diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManagerSafeMode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManagerSafeMode.java
index 883c352f977..0e9dc01098a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManagerSafeMode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManagerSafeMode.java
@@ -211,7 +211,7 @@ class BlockManagerSafeMode {
     switch (status) {
     case PENDING_THRESHOLD:
       if (areThresholdsMet()) {
-        if (extension > 0) {
+        if (blockTotal > 0 && extension > 0) {
           // PENDING_THRESHOLD -> EXTENSION
           status = BMSafeModeStatus.EXTENSION;
           reachedTime.set(monotonicNow());
@@ -527,11 +527,13 @@ class BlockManagerSafeMode {
 
   /**
    * Get time (counting in milliseconds) left to leave extension period.
+   * It should leave safemode at once if blockTotal = 0 rather than wait
+   * extension time (30s by default).
    *
    * Negative value indicates the extension period has passed.
    */
   private long timeToLeaveExtension() {
-    return reachedTime.get() + extension - monotonicNow();
+    return blockTotal > 0 ? reachedTime.get() + extension - monotonicNow() : 0;
   }
 
   /**
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockManagerSafeMode.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockManagerSafeMode.java
index af5342a3fb0..243c789e58f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockManagerSafeMode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockManagerSafeMode.java
@@ -222,6 +222,15 @@ public class TestBlockManagerSafeMode {
     }, 100, 10000);
   }
 
+  @Test
+  public void testCheckSafeMode8() throws Exception {
+    bmSafeMode.activate(0);
+    setBlockSafe(0);
+    setSafeModeStatus(BMSafeModeStatus.PENDING_THRESHOLD);
+    bmSafeMode.checkSafeMode();
+    assertEquals(BMSafeModeStatus.OFF, getSafeModeStatus());
+  }
+
   /**
    * Test that the block safe increases up to block threshold.
    *
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestHASafeMode.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestHASafeMode.java
index 6e7bd15a88a..0fc0a5551dd 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestHASafeMode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestHASafeMode.java
@@ -492,7 +492,15 @@ public class TestHASafeMode {
   private static void assertSafeMode(NameNode nn, int safe, int total,
     int numNodes, int nodeThresh) {
     String status = nn.getNamesystem().getSafemode();
-    if (safe == total) {
+    if (total == 0 && nodeThresh == 0) {
+      assertTrue("Bad safemode status: '" + status + "'",
+          status.isEmpty()
+              || status.startsWith("Safe mode is ON. The reported blocks 0 " +
+              "has reached the threshold 0.9990 of total blocks 0. The " +
+              "minimum number of live datanodes is not required. In safe " +
+              "mode extension. Safe mode will be turned off automatically " +
+              "in 0 seconds."));
+    } else if (safe == total) {
       if (nodeThresh == 0) {
         assertTrue("Bad safemode status: '" + status + "'",
             status.startsWith("Safe mode is ON. The reported blocks " + safe