Re: [PATCH v2 05/53] selftests/mm: merge map_hugetlb into hugepage-mmap

[Donet Tom <donettom@linux.ibm.com>]

Hi Mike

On 4/18/26 4:24 PM, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>
> Both tests create a hugettlb mapping, fill it with data and verify the
> data, the only difference is that one uses file-backed memory and another
> one uses anonymous memory.
>
> Merge both tests into a single file.
>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>   tools/testing/selftests/mm/Makefile        |   1 -
>   tools/testing/selftests/mm/hugepage-mmap.c | 112 ++++++++++++++++-----
>   tools/testing/selftests/mm/map_hugetlb.c   |  88 ----------------
>   tools/testing/selftests/mm/run_vmtests.sh  |   1 -
>   4 files changed, 85 insertions(+), 117 deletions(-)
>   delete mode 100644 tools/testing/selftests/mm/map_hugetlb.c
>
> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
> index cd24596cdd27..cbda989f6b6a 100644
> --- a/tools/testing/selftests/mm/Makefile
> +++ b/tools/testing/selftests/mm/Makefile
> @@ -70,7 +70,6 @@ TEST_GEN_FILES += hugepage-vmemmap
>   TEST_GEN_FILES += khugepaged
>   TEST_GEN_FILES += madv_populate
>   TEST_GEN_FILES += map_fixed_noreplace
> -TEST_GEN_FILES += map_hugetlb
>   TEST_GEN_FILES += map_populate
>   ifneq (,$(filter $(ARCH),arm64 riscv riscv64 x86 x86_64 loongarch32 loongarch64))
>   TEST_GEN_FILES += memfd_secret
> diff --git a/tools/testing/selftests/mm/hugepage-mmap.c b/tools/testing/selftests/mm/hugepage-mmap.c
> index d543419de040..f4fcc7c45875 100644
> --- a/tools/testing/selftests/mm/hugepage-mmap.c
> +++ b/tools/testing/selftests/mm/hugepage-mmap.c
> @@ -15,6 +15,7 @@
>   #include <unistd.h>
>   #include <sys/mman.h>
>   #include <fcntl.h>
> +#include "vm_util.h"
>   #include "kselftest.h"
>   
>   #define LENGTH (256UL*1024*1024)
> @@ -25,54 +26,111 @@ static void check_bytes(char *addr)
>   	ksft_print_msg("First hex is %x\n", *((unsigned int *)addr));
>   }
>   
> -static void write_bytes(char *addr)
> +static void write_bytes(char *addr, size_t length)
>   {
>   	unsigned long i;
>   
> -	for (i = 0; i < LENGTH; i++)
> +	for (i = 0; i < length; i++)
>   		*(addr + i) = (char)i;
>   }
>   
> -static int read_bytes(char *addr)
> +static bool verify_bytes(char *addr, size_t length)
>   {
>   	unsigned long i;
>   
>   	check_bytes(addr);
> -	for (i = 0; i < LENGTH; i++)
> -		if (*(addr + i) != (char)i) {
> -			ksft_print_msg("Error: Mismatch at %lu\n", i);
> -			return 1;
> -		}
> -	return 0;
> +	for (i = 0; i < length; i++)
> +		if (*(addr + i) != (char)i)
> +			return false;
> +
> +	return true;
>   }
>   
> -int main(void)
> +static bool test_mmap(size_t length, int mmap_flags, int fd,
> +		      const char *test_name)
>   {
>   	void *addr;
> -	int fd, ret;
>   
> -	ksft_print_header();
> -	ksft_set_plan(1);
> +	addr = mmap(NULL, length, PROTECTION, mmap_flags, fd, 0);
> +	if (addr == MAP_FAILED)
> +		ksft_exit_fail_perror("mmap");
> +
> +	ksft_print_msg("Returned address is %p\n", addr);
> +	check_bytes(addr);
> +	write_bytes(addr, length);
> +	if (!verify_bytes(addr, length))
> +		ksft_exit_fail_msg("%s\n", test_name);
> +
> +	/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
> +	if (munmap(addr, length))
> +		ksft_exit_fail_perror("munmap");
> +
> +	return true;
> +}
> +
> +static void test_anon_mmap(size_t length, int shift)
> +{
> +	const char *test_name = "hugetlb anonymous mmap";
> +	int mmap_flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB;
> +	bool passed;
> +
> +	if (shift)
> +		mmap_flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
> +
> +	passed = test_mmap(length, mmap_flags, -1, test_name);
> +	ksft_test_result(passed, "%s\n", test_name);
> +}
> +
> +static void test_file_mmap(size_t length, int shift)
> +{
> +	const char *test_name = "hugetlb file mmap";
> +	int mmap_flags = MAP_SHARED;
> +	bool passed;
> +	int fd;
> +
> +	if (shift)
> +		mmap_flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;

 From what I understand, selecting an alternative huge page size using 
mmap flags is typically used along with MAP_HUGETLB. Since we are not 
using MAP_HUGETLB, would this code still be necessary? please let me 
know if I might be missing something.



>   
> -	fd = memfd_create("hugepage-mmap", MFD_HUGETLB);
> +	fd = memfd_create("hugetlb-mmap", MFD_HUGETLB);
>
In my test, the default huge page size is 2MB. I passed a shift value of 
30 (for 1GB huge pages), but the mmap call failed — To support 1GB huge 
page sizes on a system with a 2MB default huge page size, I used 
MFD_HUGETLB | MFD_HUGE_1GB. With this change, file-backed mmap using 1GB 
huge pages started working. Do you think this change would be needed?

-Donet

>   	if (fd < 0)
> -		ksft_exit_fail_msg("memfd_create() failed: %s\n", strerror(errno));
> +		ksft_exit_fail_perror("memfd_create");
> +
> +	passed = test_mmap(length, mmap_flags, fd, test_name);
> +
> +	close(fd);
> +	ksft_test_result(passed, "%s\n", test_name);
> +}
> +
> +int main(int argc, char **argv)
> +{
> +	size_t hugepage_size;
> +	size_t length = LENGTH;
> +	int shift = 0;
> +
> +	ksft_print_header();
> +	ksft_set_plan(2);
> +
> +	if (argc > 1)
> +		length = atol(argv[1]) << 20;
> +	if (argc > 2)
> +		shift = atoi(argv[2]);
>   
> -	addr = mmap(NULL, LENGTH, PROTECTION, MAP_SHARED, fd, 0);
> -	if (addr == MAP_FAILED) {
> -		close(fd);
> -		ksft_exit_fail_msg("mmap(): %s\n", strerror(errno));
> +	if (shift) {
> +		hugepage_size = (1 << shift);
> +		ksft_print_msg("%u kB hugepages\n", 1 << (shift - 10));
> +	} else {
> +		hugepage_size = default_huge_page_size();
> +		ksft_print_msg("Default size hugepages (%lu Kb)\n", hugepage_size >> 10);
>   	}
>   
> -	ksft_print_msg("Returned address is %p\n", addr);
> -	check_bytes(addr);
> -	write_bytes(addr);
> -	ret = read_bytes(addr);
> +	/* munmap with fail if the length is not page aligned */
> +	if (hugepage_size > length)
> +		length = hugepage_size;
>   
> -	munmap(addr, LENGTH);
> -	close(fd);
> +	ksft_print_msg("Mapping %lu Mbytes\n", (unsigned long)length >> 20);
>   
> -	ksft_test_result(!ret, "Read same data\n");
> +	test_anon_mmap(length, shift);
> +	test_file_mmap(length, shift);
>   
> -	ksft_exit(!ret);
> +	ksft_finished();
>   }
> diff --git a/tools/testing/selftests/mm/map_hugetlb.c b/tools/testing/selftests/mm/map_hugetlb.c
> deleted file mode 100644
> index aa409107611b..000000000000
> --- a/tools/testing/selftests/mm/map_hugetlb.c
> +++ /dev/null
> @@ -1,88 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -/*
> - * Example of using hugepage memory in a user application using the mmap
> - * system call with MAP_HUGETLB flag.  Before running this program make
> - * sure the administrator has allocated enough default sized huge pages
> - * to cover the 256 MB allocation.
> - */
> -#include <stdlib.h>
> -#include <stdio.h>
> -#include <unistd.h>
> -#include <sys/mman.h>
> -#include <fcntl.h>
> -#include "vm_util.h"
> -#include "kselftest.h"
> -
> -#define LENGTH (256UL*1024*1024)
> -#define PROTECTION (PROT_READ | PROT_WRITE)
> -
> -static void check_bytes(char *addr)
> -{
> -	ksft_print_msg("First hex is %x\n", *((unsigned int *)addr));
> -}
> -
> -static void write_bytes(char *addr, size_t length)
> -{
> -	unsigned long i;
> -
> -	for (i = 0; i < length; i++)
> -		*(addr + i) = (char)i;
> -}
> -
> -static void read_bytes(char *addr, size_t length)
> -{
> -	unsigned long i;
> -
> -	check_bytes(addr);
> -	for (i = 0; i < length; i++)
> -		if (*(addr + i) != (char)i)
> -			ksft_exit_fail_msg("Mismatch at %lu\n", i);
> -
> -	ksft_test_result_pass("Read correct data\n");
> -}
> -
> -int main(int argc, char **argv)
> -{
> -	void *addr;
> -	size_t hugepage_size;
> -	size_t length = LENGTH;
> -	int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB;
> -	int shift = 0;
> -
> -	hugepage_size = default_huge_page_size();
> -	/* munmap with fail if the length is not page aligned */
> -	if (hugepage_size > length)
> -		length = hugepage_size;
> -
> -	ksft_print_header();
> -	ksft_set_plan(1);
> -
> -	if (argc > 1)
> -		length = atol(argv[1]) << 20;
> -	if (argc > 2) {
> -		shift = atoi(argv[2]);
> -		if (shift)
> -			flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
> -	}
> -
> -	if (shift)
> -		ksft_print_msg("%u kB hugepages\n", 1 << (shift - 10));
> -	else
> -		ksft_print_msg("Default size hugepages\n");
> -	ksft_print_msg("Mapping %lu Mbytes\n", (unsigned long)length >> 20);
> -
> -	addr = mmap(NULL, length, PROTECTION, flags, -1, 0);
> -	if (addr == MAP_FAILED)
> -		ksft_exit_fail_msg("mmap: %s\n", strerror(errno));
> -
> -	ksft_print_msg("Returned address is %p\n", addr);
> -	check_bytes(addr);
> -	write_bytes(addr, length);
> -	read_bytes(addr, length);
> -
> -	/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
> -	if (munmap(addr, length))
> -		ksft_exit_fail_msg("munmap: %s\n", strerror(errno));
> -
> -	ksft_finished();
> -}
> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
> index e2dc9ac87bfc..61b450032af8 100755
> --- a/tools/testing/selftests/mm/run_vmtests.sh
> +++ b/tools/testing/selftests/mm/run_vmtests.sh
> @@ -292,7 +292,6 @@ CATEGORY="hugetlb" run_test ./hugepage-shm
>   echo "$shmmax" > /proc/sys/kernel/shmmax
>   echo "$shmall" > /proc/sys/kernel/shmall
>   
> -CATEGORY="hugetlb" run_test ./map_hugetlb
>   CATEGORY="hugetlb" run_test ./hugepage-mremap
>   CATEGORY="hugetlb" run_test ./hugepage-vmemmap
>   CATEGORY="hugetlb" run_test ./hugetlb-madvise