[GitHub] [spark] HeartSaVioR commented on a change in pull request #25552: [SPARK-28849][CORE] Add a number to control transferTo calls to avoid infinite loop in some occasional cases

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

HeartSaVioR commented on a change in pull request #25552: [SPARK-28849][CORE] Add a number to control transferTo calls to avoid infinite loop in some occasional cases
URL: https://github.com/apache/spark/pull/25552#discussion_r316948762
 
 

 ##########
 File path: core/src/main/scala/org/apache/spark/util/Utils.scala
 ##########
 @@ -417,16 +418,19 @@ private[spark] object Utils extends Logging {
       input: FileChannel,
       output: WritableByteChannel,
       startPosition: Long,
-      bytesToCopy: Long): Unit = {
+      bytesToCopy: Long,
+      numTransferToCalls: Int): Unit = {
     val outputInitialState = output match {
       case outputFileChannel: FileChannel =>
         Some((outputFileChannel.position(), outputFileChannel))
       case _ => None
     }
     var count = 0L
+    var num = 0
     // In case transferTo method transferred less data than we have required.
-    while (count < bytesToCopy) {
+    while (count < bytesToCopy && num < numTransferToCalls) {
       count += input.transferTo(count + startPosition, bytesToCopy - count, output)
 
 Review comment:
   I'd rather check if the return value of `input.transferTo` goes `< 0` (javadoc doesn't mention possibility of negative, but no harm to check), not temporally but consistently.

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