Re: [PATCH v8 3/4] kselftest: mm: integrate huge page checks

[Sarthak Sharma <sarthak.sharma@arm.com>]

On 9/25/26 12:41 AM, Yeoreum Yun wrote:
> check_large_folios() only checks for large folios without distinguishing
> between anonymous and file-backed huge pages.
> 
> To add huge page type checking, integrate the huge page checks into
> __check_huge():
> 
>   1. If hpage_size == pmd_pagesize, check PAGE_IS_HUGE instead of using
>      check_large_folios(), since only the mapping type matters. This
>      identifies PMD-mapped huge pages.
> 
>   2. Otherwise, use check_large_folios() to detect large folios. This
>      covers mTHP cases.
> 
>   3. Check the folio flags according to the huge page type.
> 
> Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
> Suggested-by: Zi Yan <ziy@nvidia.com>
> Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> ---

Looks good to me, some nits below.

Reviewed-by: Sarthak Sharma <sarthak.sharma@arm.com>

[...]

> -static bool __check_pmd_huge(void *addr, size_t len, int nr_hpages,
> -		  uint64_t hpage_size, enum check_huge_type type)
> +static bool __check_huge(void *addr, size_t len, int nr_hpages,
> +		uint64_t hpage_size, enum check_huge_type type)
>  {
> -	int pagemap_fd;
> +	bool ret = false;
> +	int pagemap_fd, kpageflags_fd;
>  	int nr_pmd_mappings = 0;
> +	uint64_t pmd_pagesize, scan_mapping_size;
>  	uint64_t categories;
> +	unsigned long pfn;
> +	bool check_pmd_mapping, allow_nonpresent;
>  	char *start = addr;
>  	char *end = start + len;
>  
> +	pmd_pagesize = read_pmd_pagesize();
> +	if (!pmd_pagesize)
> +		ksft_exit_fail_msg("reading PMD pagesize failed\n");
> +
> +	check_pmd_mapping = hpage_size == pmd_pagesize;
> +	scan_mapping_size = (nr_hpages > 0) ? hpage_size : psize();
> +	/* Some mTHP tests check a partially populated PMD-sized range. */
> +	allow_nonpresent = (uint64_t)nr_hpages * hpage_size < len;
> +
>  	pagemap_fd = open(PAGEMAP_PATH, O_RDONLY);
>  	if (pagemap_fd < 0)
>  		ksft_exit_fail_msg("open pagemap fail\n");
>  
> -	for (; start < end; start += hpage_size) {
> +	kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY);
> +	if (kpageflags_fd < 0)
> +		ksft_exit_fail_msg("open kpageflags fail\n");

Again, can we change it to ksft_exit_fail_perror()?

> +
> +	if (!check_pmd_mapping &&
> +	    !check_large_folios(pagemap_fd, kpageflags_fd,
> +				addr, len, nr_hpages, hpage_size))
> +		goto out;
> +
> +	for (; start < end; start += scan_mapping_size) {
>  		categories = pagemap_scan_get_categories(pagemap_fd, start);
> -		if (!(categories & PAGE_IS_HUGE))
> -			continue;
> -		if (check_huge_type(categories, type))
> +		pfn = pagemap_get_pfn(pagemap_fd, start);
> +		if (pfn == -1UL) {
> +			if (!allow_nonpresent)
> +				goto out;
> +			else

Nit: We can skip this else here.

> +				continue;
> +		}
> +		if (check_pmd_mapping && (categories & PAGE_IS_HUGE))
>  			nr_pmd_mappings++;
> +		if (!check_huge_type(categories, type))
> +			goto out;
>  	}
> -	close(pagemap_fd);
>  
> -	return nr_hpages == nr_pmd_mappings;
> +	if (check_pmd_mapping && (nr_pmd_mappings != nr_hpages))
> +		goto out;
> +	ret = true;
> +
> +out:
> +	close(pagemap_fd);
> +	close(kpageflags_fd);
> +	return ret;
>  }