HDFS-4147. When there is a snapshot in a subtree, deletion of the subtree should fail. Contributed by Jing Zhao

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2802@1405688 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -53,3 +53,6 @@ Branch-2802 Snapshot (Unreleased)
 
   HDFS-4149. Implement the disallowSnapshot(..) in FSNamesystem and add
   resetSnapshottable(..) to SnapshotManager. (szetszwo)
+
+  HDFS-4147. When there is a snapshot in a subtree, deletion of the subtree
+  should fail. (Jing Zhao via szetszwo)

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

@@ -997,7 +997,7 @@ public class FSDirectory implements Closeable {
    * @return true on successful deletion; else false
    */
   boolean delete(String src, List<Block>collectedBlocks) 
-    throws UnresolvedLinkException {
+    throws IOException {
     if (NameNode.stateChangeLog.isDebugEnabled()) {
       NameNode.stateChangeLog.debug("DIR* FSDirectory.delete: " + src);
     }
@@ -1006,7 +1006,22 @@ public class FSDirectory implements Closeable {
     int filesRemoved;
     writeLock();
     try {
-      filesRemoved = unprotectedDelete(src, collectedBlocks, now);
+      INode[] inodes = rootDir.getExistingPathINodes(normalizePath(src), false);
+      if (checkPathINodes(inodes, src) == 0) {
+        filesRemoved = 0;
+      } else {
+        // Before removing the node, first check if the targetNode is for a
+        // snapshottable dir with snapshots, or its descendants have
+        // snapshottable dir with snapshots
+        INode targetNode = inodes[inodes.length-1];
+        INode snapshotNode = hasSnapshot(targetNode);
+        if (snapshotNode != null) {
+          throw new IOException("The direcotry " + targetNode.getFullPathName()
+              + " cannot be deleted since " + snapshotNode.getFullPathName()
+              + " is snapshottable and already has snapshots");
+        }
+        filesRemoved = unprotectedDelete(inodes, collectedBlocks, now);
+      }
     } finally {
       writeUnlock();
     }
@@ -1020,6 +1035,23 @@ public class FSDirectory implements Closeable {
     return true;
   }
   
+  private int checkPathINodes(INode[] inodes, String src) {
+    if (inodes == null || inodes.length == 0
+        || inodes[inodes.length - 1] == null) {
+      if(NameNode.stateChangeLog.isDebugEnabled()) {
+        NameNode.stateChangeLog.debug("DIR* FSDirectory.unprotectedDelete: "
+            + "failed to remove " + src + " because it does not exist");
+      }
+      return 0;
+    } else if (inodes.length == 1) { // src is the root
+      NameNode.stateChangeLog.warn("DIR* FSDirectory.unprotectedDelete: "
+          + "failed to remove " + src
+          + " because the root is not allowed to be deleted");
+      return 0;
+    }
+    return inodes.length;
+  }
+  
   /**
    * @return true if the path is a non-empty directory; otherwise, return false.
    */
@@ -1050,7 +1082,14 @@ public class FSDirectory implements Closeable {
     throws UnresolvedLinkException {
     assert hasWriteLock();
     List<Block> collectedBlocks = new ArrayList<Block>();
-    int filesRemoved = unprotectedDelete(src, collectedBlocks, mtime);
+    int filesRemoved = 0;
+
+    INode[] inodes =  rootDir.getExistingPathINodes(normalizePath(src), false);
+    if (checkPathINodes(inodes, src) == 0) {
+      filesRemoved = 0;
+    } else {
+      filesRemoved = unprotectedDelete(inodes, collectedBlocks, mtime);
+    }
     if (filesRemoved > 0) {
       getFSNamesystem().removePathAndBlocks(src, collectedBlocks);
     }
@@ -1059,32 +1098,16 @@ public class FSDirectory implements Closeable {
   /**
    * Delete a path from the name space
    * Update the count at each ancestor directory with quota
-   * @param src a string representation of a path to an inode
+   * @param inodes the INode array resolved from the path
    * @param collectedBlocks blocks collected from the deleted path
    * @param mtime the time the inode is removed
    * @return the number of inodes deleted; 0 if no inodes are deleted.
    */ 
-  int unprotectedDelete(String src, List<Block> collectedBlocks, 
-      long mtime) throws UnresolvedLinkException {
+  int unprotectedDelete(INode[] inodes, List<Block> collectedBlocks, 
+      long mtime) {
     assert hasWriteLock();
-    src = normalizePath(src);
-
-    INode[] inodes =  rootDir.getExistingPathINodes(src, false);
+    
     INode targetNode = inodes[inodes.length-1];
-
-    if (targetNode == null) { // non-existent src
-      if(NameNode.stateChangeLog.isDebugEnabled()) {
-        NameNode.stateChangeLog.debug("DIR* FSDirectory.unprotectedDelete: "
-            +"failed to remove "+src+" because it does not exist");
-      }
-      return 0;
-    }
-    if (inodes.length == 1) { // src is the root
-      NameNode.stateChangeLog.warn("DIR* FSDirectory.unprotectedDelete: " +
-          "failed to remove " + src +
-          " because the root is not allowed to be deleted");
-      return 0;
-    }
     int pos = inodes.length - 1;
     // Remove the node from the namespace
     targetNode = removeChild(inodes, pos);
@@ -1096,10 +1119,34 @@ public class FSDirectory implements Closeable {
     int filesRemoved = targetNode.collectSubtreeBlocksAndClear(collectedBlocks);
     if (NameNode.stateChangeLog.isDebugEnabled()) {
       NameNode.stateChangeLog.debug("DIR* FSDirectory.unprotectedDelete: "
-          +src+" is removed");
+          + targetNode.getFullPathName() + " is removed");
     }
     return filesRemoved;
   }
+  
+  /**
+   * Check if the given INode (or one of its descendants) is snapshottable and
+   * already has snapshots.
+   * 
+   * @param target The given INode
+   * @return The INode which is snapshottable and already has snapshots.
+   */
+  private static INode hasSnapshot(INode target) {
+    if (target instanceof INodeDirectory) {
+      INodeDirectory targetDir = (INodeDirectory) target;
+      if (targetDir.isSnapshottable()
+          && ((INodeDirectorySnapshottable) targetDir).getNumSnapshots() > 0) {
+        return target;
+      }
+      for (INode child : targetDir.getChildren()) {
+        INode snapshotDir = hasSnapshot(child);
+        if (snapshotDir != null) {
+          return snapshotDir;
+        }
+      }
+    }
+    return null;
+  }
 
   /**
    * Replaces the specified INode.

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

@@ -75,7 +75,7 @@ public class INodeDirectorySnapshottable extends INodeDirectoryWithQuota {
     setSnapshotQuota(snapshotQuota);
   }
   
-  int getNumSnapshots() {
+  public int getNumSnapshots() {
     return snapshots.size();
   }
   

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

@@ -33,9 +33,12 @@ import org.apache.hadoop.hdfs.DFSTestUtil;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
+import org.apache.hadoop.ipc.RemoteException;
 import org.junit.After;
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 /**
  * This class tests snapshot functionality. One or multiple snapshots are
@@ -50,7 +53,8 @@ public class TestSnapshot {
 
   private final Path dir = new Path("/TestSnapshot");
   private final Path sub1 = new Path(dir, "sub1");
-
+  private final Path subsub1 = new Path(sub1, "subsub1");
+  
   protected Configuration conf;
   protected MiniDFSCluster cluster;
   protected FSNamesystem fsn;
@@ -61,6 +65,9 @@ public class TestSnapshot {
    * records a snapshot root.
    */
   protected static ArrayList<Path> snapshotList = new ArrayList<Path>();
+  
+  @Rule
+  public ExpectedException exception = ExpectedException.none();
 
   @Before
   public void setUp() throws Exception {
@@ -186,6 +193,66 @@ public class TestSnapshot {
     testSnapshot(sub1, mList);
   }
 
+  /**
+   * Creating snapshots for a directory that is not snapshottable must fail.
+   * 
+   * TODO: Listing/Deleting snapshots for a directory that is not snapshottable
+   * should also fail.
+   */
+  @Test
+  public void testSnapshottableDirectory() throws Exception {
+    Path file0 = new Path(sub1, "file0");
+    Path file1 = new Path(sub1, "file1");
+    DFSTestUtil.createFile(hdfs, file0, BLOCKSIZE, REPLICATION, seed);
+    DFSTestUtil.createFile(hdfs, file1, BLOCKSIZE, REPLICATION, seed);
+
+    exception.expect(RemoteException.class);
+    hdfs.createSnapshot("s1", sub1.toString());
+  }
+    
+  /**
+   * Deleting snapshottable directory with snapshots must fail.
+   */
+  @Test
+  public void testDeleteDirectoryWithSnapshot() throws Exception {
+    Path file0 = new Path(sub1, "file0");
+    Path file1 = new Path(sub1, "file1");
+    DFSTestUtil.createFile(hdfs, file0, BLOCKSIZE, REPLICATION, seed);
+    DFSTestUtil.createFile(hdfs, file1, BLOCKSIZE, REPLICATION, seed);
+
+    // Allow snapshot for sub1, and create snapshot for it
+    hdfs.allowSnapshot(sub1.toString());
+    hdfs.createSnapshot("s1", sub1.toString());
+
+    // Deleting a snapshottable dir with snapshots should fail
+    exception.expect(RemoteException.class);
+    hdfs.delete(sub1, true);
+  }
+  
+  /**
+   * Deleting directory with snapshottable descendant with snapshots must fail.
+   */
+  @Test
+  public void testDeleteDirectoryWithSnapshot2() throws Exception {
+    Path file0 = new Path(sub1, "file0");
+    Path file1 = new Path(sub1, "file1");
+    DFSTestUtil.createFile(hdfs, file0, BLOCKSIZE, REPLICATION, seed);
+    DFSTestUtil.createFile(hdfs, file1, BLOCKSIZE, REPLICATION, seed);
+    
+    Path subfile1 = new Path(subsub1, "file0");
+    Path subfile2 = new Path(subsub1, "file1");
+    DFSTestUtil.createFile(hdfs, subfile1, BLOCKSIZE, REPLICATION, seed);
+    DFSTestUtil.createFile(hdfs, subfile2, BLOCKSIZE, REPLICATION, seed);
+
+    // Allow snapshot for subsub1, and create snapshot for it
+    hdfs.allowSnapshot(subsub1.toString());
+    hdfs.createSnapshot("s1", subsub1.toString());
+
+    // Deleting dir while its descedant subsub1 having snapshots should fail
+    exception.expect(RemoteException.class);
+    hdfs.delete(dir, true);
+  }  
+  
   /**
    * Base class to present changes applied to current file/dir. A modification
    * can be file creation, deletion, or other modifications such as appending on