linux-kernel - Re: Why is CONFIG

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Date:	Sat, 11 Jun 2011 02:10:46 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Jesper Juhl <jj@...osbits.net>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jonas Gorski <jonas.gorski@...il.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: Why is CONFIG_FHANDLE an option??

On Fri, Jun 10, 2011 at 11:39:55PM +0100, Al Viro wrote:
> On Sat, Jun 11, 2011 at 12:14:02AM +0200, Jesper Juhl wrote:
> > I just configured a new kernel based on a recent git checkout and when I 
> > had copied in my old configuration and did a "make oldconfig"I was greeted 
> > with
> > 
> >     open by fhandle syscalls (FHANDLE) [N/y/?] (NEW)
> > 
> > Ok, so I read the help text description and learn that it's about two new 
> > syscalls - open_by_handle_at(2) and name_to_handle_at(2).
> > 
> > My first thought at this point was "why are new syscalls even an option"?
> > 
> > Syscalls are in my oppinion ABI - having optional syscalls is just about 
> > as bad as removing a syscall. It basically means that users cannot know if 
> > the syscall is there and will need to test (it's bad enough having to 
> > check the kernel version, having to check for specific syscalls as well 
> > is just, well, annoying at best). 
> > 
> > Why are we making these optional?
> 
> Why not?

To avoid situations like "I need to use a program but suddenly
it requires system call which I compiled out a month before and now
I need to reboot like an idiot".

splice(2) wasn't given config option despite several times bigger .o
file compared to fshandle+exportfs.

So let's say it was always somewhat arbitrary decision.
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