HDFS-12066. When Namenode is in safemode,may not allowed to remove an user's erasure coding policy. Contributed by lufei.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -7113,6 +7113,9 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     boolean success = false;
     writeLock();
     try {
+      checkOperation(OperationCategory.WRITE);
+      checkNameNodeSafeMode("Cannot remove erasure coding policy "
+          + ecPolicyName);
       FSDirErasureCodingOp.removeErasureCodePolicy(this, ecPolicyName);
       success = true;
     } finally {

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestSafeMode.java

@@ -482,6 +482,15 @@ public class TestSafeMode {
       // expected
     }
 
+    try {
+      dfs.removeErasureCodingPolicy("testECName");
+      fail("RemoveErasureCodingPolicy should have failed.");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains(
+          "Cannot remove erasure coding policy", ioe);
+      // expected
+    }
+
     assertFalse("Could not leave SM",
         dfs.setSafeMode(SafeModeAction.SAFEMODE_LEAVE));
   }