Re: [PATCH 1/5] selftests/cgroup: detect and handle global zswap state in test_zswap

[Michal Koutný]

Hi.

On Wed, Mar 11, 2026 at 07:05:19PM +0800, Li Wang <liwang@xxxxxxxxxx> wrote:
> +static bool disable_zswap(void)
> +{
> +	int st;
> +	char n[] = "N\n";
> +
> +	st = zswap_enabled_state();
> +	if (st == 0)
> +		return true;
> +	if (st < 0)
> +		return false;
> +
> +	if (write_text("/sys/module/zswap/parameters/enabled", n, strlen(n)) >= 0) {
> +		if (zswap_enabled_state() == 0)
> +			return true;
> +	}
> +
> +	ksft_print_msg("Failed to disable zswap\n");

Hm, so this can fail?

> +	return false;
> +}
> +
>  int main(int argc, char **argv)
>  {
>  	char root[PATH_MAX];
> -	int i;
> +	int i, orig_zswap_state;
>  
>  	ksft_print_header();
>  	ksft_set_plan(ARRAY_SIZE(tests));
>  	if (cg_find_unified_root(root, sizeof(root), NULL))
>  		ksft_exit_skip("cgroup v2 isn't mounted\n");
>  
> -	if (!zswap_configured())
> +	orig_zswap_state = zswap_enabled_state();
> +
> +	if (orig_zswap_state == -1)
>  		ksft_exit_skip("zswap isn't configured\n");
> +	else if (orig_zswap_state == 0 && !enable_zswap())
> +		ksft_exit_skip("zswap is disabled and cannot be enabled\n");

I should simply check the enablement state and skip if it's not
satisfactory (possibly printing an instructive message what to tweak).
(To keep the test dummy and leave it up to who's reponsible for the environment.)

My 0.02€,
Michal

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