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selftests/mm: add PAGEMAP_SCAN test for THP PMD holes

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Add coverage for the PMD-hole case fixed by "fs/proc/task_mmu: fix
PAGEMAP_SCAN written state for PMD holes": a MAP_PRIVATE|MAP_ANON THP that
is uffd-wp'd and then dropped with MADV_DONTNEED leaves a pmd_none hole
with no page table, which PAGEMAP_SCAN must still report as written.

Factor the populate/drop/scan-both-paths sequence out of
unpopulated_scan_test() into a helper, and add unpopulated_thp_scan_test()
that reuses it with a THP.

Include <linux/mman.h> for MADV_COLLAPSE; <sys/mman.h> lacks it on older
glibc (e.g. 2.34). Same approach as commit fd5295afae ("selftests/mm:
hmm-tests: include linux/mman.h to access MADV_COLLAPSE").

Link: https://lore.kernel.org/aljWYfPRCVc6IB2b@thinkstation
Link: https://lore.kernel.org/20260715144234.442721-3-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Cc: Muhammad Usama Anjum <usama.anjum@arm.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Zenghui Yu <zenghui.yu@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Assisted-by: Claude:claude-fable-5
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kiryl Shutsemau (Meta) 2026-07-15 15:42:34 +01:00 committed by Andrew Morton
parent e105f1aa27
commit fb0493ad1a
1 changed files with 83 additions and 35 deletions
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118
tools/testing/selftests/mm/pagemap_ioctl.c
View File

@ -8,6 +8,7 @@
#include <errno.h>
#include <malloc.h>
#include <linux/types.h>
#include <linux/mman.h>
#include <linux/memfd.h>
#include <linux/userfaultfd.h>
#include <linux/fs.h>
@ -1058,50 +1059,96 @@ static void test_simple(void)
* the generic path (reached e.g. via category_anyof_mask) must report every
* page written.
*/
/*
* Populate @mem (optionally collapsing it into a THP first), drop it with
* MADV_DONTNEED, then check PAGEMAP_SCAN reports the whole range written via
* both the fast and generic query paths. A dropped THP leaves a pmd_none hole
* with no page table, exercising pagemap_scan_pte_hole(); a base-page range
* leaves pte_none entries.
*/
static void unpopulated_written_test(const char *name, char *mem, long size,
bool use_thp)
{
long npages = size / page_size, fast = 0, slow = 0, ret;
struct page_region regions[16];
int i;
wp_init(mem, size);
/* Populate, optionally collapse to a THP, then drop it. */
memset(mem, 1, size);
if (use_thp &&
(madvise(mem, size, MADV_COLLAPSE) ||
!check_huge_anon(mem, size / hpage_size, hpage_size))) {
ksft_test_result_skip("%s could not form a THP\n", name);
goto out;
}
if (madvise(mem, size, MADV_DONTNEED)) {
ksft_test_result_fail("%s MADV_DONTNEED failed\n", name);
goto out;
}
/* Fast path: category_mask == return_mask == PAGE_IS_WRITTEN. */
ret = pagemap_ioctl(mem, size, regions, ARRAY_SIZE(regions), 0, 0,
PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN);
for (i = 0; ret > 0 && i < ret; i++)
fast += LEN(regions[i]);
/* Generic path: same query expressed via category_anyof_mask. */
ret = pagemap_ioctl(mem, size, regions, ARRAY_SIZE(regions), 0, 0,
0, PAGE_IS_WRITTEN, 0, PAGE_IS_WRITTEN);
for (i = 0; ret > 0 && i < ret; i++)
slow += LEN(regions[i]);
ksft_test_result(fast == npages && slow == npages,
"%s unpopulated range reported written by both paths (%ld, %ld of %ld)\n",
name, fast, slow, npages);
out:
wp_free(mem, size);
}
static void unpopulated_scan_test(void)
{
int npages = 16, i;
long mem_size = npages * page_size;
struct page_region regions[16];
long fast = 0, slow = 0, ret;
long mem_size = 16 * page_size;
char *mem;
mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (mem == MAP_FAILED)
ksft_exit_fail_msg("%s mmap failed\n", __func__);
if (mem == MAP_FAILED) {
ksft_test_result_skip("%s mmap failed\n", __func__);
return;
}
wp_init(mem, mem_size);
/* Populate, then drop: the ptes become pte_none without a marker. */
memset(mem, 1, mem_size);
if (madvise(mem, mem_size, MADV_DONTNEED))
ksft_exit_fail_msg("%s MADV_DONTNEED failed\n", __func__);
/* Fast path: category_mask == return_mask == PAGE_IS_WRITTEN. */
ret = pagemap_ioctl(mem, mem_size, regions, npages, 0, 0,
PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN);
if (ret < 0)
ksft_exit_fail_msg("%s fast scan failed\n", __func__);
for (i = 0; i < ret; i++)
fast += LEN(regions[i]);
/* Generic path: same query expressed via category_anyof_mask. */
ret = pagemap_ioctl(mem, mem_size, regions, npages, 0, 0,
0, PAGE_IS_WRITTEN, 0, PAGE_IS_WRITTEN);
if (ret < 0)
ksft_exit_fail_msg("%s generic scan failed\n", __func__);
for (i = 0; i < ret; i++)
slow += LEN(regions[i]);
ksft_test_result(fast == npages && slow == npages,
"%s unpopulated ptes reported written by both paths (%ld, %ld of %d)\n",
__func__, fast, slow, npages);
wp_free(mem, mem_size);
unpopulated_written_test(__func__, mem, mem_size, false);
munmap(mem, mem_size);
}
/*
* Same as unpopulated_scan_test(), but the range is a THP: a full-PMD
* MADV_DONTNEED leaves a pmd_none hole with no page table.
*/
static void unpopulated_thp_scan_test(void)
{
char *area, *mem;
if (!hpage_size) {
ksft_test_result_skip("%s THP not supported\n", __func__);
return;
}
/* Over-allocate so a PMD-aligned, THP-sized range fits inside. */
area = mmap(NULL, 2 * hpage_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (area == MAP_FAILED) {
ksft_test_result_skip("%s mmap failed\n", __func__);
return;
}
mem = (char *)(((unsigned long)area + hpage_size - 1) & ~(hpage_size - 1));
unpopulated_written_test(__func__, mem, hpage_size, true);
munmap(area, 2 * hpage_size);
}
int sanity_tests(void)
{
unsigned long long mem_size, vec_size;
@ -1610,7 +1657,7 @@ int main(int __attribute__((unused)) argc, char *argv[])
if (!hugetlb_setup_default(4))
ksft_print_msg("HugeTLB test will be skipped\n");
ksft_set_plan(118);
ksft_set_plan(119);
page_size = getpagesize();
hpage_size = read_pmd_pagesize();
@ -1790,6 +1837,7 @@ int main(int __attribute__((unused)) argc, char *argv[])
/* 18. Unpopulated pte scan-path consistency */
unpopulated_scan_test();
unpopulated_thp_scan_test();
close(pagemap_fd);
ksft_finished();