Re: File copy system call proposal

[Quinn Harris]

On Sat, 2001-12-08 at 17:19, H. Peter Anvin wrote:
> 
> One thing that one could do for an in-kernel copy is to extend
> sendfile() to support any kind of file descriptor.  That'd be a very
> clean way to do it.
> 

I think the best thing would be to extend generic_file_write
(mm/filemap.c) to recognize if its writing a complete page to disk in
which case it will not duplicate that page.  (Issues with getting the
buffer cache to support this remain.)  This should make either the
mmap/write or sendfile aproach be zero-copy.  I am given the impression
that this is just what the TCP/IP version of write does to make it
zero-copy.