[PATCH 11/14] mm: use SWP_SYNCHRONOUS_IO more intelligently

[Shakeel Butt]

+Minchan Kim

On Mon, Jul 20, 2020 at 12:52 AM Christoph Hellwig <hch at lst.de> 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.  Also there is no point in
> trying a bio submission if bdev_read_page failed.

This will at least break the failure path of zram_rw_page().

>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>  mm/page_io.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_io.c b/mm/page_io.c
> index ccda7679008851..63b44b8221af0f 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -403,8 +403,11 @@ int swap_readpage(struct page *page, bool synchronous)
>                 goto out;
>         }
>
> -       ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
> -       if (!ret) {
> +       if (sis->flags & SWP_SYNCHRONOUS_IO) {
> +               ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
> +               if (ret)
> +                       goto out;
> +
>                 if (trylock_page(page)) {
>                         swap_slot_free_notify(page);
>                         unlock_page(page);
> --
> 2.27.0
>