linux-kernel - Re: [PATCH v3 3/7] mm: Add write-protect and clean utilities for address space ranges

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Message-ID: <516814a5-a616-b15e-ac87-26ede681da85@shipmail.org>
Date:   Wed, 2 Oct 2019 21:09:40 +0200
From:   Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Will Deacon <will.deacon@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...riel.com>,
        Minchan Kim <minchan@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        Huang Ying <ying.huang@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>
Subject: Re: [PATCH v3 3/7] mm: Add write-protect and clean utilities for
 address space ranges

On 10/2/19 8:06 PM, Linus Torvalds wrote:
> On Wed, Oct 2, 2019 at 6:48 AM Thomas Hellström (VMware)
> <thomas_os@...pmail.org> wrote:
>> From: Thomas Hellstrom <thellstrom@...are.com>
>>
>> Add two utilities to a) write-protect and b) clean all ptes pointing into
>> a range of an address space.
> This one I still don't exactly love.
>
> I'm not entirely sure what rubs me the wrong way, but part of it is
> naming. We don't use the name "as", because it reads as (sic) an
> English word.
>
> The name we use for address_space pointers is "mapping", both for
> variables and for existing functions.
>
> See for example "pte_same_as_swp()" which uses "as" as the _word_ 'as'.
>
> Contrast that with "unmap_mapping_range()" or
> "mapping_set_unevictable()" or "read_mapping_page()" or
> "invalidate_mapping_pages()", that all work on address spaces.
>
> So please don't use 'as' as shorthand for that - eithe rin the
> function names or the filename.
>
> I'm not sure if that's the _only_ thing that raises my heckles when I
> read this patch, but I think it might be. So I'm not saying "ack with
> naming change", but I suspect that if the naming was changed, it would
> look much better to me.
>
> Yes, it's a bit more typing. But I really think
> "clean_mapping_dirty_pages()" is just not only more in line with the
> mm naming, I think it's a lot more legible and understandable than
> "as_dirty_clean()", which just makes me go "what the heck does that
> function do?"
>
> And I really think it needs more than just "as" -> "mapping".
> "mapping_dirty_clean()" still makes me go "what?" in a way that
> "clean_mapping_dirty_pages()" does not. One name reads as a series or
> random words, the other reads as a "this is what the function does".
>
> I know I sometimes get hung up about naming, but I do think naming
> matters.  A descriptive name that just reads as what the function does
> makes it much easier to read the logic of code, imnsho.
>
>                Linus

Yes I typically tend towards using a "namespace_object_operation" naming 
scheme, with "as_dirty" being the namespace here,

But I'll give it a shot to see if I can rename it more in line with the 
above.

Looking at Matthew's suggestion but lining up with 
"unmap_mapping_range()", perhaps we could use "clean_mapping_range" and 
"wp_mapping_range"?

Thanks,

Thomas