linux-kernel - Re: [PATCH] scatterlist: don't BUG when we can trivially return a proper error.

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Message-ID: <20121114221544.GA3083@elliptictech.com>
Date:	Wed, 14 Nov 2012 17:15:44 -0500
From:	Nick Bowler <nbowler@...iptictech.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scatterlist: don't BUG when we can trivially return a
 proper error.

On 2012-11-14 13:05 -0800, Andrew Morton wrote:
> On Thu,  1 Nov 2012 15:03:00 -0400
> Nick Bowler <nbowler@...iptictech.com> wrote:
> 
> > There is absolutely no reason to crash the kernel when we have a
> > perfectly good return value already available to use for conveying
> > failure status.
> 
> Yes, I suppose that's true.  I don't see a case for BUGging the kernel
> here.
[...]
> > -	BUG_ON(nents > max_ents);
> > +	if (WARN_ON_ONCE(nents > max_ents))
> > +		return -E2BIG;
> >  #endif
> 
> OK, pet peeve: if this E2BIG gets returned to userspace, our poor user
> will look it up and see "Argument list too long; used when the
> arguments passed to a new program being executed with one of the exec
> functions occupy too much memory space".  He then gets to spend half a
> day reviewing his code's exec() callsites!
> 
> See?  Although the error's name sounds like a nice match to the
> internal state, it isn't really a match at all and our use of it is
> misleading.
> 
> Unfortunately there is no EKERNELSCREWEDUP,

Well, maybe we should add it! :P

> so we usually use EINVAL.

Fair enough.  I will prepare v2.  But perhaps EOPNOTSUPP would be a
better fit?

Thanks,
-- 
Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/)
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