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Message-ID: <52A7C2F8.4090207@huawei.com>
Date: Wed, 11 Dec 2013 09:42:16 +0800
From: Xishi Qiu <qiuxishi@huawei.com>
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To: "H. Peter Anvin" <hpa@zytor.com>
CC: Yinghai Lu <yinghai@kernel.org>, 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>
Subject: Re: [PATCH] mm,x86: fix span coverage in e820_all_mapped()
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On 2013/12/11 9:06, H. Peter Anvin wrote:

> Ok, the issue I thought we were discussing was actually [A,B) [B,C) [C,D) ...
> 

Hi Peter,

Yes, in this case the function will return 1.

Thanks,
Xishi Qiu

> Yinghai Lu <yinghai@kernel.org> wrote:
>> On Tue, Dec 10, 2013 at 2:51 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>>> On 12/10/2013 01:52 PM, Yinghai Lu wrote:
>>>>>
>>>>> 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.
>>>>
>>>
>>> Why not_all_mapped?
>>
>> [B, B+1), and [C, C+1) are not there.
>