* The allocated buffer is only used in the fallback case, so move it
there. The argument for passing it in from the caller was that if
malloc(3) were to fail, we'd want it to fail before we started
copying anything, but firstly, it was already not in the right place
to ensure that, and secondly, malloc(3) never fails (except in very
contrived circumstances, such as an unreasonable RLIMIT_AS or
RLIMIT_DATA).
* Remove the mmap(2) option. It is almost never beneficial,
especially when the alternative is copy_file_range(2), and it adds
needless complexity and indentation.
MFC after: 1 week
Sponsored by: Klara, Inc.
Reviewed by: rmacklem, mav
Differential Revision: https://reviews.freebsd.org/D38291
6c85042afc