copy on write for splice() from file to pipe?

[Linus Torvalds]

On Fri, Feb 10, 2023 at 11:56 AM Andy Lutomirski <luto at kernel.org> wrote:
>
> i think this is almost exactly what Jeremy and Stefan are asking for
> re: notification when the system is done with a zero-copy send:

Yeah, right now it's all just "incremented page counts", I think.

Even the pipe code itself doesn't know about writes that have already
been done, but that are pending elsewhere.

You'd have to ask the target file descriptor itself about "how much do
you have pending" or something.

           Linus