linux-kernel - Re: [PATCH] zram_drv: allow reclaim on bio

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Date:   Mon, 6 Sep 2021 09:38:19 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Jaewon Kim <jaewon31.kim@...sung.com>
Cc:     minchan@...nel.org, akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, ytk.lee@...sung.com,
        jaewon31.kim@...il.com
Subject: Re: [PATCH] zram_drv: allow reclaim on bio_alloc

On Mon, Sep 06, 2021 at 02:29:26PM +0900, Jaewon Kim wrote:
> The read_from_bdev_async is not called on atomic context. So GFP_NOIO is
> available rather than GFP_ATOMIC. If there were reclaimable pages with
> GFP_NOIO, we can avoid allocation failure and page fault failure.
> 
> Reported-by: Yong-Taek Lee <ytk.lee@...sung.com>
> Signed-off-by: Jaewon Kim <jaewon31.kim@...sung.com>
> ---
>  drivers/block/zram/zram_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index fcaf2750f68f..53be528a39a2 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -587,7 +587,7 @@ static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec,
>  {
>  	struct bio *bio;
>  
> -	bio = bio_alloc(GFP_ATOMIC, 1);
> +	bio = bio_alloc(GFP_NOIO|__GFP_HIGHMEM, 1);

Passing __GFP_HIGHMEM to bio_alloc does not make any sense whatsoever.