HADOOP-9152. HDFS can report negative DFS Used on clusters with very small amounts of data. Contributed by Brock Noland.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1423602 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -505,6 +505,9 @@ Release 2.0.3-alpha - Unreleased
     HADOOP-9135. JniBasedUnixGroupsMappingWithFallback should log at debug
     rather than info during fallback. (Colin Patrick McCabe via todd)
 
+    HADOOP-9152. HDFS can report negative DFS Used on clusters with very small
+    amounts of data. (Brock Noland via atm)
+
 Release 2.0.2-alpha - 2012-09-07 
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/DU.java

@@ -136,7 +136,7 @@ public class DU extends Shell {
       }
     }
     
-    return used.longValue();
+    return Math.max(used.longValue(), 0L);
   }
 
   /**

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestDU.java

@@ -103,4 +103,12 @@ public class TestDU extends TestCase {
         duSize >= writtenSize &&
         writtenSize <= (duSize + slack));
   }
+  public void testDUGetUsedWillNotReturnNegative() throws IOException {
+    File file = new File(DU_DIR, "data");
+    assertTrue(file.createNewFile());
+    DU du = new DU(file, 10000);
+    du.decDfsUsed(Long.MAX_VALUE);
+    long duSize = du.getUsed();
+    assertTrue(String.valueOf(duSize), duSize >= 0L);
+  }
 }