On Thu, Aug 20, 2026 at 08:40:16PM +0100, Yeoreum Yun wrote: > Since glibc commit 321e1fc73f (“malloc: Enable 2MB THP by default on > AArch64”), > glibc may call madvise(MADV_HUGEPAGE) for sufficiently large allocations > made by memalign(). > > The underlying VMA may start at a different address from the aligned > address returned by memalign(). Furthermore, a subsequent > madvise(MADV_HUGEPAGE) call does not split the VMA because the flag is > already set. > > This causes split_huge_page_test to fail because the check_huge_xxx() > helpers incorrectly require the address returned by memalign() to > match the VMA start address reported in /proc/self/smaps. > > Fix this by using /proc/self/pagemap and /proc/kpageflags instead of > /proc/self/smaps to detect huge pages and change the meaning of > check_huge_xxx()'s nr_hpages argument: > > - nr_hpages > 0: check all of pages in the range are huge page. > - nr_hpages < 0: check all of pages in the range are not huge page. > - nr_hpages == 0: invalid. > > Reported-by: David Hildenbrand (Arm) <[email protected]> > Signed-off-by: Yeoreum Yun <[email protected]> > --- > tools/testing/selftests/mm/khugepaged.c | 26 ++--- > tools/testing/selftests/mm/split_huge_page_test.c | 6 +- > tools/testing/selftests/mm/vm_util.c | 135 > ++++++++++++++++++---- > tools/testing/selftests/mm/vm_util.h | 1 + > 4 files changed, 131 insertions(+), 37 deletions(-) > > diff --git a/tools/testing/selftests/mm/khugepaged.c > b/tools/testing/selftests/mm/khugepaged.c > index 10e8dedcb087d..2e4665e6d5852 100644 > --- a/tools/testing/selftests/mm/khugepaged.c > +++ b/tools/testing/selftests/mm/khugepaged.c > @@ -533,7 +533,7 @@ static void __madvise_collapse(const char *msg, char *p, > int nr_hpages, > ret = madvise_collapse_retry(p, nr_hpages * hpage_pmd_size); > if (((bool)ret) == expect) > fail("Fail: Bad return value"); > - else if (!ops->check_huge(p, expect ? nr_hpages : 0)) > + else if (!ops->check_huge(p, expect ? nr_hpages : -nr_hpages)) > fail("Fail: check_huge()"); > else > success("OK"); > @@ -545,7 +545,7 @@ static void madvise_collapse(const char *msg, char *p, > int nr_hpages, > struct mem_ops *ops, bool expect) > { > /* Sanity check */ > - if (!ops->check_huge(p, 0)) > + if (!ops->check_huge(p, -nr_hpages)) > ksft_exit_fail_msg("Unexpected huge page\n"); > __madvise_collapse(msg, p, nr_hpages, ops, expect); > } > @@ -558,7 +558,7 @@ static bool wait_for_scan(const char *msg, char *p, int > nr_hpages, > int timeout = 6; /* 3 seconds */ > > /* Sanity check */ > - if (!ops->check_huge(p, 0)) > + if (!ops->check_huge(p, -nr_hpages)) > ksft_exit_fail_msg("Unexpected huge page\n"); > > madvise(p, nr_hpages * hpage_pmd_size, MADV_HUGEPAGE); > @@ -605,7 +605,7 @@ static void khugepaged_collapse(const char *msg, char *p, > int nr_hpages, > if (ops != &__anon_ops) > ops->fault(p, 0, nr_hpages * hpage_pmd_size); > > - if (ops->check_huge(p, expect ? nr_hpages : 0)) > + if (ops->check_huge(p, expect ? nr_hpages : -nr_hpages)) > success("OK"); > else > fail("Fail"); > @@ -643,7 +643,7 @@ static void alloc_at_fault(void) > > madvise(p, page_size, MADV_DONTNEED); > ksft_print_msg("Split huge PMD on MADV_DONTNEED..."); > - if (check_huge_anon(p, 0, hpage_pmd_size)) > + if (check_huge_anon(p, -1, hpage_pmd_size)) > success("OK"); > else > fail("Fail"); > @@ -815,7 +815,7 @@ static void collapse_single_pte_entry_compound(struct > collapse_context *c, struc > madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE); > ksft_print_msg("Split huge page leaving single PTE mapping compound > page..."); > madvise(p + page_size, hpage_pmd_size - page_size, MADV_DONTNEED); > - if (ops->check_huge(p, 0)) > + if (ops->check_huge(p, -1)) > success("OK"); > else > fail("Fail"); > @@ -836,7 +836,7 @@ static void collapse_full_of_compound(struct > collapse_context *c, struct mem_ops > ksft_print_msg("Split huge page leaving single PTE page table full of > compound pages..."); > madvise(p, page_size, MADV_NOHUGEPAGE); > madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE); > - if (ops->check_huge(p, 0)) > + if (ops->check_huge(p, -1)) > success("OK"); > else > fail("Fail"); > @@ -903,7 +903,7 @@ static void collapse_fork(struct collapse_context *c, > struct mem_ops *ops) > > ksft_print_msg("Allocate small page..."); > ops->fault(p, 0, page_size); > - if (ops->check_huge(p, 0)) > + if (ops->check_huge(p, -1)) > success("OK"); > else > fail("Fail"); > @@ -911,7 +911,7 @@ static void collapse_fork(struct collapse_context *c, > struct mem_ops *ops) > ksft_print_msg("Share small page over fork()..."); > if (!fork()) { > /* Do not touch settings on child exit */ > - if (ops->check_huge(p, 0)) > + if (ops->check_huge(p, -1)) > success("OK"); > else > fail("Fail"); > @@ -929,7 +929,7 @@ static void collapse_fork(struct collapse_context *c, > struct mem_ops *ops) > exit_status = WEXITSTATUS(wstatus); > > ksft_print_msg("Check if parent still has small page..."); > - if (ops->check_huge(p, 0)) > + if (ops->check_huge(p, -1)) > success("OK"); > else > fail("Fail"); > @@ -955,7 +955,7 @@ static void collapse_fork_compound(struct > collapse_context *c, struct mem_ops *o > ksft_print_msg("Split huge page PMD in child process..."); > madvise(p, page_size, MADV_NOHUGEPAGE); > madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE); > - if (ops->check_huge(p, 0)) > + if (ops->check_huge(p, -1)) > success("OK"); > else > fail("Fail"); > @@ -1003,7 +1003,7 @@ static void collapse_max_ptes_shared(struct > collapse_context *c, struct mem_ops > ksft_print_msg("Trigger CoW on page %d of %d...", > hpage_pmd_nr - max_ptes_shared - 1, > hpage_pmd_nr); > ops->fault(p, 0, (hpage_pmd_nr - max_ptes_shared - 1) * > page_size); > - if (ops->check_huge(p, 0)) > + if (ops->check_huge(p, -1)) > success("OK"); > else > fail("Fail"); > @@ -1016,7 +1016,7 @@ static void collapse_max_ptes_shared(struct > collapse_context *c, struct mem_ops > hpage_pmd_nr - max_ptes_shared, hpage_pmd_nr); > ops->fault(p, 0, (hpage_pmd_nr - max_ptes_shared) * > page_size); > - if (ops->check_huge(p, 0)) > + if (ops->check_huge(p, -1)) > success("OK"); > else > fail("Fail"); > diff --git a/tools/testing/selftests/mm/split_huge_page_test.c > b/tools/testing/selftests/mm/split_huge_page_test.c > index 99b45e5518199..4fcd330cf0726 100644 > --- a/tools/testing/selftests/mm/split_huge_page_test.c > +++ b/tools/testing/selftests/mm/split_huge_page_test.c > @@ -314,7 +314,7 @@ static void > verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int nr_hp > if (one_page[i] != (char)0) > ksft_exit_fail_msg("%ld byte corrupted\n", i); > > - if (!check_huge_anon(one_page, 0, pmd_pagesize)) > + if (!check_huge_anon(one_page, -nr_hpages, pmd_pagesize)) > ksft_exit_fail_msg("Still AnonHugePages not split\n"); > > rss_anon_after = rss_anon(); > @@ -372,7 +372,7 @@ static void split_pmd_thp_to_order(int order) > (pmd_order + 1))) > ksft_exit_fail_msg("Unexpected THP split\n"); > > - if (!check_huge_anon(one_page, 0, pmd_pagesize)) > + if (!check_huge_anon(one_page, -4, pmd_pagesize)) > ksft_exit_fail_msg("Still AnonHugePages not split\n"); > > ksft_test_result_pass("Split huge pages to order %d successful\n", > order); > @@ -746,7 +746,7 @@ static void split_thp_in_pagecache_to_order_at(size_t > fd_size, > goto out; > } > > - if (!check_huge_file(addr, 0, pmd_pagesize)) { > + if (!check_huge_file(addr, -(fd_size / pmd_pagesize), pmd_pagesize)) { > ksft_print_msg("Still FilePmdMapped not split\n"); > err = EXIT_FAILURE; > goto out; > diff --git a/tools/testing/selftests/mm/vm_util.c > b/tools/testing/selftests/mm/vm_util.c > index 311fc5b4513eb..166d5d79289f3 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -14,6 +14,8 @@ > #define PMD_SIZE_FILE_PATH > "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size" > #define SMAP_FILE_PATH "/proc/self/smaps" > #define STATUS_FILE_PATH "/proc/self/status" > +#define PAGEMAP_FILE_PATH "/proc/self/pagemap" > +#define KPAGEFLAGS_FILE_PATH "/proc/kpageflags" > #define MAX_LINE_LENGTH 500 > > unsigned int __page_size; > @@ -229,37 +231,128 @@ char *__get_smap_entry(void *addr, const char > *pattern, char *buf, size_t len) > return entry; > } > > -bool __check_huge(void *addr, char *pattern, int nr_hpages, > - uint64_t hpage_size) > -{ > - char buffer[MAX_LINE_LENGTH]; > - uint64_t thp = -1; > - char *entry; > - > - entry = __get_smap_entry(addr, pattern, buffer, sizeof(buffer)); > - if (!entry) > - goto err_out; > - > - if (sscanf(entry, "%9" SCNu64 " kB", &thp) != 1) > - ksft_exit_fail_msg("Reading smap error\n"); > - > -err_out: > - return thp == (nr_hpages * (hpage_size >> 10)); > -} > - > bool check_huge_anon(void *addr, int nr_hpages, uint64_t hpage_size) > { > - return __check_huge(addr, "AnonHugePages: ", nr_hpages, hpage_size); > + int i, pagemap_fd, nr = 0; > + uint64_t categories; > + bool expect_huge; > + > + if (nr_hpages == 0 || hpage_size == 0) > + return false; > + > + if (nr_hpages < 0) { > + nr_hpages = -nr_hpages; > + expect_huge = false; > + } else > + expect_huge = true; > + > + pagemap_fd = open(PAGEMAP_FILE_PATH, O_RDONLY); > + if (pagemap_fd < 0) > + ksft_exit_fail_msg("open pagemap: %s\n", strerror(errno)); > + > + for (i = 0; i < nr_hpages; i++, addr += hpage_size) { > + categories = pagemap_scan_get_categories(pagemap_fd, addr); > + if (!(categories & PAGE_IS_HUGE)) > + continue; > + if (categories & PAGE_IS_FILE) > + continue; > + nr++; > + } > + > + close(pagemap_fd); > + return expect_huge ? nr == nr_hpages : nr == 0; > } > > bool check_huge_file(void *addr, int nr_hpages, uint64_t hpage_size) > { > - return __check_huge(addr, "FilePmdMapped:", nr_hpages, hpage_size); > + int i, pagemap_fd, kpf_fd, nr = 0; > + unsigned long pfn; > + uint64_t categories, kpf; > + bool expect_huge; > + > + if (nr_hpages == 0 || hpage_size == 0) > + return false; > + > + if (nr_hpages < 0) { > + nr_hpages = -nr_hpages; > + expect_huge = false; > + } else > + expect_huge = true; > + > + pagemap_fd = open(PAGEMAP_FILE_PATH, O_RDONLY); > + if (pagemap_fd < 0) > + ksft_exit_fail_msg("open pagemap: %s\n", strerror(errno)); > + > + kpf_fd = open(KPAGEFLAGS_FILE_PATH, O_RDONLY); > + if (kpf_fd < 0) > + ksft_exit_fail_msg("open kpageflags: %s\n", strerror(errno)); > + > + for (i = 0; i < nr_hpages; i++, addr += hpage_size) { > + categories = pagemap_scan_get_categories(pagemap_fd, addr); > + pfn = pagemap_get_pfn(pagemap_fd, addr); > + if (pfn == -1UL) > + continue; > + if (pageflags_get(pfn, kpf_fd, &kpf)) > + ksft_exit_fail_msg("read kpageflags: %s\n", > strerror(errno)); > + if (!(categories & PAGE_IS_HUGE)) > + continue; > + if (!(categories & PAGE_IS_FILE)) > + continue; > + if (kpf & KPF_SWAPBACKED) > + continue; > + nr++; > + } > + > + close(pagemap_fd); > + close(kpf_fd); > + > + return expect_huge ? nr == nr_hpages : nr == 0; > } > > bool check_huge_shmem(void *addr, int nr_hpages, uint64_t hpage_size) > { > - return __check_huge(addr, "ShmemPmdMapped:", nr_hpages, hpage_size); > + int i, pagemap_fd, kpf_fd, nr = 0; > + unsigned long pfn; > + uint64_t categories, kpf; > + bool expect_huge; > + > + if (nr_hpages == 0 || hpage_size == 0) > + return false; > + > + if (nr_hpages < 0) { > + nr_hpages = -nr_hpages; > + expect_huge = true; > + } else > + expect_huge = false; > +
Oops... this part has mistaked compared with other function... I'll fix later... -- Sincerely, Yeoreum Yun
