linux-kernel - Re: [PATCH v2 1/2] mm/rmap: fix and simplify reusing mergeable anon

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Message-ID: <20200115012055.GC4916@richard>
Date:   Wed, 15 Jan 2020 09:20:55 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     Li Xinhai <lixinhai.lxh@...il.com>
Cc:     khlebnikov <khlebnikov@...dex-team.ru>,
        "richardw.yang" <richardw.yang@...ux.intel.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        akpm <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rik van Riel <riel@...hat.com>,
        "kirill.shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v2 1/2] mm/rmap: fix and simplify reusing mergeable
 anon_vma as parent when fork

On Tue, Jan 14, 2020 at 10:42:52PM +0800, Li Xinhai wrote:
>On 2020-01-13 at 19:07 Konstantin Khlebnikov wrote:
>
>>
>>Because I want to keep both heuristics.
>>This seems most sane way of interaction between them.
>>
>>Unfortunately even this patch is slightly broken.
>>Condition prev->anon_vma->parent == pvma->anon_vma doesn't guarantee that
>>prev vma has the same set of anon-vmas like current vma.
>>I.e. anon_vma_clone(vma, prev) might be not enough for keeping connectivity. 
>
>New patch is required?

My suggestion is separate the fix and new approach instead of mess them into
one patch.

>It is necessary to call anon_vma_clone(vma, pvma) to link all anon_vma which
>currently linked by pvma, then link the prev->anon_vma to vma. By this way,
>connectivity of vma should be maintained, right?
>
>>Building such case isn't trivial job but I see nothing that could prevent it.
>>
>

-- 
Wei Yang
Help you, Help me