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Date: Mon, 21 Sep 2015 14:31:01 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Andrzej Hajda <a.hajda@samsung.com>
Cc: linux-kernel@vger.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Alexander Kuleshov <kuleshovmail@gmail.com>,
        Tony Luck <tony.luck@intel.com>, Wei Yang <weiyang@linux.vnet.ibm.com>,
        linux-mm@kvack.org
Subject: Re: [PATCH 33/38] mm/memblock.c: remove invalid check
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On Mon, 21 Sep 2015 15:34:05 +0200 Andrzej Hajda <a.hajda@samsung.com> wrote:

> Unsigned value cannot be lesser than zero.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> ...
>
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -837,7 +837,7 @@ void __init_memblock __next_reserved_mem_region(u64 *idx,
>  {
>  	struct memblock_type *type = &memblock.reserved;
>  
> -	if (*idx >= 0 && *idx < type->cnt) {
> +	if (*idx < type->cnt) {

Linus has in the past expressed a preference for retaining checks such
as this.  iirc he finds it clearer.  And perhaps safer if the type
should change in the future.