[$] Toward a reverse splice()

The splice()
system call is, at its core, a write operation; it attempts to implement
zero-copy I/O by moving pages from a pipe to a file. At the 2019 Linux
Storage, Filesystem, and Memory-Management Summit, Miklos Szeredi described
a nascent idea for rsplice() — a 'reverse splice' system call.
There were not a lot of definitive outcomes from this discussion, but one
thing was clear: rsplice() needs a much better description (and
some code posted) before the development community can begin to form an
opinion on it.