[GitHub] [ozone] ChenSammi commented on a change in pull request #2538: HDDS-5619. Ozone data corruption issue on follower node.

[GitBox <gi...@apache.org>]

ChenSammi commented on a change in pull request #2538:
URL: https://github.com/apache/ozone/pull/2538#discussion_r692827259



##########
File path: hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/keyvalue/helpers/ChunkUtils.java
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@@ -183,17 +180,39 @@ private static long writeDataToChannel(FileChannel channel, ChunkBuffer data,
   public static void readData(File file, ByteBuffer[] buffers,
       long offset, long len, HddsVolume volume)
       throws StorageContainerException {
+    readData(file, null, buffers, offset, len, volume);
+  }
+
+  public static void readData(File file, FileChannel channel,
+      ByteBuffer[] buffers, long offset, long len, HddsVolume volume)
+      throws StorageContainerException {
 
     final Path path = file.toPath();
     final long startTime = Time.monotonicNow();
     final long bytesRead;
+    final long endOffsetToRead = offset + len;
 
     try {
+      if (file.length() > 0) {
+        Preconditions.checkArgument(file.length() >= endOffsetToRead,
+            "file length should atleast match the last offset to read");
+      }
       bytesRead = processFileExclusively(path, () -> {
-        try (FileChannel channel = open(path, READ_OPTIONS, NO_ATTRIBUTES);
-             FileLock ignored = channel.lock(offset, len, true)) {
+        // if the file handle is already cached, just use that for reads.
+        if (channel != null) {
+          try (FileLock lock = channel.lock(offset, len, true)) {
+            channel.position(offset);
+            return channel.position(offset).read(buffers);

Review comment:
       channel.position is called twice. 




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