HDFS-8051. FsVolumeList#addVolume should release volume reference if not put it into BlockScanner. (Lei (Eddy) Xu via Colin P. McCabe)

(cherry picked from commit ef591b1d6a08f08358b19763a874de6010227307)
(cherry picked from commit b26ba22a9023ac2ae058abf509db67aa8ef64b41)

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

@@ -962,6 +962,9 @@ Release 2.7.0 - UNRELEASED
     HDFS-7996. After swapping a volume, BlockReceiver reports
     ReplicaNotFoundException (Lei (Eddy) Xu via Colin P. McCabe)
 
+    HDFS-8051. FsVolumeList#addVolume should release volume reference if not
+    put it into BlockScanner. (Lei (Eddy) Xu via Colin P. McCabe)
+
     BREAKDOWN OF HDFS-7584 SUBTASKS AND RELATED JIRAS
 
       HDFS-7720. Quota by Storage Type API, tools and ClientNameNode

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

@@ -39,6 +39,7 @@ import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.VolumeChoosingPolicy;
 import org.apache.hadoop.hdfs.server.datanode.BlockScanner;
+import org.apache.hadoop.hdfs.server.protocol.DatanodeStorage;
 import org.apache.hadoop.util.DiskChecker.DiskErrorException;
 import org.apache.hadoop.util.Time;
 
@@ -290,6 +291,10 @@ class FsVolumeList {
     }
     if (blockScanner != null) {
       blockScanner.addVolumeScanner(ref);
+    } else {
+      // If the volume is not put into a volume scanner, it does not need to
+      // hold the reference.
+      IOUtils.cleanup(FsDatasetImpl.LOG, ref);
     }
     // If the volume is used to replace a failed volume, it needs to reset the
     // volume failure info for this volume.

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestFsVolumeList.java

@@ -35,6 +35,7 @@ import java.util.Collections;
 import java.util.List;
 
 import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.fail;
 import static org.mockito.Mockito.mock;
 
 public class TestFsVolumeList {
@@ -101,4 +102,22 @@ public class TestFsVolumeList {
     // checkDirs() should ignore the 2nd volume since it is closed.
     volumeList.checkDirs();
   }
+
+  @Test
+  public void testReleaseVolumeRefIfNoBlockScanner() throws IOException {
+    FsVolumeList volumeList = new FsVolumeList(
+        Collections.<VolumeFailureInfo>emptyList(), null, blockChooser);
+    File volDir = new File(baseDir, "volume-0");
+    volDir.mkdirs();
+    FsVolumeImpl volume = new FsVolumeImpl(dataset, "storage-id", volDir,
+        conf, StorageType.DEFAULT);
+    FsVolumeReference ref = volume.obtainReference();
+    volumeList.addVolume(ref);
+    try {
+      ref.close();
+      fail("Should throw exception because the reference is closed in "
+          + "VolumeList#addVolume().");
+    } catch (IllegalStateException e) {
+    }
+  }
 }