diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index dff8bd27227..72ea4fb651e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -342,6 +342,8 @@ Release 2.8.0 - UNRELEASED
     HDFS-7928. Scanning blocks from disk during rolling upgrade startup takes
     a lot of time if disks are busy (Rushabh S Shah via kihwal)
 
+    HDFS-7990. IBR delete ack should not be delayed. (daryn via kihwal)
+
   OPTIMIZATIONS
 
   BUG FIXES
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
index 10cce4545ae..3b4756cb377 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
@@ -82,12 +82,11 @@ class BPServiceActor implements Runnable {
 
   final BPOfferService bpos;
   
-  // lastBlockReport, lastDeletedReport and lastHeartbeat may be assigned/read
+  // lastBlockReport and lastHeartbeat may be assigned/read
   // by testing threads (through BPServiceActor#triggerXXX), while also 
   // assigned/read by the actor thread. Thus they should be declared as volatile
   // to make sure the "happens-before" consistency.
   volatile long lastBlockReport = 0;
-  volatile long lastDeletedReport = 0;
 
   boolean resetBlockReportTime = true;
 
@@ -417,10 +416,10 @@ class BPServiceActor implements Runnable {
   @VisibleForTesting
   void triggerDeletionReportForTests() {
     synchronized (pendingIncrementalBRperStorage) {
-      lastDeletedReport = 0;
+      sendImmediateIBR = true;
       pendingIncrementalBRperStorage.notifyAll();
 
-      while (lastDeletedReport == 0) {
+      while (sendImmediateIBR) {
         try {
           pendingIncrementalBRperStorage.wait(100);
         } catch (InterruptedException e) {
@@ -465,7 +464,6 @@ class BPServiceActor implements Runnable {
     // or we will report an RBW replica after the BlockReport already reports
     // a FINALIZED one.
     reportReceivedDeletedBlocks();
-    lastDeletedReport = startTime;
 
     long brCreateStartTime = monotonicNow();
     Map<DatanodeStorage, BlockListAsLongs> perVolumeBlockLists =
@@ -674,7 +672,6 @@ class BPServiceActor implements Runnable {
    */
   private void offerService() throws Exception {
     LOG.info("For namenode " + nnAddr + " using"
-        + " DELETEREPORT_INTERVAL of " + dnConf.deleteReportInterval + " msec "
         + " BLOCKREPORT_INTERVAL of " + dnConf.blockReportInterval + "msec"
         + " CACHEREPORT_INTERVAL of " + dnConf.cacheReportInterval + "msec"
         + " Initial delay: " + dnConf.initialBlockReportDelay + "msec"
@@ -690,7 +687,9 @@ class BPServiceActor implements Runnable {
         //
         // Every so often, send heartbeat or block-report
         //
-        if (startTime - lastHeartbeat >= dnConf.heartBeatInterval) {
+        boolean sendHeartbeat =
+            startTime - lastHeartbeat >= dnConf.heartBeatInterval;
+        if (sendHeartbeat) {
           //
           // All heartbeat messages include following info:
           // -- Datanode name
@@ -729,10 +728,8 @@ class BPServiceActor implements Runnable {
             }
           }
         }
-        if (sendImmediateIBR ||
-            (startTime - lastDeletedReport > dnConf.deleteReportInterval)) {
+        if (sendImmediateIBR || sendHeartbeat) {
           reportReceivedDeletedBlocks();
-          lastDeletedReport = startTime;
         }
 
         List<DatanodeCommand> cmds = blockReport();
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java
index 67cd1ce1aae..3406f29f4c4 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java
@@ -82,7 +82,6 @@ public class DNConf {
   final long heartBeatInterval;
   final long blockReportInterval;
   final long blockReportSplitThreshold;
-  final long deleteReportInterval;
   final long initialBlockReportDelay;
   final long cacheReportInterval;
   final long dfsclientSlowIoWarningThresholdMs;
@@ -164,7 +163,6 @@ public class DNConf {
     heartBeatInterval = conf.getLong(DFS_HEARTBEAT_INTERVAL_KEY,
         DFS_HEARTBEAT_INTERVAL_DEFAULT) * 1000L;
     
-    this.deleteReportInterval = 100 * heartBeatInterval;
     // do we need to sync block file contents to disk when blockfile is closed?
     this.syncOnClose = conf.getBoolean(DFS_DATANODE_SYNCONCLOSE_KEY, 
         DFS_DATANODE_SYNCONCLOSE_DEFAULT);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
index 5c7b4ac41fb..23fc95bf3c8 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
@@ -84,7 +84,7 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
     @Override
     public SimulatedFSDataset newInstance(DataNode datanode,
         DataStorage storage, Configuration conf) throws IOException {
-      return new SimulatedFSDataset(storage, conf);
+      return new SimulatedFSDataset(datanode, storage, conf);
     }
 
     @Override
@@ -509,8 +509,15 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
   private final SimulatedStorage storage;
   private final SimulatedVolume volume;
   private final String datanodeUuid;
+  private final DataNode datanode;
   
+
   public SimulatedFSDataset(DataStorage storage, Configuration conf) {
+    this(null, storage, conf);
+  }
+
+  public SimulatedFSDataset(DataNode datanode, DataStorage storage, Configuration conf) {
+    this.datanode = datanode;
     if (storage != null) {
       for (int i = 0; i < storage.getNumStorageDirs(); ++i) {
         storage.createStorageID(storage.getStorageDir(i), false);
@@ -737,6 +744,10 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
       }
       storage.free(bpid, binfo.getNumBytes());
       map.remove(b);
+      if (datanode != null) {
+        datanode.notifyNamenodeDeletedBlock(new ExtendedBlock(bpid, b),
+            binfo.getStorageUuid());
+      }
     }
     if (error) {
       throw new IOException("Invalidate: Missing blocks.");
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestIncrementalBlockReports.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestIncrementalBlockReports.java
index b5aa93f6e64..cd2c1254245 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestIncrementalBlockReports.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestIncrementalBlockReports.java
@@ -159,8 +159,8 @@ public class TestIncrementalBlockReports {
           anyString(),
           any(StorageReceivedDeletedBlocks[].class));
 
-      // Trigger a block report, this also triggers an IBR.
-      DataNodeTestUtils.triggerBlockReport(singletonDn);
+      // Trigger a heartbeat, this also triggers an IBR.
+      DataNodeTestUtils.triggerHeartbeat(singletonDn);
       Thread.sleep(2000);
 
       // Ensure that the deleted block is reported.