Sendfile() works fine and is pretty fast and avoids this whole problem so you’re not going to convince me it’s impossible or that having the kernel read a file

Sendfile() works fine and is pretty fast and avoids this whole problem so you’re not going to convince me it’s impossible or that having the kernel read a file into a buffer and then send it somewhere is fast while taking a copy-on-write on the pages when it is already in memory is slow. It’s just that Linus doesn’t want to change splice() to do what the Samba people want, which is fine but doesn’t mean it’d be impossible.