linux-kernel - Re: [PATCH V1] mm/damon/schemes: Add the validity judgment of thresholds

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Date:   Thu, 18 Nov 2021 11:51:13 +0000
From:   SeongJae Park <sj@...nel.org>
To:     Xin Hao <xhao@...ux.alibaba.com>
Cc:     sjpark@...zon.de, sj@...nel.org, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V1] mm/damon/schemes: Add the validity judgment of thresholds

Hi Xin,


Thank you for this patch.

>From next time, please send patches for DAMON to sj@...nel.org instead of
sjpark@...zon.de.

On Thu, 18 Nov 2021 12:16:02 +0800 Xin Hao <xhao@...ux.alibaba.com> wrote:

> In dbgfs "schemes" interface, i do some test like this:
>     # cd /sys/kernel/debug/damon
>     # echo "2 1 2 1 10 1 3 10 1 1 1 1 1 1 1 1 2 3" > schemes
>     # cat schemes
>     # 2 1 2 1 10 1 3 10 1 1 1 1 1 1 1 1 2 3 0 0
> 
> There have some unreasonable places, i set the valules of these variables
> "<min_sz, max_sz> <min_nr_a, max_nr_a>, <min_age, max_age>, <wmarks.high,
> wmarks.mid, wmarks.low>" as "<2, 1>, <2, 1>, <10, 1>, <1, 2, 3>.
> 
> So there add a validity judgment for these threshold values.
> 
> Signed-off-by: Xin Hao <xhao@...ux.alibaba.com>
> ---
>  mm/damon/dbgfs.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
> index befb27a29aab..a4c94d563d3d 100644
> --- a/mm/damon/dbgfs.c
> +++ b/mm/damon/dbgfs.c
> @@ -215,6 +215,17 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
>  			goto fail;
>  		}
>  
> +		if (min_sz > max_sz || min_nr_a > max_nr_a || min_age > max_age) {
> +			pr_err("mininum > maxinum\n");

I think this error message is not really needed.

> +			goto fail;
> +		}
> +
> +		if (wmarks.high < wmarks.mid || wmarks.high < wmarks.low ||
> +		    wmarks.mid <  wmarks.low) {
> +			pr_err("wrong wmarks\n");

Ditto.


Thanks,
SJ

> +			goto fail;
> +		}
> +
>  		pos += parsed;
>  		scheme = damon_new_scheme(min_sz, max_sz, min_nr_a, max_nr_a,
>  				min_age, max_age, action, &quota, &wmarks);
> -- 
> 2.31.0