+ * @return the unreserved number of bytes left in this filesystem. May be
+ * zero.
  */
  @VisibleForTesting
  public long getCapacity() {
@@ -329,10 +331,16 @@ public void setCapacityForTesting(long capacity) {
  this.configuredCapacity = capacity;
  }
 
+ /*
+ * Calculate the available space of the filesystem, excluding space reserved
+ * for non-HDFS and space reserved for RBW
+ * 
+ * @return the available number of bytes left in this filesystem. May be zero.
+ */
  @Override
  public long getAvailable() throws IOException {
  long remaining = getCapacity() - getDfsUsed() - reservedForRbw.get();
- long available = usage.getAvailable();
+ long available = usage.getAvailable() - reserved - reservedForRbw.get();
  if (remaining > available) {
  remaining = available;
  }