Add test cases to test the correctness of PFN ZERO flag of pagemap_scan ioctl. Test with normal pages backed memory and huge pages backed memory.

Cc: David Hildenbrand david@redhat.com Signed-off-by: Muhammad Usama Anjum usama.anjum@collabora.com --- The bug has been fixed [1].

[1] https://lore.kernel.org/all/20250617143532.2375383-1-david@redhat.com Changes since v1: - Skip if madvise() fails - Skip test if use_zero_page isn't set to 1 - Keep on using memalign()+free() to allocate huge pages --- tools/testing/selftests/mm/pagemap_ioctl.c | 86 +++++++++++++++++++++- 1 file changed, 85 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/pagemap_ioctl.c b/tools/testing/selftests/mm/pagemap_ioctl.c index 57b4bba2b45f3..976ab357f4651 100644 --- a/tools/testing/selftests/mm/pagemap_ioctl.c +++ b/tools/testing/selftests/mm/pagemap_ioctl.c @@ -1,4 +1,5 @@ // SPDX-License-Identifier: GPL-2.0 + #define _GNU_SOURCE #include <stdio.h> #include <fcntl.h> @@ -1480,6 +1481,86 @@ static void transact_test(int page_size) extra_thread_faults); }

+bool is_use_zero_page_set(void) +{ + ssize_t bytes_read; + char buffer[2]; + int fd; + + fd = open("/sys/kernel/mm/transparent_hugepage/use_zero_page", O_RDONLY); + if (fd < 0) + return 0; + + bytes_read = read(fd, buffer, sizeof(buffer) - 1); + if (bytes_read <= 0) { + close(fd); + return 0; + } + + close(fd); + if (atoi(buffer) != 1) + return 0; + + return 1; +} + +void zeropfn_tests(void) +{ + unsigned long long mem_size; + struct page_region vec; + int i, ret; + char *mem; + + /* Test with normal memory */ + mem_size = 10 * page_size; + mem = mmap(NULL, mem_size, PROT_READ, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + + /* Touch each page to ensure it's mapped */ + for (i = 0; i < mem_size; i += page_size) + (void)((volatile char *)mem)[i]; + + ret = pagemap_ioctl(mem, mem_size, &vec, 1, 0, + (mem_size / page_size), PAGE_IS_PFNZERO, 0, 0, PAGE_IS_PFNZERO); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && LEN(vec) == (mem_size / page_size), + "%s all pages must have PFNZERO set\n", __func__); + + munmap(mem, mem_size); + + /* Test with huge page if user_zero_page is set to 1 */ + if (!is_use_zero_page_set()) { + ksft_test_result_skip("%s use_zero_page not supported or set to 1\n", __func__); + return; + } + + mem_size = 10 * hpage_size; + mem = memalign(hpage_size, mem_size); + if (!mem) + ksft_exit_fail_msg("error nomem\n"); + + ret = madvise(mem, mem_size, MADV_HUGEPAGE); + if (!ret) { + for (i = 0; i < mem_size; i += hpage_size) + (void)((volatile char *)mem)[i]; + + ret = pagemap_ioctl(mem, mem_size, &vec, 1, 0, + (mem_size / page_size), PAGE_IS_PFNZERO, 0, 0, PAGE_IS_PFNZERO); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && LEN(vec) == (mem_size / page_size), + "%s all huge pages must have PFNZERO set\n", __func__); + + free(mem); + } else { + ksft_test_result_skip("%s huge page not supported\n", __func__); + } +} + int main(int __attribute__((unused)) argc, char *argv[]) { int shmid, buf_size, fd, i, ret; @@ -1494,7 +1575,7 @@ int main(int __attribute__((unused)) argc, char *argv[]) if (init_uffd()) ksft_exit_pass();

- ksft_set_plan(115); + ksft_set_plan(117);

page_size = getpagesize(); hpage_size = read_pmd_pagesize(); @@ -1669,6 +1750,9 @@ int main(int __attribute__((unused)) argc, char *argv[]) /* 16. Userfaultfd tests */ userfaultfd_tests();

+ /* 17. ZEROPFN tests */ + zeropfn_tests(); + close(pagemap_fd); ksft_exit_pass(); }