linux-kernel - Re: [PATCH] mm/page-writeback: drop usage of folio

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Message-ID: <aJ8m42sM1NX_wEE9@casper.infradead.org>
Date: Fri, 15 Aug 2025 13:24:03 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Kairui Song <kasong@...cent.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/page-writeback: drop usage of folio_index

On Fri, Aug 15, 2025 at 08:12:52PM +0800, Kairui Song wrote:
> +++ b/mm/page-writeback.c
> @@ -2739,8 +2739,8 @@ void __folio_mark_dirty(struct folio *folio, struct address_space *mapping,
>  	if (folio->mapping) {	/* Race with truncate? */
>  		WARN_ON_ONCE(warn && !folio_test_uptodate(folio));
>  		folio_account_dirtied(folio, mapping);
> -		__xa_set_mark(&mapping->i_pages, folio_index(folio),
> -				PAGECACHE_TAG_DIRTY);
> +		__xa_set_mark(&mapping->i_pages, folio->index,
> +			      PAGECACHE_TAG_DIRTY);
>  	}
>  	xa_unlock_irqrestore(&mapping->i_pages, flags);
>  }

What about a shmem folio that's been moved to the swap cache?  I used
folio_index() here because I couldn't prove to my satisfaction that this
couldn't happen.