netdev - Re: [PATCH net-next 1/2] packet: clean up error variable assignments

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Date:	Tue, 23 Oct 2012 19:25:19 +0200
From:	Daniel Borkmann <danborkmann@...earbox.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] packet: clean up error variable assignments

On Tue, Oct 23, 2012 at 7:05 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Tue, 2012-10-23 at 13:56 +0200, Daniel Borkmann wrote:
>> This patch performs clean-ups of packet's err variables where appropriate.
>> In particular, errnos are *only* assigned in error cases, which saves
>> useless instructions in non-error cases and makes the code more readable
>> in terms of which error type belongs to which evaluated error condition.
>> Also, in some cases an errno was set, but not used until the next assignment.
>
> I see no value in this patch.
>
> Setting err before a test is a common way to handle error cases and
> generates smaller code in linux kernel.
>
> Better live with it than trying to change it ?
>
> err = -ENOMEM;
> match = kzalloc(xxxx);
> if (!match)
>         goto error;
>
>
> is smaller (source code & generated code) than :
>
> match = kzalloc(xxxx);
> if (!match) {
>         err = -ENOMEM;
>         goto error;
> }
>
> An immediate load is basically free, but code size matters.

Good to know, thanks for the feedback Eric!
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