Re: [PATCH v7 3/3] kselftest: mm: remove check_huge_shmem()

["Lorenzo Stoakes (ARM)" <ljs@kernel.org>]

On Mon, Sep 21, 2026 at 11:40:09AM +0100, Yeoreum Yun wrote:
> check_huge_shmem() was required to distinguish shmem huge pages because
> /proc/self/smaps reports them using a dedicated “ShmemPmdMapped” entry,
> as opposed to “FilePmdMapped” for file-backed huge pages.
>
> Now that /proc/self/smaps is no longer used to detect huge pages and
> /proc/kpageflags is used instead, it is sufficient to distinguish
> between file-backed and anonymous pages since the ShmemPmdMapped is also
> kind of file-backed.
>
> Therefore, remove check_huge_shmem() and use check_huge_file() instead
> and cleanup khugepaged's check_huge operation in mem_ops.
>
> Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
> Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>

LGTM so:

Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

> ---
>  tools/testing/selftests/mm/folio_split_race_test.c |  2 +-
>  tools/testing/selftests/mm/khugepaged.c            | 38 ++++------------------
>  tools/testing/selftests/mm/uffd-common.c           |  4 +--
>  tools/testing/selftests/mm/vm_util.c               |  5 ---
>  tools/testing/selftests/mm/vm_util.h               |  1 -
>  5 files changed, 9 insertions(+), 41 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/folio_split_race_test.c b/tools/testing/selftests/mm/folio_split_race_test.c
> index 1960635a953eb..4c0d3b6a411b8 100644
> --- a/tools/testing/selftests/mm/folio_split_race_test.c
> +++ b/tools/testing/selftests/mm/folio_split_race_test.c
> @@ -182,7 +182,7 @@ static uint64_t run_iteration(void)
>  	for (i = 0; i < TOTAL_PAGES; i++)
>  		fill_page(mmap_base, i);
>
> -	if (!check_huge_shmem(mmap_base, FILE_SIZE, NR_PMD_PAGE, pmd_pagesize))
> +	if (!check_huge_file(mmap_base, FILE_SIZE, NR_PMD_PAGE, pmd_pagesize))
>  		ksft_exit_fail_msg("No shmem THP is allocated\n");
>
>  	if (pthread_barrier_init(&ctl.barrier, NULL, NUM_READER_THREADS + 1) != 0)
> diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
> index f82673f5f6b47..f448278823678 100644
> --- a/tools/testing/selftests/mm/khugepaged.c
> +++ b/tools/testing/selftests/mm/khugepaged.c
> @@ -53,7 +53,7 @@ struct mem_ops {
>  	void *(*setup_area)(int nr_hpages);
>  	void (*cleanup_area)(void *p, unsigned long size);
>  	void (*fault)(void *p, unsigned long start, unsigned long end);
> -	bool (*check_huge)(void *addr, size_t len, int nr_hpages, unsigned long hpage_size);
> +	bool (*check_huge)(void *addr, size_t len, int nr_hpages, uint64_t hpage_size);
>  	const char *name;
>  };
>
> @@ -314,12 +314,6 @@ static void anon_fault(void *p, unsigned long start, unsigned long end)
>  	fill_memory(p, start, end);
>  }
>
> -static bool anon_check_huge(void *addr, size_t len, int nr_hpages,
> -		unsigned long hpage_size)
> -{
> -	return check_huge_anon(addr, len, nr_hpages, hpage_size);
> -}
> -
>  static void *file_setup_area_common(int nr_hpages, enum file_setup_ops setup)
>  {
>  	const int open_opt = setup == FILE_SETUP_READ_ONLY_FS ? O_RDONLY : O_RDWR;
> @@ -411,20 +405,6 @@ static void file_fault_write(void *p, unsigned long start, unsigned long end)
>  		ksft_exit_fail_perror("madvise(MADV_POPULATE_WRITE)");
>  }
>
> -static bool file_check_huge(void *addr, size_t len, int nr_hpages,
> -		unsigned long hpage_size)
> -{
> -	switch (finfo.type) {
> -	case VMA_FILE:
> -		return check_huge_file(addr, len, nr_hpages, hpage_size);
> -	case VMA_SHMEM:
> -		return check_huge_shmem(addr, len, nr_hpages, hpage_size);
> -	default:
> -		ksft_exit_fail_msg("Unknown VMA type\n");
> -		return false;
> -	}
> -}
> -
>  static void *shmem_setup_area(int nr_hpages)
>  {
>  	void *p;
> @@ -448,17 +428,11 @@ static void shmem_cleanup_area(void *p, unsigned long size)
>  	close(finfo.fd);
>  }
>
> -static bool shmem_check_huge(void *addr, size_t len, int nr_hpages,
> -		unsigned long hpage_size)
> -{
> -	return check_huge_shmem(addr, len, nr_hpages, hpage_size);
> -}
> -
>  static struct mem_ops __anon_ops = {
>  	.setup_area = &anon_setup_area,
>  	.cleanup_area = &anon_cleanup_area,
>  	.fault = &anon_fault,
> -	.check_huge = &anon_check_huge,
> +	.check_huge = &check_huge_anon,
>  	.name = "anon",
>  };
>
> @@ -466,7 +440,7 @@ static struct mem_ops __read_only_file_ops = {
>  	.setup_area = &file_setup_read_only_area,
>  	.cleanup_area = &file_cleanup_area,
>  	.fault = &file_fault_read,
> -	.check_huge = &file_check_huge,
> +	.check_huge = &check_huge_file,
>  	.name = "file",
>  };
>
> @@ -474,7 +448,7 @@ static struct mem_ops __read_write_file_read_ops = {
>  	.setup_area = &file_setup_read_write_fs_read_area,
>  	.cleanup_area = &file_cleanup_area,
>  	.fault = &file_fault_read_and_flush,
> -	.check_huge = &file_check_huge,
> +	.check_huge = &check_huge_file,
>  	.name = "file",
>  };
>
> @@ -482,7 +456,7 @@ static struct mem_ops __read_write_file_write_ops = {
>  	.setup_area = &file_setup_read_write_fs_write_area,
>  	.cleanup_area = &file_cleanup_area,
>  	.fault = &file_fault_write,
> -	.check_huge = &file_check_huge,
> +	.check_huge = &check_huge_file,
>  	.name = "file",
>  };
>
> @@ -490,7 +464,7 @@ static struct mem_ops __shmem_ops = {
>  	.setup_area = &shmem_setup_area,
>  	.cleanup_area = &shmem_cleanup_area,
>  	.fault = &anon_fault,
> -	.check_huge = &shmem_check_huge,
> +	.check_huge = &check_huge_file,
>  	.name = "shmem",
>  };
>
> diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c
> index 1fb967ef49854..a76851aced4d0 100644
> --- a/tools/testing/selftests/mm/uffd-common.c
> +++ b/tools/testing/selftests/mm/uffd-common.c
> @@ -196,8 +196,8 @@ static void shmem_check_pmd_mapping(uffd_global_test_opts_t *gopts, void *p, int
>  {
>  	size_t len = expect_nr_hpages * read_pmd_pagesize();
>
> -	if (!check_huge_shmem(gopts->area_dst_alias, len, expect_nr_hpages,
> -			      read_pmd_pagesize()))
> +	if (!check_huge_file(gopts->area_dst_alias, len, expect_nr_hpages,
> +			     read_pmd_pagesize()))
>  		err("Did not find expected %d number of hugepages",
>  		    expect_nr_hpages);
>  }
> diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
> index a7c5caf6925e0..e31e88d5af76d 100644
> --- a/tools/testing/selftests/mm/vm_util.c
> +++ b/tools/testing/selftests/mm/vm_util.c
> @@ -475,11 +475,6 @@ bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)
>  	return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_FILE);
>  }
>
> -bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)
> -{
> -	return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_FILE);
> -}
> -
>  int64_t allocate_transhuge(void *ptr, int pagemap_fd)
>  {
>  	uint64_t ent[2];
> diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
> index 9a49af88702e4..fc9c93235f6fa 100644
> --- a/tools/testing/selftests/mm/vm_util.h
> +++ b/tools/testing/selftests/mm/vm_util.h
> @@ -92,7 +92,6 @@ uint64_t read_pmd_pagesize(void);
>  unsigned long rss_anon(void);
>  bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size);
>  bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size);
> -bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size);
>  int64_t allocate_transhuge(void *ptr, int pagemap_fd);
>  int pageflags_get(unsigned long pfn, int kpageflags_fd, uint64_t *flags);
>  int gather_folio_orders(char *vaddr_start, size_t len,
>
> --
> 2.43.0
>

--
Cheers, Lorenzo