linux-kernel - Re: [PATCH 1/2] mm/damon/dbgfs: reduce stack usage in str_to

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Message-ID: <c7a050b2-4ceb-9888-5e69-36aeec0989cc@kernel.org>
Date:   Mon, 17 Jul 2023 11:41:01 +0800
From:   Chao Yu <chao@...nel.org>
To:     sj@...nel.org, akpm@...ux-foundation.org, damon@...ts.linux.dev
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm/damon/dbgfs: reduce stack usage in
 str_to_schemes()

Hi all,

It warned because my config is wrong, sorry for the mistake, please
ignore the patchset. :-P

Thanks,

On 2023/7/16 9:09, Chao Yu wrote:
> struct damos_quota quota caused the stack usage of str_to_schemes() to
> grow beyond the warning limit on 32-bit architectures w/ gcc.
> 
> mm/damon/dbgfs.c: In function ‘str_to_schemes’:
> mm/damon/dbgfs.c:292:1: warning: the frame size of 1496 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> Allocating dynamic memory in str_to_schemes() to fix this issue.
> 
> Signed-off-by: Chao Yu <chao@...nel.org>
> ---
>   mm/damon/dbgfs.c | 22 ++++++++++++++++------
>   1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
> index 124f0f8c97b7..78acc7366895 100644
> --- a/mm/damon/dbgfs.c
> +++ b/mm/damon/dbgfs.c
> @@ -237,18 +237,26 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
>   	int pos = 0, parsed, ret;
>   	unsigned int action_input;
>   	enum damos_action action;
> +	struct damos_quota *quota;
>   
>   	schemes = kmalloc_array(max_nr_schemes, sizeof(scheme),
>   			GFP_KERNEL);
>   	if (!schemes)
>   		return NULL;
>   
> +	quota = kmalloc(sizeof(struct damos_quota), GFP_KERNEL);
> +	if (!quota) {
> +		kfree(schemes);
> +		return NULL;
> +	}
> +
>   	*nr_schemes = 0;
>   	while (pos < len && *nr_schemes < max_nr_schemes) {
>   		struct damos_access_pattern pattern = {};
> -		struct damos_quota quota = {};
>   		struct damos_watermarks wmarks;
>   
> +		memset(quota, 0, sizeof(struct damos_quota));
> +
>   		ret = sscanf(&str[pos],
>   				"%lu %lu %u %u %u %u %u %lu %lu %lu %u %u %u %u %lu %lu %lu %lu%n",
>   				&pattern.min_sz_region, &pattern.max_sz_region,
> @@ -256,10 +264,10 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
>   				&pattern.max_nr_accesses,
>   				&pattern.min_age_region,
>   				&pattern.max_age_region,
> -				&action_input, &quota.ms,
> -				&quota.sz, &quota.reset_interval,
> -				&quota.weight_sz, &quota.weight_nr_accesses,
> -				&quota.weight_age, &wmarks.metric,
> +				&action_input, &quota->ms,
> +				&quota->sz, &quota->reset_interval,
> +				&quota->weight_sz, &quota->weight_nr_accesses,
> +				&quota->weight_age, &wmarks.metric,
>   				&wmarks.interval, &wmarks.high, &wmarks.mid,
>   				&wmarks.low, &parsed);
>   		if (ret != 18)
> @@ -278,15 +286,17 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
>   			goto fail;
>   
>   		pos += parsed;
> -		scheme = damon_new_scheme(&pattern, action, &quota, &wmarks);
> +		scheme = damon_new_scheme(&pattern, action, quota, &wmarks);
>   		if (!scheme)
>   			goto fail;
>   
>   		schemes[*nr_schemes] = scheme;
>   		*nr_schemes += 1;
>   	}
> +	kfree(quota);
>   	return schemes;
>   fail:
> +	kfree(quota);
>   	free_schemes_arr(schemes, *nr_schemes);
>   	return NULL;
>   }