RFR: 8310902: (fc) FileChannel.transferXXX async close and interrupt issues [v3]

[Brian Burkhalter]

On Wed, 28 Jun 2023 06:18:35 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> This change fixes a number of bugs with FileChannel.transferTo/transerFrom that arise when the source or target channel is closed, or the thread is interrupted, during the transfer. More specifically:
>> 
>> - The direct implementations operate on the raw file descriptor and don't prevent the target/source channel from being closed during the transfer. For this PR, the direct transferTo is limited to cases where the target is a FileChannel or SocketChannel. It could be extended to other SelChImpl implementations (SinkChannel, DatagramChannel) if needed, but they are less interesting at this time.
>> 
>> - The transferTo/transferFrom methods are specified to throw ClosedByInterruptException after closing both channels. This is implemented inconsistently, and leaves one channel open in several cases.
>
> Alan Bateman has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:
> 
>  - Merge
>  - Make transferFromDirect more consistent
>  - Merge
>  - More robustness
>  - Update
>  - Update
>  - Initial commit

src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java line 657:

> 655:                     long n = transferToFileDescriptor(position, count, target.fd);
> 656:                     if (n == IOStatus.UNSUPPORTED_CASE) {
> 657:                         transferToFileDirectNotSupported = true;

On Linux, `transferToFileDescriptor` will fail with `UNSUPPORTED_CASE` if the target is open for appending. I don't think that this should mean that all future fast transfers to a file should be suppressed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14656#discussion_r1245585805