diff --git a/src/main/java/org/apache/hadoop/fs/CosNFSInputStream.java b/src/main/java/org/apache/hadoop/fs/CosNFSInputStream.java
index e4163f4..6bc7c37 100644
--- a/src/main/java/org/apache/hadoop/fs/CosNFSInputStream.java
+++ b/src/main/java/org/apache/hadoop/fs/CosNFSInputStream.java
@@ -11,6 +11,7 @@
 import java.io.IOException;
 import java.util.ArrayDeque;
 import java.util.Deque;
+import java.util.Objects;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -18,6 +19,8 @@
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
+import javax.annotation.Nullable;
+
 
 public class CosNFSInputStream extends FSInputStream {
     public static final Logger LOG =
@@ -61,8 +64,13 @@ public void signalAll() {
             readyCondition.signalAll();
         }
 
+        @Nullable
         public byte[] getBuffer() {
-            return this.memory.array();
+            final MemoryAllocator.Memory finalMemory = memory;
+            if (finalMemory == null) {
+                return null;
+            }
+            return finalMemory.array();
         }
 
         public int length() {
@@ -358,6 +366,7 @@ public int read() throws IOException {
         int byteRead = -1;
         if (this.partRemaining != 0) {
             byte[] buffer = currentReadBuffer.getBuffer();
+            Objects.requireNonNull(buffer);
             byteRead = buffer[(int) (buffer.length - this.partRemaining)] & 0xff;
         }
         if (byteRead >= 0) {
@@ -391,6 +400,7 @@ public int read(byte[] b, int off, int len) throws IOException {
 
             int bytes = 0;
             byte[] buffer = currentReadBuffer.getBuffer();
+            Objects.requireNonNull(buffer);
             for (int i = buffer.length - (int) partRemaining;
                  i < buffer.length; i++) {
                 b[off + bytesRead] = buffer[i];
diff --git a/src/main/java/org/apache/hadoop/fs/CosNFileReadTask.java b/src/main/java/org/apache/hadoop/fs/CosNFileReadTask.java
index 0d4462d..4d528e0 100644
--- a/src/main/java/org/apache/hadoop/fs/CosNFileReadTask.java
+++ b/src/main/java/org/apache/hadoop/fs/CosNFileReadTask.java
@@ -8,10 +8,13 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.SocketException;
+import java.util.Objects;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import static org.apache.hadoop.fs.CosNConfigKeys.DEFAULT_READ_BUFFER_ALLOCATE_TIMEOUT_SECONDS;
+
 public class CosNFileReadTask implements Runnable {
     static final Logger LOG = LoggerFactory.getLogger(CosNFileReadTask.class);
 
@@ -59,14 +62,11 @@ public void run() {
         currentThread.setContextClassLoader(this.getClass().getClassLoader());
         try {
             this.readBuffer.lock();
-            if (closed.get()) {
-                this.setFailResult("the input stream has been canceled.", new IOException("the input stream has been canceled."));
-                return;
-            }
+            checkStreamClosed();
             try {
                 this.readBuffer.allocate(
-                    conf.getInt(CosNConfigKeys.COSN_READ_BUFFER_ALLOCATE_TIMEOUT_SECONDS, 5),
-                    TimeUnit.SECONDS);
+                    conf.getLong(CosNConfigKeys.COSN_READ_BUFFER_ALLOCATE_TIMEOUT_SECONDS,
+                        DEFAULT_READ_BUFFER_ALLOCATE_TIMEOUT_SECONDS), TimeUnit.SECONDS);
             } catch (Exception e) {
                 this.setFailResult("allocate read buffer failed.", new IOException(e));
                 return;
@@ -107,15 +107,17 @@ public void run() {
                             this.readBuffer.getStart(), this.readBuffer.getEnd(), ioException);
                     this.setFailResult(errMsg, ioException);
                     break;
-                } catch (Throwable throwable) {
-                    this.setFailResult("retrieve block failed", new IOException(throwable));
-                    break;
                 }
 
                 if (!needRetry) {
                     break;
                 }
             } // end of retry
+        } catch (Throwable throwable) {
+            this.setFailResult(
+                String.format("retrieve block failed, key: %s, range: [%d , %d], exception: %s",
+                    this.key, this.readBuffer.getStart(), this.readBuffer.getEnd(), throwable),
+                new IOException(throwable));
         } finally {
             this.readBuffer.signalAll();
             this.readBuffer.unLock();
@@ -125,17 +127,25 @@ public void run() {
     public void setFailResult(String msg, IOException e) {
         this.readBuffer.setStatus(CosNFSInputStream.ReadBuffer.ERROR);
         this.readBuffer.setException(e);
-        LOG.error(msg);
+        if (e.getCause() != null && e.getCause() instanceof CancelledException) {
+            // 预期操作，以warn级别导出
+            LOG.warn(msg);
+        } else {
+            LOG.error(msg);
+        }
     }
 
     // not thread safe
-    public void retrieveBlock() throws IOException {
+    private void retrieveBlock() throws IOException, CancelledException {
+        byte[] dataBuf = readBuffer.getBuffer();
+        checkStreamClosed();
+        Objects.requireNonNull(dataBuf);
         InputStream inputStream = this.store.retrieveBlock(
                 this.key, this.readBuffer.getStart(),
                 this.readBuffer.getEnd());
         IOUtils.readFully(
-                inputStream, this.readBuffer.getBuffer(), 0,
-                readBuffer.getBuffer().length);
+            inputStream, dataBuf, 0,
+            dataBuf.length);
         int readEof = inputStream.read();
         if (readEof != -1) {
             LOG.error("Expect to read the eof, but the return is not -1. key: {}.", this.key);
@@ -143,4 +153,18 @@ public void retrieveBlock() throws IOException {
         inputStream.close();
         this.readBuffer.setStatus(CosNFSInputStream.ReadBuffer.SUCCESS);
     }
+
+    private void checkStreamClosed() throws CancelledException {
+        if (closed.get()) {
+            throw new CancelledException("the input stream has been canceled.");
+        }
+    }
+
+
+    private static class CancelledException extends Exception {
+        public CancelledException(String message) {
+            super(message);
+        }
+    }
 }
+