add closefrom() call

[Julian Elischer]

Ed Schouten wrote:
> * Julian Elischer <julian at elischer.org> wrote:
>> Ed Schouten wrote:
>>> Wouldn't it be better to just implement it through fcntl() and implement
>>> closefrom() in libc?
>> that's a possibility but I personally thing the huge difference in 
>> efficiency
>> makes it worth putting it in the kernel.
>> Quite a few programs I know of could really help their startup time with 
>> this as the first thing they do is "close the first 2000 file descriptors.
> 
> Woops! Sorry for responding this late, but it looks like I didn't
> explain myself good enough. Sorry. :) To rephrase myself:
> 
> Wouldn't it be better to just implement fcntl(..., F_CLOSEM, ...) in the
> kernel and make closefrom() a simple libc routine:
> 
> void
> closefrom(int lowfd)
> {
> 	fcntl(lowfd, F_CLOSEM, NULL);
> }
> 

what on earth would that achieve?
(as opposed to just a simple syscall)

> Similar to creat(2).
>