Re: [Differential] D20584: add a linux compatible copy_file_range(2) syscall

On Fri, Jul 5, 2019 at 9:28 AM Rick Macklem <rmacklem_at_uoguelph.ca> wrote:
>
> jilles wrote in copy_file_range.2:99
> > The Linux man page (from http://man7.org/linux/man->pages/man2/copy_file_range.2.html ) says that a non-zero flags argument will cause >the call to return an [EINVAL] error. I think that is better than ignoring the argument >completely since it allows adding flags more safely (since there will not be existing >applications that pass in, for example, uninitialized data as flags).
>
> The fun part is that the Linux folks are already discussing adding flags.
> I don't know if they are already in Linux-next (or whatever they call their next
> release), but it sounded like they were headed that way.
>
> As such, I thought ignoring "flags" would be easier than returning EINVAL for
> code that works on Linux.
>
> However, I can see the counter argument, which is "returning EINVAL will
> indicate that the Linux flag isn't used on FreeBSD", so that developers will
> become aware of that.
>
> What do others think w.r.t. which is the better approach? rick

Better to return EINVAL.  That way a program written for FreeBSD 14
which uses a FreeBSD 14-specific flag will fail when run on FreeBSD
13, which lacks that flag.
-Alan