linux-kernel - Re: [RFC PATCH resend 3/6] mm: Add refcount for preserving mm

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Message-ID: <4f428d8e-b660-9e31-6968-b28f6d7088f5@nvidia.com>
Date:   Tue, 3 Nov 2020 11:18:49 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Jason Gunthorpe <jgg@...pe.ca>, Jann Horn <jannh@...gle.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Oleg Nesterov <oleg@...hat.com>,
        kernel list <linux-kernel@...r.kernel.org>,
        Will Deacon <will@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [RFC PATCH resend 3/6] mm: Add refcount for preserving mm_struct
 without pgd

On 11/3/20 5:21 AM, Jason Gunthorpe wrote:
> On Tue, Nov 03, 2020 at 04:19:11AM +0100, Jann Horn wrote:
>> On Tue, Nov 3, 2020 at 3:11 AM Jann Horn <jannh@...gle.com> wrote:
>>> On Sat, Oct 17, 2020 at 2:30 AM Jann Horn <jannh@...gle.com> wrote:
>>>> On Sat, Oct 17, 2020 at 1:21 AM Jason Gunthorpe <jgg@...pe.ca> wrote:
>>>>> On Sat, Oct 17, 2020 at 01:09:12AM +0200, Jann Horn wrote:
>>>>>> Currently, mm_struct has two refcounts:
...
> Either way can work, I liked the suggestion because it suggests an
> good name for the ref: 'mmget_pgd' or somesuch
> 
> What I don't like is how nonsensical the names here are becoming:
> mmget/mmgrab/mm_ref
> 
> Gives no impression at the callsite what is right/wrong
> 
> Names like this:
>   mmget_struct
>   mmget_pgd
>   mmget_tables
> 

What?! I had just resigned myself to a bimonthly exercise, re-memorizing
the mm_struct naming correlation between grab, drop, get, put, count,
and users. And now you want to make it directly understandable? :)

> Make alot more sense to me..
> 
> I think this patch needs to do something about the naming..
> 

A third counter also seems like the tipping point, to me.

thanks,
-- 
John Hubbard
NVIDIA