linux-kernel - Re: [PATCH 16/17] writeback: Remove a use of write_cache_pages() from do

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Date: Thu, 21 Dec 2023 12:53:45 +0100
From: Jan Kara <jack@...e.cz>
To: Christoph Hellwig <hch@....de>
Cc: linux-mm@...ck.org, "Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Jan Kara <jack@...e.com>, David Howells <dhowells@...hat.com>,
	Brian Foster <bfoster@...hat.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 16/17] writeback: Remove a use of write_cache_pages()
 from do_writepages()

On Mon 18-12-23 16:35:52, Christoph Hellwig wrote:
> From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> 
> Use the new for_each_writeback_folio() directly instead of indirecting
> through a callback.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> Signed-off-by: Christoph Hellwig <hch@....de>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  mm/page-writeback.c | 27 +++++++++++++++------------
>  1 file changed, 15 insertions(+), 12 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index fbffd30a9cc93f..d3c2c78e0c67ce 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2564,13 +2564,21 @@ int write_cache_pages(struct address_space *mapping,
>  }
>  EXPORT_SYMBOL(write_cache_pages);
>  
> -static int writepage_cb(struct folio *folio, struct writeback_control *wbc,
> -		void *data)
> +static int writeback_use_writepage(struct address_space *mapping,
> +		struct writeback_control *wbc)
>  {
> -	struct address_space *mapping = data;
> -	int ret = mapping->a_ops->writepage(&folio->page, wbc);
> -	mapping_set_error(mapping, ret);
> -	return ret;
> +	struct blk_plug plug;
> +	struct folio *folio;
> +	int err;
> +
> +	blk_start_plug(&plug);
> +	for_each_writeback_folio(mapping, wbc, folio, err) {
> +		err = mapping->a_ops->writepage(&folio->page, wbc);
> +		mapping_set_error(mapping, err);
> +	}
> +	blk_finish_plug(&plug);
> +
> +	return err;
>  }
>  
>  int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
> @@ -2586,12 +2594,7 @@ int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
>  		if (mapping->a_ops->writepages) {
>  			ret = mapping->a_ops->writepages(mapping, wbc);
>  		} else if (mapping->a_ops->writepage) {
> -			struct blk_plug plug;
> -
> -			blk_start_plug(&plug);
> -			ret = write_cache_pages(mapping, wbc, writepage_cb,
> -						mapping);
> -			blk_finish_plug(&plug);
> +			ret = writeback_use_writepage(mapping, wbc);
>  		} else {
>  			/* deal with chardevs and other special files */
>  			ret = 0;
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR