do_splice_direct — splices data directly between two files
long do_splice_direct
(struct file * in, loff_t * ppos, struct file * out, size_t len, unsigned int flags);
file to splice from
input file offset
file to splice to
number of bytes to splice
splice modifier flags
For use by do_sendfile. splice can easily emulate sendfile, but doing it in the application would incur an extra system call (splice in + splice out, as compared to just sendfile). So this helper can splice directly through a process-private pipe.