Re: [PATCH v4 08/15] selftest/mm: align memory size to huge page size in hugepage-mremap test

[Zi Yan <ziy@nvidia.com>]

On 6 Apr 2026, at 5:19, Sayali Patil wrote:

> The hugepage-mremap selftest uses a default mapping size of 10MB
> when no argument is provided. This size is not guaranteed to be
> aligned to the system hugepage size, which can cause munmap() to fail
> and mremap() to succeed where a failure is expected.
>
> Align the mapping length to the runtime hugepage size using
> default_huge_page_size() to ensure the mapping is properly
> aligned. Also handle the case where
> default_huge_page_size() returns 0 by skipping the test.
>
> Before patch:
>   running ./hugepage-mremap
>   ------------------------------
>   TAP version 13
>   1..1
>   Map haddr: Returned address is 0x7eaa40000000
>   Map daddr: Returned address is 0x7daa40000000
>   Map vaddr: Returned address is 0x7faa40000000
>   Address returned by mmap() = 0x7fffaa600000
>   Mremap: Returned address is 0x7faa40000000
>   First hex is 0
>   First hex is 3020100
>   Bail out! mremap: Expected failure, but call succeeded
>   Planned tests != run tests (1 != 0)
>   Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
>   [FAIL]
> not ok 1 hugepage-mremap # exit=1
>
> After patch:
>   running ./hugepage-mremap
>   -------------------------
>   TAP version 13
>   1..1
>   Map haddr: Returned address is 0x7eaa40000000
>   Map daddr: Returned address is 0x7daa40000000
>   Map vaddr: Returned address is 0x7faa40000000
>   Address returned by mmap() = 0x7fff13000000
>   Mremap: Returned address is 0x7faa40000000
>   First hex is 0
>   First hex is 3020100
>   ok 1 Read same data
>   Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
>   [PASS]
> ok 1 hugepage-mremap
>
> Fixes: f77a286de48c ("mm, hugepages: make memory size variable in hugepage-mremap selftest")
> Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
> ---
>  tools/testing/selftests/mm/hugepage-mremap.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/hugepage-mremap.c b/tools/testing/selftests/mm/hugepage-mremap.c
> index b8f7d92e5a35..f66e4d806477 100644
> --- a/tools/testing/selftests/mm/hugepage-mremap.c
> +++ b/tools/testing/selftests/mm/hugepage-mremap.c
> @@ -32,6 +32,7 @@
>
>  #define PROTECTION (PROT_READ | PROT_WRITE | PROT_EXEC)
>  #define FLAGS (MAP_SHARED | MAP_ANONYMOUS)
> +#define ALIGN(x, a) (((x) + ((a) - 1)) & ~((a) - 1))
>
>  static void check_bytes(char *addr)
>  {
> @@ -110,6 +111,7 @@ int main(int argc, char *argv[])
>  {
>  	size_t length = 0;
>  	int ret = 0, fd;
> +	size_t hpage_size;
>
>  	ksft_print_header();
>  	ksft_set_plan(1);
> @@ -126,6 +128,14 @@ int main(int argc, char *argv[])
>  		length = DEFAULT_LENGTH_MB;
>
>  	length = MB_TO_BYTES(length);
> +
> +	hpage_size = default_huge_page_size();
> +	if (!hpage_size)
> +		ksft_exit_skip("Unable to determine huge page size\n");
> +
> +	/* Ensure length is hugepage aligned */
> +	length = ALIGN(length, hpage_size);
> +
>  	fd = memfd_create(argv[0], MFD_HUGETLB);
>  	if (fd < 0)
>  		ksft_exit_fail_msg("Open failed: %s\n", strerror(errno));
> -- 
> 2.52.0

LGTM. BTW, it seems that multiple files, pkey-helpers.h, migration.c,
uffed-unit-test.c, hmm-tests.c, have their own ALIGN or ALIGN_UP.
They can be moved to vm_utils.h, later if someone wants to do a cleanup.

Reviewed-by: Zi Yan <ziy@nvidia.com>

Best Regards,
Yan, Zi