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Subject: Re: [PATCH 1/3] mm/gup: documentation corrections for gup/pup
To:     Matthew Wilcox <willy@infradead.org>
CC:     Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
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From:   John Hubbard <jhubbard@nvidia.com>
Message-ID: <33b4673a-0509-79fd-2572-5f88255bf585@nvidia.com>
Date:   Tue, 10 Aug 2021 14:19:37 -0700
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On 8/8/21 6:39 PM, Matthew Wilcox wrote:
...
>> + *    FOLL_PIN on compound pages that are > two pages long: page's refcount will
>> + *        be incremented by refs, and page[2].hpage_pinned_refcount will be
>> + *        incremented by refs * GUP_PIN_COUNTING_BIAS.
>> + *
>> + *    FOLL_PIN on normal pages, or compound pages that are two pages long:
>> + *        page's refcount will be incremented by refs * GUP_PIN_COUNTING_BIAS.
>>    *
>>    * Return: head page (with refcount appropriately incremented) for success, or
>>    * NULL upon failure. If neither FOLL_GET nor FOLL_PIN was set, that's
> 
> Did you run 'make htmldocs' and see how it renders?  I haven't looked,
> but this might work better as an rst list?
> 

OK, after a certain amount of sphinx and sphinx-extension-related
unhappiness, I can finally report, "nope, rst lists do not help here".
That's because the rendered kerneldoc HTML versions of non-numbered
lists look identical to paragraphs that are not lists. And the numbered
lists either look identical (if you used the "1." format), or different
in a way that hurts the source code (if you used the "#." format).

And the lists are also fussier to maintain, because if you do not
*exactly* line up the second and following lines in a paragraph, then
HTML version of the list breaks. Whereas, the HTML looks fine either way
if it is not a list.

I probably shouldn't mention that the only function in gup.c that is
listed as "make this show up in the docs" is get_user_pages_fast(),
because that might lead to people asking to add more items to the
:functions: list in mm-api.rst. And then I'd have to explain that the
kerneldoc rendered output for functions is still mostly useless: kernel
developers need to see the implementation as well; non-kernel developers
will find it incomplete and cryptic; and it's hard to read for anyone,
due to being spread over a country mile's worth of whitespace. So I
won't bring that up. :)


thanks,
-- 
John Hubbard
NVIDIA