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

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Message-ID: <YPgDne2ORs+tJsk2@casper.infradead.org>
Date:   Wed, 21 Jul 2021 12:23:09 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Mike Rapoport <rppt@...nel.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 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:

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)