HDFS-10956. Remove rename/delete performance penalty when not using snapshots. Contributed by Daryn Sharp.

(cherry picked from commit 44f48ee96ee6b2a3909911c37bfddb0c963d5ffc)

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

@@ -57,7 +57,7 @@ class FSDirDeleteOp {
     try {
       if (deleteAllowed(iip, iip.getPath()) ) {
         List<INodeDirectory> snapshottableDirs = new ArrayList<>();
-        FSDirSnapshotOp.checkSnapshot(iip.getLastINode(), snapshottableDirs);
+        FSDirSnapshotOp.checkSnapshot(fsd, iip, snapshottableDirs);
         ReclaimContext context = new ReclaimContext(
             fsd.getBlockStoragePolicySuite(), collectedBlocks, removedINodes,
             removedUCFiles);
@@ -140,7 +140,7 @@ class FSDirDeleteOp {
       return;
     }
     List<INodeDirectory> snapshottableDirs = new ArrayList<>();
-    FSDirSnapshotOp.checkSnapshot(iip.getLastINode(), snapshottableDirs);
+    FSDirSnapshotOp.checkSnapshot(fsd, iip, snapshottableDirs);
     boolean filesRemoved = unprotectedDelete(fsd, iip,
         new ReclaimContext(fsd.getBlockStoragePolicySuite(),
             collectedBlocks, removedINodes, removedUCFiles),

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

@@ -156,7 +156,7 @@ class FSDirRenameOp {
     assert fsd.hasWriteLock();
     final INode srcInode = srcIIP.getLastINode();
     try {
-      validateRenameSource(srcIIP);
+      validateRenameSource(fsd, srcIIP);
     } catch (SnapshotException e) {
       throw e;
     } catch (IOException ignored) {
@@ -346,7 +346,7 @@ class FSDirRenameOp {
     final String dst = dstIIP.getPath();
     final String error;
     final INode srcInode = srcIIP.getLastINode();
-    validateRenameSource(srcIIP);
+    validateRenameSource(fsd, srcIIP);
 
     // validate the destination
     if (dst.equals(src)) {
@@ -368,7 +368,7 @@ class FSDirRenameOp {
     List<INodeDirectory> snapshottableDirs = new ArrayList<>();
     if (dstInode != null) { // Destination exists
       validateOverwrite(src, dst, overwrite, srcInode, dstInode);
-      FSDirSnapshotOp.checkSnapshot(dstInode, snapshottableDirs);
+      FSDirSnapshotOp.checkSnapshot(fsd, dstIIP, snapshottableDirs);
     }
 
     INode dstParent = dstIIP.getINode(-2);
@@ -540,8 +540,8 @@ class FSDirRenameOp {
     }
   }
 
-  private static void validateRenameSource(INodesInPath srcIIP)
-      throws IOException {
+  private static void validateRenameSource(FSDirectory fsd,
+      INodesInPath srcIIP) throws IOException {
     String error;
     final INode srcInode = srcIIP.getLastINode();
     // validate source
@@ -559,7 +559,7 @@ class FSDirRenameOp {
     }
     // srcInode and its subtree cannot contain snapshottable directories with
     // snapshots
-    FSDirSnapshotOp.checkSnapshot(srcInode, null);
+    FSDirSnapshotOp.checkSnapshot(fsd, srcIIP, null);
   }
 
   private static class RenameOperation {

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

@@ -35,7 +35,6 @@ import org.apache.hadoop.util.ChunkedArrayList;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.ListIterator;
 import java.util.List;
 
 class FSDirSnapshotOp {
@@ -252,7 +251,7 @@ class FSDirSnapshotOp {
    * @param snapshottableDirs The list of directories that are snapshottable
    *                          but do not have snapshots yet
    */
-  static void checkSnapshot(
+  private static void checkSnapshot(
       INode target, List<INodeDirectory> snapshottableDirs)
       throws SnapshotException {
     if (target.isDirectory()) {
@@ -276,4 +275,23 @@ class FSDirSnapshotOp {
       }
     }
   }
+
+  /**
+   * Check if the given path (or one of its descendants) is snapshottable and
+   * already has snapshots.
+   *
+   * @param fsd the FSDirectory
+   * @param iip inodes of the path
+   * @param snapshottableDirs The list of directories that are snapshottable
+   *                          but do not have snapshots yet
+   */
+  static void checkSnapshot(FSDirectory fsd, INodesInPath iip,
+      List<INodeDirectory> snapshottableDirs) throws SnapshotException {
+    // avoid the performance penalty of recursing the tree if snapshots
+    // are not in use
+    SnapshotManager sm = fsd.getFSNamesystem().getSnapshotManager();
+    if (sm.getNumSnapshottableDirs() > 0) {
+      checkSnapshot(iip.getLastINode(), snapshottableDirs);
+    }
+  }
 }

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

@@ -22,6 +22,7 @@ import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
 import java.io.FileNotFoundException;
+import java.util.ArrayList;
 import java.util.List;
 
 import org.apache.hadoop.conf.Configuration;
@@ -30,12 +31,15 @@ import org.apache.hadoop.hdfs.DFSTestUtil;
 import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.protocol.SnapshotException;
 import org.apache.hadoop.hdfs.server.namenode.snapshot.Snapshot;
+import org.apache.hadoop.hdfs.server.namenode.snapshot.SnapshotManager;
 import org.junit.AfterClass;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
+import org.mockito.Mockito;
 
 /** Test snapshot related operations. */
 public class TestSnapshotPathINodes {
@@ -426,4 +430,16 @@ public class TestSnapshotPathINodes {
     hdfs.deleteSnapshot(sub1, "s3");
     hdfs.disallowSnapshot(sub1);
   }
+
+  @Test
+  public void testShortCircuitSnapshotSearch() throws SnapshotException {
+    FSNamesystem fsn = cluster.getNamesystem();
+    SnapshotManager sm = fsn.getSnapshotManager();
+    assertEquals(0, sm.getNumSnapshottableDirs());
+
+    INodesInPath iip = Mockito.mock(INodesInPath.class);
+    List<INodeDirectory> snapDirs = new ArrayList<>();
+    FSDirSnapshotOp.checkSnapshot(fsn.getFSDirectory(), iip, snapDirs);
+    Mockito.verifyZeroInteractions(iip);
+  }
 }