linux-kernel - Re: [PATCH 12/17] writeback: Factor writeback_iter_init() out of write_cache

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Date: Thu, 21 Dec 2023 12:29:59 +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 12/17] writeback: Factor writeback_iter_init() out of
 write_cache_pages()

On Mon 18-12-23 16:35:48, Christoph Hellwig wrote:
> From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> 
> Make it return the first folio in the batch so that we can use it
> in a typical for() pattern.
> 
> 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 | 39 ++++++++++++++++++++-------------------
>  1 file changed, 20 insertions(+), 19 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 70f42fd9a95b5d..efcfffa800884d 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2442,6 +2442,22 @@ static bool should_writeback_folio(struct address_space *mapping,
>  	return true;
>  }
>  
> +static struct folio *writeback_iter_init(struct address_space *mapping,
> +		struct writeback_control *wbc)
> +{
> +	if (wbc->range_cyclic)
> +		wbc->index = mapping->writeback_index; /* prev offset */
> +	else
> +		wbc->index = wbc->range_start >> PAGE_SHIFT;
> +
> +	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
> +		tag_pages_for_writeback(mapping, wbc->index, wbc_end(wbc));
> +
> +	wbc->err = 0;
> +	folio_batch_init(&wbc->fbatch);
> +	return writeback_get_next(mapping, wbc);
> +}
> +
>  /**
>   * write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
>   * @mapping: address space structure to write
> @@ -2477,29 +2493,14 @@ int write_cache_pages(struct address_space *mapping,
>  		      struct writeback_control *wbc, writepage_t writepage,
>  		      void *data)
>  {
> +	struct folio *folio;
>  	int error;
> -	pgoff_t end;		/* Inclusive */
>  
> -	if (wbc->range_cyclic) {
> -		wbc->index = mapping->writeback_index; /* prev offset */
> -		end = -1;
> -	} else {
> -		wbc->index = wbc->range_start >> PAGE_SHIFT;
> -		end = wbc->range_end >> PAGE_SHIFT;
> -	}
> -	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
> -		tag_pages_for_writeback(mapping, wbc->index, end);
> -
> -	folio_batch_init(&wbc->fbatch);
> -	wbc->err = 0;
> -
> -	for (;;) {
> -		struct folio *folio = writeback_get_next(mapping, wbc);
> +	for (folio = writeback_iter_init(mapping, wbc);
> +	     folio;
> +	     folio = writeback_get_next(mapping, wbc)) {
>  		unsigned long nr;
>  
> -		if (!folio)
> -			break;
> -
>  		folio_lock(folio);
>  		if (!should_writeback_folio(mapping, wbc, folio)) {
>  			folio_unlock(folio);
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR