Re: [PATCH v2 1/3] selftests/mm: compaction_test: Fix bogus test success on Aarch64

[Dev Jain <dev.jain@arm.com>]

Sorry, I was just sending to myself for testing, git send-email picked

up stable@vger.kernel.org too. Please ignore this.

On 5/21/24 12:07, Dev Jain wrote:
> Currently, if at runtime we are not able to allocate a huge page, the
> test will trivially pass on Aarch64 due to no exception being raised on
> division by zero while computing compaction_index. Fix that by checking
> for nr_hugepages == 0. Anyways, in general, avoid a division by zero by
> exiting the program beforehand. While at it, fix a typo.
>
> Changes in v2:
> - Combine with this series, handle unsigned long number of hugepages
>
> Fixes: bd67d5c15cc1 ("Test compaction of mlocked memory")
> Cc: stable@vger.kernel.org
> Signed-off-by: Dev Jain <dev.jain@arm.com>
> ---
>   tools/testing/selftests/mm/compaction_test.c | 20 +++++++++++++-------
>   1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/compaction_test.c b/tools/testing/selftests/mm/compaction_test.c
> index 4f42eb7d7636..0b249a06a60b 100644
> --- a/tools/testing/selftests/mm/compaction_test.c
> +++ b/tools/testing/selftests/mm/compaction_test.c
> @@ -82,12 +82,13 @@ int prereq(void)
>   	return -1;
>   }
>   
> -int check_compaction(unsigned long mem_free, unsigned int hugepage_size)
> +int check_compaction(unsigned long mem_free, unsigned long hugepage_size)
>   {
> +	unsigned long nr_hugepages_ul;
>   	int fd, ret = -1;
>   	int compaction_index = 0;
> -	char initial_nr_hugepages[10] = {0};
> -	char nr_hugepages[10] = {0};
> +	char initial_nr_hugepages[20] = {0};
> +	char nr_hugepages[20] = {0};
>   
>   	/* We want to test with 80% of available memory. Else, OOM killer comes
>   	   in to play */
> @@ -134,7 +135,12 @@ int check_compaction(unsigned long mem_free, unsigned int hugepage_size)
>   
>   	/* We should have been able to request at least 1/3 rd of the memory in
>   	   huge pages */
> -	compaction_index = mem_free/(atoi(nr_hugepages) * hugepage_size);
> +	nr_hugepages_ul = strtoul(nr_hugepages, NULL, 10);
> +	if (!nr_hugepages_ul) {
> +		ksft_print_msg("ERROR: No memory is available as huge pages\n");
> +		goto close_fd;
> +	}
> +	compaction_index = mem_free/(nr_hugepages_ul * hugepage_size);
>   
>   	lseek(fd, 0, SEEK_SET);
>   
> @@ -145,11 +151,11 @@ int check_compaction(unsigned long mem_free, unsigned int hugepage_size)
>   		goto close_fd;
>   	}
>   
> -	ksft_print_msg("Number of huge pages allocated = %d\n",
> -		       atoi(nr_hugepages));
> +	ksft_print_msg("Number of huge pages allocated = %lu\n",
> +		       nr_hugepages_ul);
>   
>   	if (compaction_index > 3) {
> -		ksft_print_msg("ERROR: Less that 1/%d of memory is available\n"
> +		ksft_print_msg("ERROR: Less than 1/%d of memory is available\n"
>   			       "as huge pages\n", compaction_index);
>   		goto close_fd;
>   	}