HDFS-15334. INodeAttributeProvider's new API checkPermissionWithContext not getting called in for authorization. (#1998)

Reviewed-by: Arpit Agarwal <arp@apache.org>
(cherry picked from commit adecdb8b534c536354f4f47789467ffb82dd1496)
(cherry picked from commit f4c05f1d93718c5cd574abf40c14510886289353)

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

@@ -73,6 +73,7 @@ import javax.annotation.Nullable;
 import java.io.Closeable;
 import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -225,8 +226,18 @@ public class FSDirectory implements Closeable {
     Class[] cArg = new Class[1];
     cArg[0] = INodeAttributeProvider.AuthorizationContext.class;
 
+    INodeAttributeProvider.AccessControlEnforcer enforcer =
+        attributeProvider.getExternalAccessControlEnforcer(null);
+
+    // If external enforcer is null, we use the default enforcer, which
+    // supports the new API.
+    if (enforcer == null) {
+      useAuthorizationWithContextAPI = true;
+      return;
+    }
+
     try {
-      Class<?> clazz = attributeProvider.getClass();
+      Class<?> clazz = enforcer.getClass();
       clazz.getDeclaredMethod("checkPermissionWithContext", cArg);
       useAuthorizationWithContextAPI = true;
       LOG.info("Use the new authorization provider API");