HDFS-4230. Support listing of all the snapshottable directories. Contributed by Jing Zhao

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2802@1429643 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt

@@ -92,3 +92,6 @@ Branch-2802 Snapshot (Unreleased)
 
   HDFS-4357. Fix a bug that if an inode is replaced, further INode operations
   should apply to the new inode. (Jing Zhao via szetszwo)
+
+  HDFS-4230. Support listing of all the snapshottable directories.  (Jing Zhao
+  via szetszwo)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java

@@ -118,6 +118,7 @@ import org.apache.hadoop.hdfs.protocol.HdfsProtoUtil;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
 import org.apache.hadoop.hdfs.protocol.NSQuotaExceededException;
+import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.protocol.UnresolvedPathException;
 import org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferEncryptor;
 import org.apache.hadoop.hdfs.protocol.datatransfer.IOStreamPair;
@@ -1929,6 +1930,18 @@ public class DFSClient implements java.io.Closeable {
     checkOpen();
     namenode.renameSnapshot(snapshotDir, snapshotOldName, snapshotNewName);
   }
+  
+  /**
+   * Get all the current snapshottable directories.
+   * @return All the current snapshottable directories
+   * @throws IOException
+   * @see ClientProtocol#getSnapshottableDirListing()
+   */
+  public SnapshottableDirectoryStatus[] getSnapshottableDirListing()
+      throws IOException {
+    checkOpen();
+    return namenode.getSnapshottableDirListing();
+  }
 
   /**
    * Allow snapshot on a directory.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java

@@ -58,6 +58,7 @@ import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.HdfsLocatedFileStatus;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
+import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.security.token.block.InvalidBlockTokenException;
 import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenIdentifier;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
@@ -942,4 +943,13 @@ public class DistributedFileSystem extends FileSystem {
       String snapshotNewName) throws IOException {
     dfs.renameSnapshot(path, snapshotOldName, snapshotNewName);
   }
+  
+  /**
+   * @return All the snapshottable directories
+   * @throws IOException
+   */
+  public SnapshottableDirectoryStatus[] getSnapshottableDirListing()
+      throws IOException {
+    return dfs.getSnapshottableDirListing();
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java

@@ -525,6 +525,16 @@ public interface ClientProtocol {
                                      boolean needLocation)
       throws AccessControlException, FileNotFoundException,
       UnresolvedLinkException, IOException;
+  
+  /**
+   * Get listing of all the snapshottable directories
+   * 
+   * @return Information about all the current snapshottable directory
+   * @throws IOException If an I/O error occurred
+   */
+  @Idempotent
+  public SnapshottableDirectoryStatus[] getSnapshottableDirListing()
+      throws IOException;
 
   ///////////////////////////////////////
   // System issues and management

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/SnapshottableDirectoryStatus.java

@@ -0,0 +1,87 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.protocol;
+
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.hdfs.DFSUtil;
+
+/**
+ * Metadata about a snapshottable directory
+ */
+public class SnapshottableDirectoryStatus {
+  /** Basic information of the snapshottable directory */
+  private HdfsFileStatus dirStatus;
+  
+  /** Number of snapshots that have been taken*/
+  private int snapshotNumber;
+  
+  /** Number of snapshots allowed. */
+  private int snapshotQuota;
+  
+  /** Full path of the parent. */
+  private byte[] parentFullPath;
+  
+  public SnapshottableDirectoryStatus(long modification_time, long access_time,
+      FsPermission permission, String owner, String group, byte[] localName,
+      int snapshotNumber, int snapshotQuota, byte[] parentFullPath) {
+    this.dirStatus = new HdfsFileStatus(0, true, 0, 0, modification_time,
+        access_time, permission, owner, group, null, localName);
+    this.snapshotNumber = snapshotNumber;
+    this.snapshotQuota = snapshotQuota;
+    this.parentFullPath = parentFullPath;
+  }
+
+  /**
+   * @return Number of snapshots that have been taken for the directory
+   */
+  public int getSnapshotNumber() {
+    return snapshotNumber;
+  }
+
+  /**
+   * @return Number of snapshots allowed for the directory
+   */
+  public int getSnapshotQuota() {
+    return snapshotQuota;
+  }
+  
+  /**
+   * @return Full path of the parent
+   */
+  public byte[] getParentFullPath() {
+    return parentFullPath;
+  }
+
+  /**
+   * @return The basic information of the directory
+   */
+  public HdfsFileStatus getDirStatus() {
+    return dirStatus;
+  }
+  
+  /**
+   * @return Full path of the file
+   */
+  public Path getFullPath() {
+    String parentFullPathStr = (parentFullPath == null || parentFullPath.length == 0) ? null
+        : DFSUtil.bytes2String(parentFullPath);
+    return parentFullPathStr == null ? new Path(dirStatus.getLocalName())
+        : new Path(parentFullPathStr, dirStatus.getLocalName());
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java

@@ -32,6 +32,7 @@ import org.apache.hadoop.hdfs.protocol.DirectoryListing;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
+import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AbandonBlockRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AbandonBlockResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddBlockRequestProto;
@@ -87,6 +88,8 @@ import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetPre
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetPreferredBlockSizeResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetServerDefaultsRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetServerDefaultsResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSnapshottableDirListingRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSnapshottableDirListingResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCorruptFileBlocksRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCorruptFileBlocksResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MetaSaveRequestProto;
@@ -906,4 +909,24 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
       throw new ServiceException(e);
     }
   }
+
+  static final GetSnapshottableDirListingResponseProto NULL_GET_SNAPSHOTTABLE_DIR_LISTING_RESPONSE 
+             = GetSnapshottableDirListingResponseProto.newBuilder().build();
+  @Override
+  public GetSnapshottableDirListingResponseProto getSnapshottableDirListing(
+      RpcController controller, GetSnapshottableDirListingRequestProto request)
+      throws ServiceException {
+    try {
+      SnapshottableDirectoryStatus[] result = server
+          .getSnapshottableDirListing();
+      if (result != null) {
+        return GetSnapshottableDirListingResponseProto.newBuilder().
+            setSnapshottableDirList(PBHelper.convert(result)).build();
+      } else {
+        return NULL_GET_SNAPSHOTTABLE_DIR_LISTING_RESPONSE;
+      }
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java

@@ -42,11 +42,11 @@ import org.apache.hadoop.hdfs.protocol.DirectoryListing;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants.DatanodeReportType;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
-import org.apache.hadoop.ipc.ProtocolTranslator;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
 import org.apache.hadoop.hdfs.protocol.NSQuotaExceededException;
+import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AbandonBlockRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddBlockRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AllowSnapshotRequestProto;
@@ -63,10 +63,10 @@ import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.Disall
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.FinalizeUpgradeRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.FsyncRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetAdditionalDatanodeRequestProto;
-import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetDataEncryptionKeyRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetBlockLocationsRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetBlockLocationsResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetContentSummaryRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetDataEncryptionKeyRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetDatanodeReportRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetDelegationTokenRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetFileInfoRequestProto;
@@ -79,6 +79,8 @@ import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetLis
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetListingResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetPreferredBlockSizeRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetServerDefaultsRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSnapshottableDirListingRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSnapshottableDirListingResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCorruptFileBlocksRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MetaSaveRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MkdirsRequestProto;
@@ -111,6 +113,7 @@ import org.apache.hadoop.io.EnumSetWritable;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.ipc.ProtobufHelper;
 import org.apache.hadoop.ipc.ProtocolMetaInterface;
+import org.apache.hadoop.ipc.ProtocolTranslator;
 import org.apache.hadoop.ipc.RPC;
 import org.apache.hadoop.ipc.RpcClientUtil;
 import org.apache.hadoop.security.AccessControlException;
@@ -877,4 +880,22 @@ public class ClientNamenodeProtocolTranslatorPB implements
       throw ProtobufHelper.getRemoteException(e);
     }
   }
+
+  @Override
+  public SnapshottableDirectoryStatus[] getSnapshottableDirListing()
+      throws IOException {
+    GetSnapshottableDirListingRequestProto req = 
+        GetSnapshottableDirListingRequestProto.newBuilder().build();
+    try {
+      GetSnapshottableDirListingResponseProto result = rpcProxy
+          .getSnapshottableDirListing(null, req);
+      
+      if (result.hasSnapshottableDirList()) {
+        return PBHelper.convert(result.getSnapshottableDirList());
+      }
+      return null;
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/PBHelper.java

@@ -43,6 +43,7 @@ import org.apache.hadoop.hdfs.protocol.HdfsLocatedFileStatus;
 import org.apache.hadoop.hdfs.protocol.HdfsProtoUtil;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
+import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.CreateFlagProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.DatanodeReportTypeProto;
@@ -93,6 +94,8 @@ import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.RemoteEditLogManifestPro
 import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.RemoteEditLogProto;
 import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.NamenodeRegistrationProto.NamenodeRoleProto;
 import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.ReplicaStateProto;
+import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.SnapshottableDirectoryListingProto;
+import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.SnapshottableDirectoryStatusProto;
 import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.StorageInfoProto;
 import org.apache.hadoop.hdfs.protocol.proto.JournalProtocolProtos.JournalInfoProto;
 import org.apache.hadoop.hdfs.security.token.block.DataEncryptionKey;
@@ -1021,7 +1024,6 @@ public class PBHelper {
     return new EnumSetWritable<CreateFlag>(result);
   }
   
-  
   public static HdfsFileStatus convert(HdfsFileStatusProto fs) {
     if (fs == null)
       return null;
@@ -1036,6 +1038,21 @@ public class PBHelper {
         fs.hasLocations() ? PBHelper.convert(fs.getLocations()) : null);
   }
 
+  public static SnapshottableDirectoryStatus convert(
+      SnapshottableDirectoryStatusProto sdirStatusProto) {
+    if (sdirStatusProto == null) {
+      return null;
+    }
+    return new SnapshottableDirectoryStatus(sdirStatusProto.getDirStatus()
+        .getModificationTime(), sdirStatusProto.getDirStatus().getAccessTime(),
+        PBHelper.convert(sdirStatusProto.getDirStatus().getPermission()),
+        sdirStatusProto.getDirStatus().getOwner(), sdirStatusProto
+            .getDirStatus().getGroup(), sdirStatusProto.getDirStatus()
+            .getPath().toByteArray(), sdirStatusProto.getSnapshotNumber(),
+        sdirStatusProto.getSnapshotQuota(), sdirStatusProto.getParentFullpath()
+            .toByteArray());
+  }
+  
   public static HdfsFileStatusProto convert(HdfsFileStatus fs) {
     if (fs == null)
       return null;
@@ -1070,6 +1087,25 @@ public class PBHelper {
     return builder.build();
   }
   
+  public static SnapshottableDirectoryStatusProto convert(
+      SnapshottableDirectoryStatus status) {
+    if (status == null) {
+      return null;
+    }
+    int snapshotNumber = status.getSnapshotNumber();
+    int snapshotQuota = status.getSnapshotQuota();
+    byte[] parentFullPath = status.getParentFullPath();
+    ByteString parentFullPathBytes = ByteString
+        .copyFrom(parentFullPath == null ? new byte[0] : parentFullPath);
+    HdfsFileStatusProto fs = convert(status.getDirStatus());
+    SnapshottableDirectoryStatusProto.Builder builder = 
+        SnapshottableDirectoryStatusProto
+        .newBuilder().setSnapshotNumber(snapshotNumber)
+        .setSnapshotQuota(snapshotQuota).setParentFullpath(parentFullPathBytes)
+        .setDirStatus(fs);
+    return builder.build();
+  }
+  
   public static HdfsFileStatusProto[] convert(HdfsFileStatus[] fs) {
     if (fs == null) return null;
     final int len = fs.length;
@@ -1311,5 +1347,38 @@ public class PBHelper {
     return JournalInfoProto.newBuilder().setClusterID(j.getClusterId())
         .setLayoutVersion(j.getLayoutVersion())
         .setNamespaceID(j.getNamespaceId()).build();
+  } 
+  
+  public static SnapshottableDirectoryStatus[] convert(
+      SnapshottableDirectoryListingProto sdlp) {
+    if (sdlp == null)
+      return null;
+    List<SnapshottableDirectoryStatusProto> list = sdlp
+        .getSnapshottableDirListingList();
+    if (list.isEmpty()) {
+      return new SnapshottableDirectoryStatus[0];
+    } else {
+      SnapshottableDirectoryStatus[] result = 
+          new SnapshottableDirectoryStatus[list.size()];
+      for (int i = 0; i < list.size(); i++) {
+        result[i] = (SnapshottableDirectoryStatus) PBHelper
+            .convert(list.get(i));
+      }
+      return result;
+    }
+  }
+  
+  public static SnapshottableDirectoryListingProto convert(
+      SnapshottableDirectoryStatus[] status) {
+    if (status == null)
+      return null;
+    SnapshottableDirectoryStatusProto[] protos = 
+        new SnapshottableDirectoryStatusProto[status.length];
+    for (int i = 0; i < status.length; i++) {
+      protos[i] = PBHelper.convert(status[i]);
+    }
+    List<SnapshottableDirectoryStatusProto> protoList = Arrays.asList(protos);
+    return SnapshottableDirectoryListingProto.newBuilder()
+        .addAllSnapshottableDirListing(protoList).build();
   }
 }

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

@@ -23,6 +23,7 @@ import java.io.Closeable;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
@@ -677,6 +678,8 @@ public class FSDirectory implements Closeable {
           + error);
       throw new IOException(error);
     }
+    List<INodeDirectorySnapshottable> snapshottableDirs = 
+        new ArrayList<INodeDirectorySnapshottable>();
     if (dstInode != null) { // Destination exists
       // It's OK to rename a file to a symlink and vice versa
       if (dstInode.isDirectory() != srcInode.isDirectory()) {
@@ -702,7 +705,7 @@ public class FSDirectory implements Closeable {
           throw new IOException(error);
         }
       }
-      INode snapshotNode = hasSnapshot(dstInode);
+      INode snapshotNode = hasSnapshot(dstInode, snapshottableDirs);
       if (snapshotNode != null) {
         error = "The direcotry " + dstInode.getFullPathName()
             + " cannot be deleted for renaming since "
@@ -770,6 +773,12 @@ public class FSDirectory implements Closeable {
           filesDeleted = rmdst.collectSubtreeBlocksAndClear(collectedBlocks);
           getFSNamesystem().removePathAndBlocks(src, collectedBlocks);
         }
+
+        if (snapshottableDirs.size() > 0) {
+          // There are snapshottable directories (without snapshots) to be
+          // deleted. Need to update the SnapshotManager.
+          namesystem.removeSnapshottableDirs(snapshottableDirs);
+        }
         return filesDeleted >0;
       }
     } finally {
@@ -1034,13 +1043,20 @@ public class FSDirectory implements Closeable {
         // snapshottable dir with snapshots, or its descendants have
         // snapshottable dir with snapshots
         INode targetNode = inodes[inodes.length-1];
-        INode snapshotNode = hasSnapshot(targetNode);
+        List<INodeDirectorySnapshottable> snapshottableDirs = 
+            new ArrayList<INodeDirectorySnapshottable>();
+        INode snapshotNode = hasSnapshot(targetNode, snapshottableDirs);
         if (snapshotNode != null) {
           throw new IOException("The direcotry " + targetNode.getFullPathName()
               + " cannot be deleted since " + snapshotNode.getFullPathName()
               + " is snapshottable and already has snapshots");
         }
         filesRemoved = unprotectedDelete(inodesInPath, collectedBlocks, now);
+        if (snapshottableDirs.size() > 0) {
+          // There are some snapshottable directories without snapshots to be
+          // deleted. Need to update the SnapshotManager.
+          namesystem.removeSnapshottableDirs(snapshottableDirs);
+        }
       }
     } finally {
       writeUnlock();
@@ -1160,18 +1176,28 @@ public class FSDirectory implements Closeable {
    * Check if the given INode (or one of its descendants) is snapshottable and
    * already has snapshots.
    * 
-   * @param target The given INode
+   * @param target
+   *          The given INode
+   * @param snapshottableDirs
+   *          The list of directories that are snapshottable but do not have
+   *          snapshots yet
    * @return The INode which is snapshottable and already has snapshots.
    */
-  private static INode hasSnapshot(INode target) {
+  private static INode hasSnapshot(INode target,
+      List<INodeDirectorySnapshottable> snapshottableDirs) {
     if (target instanceof INodeDirectory) {
       INodeDirectory targetDir = (INodeDirectory) target;
-      if (targetDir.isSnapshottable()
-          && ((INodeDirectorySnapshottable) targetDir).getNumSnapshots() > 0) {
-        return target;
-      }
+      if (targetDir.isSnapshottable()) {
+        INodeDirectorySnapshottable ssTargetDir = 
+            (INodeDirectorySnapshottable) targetDir;
+        if (ssTargetDir.getNumSnapshots() > 0) {
+          return target;
+        } else {
+          snapshottableDirs.add(ssTargetDir);
+        }
+      } 
       for (INode child : targetDir.getChildrenList(null)) {
-        INode snapshotDir = hasSnapshot(child);
+        INode snapshotDir = hasSnapshot(child, snapshottableDirs);
         if (snapshotDir != null) {
           return snapshotDir;
         }

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

@@ -137,6 +137,7 @@ import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.DirectoryListing;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
+import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants.DatanodeReportType;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
@@ -175,6 +176,7 @@ import org.apache.hadoop.hdfs.server.namenode.ha.HAState;
 import org.apache.hadoop.hdfs.server.namenode.ha.StandbyCheckpointer;
 import org.apache.hadoop.hdfs.server.namenode.metrics.FSNamesystemMBean;
 import org.apache.hadoop.hdfs.server.namenode.metrics.NameNodeMetrics;
+import org.apache.hadoop.hdfs.server.namenode.snapshot.INodeDirectorySnapshottable;
 import org.apache.hadoop.hdfs.server.namenode.snapshot.INodeFileWithLink;
 import org.apache.hadoop.hdfs.server.namenode.snapshot.Snapshot;
 import org.apache.hadoop.hdfs.server.namenode.snapshot.SnapshotManager;
@@ -5750,6 +5752,39 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
           newSnapshotRoot.toString(), null);
     }
   }
+  
+  /**
+   * Get the list of all the current snapshottable directories
+   * @return The list of all the current snapshottable directories
+   * @throws IOException
+   */
+  public SnapshottableDirectoryStatus[] getSnapshottableDirListing()
+      throws IOException {
+    readLock();
+    try {
+      checkOperation(OperationCategory.READ);
+      
+      SnapshottableDirectoryStatus[] status = snapshotManager
+          .getSnapshottableDirListing();
+      if (auditLog.isInfoEnabled() && isExternalInvocation()) {
+        logAuditEvent(UserGroupInformation.getCurrentUser(), getRemoteIp(),
+              "listSnapshottableDirectory", null, null, null);
+      }
+      return status;
+    } finally {
+      readUnlock();
+    }
+  }
+
+  /**
+   * Remove a list of INodeDirectorySnapshottable from the SnapshotManager
+   * @param toRemove the list of INodeDirectorySnapshottable to be removed
+   */
+  void removeSnapshottableDirs(List<INodeDirectorySnapshottable> toRemove) {
+    if (snapshotManager != null) {
+      snapshotManager.removeSnapshottableDirs(toRemove);
+    }
+  }
 
   /**
    * Default AuditLogger implementation; used when no access logger is

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

@@ -62,6 +62,7 @@ import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
+import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.protocol.UnregisteredNodeException;
 import org.apache.hadoop.hdfs.protocol.UnresolvedPathException;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ClientNamenodeProtocol;
@@ -1115,4 +1116,13 @@ class NameNodeRpcServer implements NamenodeProtocols {
     metrics.incrRenameSnapshotOps();
     namesystem.renameSnapshot(snapshotRoot, snapshotOldName, snapshotNewName);
   }
+
+  @Override // Client Protocol
+  public SnapshottableDirectoryStatus[] getSnapshottableDirListing()
+      throws IOException {
+    SnapshottableDirectoryStatus[] status = namesystem
+        .getSnapshottableDirListing();
+    metrics.incrListSnapshottableDirOps();
+    return status;
+  }
 }

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

@@ -65,6 +65,8 @@ public class NameNodeMetrics {
   MutableCounterLong createSnapshotOps;
   @Metric("Number of renameSnapshot operations")
   MutableCounterLong renameSnapshotOps;
+  @Metric("Number of listSnapshottableDirectory operations")
+  MutableCounterLong listSnapshottableDirOps;
 
   @Metric("Journal transactions") MutableRate transactions;
   @Metric("Journal syncs") MutableRate syncs;
@@ -183,6 +185,10 @@ public class NameNodeMetrics {
     renameSnapshotOps.incr();
   }
   
+  public void incrListSnapshottableDirOps() {
+    listSnapshottableDirOps.incr();
+  }
+  
   public void addTransaction(long latency) {
     transactions.add(latency);
   }

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

@@ -22,6 +22,8 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
 
+import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.server.namenode.FSDirectory;
 import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
 import org.apache.hadoop.hdfs.server.namenode.INodeDirectory;
@@ -156,4 +158,35 @@ public class SnapshotManager implements SnapshotStats {
     return numSnapshots.get();
   }
   
+  /**
+   * @return All the current snapshottable directories
+   */
+  public SnapshottableDirectoryStatus[] getSnapshottableDirListing() {
+    if (snapshottables.isEmpty()) {
+      return null;
+    }
+    
+    SnapshottableDirectoryStatus[] status = 
+        new SnapshottableDirectoryStatus[snapshottables.size()];
+    for (int i = 0; i < snapshottables.size(); i++) {
+      INodeDirectorySnapshottable dir = snapshottables.get(i);
+      status[i] = new SnapshottableDirectoryStatus(dir.getModificationTime(),
+          dir.getAccessTime(), dir.getFsPermission(), dir.getUserName(),
+          dir.getGroupName(), dir.getLocalNameBytes(), dir.getNumSnapshots(),
+          dir.getSnapshotQuota(), dir.getParent() == null ? new byte[0]
+              : DFSUtil.string2Bytes(dir.getParent().getFullPathName()));
+    }
+    return status;
+  }
+  
+  /**
+   * Remove snapshottable directories from {@link #snapshottables}
+   * @param toRemoveList A list of INodeDirectorySnapshottable to be removed
+   */
+  public void removeSnapshottableDirs(
+      List<INodeDirectorySnapshottable> toRemoveList) {
+    if (toRemoveList != null) {
+      this.snapshottables.removeAll(toRemoveList);
+    }
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientNamenodeProtocol.proto

@@ -208,6 +208,12 @@ message GetListingResponseProto {
   optional DirectoryListingProto dirList = 1;
 }
 
+message GetSnapshottableDirListingRequestProto { // no input parameters
+}
+message GetSnapshottableDirListingResponseProto {
+  optional SnapshottableDirectoryListingProto snapshottableDirList = 1;
+}
+
 message RenewLeaseRequestProto {
   required string clientName = 1;
 }
@@ -557,4 +563,6 @@ service ClientNamenodeProtocol {
       returns(AllowSnapshotResponseProto);
   rpc disallowSnapshot(DisallowSnapshotRequestProto)
       returns(DisallowSnapshotResponseProto);   
+  rpc getSnapshottableDirListing(GetSnapshottableDirListingRequestProto)
+      returns(GetSnapshottableDirListingResponseProto);
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/proto/hdfs.proto

@@ -152,7 +152,7 @@ message LocatedBlocksProto {
 
 
 /**
- * Status of a file, directory  or symlink
+ * Status of a file, directory or symlink
  * Optionally includes a file's block locations if requested by client on the rpc call.
  */
 message HdfsFileStatusProto {
@@ -213,6 +213,27 @@ message DirectoryListingProto {
   required uint32 remainingEntries  = 2;
 }
 
+/**
+ * Status of a snapshottable directory: besides the normal information for 
+ * a directory status, also include snapshot quota, number of snapshots, and
+ * the full path of the parent directory. 
+ */
+message SnapshottableDirectoryStatusProto {
+  required HdfsFileStatusProto dirStatus = 1;
+
+  // Fields specific for snapshottable directory
+  required uint32 snapshot_quota = 2;
+  required uint32 snapshot_number = 3;
+  required bytes parent_fullpath = 4;
+}
+
+/**
+ * Snapshottable directory listing
+ */
+message SnapshottableDirectoryListingProto {
+  repeated SnapshottableDirectoryStatusProto snapshottableDirListing = 1;
+}
+
 /**
  * Common node information shared by all the nodes in the cluster
  */

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshottableDirListing.java

@@ -0,0 +1,149 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.namenode.snapshot;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.Options.Rename;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hdfs.DFSTestUtil;
+import org.apache.hadoop.hdfs.DistributedFileSystem;
+import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
+import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class TestSnapshottableDirListing {
+
+  static final long seed = 0;
+  static final short REPLICATION = 3;
+  static final long BLOCKSIZE = 1024;
+
+  private final Path dir1 = new Path("/TestSnapshot1");
+  private final Path dir2 = new Path("/TestSnapshot2");
+  
+  Configuration conf;
+  MiniDFSCluster cluster;
+  FSNamesystem fsn;
+  DistributedFileSystem hdfs;
+  
+  @Before
+  public void setUp() throws Exception {
+    conf = new Configuration();
+    cluster = new MiniDFSCluster.Builder(conf).numDataNodes(REPLICATION)
+        .build();
+    cluster.waitActive();
+    fsn = cluster.getNamesystem();
+    hdfs = cluster.getFileSystem();
+    hdfs.mkdirs(dir1);
+    hdfs.mkdirs(dir2);
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    if (cluster != null) {
+      cluster.shutdown();
+    }
+  }
+  
+  /**
+   * Test listing all the snapshottable directories
+   */
+  @Test
+  public void testListSnapshottableDir() throws Exception {
+    // Initially there is no snapshottable directories in the system
+    SnapshottableDirectoryStatus[] dirs = hdfs.getSnapshottableDirListing();
+    assertNull(dirs);
+    
+    // Make dir1 as snapshottable
+    hdfs.allowSnapshot(dir1.toString());
+    dirs = hdfs.getSnapshottableDirListing();
+    assertEquals(1, dirs.length);
+    assertEquals(dir1.getName(), dirs[0].getDirStatus().getLocalName());
+    assertEquals(dir1, dirs[0].getFullPath());
+    // There is no snapshot for dir1 yet
+    assertEquals(0, dirs[0].getSnapshotNumber());
+    
+    // Make dir2 as snapshottable
+    hdfs.allowSnapshot(dir2.toString());
+    dirs = hdfs.getSnapshottableDirListing();
+    assertEquals(2, dirs.length);
+    assertEquals(dir1.getName(), dirs[0].getDirStatus().getLocalName());
+    assertEquals(dir1, dirs[0].getFullPath());
+    assertEquals(dir2.getName(), dirs[1].getDirStatus().getLocalName());
+    assertEquals(dir2, dirs[1].getFullPath());
+    // There is no snapshot for dir2 yet
+    assertEquals(0, dirs[1].getSnapshotNumber());
+    
+    // Create dir3
+    final Path dir3 = new Path("/TestSnapshot3");
+    hdfs.mkdirs(dir3);
+    // Rename dir3 to dir2
+    hdfs.rename(dir3, dir2, Rename.OVERWRITE);
+    // Now we only have one snapshottable dir: dir1
+    dirs = hdfs.getSnapshottableDirListing();
+    assertEquals(1, dirs.length);
+    assertEquals(dir1, dirs[0].getFullPath());
+    
+    // Make dir2 snapshottable again
+    hdfs.allowSnapshot(dir2.toString());
+    // Create a snapshot for dir2
+    hdfs.createSnapshot("s1", dir2.toString());
+    hdfs.createSnapshot("s2", dir2.toString());
+    dirs = hdfs.getSnapshottableDirListing();
+    // There are now 2 snapshots for dir2
+    assertEquals(dir2, dirs[1].getFullPath());
+    assertEquals(2, dirs[1].getSnapshotNumber());
+    
+    // Create sub-dirs under dir1
+    Path sub1 = new Path(dir1, "sub1");
+    Path file1 =  new Path(sub1, "file1");
+    Path sub2 = new Path(dir1, "sub2");
+    Path file2 =  new Path(sub2, "file2");
+    DFSTestUtil.createFile(hdfs, file1, BLOCKSIZE, REPLICATION, seed);
+    DFSTestUtil.createFile(hdfs, file2, BLOCKSIZE, REPLICATION, seed);
+    // Make sub1 and sub2 snapshottable
+    hdfs.allowSnapshot(sub1.toString());
+    hdfs.allowSnapshot(sub2.toString());
+    dirs = hdfs.getSnapshottableDirListing();
+    assertEquals(4, dirs.length);
+    assertEquals(dir1, dirs[0].getFullPath());
+    assertEquals(dir2, dirs[1].getFullPath());
+    assertEquals(sub1, dirs[2].getFullPath());
+    assertEquals(sub2, dirs[3].getFullPath());
+    
+    // reset sub1
+    hdfs.disallowSnapshot(sub1.toString());
+    dirs = hdfs.getSnapshottableDirListing();
+    assertEquals(3, dirs.length);
+    assertEquals(dir1, dirs[0].getFullPath());
+    assertEquals(dir2, dirs[1].getFullPath());
+    assertEquals(sub2, dirs[2].getFullPath());
+    
+    // Remove dir1, both dir1 and sub2 will be removed
+    hdfs.delete(dir1, true);
+    dirs = hdfs.getSnapshottableDirListing();
+    assertEquals(1, dirs.length);
+    assertEquals(dir2.getName(), dirs[0].getDirStatus().getLocalName());
+    assertEquals(dir2, dirs[0].getFullPath());
+  }
+}