linux-kernel - Re: [PATCH 1/6] mm/page_io: use a folio in __end_swap_bio

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Date:   Mon, 17 Jul 2023 14:34:26 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Peng Zhang <zhangpeng362@...wei.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        sidhartha.kumar@...cle.com, akpm@...ux-foundation.org,
        wangkefeng.wang@...wei.com, sunnanyong@...wei.com
Subject: Re: [PATCH 1/6] mm/page_io: use a folio in __end_swap_bio_read()

On Mon, Jul 17, 2023 at 09:25:57PM +0800, Peng Zhang wrote:
> +++ b/mm/page_io.c
> @@ -58,18 +58,18 @@ static void end_swap_bio_write(struct bio *bio)
>  
>  static void __end_swap_bio_read(struct bio *bio)
>  {
> -	struct page *page = bio_first_page_all(bio);
> +	struct folio *folio = page_folio(bio_first_page_all(bio));

Should we have a bio_first_folio_all()?  It wouldn't save any calls to
compound_head(), but it's slightly easier to use.

>  	if (bio->bi_status) {
> -		SetPageError(page);
> -		ClearPageUptodate(page);
> +		folio_set_error(folio);

I appreciate this is a 1:1 conversion, but maybe we could think about
this a bit.  Is there anybody who checks the
PageError()/folio_test_error() for this page/folio?

> +		folio_clear_uptodate(folio);

Similarly ... surely the folio is already !uptodate, so we don't need to
clear the flag?