On 19 Feb 2020, at 16:00, Matthew Wilcox wrote:

> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
>
> Simplify the callers by moving the check for nr_pages and the BUG_ON
> into read_pages().
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  mm/readahead.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/mm/readahead.c b/mm/readahead.c
> index 61b15b6b9e72..9fcd4e32b62d 100644
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -119,6 +119,9 @@ static void read_pages(struct address_space *mapping, struct file *filp,
>  	struct blk_plug plug;
>  	unsigned page_idx;
>
> +	if (!nr_pages)
> +		return;
> +
>  	blk_start_plug(&plug);
>
>  	if (mapping->a_ops->readpages) {
> @@ -138,6 +141,8 @@ static void read_pages(struct address_space *mapping, struct file *filp,
>
>  out:
>  	blk_finish_plug(&plug);
> +
> +	BUG_ON(!list_empty(pages));
>  }
>
>  /*
> @@ -180,8 +185,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
>  			 * contiguous pages before continuing with the next
>  			 * batch.
>  			 */
> -			if (nr_pages)
> -				read_pages(mapping, filp, &page_pool, nr_pages,
> +			read_pages(mapping, filp, &page_pool, nr_pages,
>  						gfp_mask);
>  			nr_pages = 0;
>  			continue;
> @@ -202,9 +206,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
>  	 * uptodate then the caller will launch readpage again, and
>  	 * will then handle the error.
>  	 */
> -	if (nr_pages)
> -		read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask);
> -	BUG_ON(!list_empty(&page_pool));
> +	read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask);
>  }
>
>  /*
> -- 
> 2.25.0

Looks good to me. Thanks.

Reviewed-by: Zi Yan <ziy@nvidia.com>


--
Best Regards,
Yan Zi