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

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Message-ID: <CAFLxGvyXwbwWYnrRA1qza2+CEO_pL=rC82=CkfGOSHNVyA5x+g@mail.gmail.com>
Date:	Wed, 14 Nov 2012 23:27:29 +0100
From:	richard -rw- weinberger <richard.weinberger@...il.com>
To:	Nick Bowler <nbowler@...iptictech.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scatterlist: don't BUG when we can trivially return a
 proper error.

On Wed, Nov 14, 2012 at 11:15 PM, Nick Bowler <nbowler@...iptictech.com> wrote:
> 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?

IMHO this would be even more confusing...

-- 
Thanks,
//richard
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