增加hdfs代码注释

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

@@ -201,6 +201,9 @@ private static INodeDirectory createRoot(FSNamesystem namesystem) {
   private final String supergroup;
   private final INodeId inodeId;
 
+  /**
+   * 写editlog。
+   */
   private final FSEditLog editLog;
 
   private HdfsFileStatus[] reservedStatuses;

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

@@ -1233,6 +1233,7 @@ private void loadFSImage(StartupOption startOpt) throws IOException {
     writeLock();
     try {
       // We shouldn't be calling saveNamespace if we've come up in standby state.
+      // 根据启动选项及其对应存储目录(${dfs.name.dir})，分析存储目录，必要的话从先前的事务恢复过来
       MetaRecoveryContext recovery = startOpt.createRecoveryContext();
       final boolean staleImage
           = fsImage.recoverTransitionRead(startOpt, this, recovery);

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

@@ -34,6 +34,7 @@
 @InterfaceStability.Unstable
 public abstract class INodeAttributeProvider {
 
+  // 访问控制执行者接口
   public static class AuthorizationContext {
     private String fsOwner;
     private String supergroup;