Re: [PATCH 3/8] execmem: rework execmem_cache_free()

[Peter Zijlstra]

On Fri, Jul 04, 2025 at 04:49:38PM +0300, Mike Rapoport wrote:
>  static bool execmem_cache_free(void *ptr)
>  {
>  	struct maple_tree *busy_areas = &execmem_cache.busy_areas;
>  	unsigned long addr = (unsigned long)ptr;
>  	MA_STATE(mas, busy_areas, addr, addr);
>  	void *area;
> +	int err;
> +
> +	guard(mutex)(&execmem_cache.mutex);
>  
>  	area = mas_walk(&mas);
> +	if (!area)
>  		return false;
>  
> +	err = __execmem_cache_free(&mas, ptr, GFP_KERNEL | __GFP_NORETRY);
> +	if (err)
> +		goto err_slowpath;
>  
>  	schedule_work(&execmem_cache_clean_work);
>  
>  	return true;
> +
> +err_slowpath:
> +	mas_store_gfp(&mas, pending_free_set(ptr), GFP_KERNEL);
> +	execmem_cache.pending_free_cnt++;
> +	schedule_delayed_work(&execmem_cache_free_work, FREE_DELAY);
> +	return true;
>  }

This is a bit if an anti-pattern, using guard() and error goto. Since
there is only the one site, its best to write it like so:

static bool execmem_cache_free(void *ptr)
{
	struct maple_tree *busy_areas = &execmem_cache.busy_areas;
	unsigned long addr = (unsigned long)ptr;
	MA_STATE(mas, busy_areas, addr, addr);
	void *area;
	int err;

	guard(mutex)(&execmem_cache.mutex);

	area = mas_walk(&mas);
	if (!area)
		return false;

	err = __execmem_cache_free(&mas, ptr, GFP_KERNEL | __GFP_NORETRY);
	if (err) {
		mas_store_gfp(&mas, pending_free_set(ptr), GFP_KERNEL);
		execmem_cache.pending_free_cnt++;
		schedule_delayed_work(&execmem_cache_free_work, FREE_DELAY);
		return true;
	}

	schedule_work(&execmem_cache_clean_work);
	return true;
}

And now I have to ask what happens if mas_store_gfp() returns an error?