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Date: Tue, 10 Dec 2013 13:52:16 -0800
Message-ID: <CAE9FiQU8Y_thGxZamz0Uwt4FGXh7KJu7jGP8ED3dbjQuyq7vcQ@mail.gmail.com>
Subject: Re: [PATCH] mm,x86: fix span coverage in e820_all_mapped()
From: Yinghai Lu <yinghai@kernel.org>
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To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, the arch/x86 maintainers <x86@kernel.org>, Linn Crosetto <linn@hp.com>, Pekka Enberg <penberg@kernel.org>, LKML <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Linux MM <linux-mm@kvack.org>

On Tue, Dec 10, 2013 at 1:29 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 12/10/2013 01:06 PM, Yinghai Lu wrote:
>> On Tue, Dec 10, 2013 at 1:06 AM, Xishi Qiu <qiuxishi@huawei.com> wrote:
>>> In the following case, e820_all_mapped() will return 1.
>>> A < start < B-1 and B < end < C, it means <start, end> spans two regions.
>>> <start, end>:           [start - end]
>>> e820 addr:          ...[A - B-1][B - C]...
>>
>> should be [start, end) right?
>> and
>> [A, B),[B, C)
>>
>
> What happens if it spans more than two regions?

[A, B), [B+1, C), [C+1, D) ?
start in [A, B), and end in [C+1, D).

old code:
first with [A, B), start set to B.
then with [B+1, C), start still keep as B.
then with [C+1, D), start still keep as B.
at last still return 0...aka not_all_mapped.

old code is still right.

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