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

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

On 10/1/26 15:52, Yeoreum Yun wrote:
>> On 9/29/26 12:01, Yeoreum Yun wrote:
>>>
>>> Okay. I'll change like below in next-spin:
>>>
>>> -------&<-------
>>>
>>> @@ -411,57 +400,78 @@ static bool check_huge_type(uint64_t categories, enum check_huge_type type)
>>>         return false;
>>>  }
>>>
>>> -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_perror("open pagemap");
>>>
>>> -       for (; start < end; start += hpage_size) {
>>> +       kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY);
>>> +       if (kpageflags_fd < 0)
>>> +               ksft_exit_fail_perror("open kpageflags");
>>> +
>>> +       for (; start < end; start += scan_mapping_size) {
>>>                 categories = pagemap_scan_get_categories(pagemap_fd, start);
>>> -               if (!(categories & PAGE_IS_HUGE))
>>> +               pfn = pagemap_get_pfn(pagemap_fd, start);
>>> +               if (pfn == -1UL) {
>>> +                       if (!allow_nonpresent)
>>> +                               goto out;
>>>                         continue;
>>> -               if (check_huge_type(categories, type))
>>> +               }
>>> +               if (!check_huge_type(categories, type))
>>> +                       goto out;
>>> +       }
>>> +
>>> +       if (!check_pmd_mapping) {
>>> +               ret = check_large_folios(pagemap_fd, kpageflags_fd,
>>> +                               addr, len, nr_hpages, hpage_size);
>>> +               goto out;
>>> +       }
>>> +
>>> +       for (start = addr; start < end; start += scan_mapping_size) {
>>> +               categories = pagemap_scan_get_categories(pagemap_fd, start);
>>> +               if (categories & PAGE_IS_HUGE)
>>>                         nr_pmd_mappings++;
>>>         }
>>> -       close(pagemap_fd);
>>>
>>> -       return nr_hpages == nr_pmd_mappings;
>>> +       if (nr_pmd_mappings != nr_hpages)
>>> +               goto out;
>>> +       ret = true;
>>> +
>>> +out:
>>> +       close(pagemap_fd);
>>> +       close(kpageflags_fd);
>>> +       return ret;
>>>  }
>>>
>>
>> I'd leave existing __check_huge() mostly alone, and instead have an additional
>> function that checks the type.
>>
>> Essentially a __check_type() or sth that we run after the large folio / pmd check.
> 
> So, You mean like this?
> 
> -------&<-------
> 
> -enum check_huge_type {
> -       CHECK_HUGE_ANON,
> -       CHECK_HUGE_FILE,
> +enum check_type {
> +       CHECK_TYPE_ANON,
> +       CHECK_TYPE_FILE,
>  };
> 
> -static bool check_huge_type(uint64_t categories, enum check_huge_type type)
> +static bool __check_type(void *addr, size_t len, uint64_t page_size,
> +               bool allow_nonpresent, enum check_type type)


As discussed off-list, maybe we can avoid the allow_nonpresent handling!


-- 
Cheers,

David