linux-kernel - Re: [PATCH v14 011/138] mm/lru: Add folio LRU functions

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Message-ID: <YPgw2AVMuK2YkCIT@kernel.org>
Date:   Wed, 21 Jul 2021 17:36:08 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v14 011/138] mm/lru: Add folio LRU functions

On Wed, Jul 21, 2021 at 12:23:09PM +0100, Matthew Wilcox wrote:
> On Wed, Jul 21, 2021 at 11:39:15AM +0300, Mike Rapoport wrote:
> > On Wed, Jul 21, 2021 at 05:08:44AM +0100, Matthew Wilcox wrote:
> > > I wanted to turn those last two sentences into a list, but my
> > > kernel-doc-fu abandoned me.  Feel free to submit a follow-on patch to
> > > fix that ;-)
> > 
> > Here it is ;-)
> 
> Did you try it?  Here's what that turns into with htmldoc:

Yes, but I was so happy to see bullets that I missed the fact they are in
the wrong section :(
 
> Description
> 
> We would like to get this info without a page flag, but the state needs
> to survive until the folio is last deleted from the LRU, which could be
> as far down as __page_cache_release.
> 
>  * 1 if folio is a regular filesystem backed page cache folio or a
>    lazily freed anonymous folio (e.g. via MADV_FREE).
>  * 0 if folio is a normal anonymous folio, a tmpfs folio or otherwise
>    ram or swap backed folio.
> 
> Return
> 
> An integer (not a boolean!) used to sort a folio onto the right LRU list
> and to account folios correctly.
> 
> Yes, we get a bulleted list, but it's placed in the wrong section!
> 
> Adding linux-doc for additional insight into this problem.
> For their reference, here's the input:
>
> /**
>  * folio_is_file_lru - Should the folio be on a file LRU or anon LRU?
>  * @folio: The folio to test.
>  *
>  * We would like to get this info without a page flag, but the state
>  * needs to survive until the folio is last deleted from the LRU, which
>  * could be as far down as __page_cache_release.
>  *
>  * Return: An integer (not a boolean!) used to sort a folio onto the
>  * right LRU list and to account folios correctly.
>  *
>  * - 1 if @folio is a regular filesystem backed page cache folio
>  *   or a lazily freed anonymous folio (e.g. via MADV_FREE).
>  * - 0 if @folio is a normal anonymous folio, a tmpfs folio or otherwise
>  *   ram or swap backed folio.
>  */
> static inline int folio_is_file_lru(struct folio *folio)

Hmm, there is some contradiction between kernel-doc assumption that
anything after a blank line is the default (i.e. Description) section and
the sphynx ideas where empty blank lines should be:


	if ($state == STATE_BODY_WITH_BLANK_LINE && /^\s*\*\s?\S/) {
		dump_section($file, $section, $contents);
		$section = $section_default;
		$new_start_line = $.;
		$contents = "";
	}

(from scripts/kernel-doc::process_body())

-- 
Sincerely yours,
Mike.