linux-kernel - Re: [PATCH] userns: simplify map_id_range

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Message-ID: <878ua26x5v.fsf@x220.int.ebiederm.org>
Date:	Sun, 26 Jul 2015 23:29:16 -0500
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Nicolas Iooss <nicolas.iooss_linux@....org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] userns: simplify map_id_range_* functions

Nicolas Iooss <nicolas.iooss_linux@....org> writes:

> Functions map_id_range_down, map_id_down and map_id_up all used the
> construction:
>
>     if (...)
>         id = ...
>     else
>         id = ...
>     return id;
>
> which can be simplified by directly returning the result of the
> computations in each branch.
>
> Moreover as the condition tested whether the "break;" in the previous
> for loop was hit, it is simpler to directly compute the result and
> return it.

It is not a simplification, it is just code motion.

Further at least to my eyes adding multiple exit points and setting the
same value in two different places actually obscures what the functions
are doing.

If we could talk about speeding up the performance of the stat system
call I think there would be a point in mucking with these functions.

As it is I think it is I think merging your patch will just make it more
difficult to understand what the code is doing in the future, with no 
benefit except a reduction in line count.

Eric
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