# Re: \[PATCH 09/12\] mm: use SWP\_SYNCHRONOUS\_IO more intelligently

- From: Jan Kara \<jack@suse.cz\>
- Date: 2020-09-17 09:07:06 
- List: linux-raid
- Page: https://ratatoskr.run/linux-raid/2020/09/188915
- Thread: https://ratatoskr.run/linux-block/2020/09/188389/t.md

```text
On Thu 10-09-20 16:48:29, Christoph Hellwig wrote:
> There is no point in trying to call bdev_read_page if SWP_SYNCHRONOUS_IO
> is not set, as the device won't support it.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good to me. You can add:

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

								Honza

> ---
>  mm/page_io.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/page_io.c b/mm/page_io.c
> index e485a6e8a6cddb..b199b87e0aa92b 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -403,15 +403,17 @@ int swap_readpage(struct page *page, bool synchronous)
>  		goto out;
>  	}
>  
> -	ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
> -	if (!ret) {
> -		if (trylock_page(page)) {
> -			swap_slot_free_notify(page);
> -			unlock_page(page);
> -		}
> +	if (sis->flags & SWP_SYNCHRONOUS_IO) {
> +		ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
> +		if (!ret) {
> +			if (trylock_page(page)) {
> +				swap_slot_free_notify(page);
> +				unlock_page(page);
> +			}
>  
> -		count_vm_event(PSWPIN);
> -		goto out;
> +			count_vm_event(PSWPIN);
> +			goto out;
> +		}
>  	}
>  
>  	ret = 0;
> -- 
> 2.28.0
> 
-- 
Jan Kara [ref]
SUSE Labs, CR
```