linux-kernel - Re: [PATCH 11/14] mm: use SWP_SYNCHRONOUS

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Date:   Mon, 20 Jul 2020 10:52:55 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Christoph Hellwig <hch@....de>, Minchan Kim <minchan@...nel.org>
Cc:     Jens Axboe <axboe@...nel.dk>, Song Liu <song@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Richard Weinberger <richard@....at>,
        linux-mtd@...ts.infradead.org, dm-devel@...hat.com,
        "open list:BLOCK LAYER" <linux-block@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, drbd-dev@...ts.linbit.com,
        linux-raid@...r.kernel.org,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Cgroups <cgroups@...r.kernel.org>
Subject: Re: [PATCH 11/14] mm: use SWP_SYNCHRONOUS_IO more intelligently

+Minchan Kim

On Mon, Jul 20, 2020 at 12:52 AM Christoph Hellwig <hch@....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@....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
>