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https://issues.apache.org/jira/browse/HADOOP-18521?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17632535#comment-17632535
 ] 

ASF GitHub Bot commented on HADOOP-18521:
-----------------------------------------

steveloughran commented on code in PR #5117:
URL: https://github.com/apache/hadoop/pull/5117#discussion_r1020503409


##########
hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/services/ReadBufferManager.java:
##########
@@ -454,31 +588,65 @@ ReadBuffer getNextBlockToRead() throws 
InterruptedException {
    */
   void doneReading(final ReadBuffer buffer, final ReadBufferStatus result, 
final int bytesActuallyRead) {
     if (LOGGER.isTraceEnabled()) {
-      LOGGER.trace("ReadBufferWorker completed read file {} for offset {} 
outcome {} bytes {}",
-          buffer.getStream().getPath(),  buffer.getOffset(), result, 
bytesActuallyRead);
-    }
-    synchronized (this) {
-      // If this buffer has already been purged during
-      // close of InputStream then we don't update the lists.
-      if (inProgressList.contains(buffer)) {
-        inProgressList.remove(buffer);
+      LOGGER.trace("ReadBufferWorker completed file {} for offset {} bytes {}; 
{}",
+          buffer.getStream().getPath(),  buffer.getOffset(), 
bytesActuallyRead, buffer);
+    }
+    // decrement counter.
+    buffer.prefetchFinished();
+
+    try {
+      synchronized (this) {
+        // remove from the list
+        if (!inProgressList.remove(buffer)) {
+          // this is a sign of inconsistent state, so a major problem
+          String message =
+              String.format("Read completed from an operation not declared as 
in progress %s",
+                  buffer);
+          LOGGER.warn(message);
+          // release the buffer (which may raise an exception)
+          placeBufferOnFreeList("read not in progress", buffer);
+          // report the failure
+          throw new IllegalStateException(message);
+        }
+
+        boolean shouldFreeBuffer = false;
+        String freeBufferReason = "";
         if (result == ReadBufferStatus.AVAILABLE && bytesActuallyRead > 0) {
           buffer.setStatus(ReadBufferStatus.AVAILABLE);
           buffer.setLength(bytesActuallyRead);
         } else {
-          freeList.push(buffer.getBufferindex());
-          // buffer will be deleted as per the eviction policy.
+          // read failed or there was no data, -the buffer can be returned to 
the free list.
+          shouldFreeBuffer = true;
+          freeBufferReason = "failed read";
         }
         // completed list also contains FAILED read buffers
         // for sending exception message to clients.
         buffer.setStatus(result);
         buffer.setTimeStamp(currentTimeMillis());
-        completedReadList.add(buffer);
+        if (!buffer.isStreamClosed()) {
+          // completed reads are added to the list.
+          LOGGER.trace("Adding buffer to completed list {}", buffer);
+          completedReadList.add(buffer);

Review Comment:
   making some changes. this is a complex bit of code and why I plan to write 
some unit tests to explore the results; i will take what you've done too 
@pranavsaxena-microsoft 





> ABFS ReadBufferManager buffer sharing across concurrent HTTP requests
> ---------------------------------------------------------------------
>
>                 Key: HADOOP-18521
>                 URL: https://issues.apache.org/jira/browse/HADOOP-18521
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs/azure
>    Affects Versions: 3.3.2, 3.3.3, 3.3.4
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>            Priority: Critical
>              Labels: pull-request-available
>
> AbfsInputStream.close() can trigger the return of buffers used for active 
> prefetch GET requests into the ReadBufferManager free buffer pool.
> A subsequent prefetch by a different stream in the same process may acquire 
> this same buffer. This can lead to risk of corruption of its own prefetched 
> data, data which may then be returned to that other thread.
> On releases without the fix for this (3.3.2 to 3.3.4), the bug can be avoided 
> by disabling all prefetching 
> {code}
> fs.azure.readaheadqueue.depth
> {code}



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