RFR: 8269074: (fs) Files.copy fails to copy from /proc on some linux kernel versions [v2]

[Alan Bateman]

On Tue, 22 Jun 2021 17:17:59 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> On Linux, if while executing `java.nio.file.Files.copy(Path,Path,CopyOption...)` the native function `sendfile(2)` fails with `EINVAL`, fall back to transferring via user-space buffers.
>
> Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8269074: Move user-space copy to separate function

src/java.base/unix/native/libnio/fs/UnixCopyFile.c line 40:

> 38: #include "sun_nio_fs_UnixCopyFile.h"
> 39: 
> 40: #if ! defined(_ALLBSD_SOURCE)

The "#if  ! defined(_ALLBSD_SOURCE)" looks odd here. Maybe we can get rid of it, it doesn't matter if this tiny function is compiled on macOS.

src/java.base/unix/native/libnio/fs/UnixCopyFile.c line 107:

> 105:     } while (bytes_sent > 0);
> 106: 
> 107:     transfer(env, dst, src, cancel);

An alternative might be to call the transfer method at L95 so that it's
if (errno == EINVAL) {
    transfer(env, dst, src, cancel);
} else {
    throwUnixExceptin(env, errno);
 }
return

I suspect it might be clearer.

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PR: https://git.openjdk.java.net/jdk/pull/4543