linux-kernel - Re: [PATCH v4 11/12] mm: drop page_index and convert folio

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Date: Thu, 2 May 2024 17:32:07 +0800
From: Kairui Song <ryncsn@...il.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, 
	"Huang, Ying" <ying.huang@...el.com>, Matthew Wilcox <willy@...radead.org>, Chris Li <chrisl@...nel.org>, 
	Barry Song <v-songbaohua@...o.com>, Ryan Roberts <ryan.roberts@....com>, Neil Brown <neilb@...e.de>, 
	Minchan Kim <minchan@...nel.org>, Hugh Dickins <hughd@...gle.com>, 
	Yosry Ahmed <yosryahmed@...gle.com>, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 11/12] mm: drop page_index and convert folio_index to
 use folio

On Thu, May 2, 2024 at 5:12 PM David Hildenbrand <david@...hat.com> wrote:
>
> On 02.05.24 10:49, Kairui Song wrote:
> > From: Kairui Song <kasong@...cent.com>
> >
> > There are two helpers for retrieving the index within address space
> > for mixed usage of swap cache and page cache:
> >
> > - page_index
> > - folio_index (wrapper of page_index)
> >
> > This commit drops page_index, as we have eliminated all users, and
> > converts folio_index to use folio internally.
>
> The latter does not make sense. folio_index() already is using a folio
> internally. Maybe a leftover from reshuffling/reworking patches?

Hi, David,

folio_index calls swapcache_index, and swapcache_index is defined as:

#define swapcache_index(folio) __page_file_index(&(folio)->page)

Where it casts the folio to page first, then call __page_file_index,
__page_file_index is a function and works on pages.

After this commit __page_file_index is converted to
__folio_swap_cache_index. This change is a bit of trivial but we get
rid of the internal page conversion.

I can simplify the commit message, just say drop page_index to make
the code cleaner, if this is confusing.