Re: [PATCH 13/13] writeback: Remove a use of write_cache_pages() from do_writepages()

[Brian Foster]

On Sat, Feb 03, 2024 at 08:11:47AM +0100, Christoph Hellwig wrote:
> From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
> 
> Use the new writeback_iter() directly instead of indirecting
> through a callback.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> [hch: ported to the while based iter style]
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---

LGTM, modulo Jan's comments:

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

>  mm/page-writeback.c | 31 +++++++++++++++++++------------
>  1 file changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 5fe4cdb7dbd61a..53ff2d8219ddb6 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2577,13 +2577,25 @@ 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 folio *folio = NULL;
> +	struct blk_plug plug;
> +	int err;
> +
> +	blk_start_plug(&plug);
> +	while ((folio = writeback_iter(mapping, wbc, folio, &err))) {
> +		err = mapping->a_ops->writepage(&folio->page, wbc);
> +		mapping_set_error(mapping, err);
> +		if (err == AOP_WRITEPAGE_ACTIVATE) {
> +			folio_unlock(folio);
> +			err = 0;
> +		}
> +	}
> +	blk_finish_plug(&plug);
> +
> +	return err;
>  }
>  
>  int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
> @@ -2599,12 +2611,7 @@ 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
>