linux-kernel - Re: [PATCH] mm/mlock: remove unneeded start >= vma->vm

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Message-ID: <c0ff39e2-27fc-170f-00f5-d5e9ab5a22cd@huawei.com>
Date:   Tue, 15 Mar 2022 20:30:49 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     <akpm@...ux-foundation.org>, <hughd@...gle.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/mlock: remove unneeded start >= vma->vm_end check

On 2022/3/15 0:17, Matthew Wilcox wrote:
> On Mon, Mar 14, 2022 at 11:32:23PM +0800, Miaohe Lin wrote:
>> If find_vma returns a vma, it must satisfies that start < vma->vm_end.
>> Since vma list is sorted in the ascending order, so we will never see
>> start >= vma->vm_end here. Remove this unneeded check.
> 
> faulty logic; vm_start + len might wrap.

Many thanks for comment. I agree with you about "vm_start + len" might wrap.
But what I mean here is that we will never see "start" >= vma->vm_end here
as find_vma guarantees this. And I leave the "start + len <=  vma->vm_start"
check untouched. So my cleanup should be right. Or am I miss something?

Thanks.

> 
> .
>