Re: [PATCH 2/2] selftests/mm: verify droppable mappings cannot be locked

["David Hildenbrand (Arm)" <david@kernel.org>]

> +
> +/*
> + * Droppable memory should not be lockable.
> + */
> +static void test_mlock_droppable(void)
> +{
> +	char *map;
> +	unsigned long page_size = getpagesize();
> +
> +	/*
> +	 * Ensure MCL_FUTURE is not set.
> +	 */
> +	if (mlockall(MCL_CURRENT))
> +		ksft_exit_fail_msg("mlockall(MCL_CURRENT): %s\n", strerror(errno));

Why do we need the prior mlockall()? If that is really required, the
comment should be clearer why the munlockall() is insufficient.

Also, why can't we fail only the test?

> +	if (munlockall())
> +		ksft_exit_fail_msg("munlockall() %s\n", strerror(errno));

Why can't we fail only the test?

> +
> +	map = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE,
> +		   MAP_ANONYMOUS | MAP_DROPPABLE, -1, 0);
> +	if (map == MAP_FAILED) {
> +		if (errno == EOPNOTSUPP) {
> +			ksft_test_result_skip("%s: MAP_DROPPABLE not supported\n", __func__);
> +			return;
> +		}
> +		ksft_exit_fail_msg("mmap error: %s\n", strerror(errno));

same.

> +	}
> +
> +	if (mlock2_(map, 2 * page_size, 0)) {
> +		munmap(map, 2 * page_size);

Not required when exiting either way?

> +		ksft_exit_fail_msg("mlock2(0): %s\n", strerror(errno));
> +	}
> +
> +	ksft_test_result(!unlock_lock_check(map, false), "%s: droppable memory not locked\n",
> +			__func__);
> +
> +	munmap(map, 2 * page_size);
> +}
> +
> +static void test_mlockall_future_droppable(void)
> +{
> +	char *map;
> +	unsigned long page_size = getpagesize();
> +
> +	if (mlockall(MCL_CURRENT | MCL_FUTURE))
> +		ksft_exit_fail_msg("mlockall(MCL_CURRENT | MCL_FUTURE): %s\n", strerror(errno));

Similar comments as for the other path regarding ksft_exit_fail_msg() etc.

> +
> +	map = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE,
> +		   MAP_ANONYMOUS | MAP_DROPPABLE, -1, 0);
> +
> +	if (map == MAP_FAILED) {
> +		if (errno == EOPNOTSUPP) {
> +			ksft_test_result_skip("%s: MAP_DROPPABLE not supported\n", __func__);
> +			return;
> +		}
> +		ksft_exit_fail_msg("mmap error: %s\n", strerror(errno));
> +	}
> +
> +	ksft_test_result(!unlock_lock_check(map, false), "%s: droppable memory not locked\n",
> +			__func__);
> +
> +	if (munlockall()) {
> +		munmap(map, 2 * page_size);
> +		ksft_exit_fail_msg("munlockall() %s\n", strerror(errno));
> +	}
> +
>  	munmap(map, 2 * page_size);
>  }

-- 
Cheers,

David