HDFS-14925. Rename operation should check nest snapshot (#1670)

If the src directory or any of its descendant is snapshottable
and the dst directory or any of its ancestors is snapshottable,
we consider this as nested snapshot, which should be denied.

Reviewed-by: Shashikant Banerjee <shashikant@apache.org>

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

@@ -143,8 +143,8 @@ private static INodesInPath dstForRenameTo(
    * Change a path name
    *
    * @param fsd FSDirectory
-   * @param src source path
+   * @param srcIIP source path
-   * @param dst destination path
+   * @param dstIIP destination path
    * @return true INodesInPath if rename succeeds; null otherwise
    * @deprecated See {@link #renameToInt(FSDirectory, String, String,
    * boolean, Options.Rename...)}
@@ -155,8 +155,9 @@ static INodesInPath unprotectedRenameTo(FSDirectory fsd,
       throws IOException {
     assert fsd.hasWriteLock();
     final INode srcInode = srcIIP.getLastINode();
+    List<INodeDirectory> snapshottableDirs = new ArrayList<>();
     try {
-      validateRenameSource(fsd, srcIIP);
+      validateRenameSource(fsd, srcIIP, snapshottableDirs);
     } catch (SnapshotException e) {
       throw e;
     } catch (IOException ignored) {
@@ -190,6 +191,8 @@ static INodesInPath unprotectedRenameTo(FSDirectory fsd,
       return null;
     }
 
+    validateNestSnapshot(fsd, src, dstParent.asDirectory(), snapshottableDirs);
+
     fsd.ezManager.checkMoveValidity(srcIIP, dstIIP);
     // Ensure dst has quota to accommodate rename
     verifyFsLimitsForRename(fsd, srcIIP, dstIIP);
@@ -342,8 +345,8 @@ static void renameForEditLog(
    * for details related to rename semantics and exceptions.
    *
    * @param fsd             FSDirectory
-   * @param src             source path
+   * @param srcIIP          source path
-   * @param dst             destination path
+   * @param dstIIP          destination path
    * @param timestamp       modification time
    * @param collectedBlocks blocks to be removed
    * @param options         Rename options
@@ -361,7 +364,8 @@ static RenameResult unprotectedRenameTo(FSDirectory fsd,
     final String dst = dstIIP.getPath();
     final String error;
     final INode srcInode = srcIIP.getLastINode();
-    validateRenameSource(fsd, srcIIP);
+    List<INodeDirectory> srcSnapshottableDirs = new ArrayList<>();
+    validateRenameSource(fsd, srcIIP, srcSnapshottableDirs);
 
     // validate the destination
     if (dst.equals(src)) {
@@ -380,10 +384,10 @@ static RenameResult unprotectedRenameTo(FSDirectory fsd,
     BlockStoragePolicySuite bsps = fsd.getBlockStoragePolicySuite();
     fsd.ezManager.checkMoveValidity(srcIIP, dstIIP);
     final INode dstInode = dstIIP.getLastINode();
-    List<INodeDirectory> snapshottableDirs = new ArrayList<>();
+    List<INodeDirectory> dstSnapshottableDirs = new ArrayList<>();
     if (dstInode != null) { // Destination exists
       validateOverwrite(src, dst, overwrite, srcInode, dstInode);
-      FSDirSnapshotOp.checkSnapshot(fsd, dstIIP, snapshottableDirs);
+      FSDirSnapshotOp.checkSnapshot(fsd, dstIIP, dstSnapshottableDirs);
     }
 
     INode dstParent = dstIIP.getINode(-2);
@@ -400,6 +404,9 @@ static RenameResult unprotectedRenameTo(FSDirectory fsd,
       throw new ParentNotDirectoryException(error);
     }
 
+    validateNestSnapshot(fsd, src,
+            dstParent.asDirectory(), srcSnapshottableDirs);
+
     // Ensure dst has quota to accommodate rename
     verifyFsLimitsForRename(fsd, srcIIP, dstIIP);
     verifyQuotaForRename(fsd, srcIIP, dstIIP);
@@ -439,10 +446,10 @@ static RenameResult unprotectedRenameTo(FSDirectory fsd,
           }
         }
 
-        if (snapshottableDirs.size() > 0) {
+        if (dstSnapshottableDirs.size() > 0) {
           // There are snapshottable directories (without snapshots) to be
           // deleted. Need to update the SnapshotManager.
-          fsd.getFSNamesystem().removeSnapshottableDirs(snapshottableDirs);
+          fsd.getFSNamesystem().removeSnapshottableDirs(dstSnapshottableDirs);
         }
 
         tx.updateQuotasInSourceTree(bsps);
@@ -556,7 +563,8 @@ private static void validateOverwrite(
   }
 
   private static void validateRenameSource(FSDirectory fsd,
-      INodesInPath srcIIP) throws IOException {
+      INodesInPath srcIIP, List<INodeDirectory> snapshottableDirs)
+      throws IOException {
     String error;
     final INode srcInode = srcIIP.getLastINode();
     // validate source
@@ -574,7 +582,32 @@ private static void validateRenameSource(FSDirectory fsd,
     }
     // srcInode and its subtree cannot contain snapshottable directories with
     // snapshots
-    FSDirSnapshotOp.checkSnapshot(fsd, srcIIP, null);
+    FSDirSnapshotOp.checkSnapshot(fsd, srcIIP, snapshottableDirs);
+  }
+
+  private static void validateNestSnapshot(FSDirectory fsd, String srcPath,
+      INodeDirectory dstParent, List<INodeDirectory> snapshottableDirs)
+      throws SnapshotException {
+
+    if (fsd.getFSNamesystem().getSnapshotManager().isAllowNestedSnapshots()) {
+      return;
+    }
+
+    /*
+     * snapshottableDirs is a list of snapshottable directory (child of rename
+     * src) which do not have snapshots yet. If this list is not empty, that
+     * means rename src has snapshottable descendant directories.
+     */
+    if (snapshottableDirs != null && snapshottableDirs.size() > 0) {
+      if (fsd.getFSNamesystem().getSnapshotManager()
+              .isDescendantOfSnapshotRoot(dstParent)) {
+        String dstPath = dstParent.getFullPathName();
+        throw new SnapshotException("Unable to rename because " + srcPath
+                + " has snapshottable descendant directories and " + dstPath
+                + " is a descent of a snapshottable directory, and HDFS does"
+                + " not support nested snapshottable directory.");
+      }
+    }
   }
 
   private static class RenameOperation {

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

@@ -155,6 +155,10 @@ void setAllowNestedSnapshots(boolean allowNestedSnapshots) {
     this.allowNestedSnapshots = allowNestedSnapshots;
   }
 
+  public boolean isAllowNestedSnapshots() {
+    return allowNestedSnapshots;
+  }
+
   private void checkNestedSnapshottable(INodeDirectory dir, String path)
       throws SnapshotException {
     if (allowNestedSnapshots) {
@@ -288,6 +292,19 @@ public INodeDirectory getSnapshottableAncestorDir(final INodesInPath iip)
     }
   }
 
+  public boolean isDescendantOfSnapshotRoot(INodeDirectory dir) {
+    if (dir.isSnapshottable()) {
+      return true;
+    } else {
+      for (INodeDirectory p = dir; p != null; p = p.getParent()) {
+        if (this.snapshottables.containsValue(p)) {
+          return true;
+        }
+      }
+      return false;
+    }
+  }
+
   /**
    * Create a snapshot of the given path.
    * It is assumed that the caller will perform synchronization.

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

@@ -1116,6 +1116,44 @@ public void testRenameAndUpdateSnapshottableDirs() throws Exception {
     assertEquals(fooId, dirs[0].getDirStatus().getFileId());
   }
 
+  /**
+   * Test rename where src has snapshottable descendant directories and
+   * dst is a descent of a snapshottable directory. Such case will cause
+   * nested snapshot which HDFS currently not fully supported.
+   */
+  @Test
+  public void testRenameWithNestedSnapshottableDirs() throws Exception {
+    final Path sdir1 = new Path("/dir1");
+    final Path sdir2 = new Path("/dir2");
+    final Path foo = new Path(sdir1, "foo");
+    final Path bar = new Path(sdir2, "bar");
+
+    hdfs.mkdirs(foo);
+    hdfs.mkdirs(bar);
+
+    hdfs.allowSnapshot(foo);
+    hdfs.allowSnapshot(sdir2);
+
+    try {
+      hdfs.rename(foo, bar, Rename.OVERWRITE);
+      fail("Except exception since " + "Unable to rename because "
+          + foo.toString() + " has snapshottable descendant directories and "
+          + sdir2.toString() + " is a descent of a snapshottable directory, "
+          + "and HDFS does not support nested snapshottable directory.");
+    } catch (IOException e) {
+      GenericTestUtils.assertExceptionContains("Unable to rename because "
+            + foo.toString() + " has snapshottable descendant directories and "
+            + sdir2.toString() + " is a descent of a snapshottable directory, "
+            + "and HDFS does not support nested snapshottable directory.", e);
+    }
+
+    hdfs.disallowSnapshot(foo);
+    hdfs.rename(foo, bar, Rename.OVERWRITE);
+    SnapshottableDirectoryStatus[] dirs = fsn.getSnapshottableDirListing();
+    assertEquals(1, dirs.length);
+    assertEquals(sdir2, dirs[0].getFullPath());
+  }
+
   /**
    * After rename, delete the snapshot in src
    */