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Message-ID: <20250707073321.106431-1-usama.anjum@collabora.com>
Date: Mon, 7 Jul 2025 12:33:20 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Shuah Khan <shuah@...nel.org>
Cc: Muhammad Usama Anjum <usama.anjum@...labora.com>,
kernel@...labora.com,
David Hildenbrand <david@...hat.com>,
linux-mm@...ck.org,
linux-kselftest@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v3] selftests/mm: pagemap_scan ioctl: add PFN ZERO test cases
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@...hat.com>
Signed-off-by: Muhammad Usama Anjum <usama.anjum@...labora.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
Changes sice v2:
- Move zero page detection code out to vm_util and use that
- Use mmap instead of memalign to allocate hugepage
---
tools/testing/selftests/mm/cow.c | 27 +-------
tools/testing/selftests/mm/pagemap_ioctl.c | 72 +++++++++++++++++++++-
tools/testing/selftests/mm/vm_util.c | 23 +++++++
tools/testing/selftests/mm/vm_util.h | 2 +
4 files changed, 95 insertions(+), 29 deletions(-)
diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
index b6cfe0a4b7dfd..b26bbf6ec4617 100644
--- a/tools/testing/selftests/mm/cow.c
+++ b/tools/testing/selftests/mm/cow.c
@@ -72,31 +72,6 @@ static int detect_thp_sizes(size_t sizes[], int max)
return count;
}
-static void detect_huge_zeropage(void)
-{
- int fd = open("/sys/kernel/mm/transparent_hugepage/use_zero_page",
- O_RDONLY);
- size_t enabled = 0;
- char buf[15];
- int ret;
-
- if (fd < 0)
- return;
-
- ret = pread(fd, buf, sizeof(buf), 0);
- if (ret > 0 && ret < sizeof(buf)) {
- buf[ret] = 0;
-
- enabled = strtoul(buf, NULL, 10);
- if (enabled == 1) {
- has_huge_zeropage = true;
- ksft_print_msg("[INFO] huge zeropage is enabled\n");
- }
- }
-
- close(fd);
-}
-
static bool range_is_swapped(void *addr, size_t size)
{
for (; size; addr += pagesize, size -= pagesize)
@@ -1791,7 +1766,7 @@ int main(int argc, char **argv)
}
nr_hugetlbsizes = detect_hugetlb_page_sizes(hugetlbsizes,
ARRAY_SIZE(hugetlbsizes));
- detect_huge_zeropage();
+ has_huge_zeropage = detect_huge_zeropage();
ksft_set_plan(ARRAY_SIZE(anon_test_cases) * tests_per_anon_test_case() +
ARRAY_SIZE(anon_thp_test_cases) * tests_per_anon_thp_test_case() +
diff --git a/tools/testing/selftests/mm/pagemap_ioctl.c b/tools/testing/selftests/mm/pagemap_ioctl.c
index 57b4bba2b45f3..059c6d5f971e7 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>
@@ -34,8 +35,8 @@
#define PAGEMAP "/proc/self/pagemap"
int pagemap_fd;
int uffd;
-unsigned int page_size;
-unsigned int hpage_size;
+size_t page_size;
+size_t hpage_size;
const char *progname;
#define LEN(region) ((region.end - region.start)/page_size)
@@ -1480,6 +1481,68 @@ static void transact_test(int page_size)
extra_thread_faults);
}
+void zeropfn_tests(void)
+{
+ unsigned long long mem_size;
+ struct page_region vec;
+ int i, ret;
+ char *mmap_mem, *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 (!detect_huge_zeropage()) {
+ ksft_test_result_skip("%s use_zero_page not supported or set to 1\n", __func__);
+ return;
+ }
+
+ mem_size = 2 * hpage_size;
+ mmap_mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (mmap_mem == MAP_FAILED)
+ ksft_exit_fail_msg("error nomem\n");
+
+ /* We need a THP-aligned memory area. */
+ mem = (char *)(((uintptr_t)mmap_mem + hpage_size) & ~(hpage_size - 1));
+
+ ret = madvise(mem, hpage_size, MADV_HUGEPAGE);
+ if (!ret) {
+ char tmp = *mem;
+
+ asm volatile("" : "+r" (tmp));
+
+ ret = pagemap_ioctl(mem, hpage_size, &vec, 1, 0,
+ 0, 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) == (hpage_size / page_size),
+ "%s all huge pages must have PFNZERO set\n", __func__);
+ } else {
+ ksft_test_result_skip("%s huge page not supported\n", __func__);
+ }
+
+ munmap(mmap_mem, mem_size);
+}
+
int main(int __attribute__((unused)) argc, char *argv[])
{
int shmid, buf_size, fd, i, ret;
@@ -1494,7 +1557,7 @@ 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 +1732,9 @@ int main(int __attribute__((unused)) argc, char *argv[])
/* 16. Userfaultfd tests */
userfaultfd_tests();
+ /* 17. ZEROPFN tests */
+ zeropfn_tests();
+
close(pagemap_fd);
ksft_exit_pass();
}
diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index a36734fb62f38..dde9e8ab4dc46 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -424,3 +424,26 @@ bool check_vmflag_io(void *addr)
flags += flaglen;
}
}
+
+bool detect_huge_zeropage(void)
+{
+ int fd = open("/sys/kernel/mm/transparent_hugepage/use_zero_page",
+ O_RDONLY);
+ bool enabled = 0;
+ char buf[15];
+ int ret;
+
+ if (fd < 0)
+ return 0;
+
+ ret = pread(fd, buf, sizeof(buf), 0);
+ if (ret > 0 && ret < sizeof(buf)) {
+ buf[ret] = 0;
+
+ if (strtoul(buf, NULL, 10) == 1)
+ enabled = 1;
+ }
+
+ close(fd);
+ return enabled;
+}
diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
index 6effafdc4d8a2..ca4c1f78ce18c 100644
--- a/tools/testing/selftests/mm/vm_util.h
+++ b/tools/testing/selftests/mm/vm_util.h
@@ -74,6 +74,8 @@ int uffd_register_with_ioctls(int uffd, void *addr, uint64_t len,
unsigned long get_free_hugepages(void);
bool check_vmflag_io(void *addr);
+bool detect_huge_zeropage(void);
+
/*
* On ppc64 this will only work with radix 2M hugepage size
*/
--
2.43.0
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