Re: [PATCH v2] mm/damon/core: Fix return value from damos_wmark_metric_value

[SeongJae Park <sj@kernel.org>]

Hi Alex,

On Sun, 28 Apr 2024 21:41:59 +0300 Alex Rusuf <yorha.op@gmail.com> wrote:

> damos_wmark_metric_value's return value is 'unsigned long', so
> returning -EINVAL as 'unsigned long' may turn out to be
> very different from the expected one (using 2's complement) and
> treat as usual matric's value. So, fix that, checking if
> returned value is not 0.
> 
> Fixes: ee801b7dd782 ("mm/damon/schemes: activate schemes based on a watermarks mechanism")
> Signed-off-by: Alex Rusuf <yorha.op@gmail.com>
> ---

We usually post new revisions of patches as new thread, instead of reply to
previous revision.  If you want to kindly letting reviewers understand the
revision history of the patch, you could put the summary of the changes in each
revisions here[1].

[1] https://www.kernel.org/doc/html/v4.17/process/submitting-patches.html#the-canonical-patch-format

>  mm/damon/core.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index 6d503c1c125e..53d33b2fa0b9 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -1480,12 +1480,17 @@ static bool kdamond_need_stop(struct damon_ctx *ctx)
>  	return true;
>  }
>  
> -static unsigned long damos_wmark_metric_value(enum damos_wmark_metric metric)
> +static int damos_get_wmark_metric_value(enum damos_wmark_metric metric,
> +					unsigned long *metric_value)
>  {
> +	if (metric == DAMOS_WMARK_NONE)
> +		return -EINVAL;
> +

Below switch-case will handle this case too.  How about removing this if
statement?

>  	switch (metric) {
>  	case DAMOS_WMARK_FREE_MEM_RATE:
> -		return global_zone_page_state(NR_FREE_PAGES) * 1000 /
> +		*metric_value = global_zone_page_state(NR_FREE_PAGES) * 1000 /
>  		       totalram_pages();
> +		return 0;
>  	default:
>  		break;
>  	}
> @@ -1500,10 +1505,9 @@ static unsigned long damos_wmark_wait_us(struct damos *scheme)
>  {
>  	unsigned long metric;
>  
> -	if (scheme->wmarks.metric == DAMOS_WMARK_NONE)
> +	if (damos_get_wmark_metric_value(scheme->wmarks.metric, &metric))
>  		return 0;
>  
> -	metric = damos_wmark_metric_value(scheme->wmarks.metric);
>  	/* higher than high watermark or lower than low watermark */
>  	if (metric > scheme->wmarks.high || scheme->wmarks.low > metric) {
>  		if (scheme->wmarks.activated)
> -- 
> 2.42.0


Thanks,
SJ