On Sat Aug 1, 2026 at 2:26 AM EDT, Baolin Wang wrote:
> Implement mTHP-sized hugepage checking helpers using gather_folio_orders().
> Also rename the existing PMD-sized huge page check function to
> __check_pmd_huge() for clarity.
>
> Signed-off-by: Baolin Wang <[email protected]>
> ---
> tools/testing/selftests/mm/vm_util.c | 60 ++++++++++++++++++++++++++--
> 1 file changed, 56 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/vm_util.c
> b/tools/testing/selftests/mm/vm_util.c
> index 09e5d5cabe21..1240d783669c 100644
> --- a/tools/testing/selftests/mm/vm_util.c
> +++ b/tools/testing/selftests/mm/vm_util.c
> @@ -15,6 +15,10 @@
> #define SMAP_FILE_PATH "/proc/self/smaps"
> #define STATUS_FILE_PATH "/proc/self/status"
> #define MAX_LINE_LENGTH 500
> +#define PAGEMAP_PATH "/proc/self/pagemap"
> +#define KPAGEFLAGS_PATH "/proc/kpageflags"
> +#define GET_ORDER(nr_pages) (31 - __builtin_clz(nr_pages))
This is a fast way of getting log2, but there is no check of the type of
nr_pages. What prevents one using it on a long variable?
At least you can convert nr_pages to unsigned int and add a comment.
> +#define NR_ORDERS 20
Why 20? mTHP orders can only be in [1, pmd_order - 1] and different arch
has different pmd_orders. check_large_folios() probably should just cap
NR_ORDERS at pmd_order.
>
> unsigned int __page_size;
> unsigned int __page_shift;
> @@ -348,7 +352,7 @@ char *__get_smap_entry(void *addr, const char *pattern,
> char *buf, size_t len)
> return entry;
> }
>
> -bool __check_huge(void *addr, char *pattern, int nr_hpages,
> +static bool __check_pmd_huge(void *addr, char *pattern, int nr_hpages,
> uint64_t hpage_size)
> {
> char buffer[MAX_LINE_LENGTH];
> @@ -366,19 +370,67 @@ bool __check_huge(void *addr, char *pattern, int
> nr_hpages,
> return thp == (nr_hpages * (hpage_size >> 10));
> }
>
> +static bool check_large_folios(void *addr, unsigned long size, int
> nr_hpages, uint64_t hpage_size)
> +{
> + int order = 0, pagesize = getpagesize();
> + int nr_pages = hpage_size / pagesize;
> + int pagemap_fd, kpageflags_fd;
> + int orders[NR_ORDERS], status;
NR_ORDERS is a constant, so you can put orders on stack. I think you can
rename it to MAX_NR_ORDERS, use 20, and check pmd_order is not bigger
than MAX_NR_ORDERS.
> + bool ret = false;
> +
> + if (nr_pages > 0)
> + order = GET_ORDER(nr_pages);
This funciton can fail early if nr_pages is 0.
> +
> + if (!order || order >= NR_ORDERS)
> + ksft_exit_fail_msg("invalid order\n");
It should check against pmd_order.
> +
> + memset(orders, 0, sizeof(int) * NR_ORDERS);
> + pagemap_fd = open(PAGEMAP_PATH, O_RDONLY);
> + if (pagemap_fd == -1)
> + ksft_exit_fail_msg("read pagemap fail\n");
> +
> + kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY);
> + if (kpageflags_fd == -1) {
> + close(pagemap_fd);
> + ksft_exit_fail_msg("read kpageflags fail\n");
> + }
> +
> + status = gather_folio_orders(addr, size, pagemap_fd,
> + kpageflags_fd, orders, NR_ORDERS);
> + if (status)
> + goto out;
> +
> + if (orders[order] == nr_hpages)
> + ret = true;
> +
> +out:
> + close(pagemap_fd);
> + close(kpageflags_fd);
> + return ret;
> +}
> +
> bool check_huge_anon(void *addr, unsigned long size, int nr_hpages, uint64_t
> hpage_size)
> {
> - return __check_huge(addr, "AnonHugePages: ", nr_hpages, hpage_size);
> + if (hpage_size == read_pmd_pagesize())
read_pmd_pagesize() can fail and return 0. Either you need a check here
or add a ksft_exit_fail_msg() in read_pmd_pagesize() to remove the
burden from all callers.
> + return __check_pmd_huge(addr, "AnonHugePages: ", nr_hpages,
> hpage_size);
> +
> + return check_large_folios(addr, size, nr_hpages, hpage_size);
> }
>
> bool check_huge_file(void *addr, unsigned long size, int nr_hpages, uint64_t
> hpage_size)
> {
> - return __check_huge(addr, "FilePmdMapped:", nr_hpages, hpage_size);
> + if (hpage_size == read_pmd_pagesize())
> + return __check_pmd_huge(addr, "FilePmdMapped:", nr_hpages,
> hpage_size);
> +
> + return check_large_folios(addr, size, nr_hpages, hpage_size);
> }
>
> bool check_huge_shmem(void *addr, unsigned long size, int nr_hpages,
> uint64_t hpage_size)
> {
> - return __check_huge(addr, "ShmemPmdMapped:", nr_hpages, hpage_size);
> + if (hpage_size == read_pmd_pagesize())
> + return __check_pmd_huge(addr, "ShmemPmdMapped:", nr_hpages,
> hpage_size);
> +
> + return check_large_folios(addr, size, nr_hpages, hpage_size);
> }
>
> int64_t allocate_transhuge(void *ptr, int pagemap_fd)
All read_pmd_pagesize()s above need to be handled.
--
Best Regards,
Yan, Zi
