linux-kernel - Re: [RFC v9 PATCH 2/4] mm: mmap: zap pages with read mmap

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Message-ID: <26cf9c0e-51dd-5fcf-e2c9-0b12df1e2061@linux.alibaba.com>
Date:   Wed, 12 Sep 2018 10:15:20 -0700
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     Michal Hocko <mhocko@...nel.org>,
        Matthew Wilcox <willy@...radead.org>
Cc:     ldufour@...ux.vnet.ibm.com, vbabka@...e.cz,
        akpm@...ux-foundation.org, dave.hansen@...el.com, oleg@...hat.com,
        srikar@...ux.vnet.ibm.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v9 PATCH 2/4] mm: mmap: zap pages with read mmap_sem in
 munmap



On 9/12/18 2:11 AM, Michal Hocko wrote:
> On Tue 11-09-18 19:29:21, Matthew Wilcox wrote:
>> On Tue, Sep 11, 2018 at 04:35:03PM -0700, Yang Shi wrote:
> [...]
>
> I didn't get to read the patch yet.

If you guys think this is the better way I could convert my patches to 
go this way. It is simple to do the conversion.

Thanks,
Yang

>
>>> And, Michal prefers have VM_HUGETLB and VM_PFNMAP handled separately for
>>> safe and bisectable sake, which needs call the regular do_munmap().
>> That can be introduced and then taken out ... indeed, you can split this into
>> many patches, starting with this:
>>
>> +		if (tmp->vm_file)
>> +			downgrade = false;
>>
>> to only allow this optimisation for anonymous mappings at first.
> or add a helper function to check for special cases and make the
> downgrade behavior conditional on it.