add closefrom() call

[Joerg Sonnenberger]

On Tue, Jul 10, 2007 at 10:53:02AM -0700, Julian Elischer wrote:
> Joerg Sonnenberger wrote:
> >On Mon, Jul 09, 2007 at 11:46:14PM -0400, Ighighi wrote:
> >>Calling F_MAXFD everytime we close a file descriptor would be heavy 
> >>having too much fd's.
> >>On the other hand, it wouldn't make much a difference to just start from 
> >>getdtablesize() - 1.
> >
> >I fully agree. That is the second version of closefrom in DragonFly --
> >for the purpose of libc_r BTW.
> 
> This is silly..
> All the code needed to do this is already in the kernel.
> It's needed at exit time.
> Make a syscall as a front end to it and be done with it.

As I said -- this was done only in libc_r because of the additional
constraints of not closing the internal pipe. For any other use case, I
full heartedly agree.

Joerg