On Fri, Aug 28, 2026 at 09:11:34AM +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.
Hmm, is the test correctly putting sentinels either side of the VMA? Any test that doesn't risks flaking due to unwanted VMA merges. > > Fix this by using /proc/self/pagemap and /proc/kpageflags instead of > /proc/self/smaps to detect huge pages. You should probably call out the fact you're doing some refactoring here also! > > Reported-by: David Hildenbrand (Arm) <[email protected]> Should always have a Closes: tag if Reported-by: ideally. > Suggested-by: Zi Yan <[email protected]> > Signed-off-by: Yeoreum Yun <[email protected]> Generally looks reasonable to me, some nits above and below though :) Acked-by: Lorenzo Stoakes (ARM) <[email protected]> > --- > tools/testing/selftests/mm/vm_util.c | 145 > ++++++++++++++++++++++------------- > tools/testing/selftests/mm/vm_util.h | 1 + > 2 files changed, 92 insertions(+), 54 deletions(-) > > diff --git a/tools/testing/selftests/mm/vm_util.c > b/tools/testing/selftests/mm/vm_util.c > index 4821a3563036..083b72d92b14 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -351,31 +351,13 @@ char *__get_smap_entry(void *addr, const char *pattern, > char *buf, size_t len) > return entry; > } > > -static bool __check_pmd_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)); > -} > - > -static bool check_large_folios(void *addr, size_t len, int nr_hpages, > - uint64_t hpage_size) > +static bool check_large_folios(int pagemap_fd, int kpageflags_fd, > + void *addr, size_t len, int nr_hpages, > + uint64_t hpage_size) > { > int order = 0, pagesize = getpagesize(); > unsigned int nr_pages = hpage_size / pagesize; > int orders[MAX_NR_ORDERS], status; > - int pagemap_fd, kpageflags_fd; > bool ret = false; > > if (!nr_pages) > @@ -386,15 +368,6 @@ static bool check_large_folios(void *addr, size_t len, > int nr_hpages, > ksft_exit_fail_msg("invalid order\n"); > > memset(orders, 0, sizeof(int) * MAX_NR_ORDERS); > - pagemap_fd = open(PAGEMAP_PATH, O_RDONLY); > - if (pagemap_fd == -1) > - ksft_exit_fail_msg("read pagemap fail\n"); > - > - kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY); > - if (kpageflags_fd == -1) { > - close(pagemap_fd); > - ksft_exit_fail_msg("read kpageflags fail\n"); > - } > > status = gather_folio_orders(addr, len, pagemap_fd, > kpageflags_fd, orders, MAX_NR_ORDERS); > @@ -405,48 +378,112 @@ static bool check_large_folios(void *addr, size_t len, > int nr_hpages, > ret = true; > > out: > - close(pagemap_fd); > - close(kpageflags_fd); > return ret; > } > > -bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t > hpage_size) > -{ > - uint64_t pmd_pagesize = read_pmd_pagesize(); > - > - if (!pmd_pagesize) > - ksft_exit_fail_msg("reading PMD pagesize failed\n"); > +enum check_huge_type { > + CHECK_HUGE_ANON, > + CHECK_HUGE_FILE, > + CHECK_HUGE_SHMEM, > +}; > > - if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "AnonHugePages: ", nr_hpages, > hpage_size); > +static bool check_huge_type(uint64_t categories, uint64_t kpageflags, > + enum check_huge_type type) > +{ > + bool file = categories & PAGE_IS_FILE; > + bool swapbacked = kpageflags & KPF_SWAPBACKED; NIT: nice to const these :) > + > + switch (type) { > + case CHECK_HUGE_ANON: > + return !file; > + case CHECK_HUGE_FILE: > + return file && !swapbacked; > + case CHECK_HUGE_SHMEM: > + return file & swapbacked; > + } > > - return check_large_folios(addr, len, nr_hpages, hpage_size); > + return false; > } > > -bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t > hpage_size) > +static bool __check_huge(void *addr, size_t len, int nr_hpages, > + uint64_t hpage_size, enum check_huge_type type) > { > - uint64_t pmd_pagesize = read_pmd_pagesize(); > + bool ret = false; > + int pagemap_fd, kpageflags_fd; > + int nr_pmd_mappings = 0; > + uint64_t pmd_pagesize, scan_mapping_size; > + uint64_t categories, kpf; > + unsigned long pfn; > + bool check_pmd_mapping, allow_nonpresent; > + char *start = addr; > + char *end = start + len; > > + pmd_pagesize = read_pmd_pagesize(); > if (!pmd_pagesize) > ksft_exit_fail_msg("reading PMD pagesize failed\n"); > > - if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "FilePmdMapped:", nr_hpages, > hpage_size); > + check_pmd_mapping = (hpage_size == pmd_pagesize); > + scan_mapping_size = (nr_hpages > 0) ? hpage_size : psize(); > + /* Some mTHP tests check a partially populated PMD-sized range. */ > + allow_nonpresent = (uint64_t)nr_hpages * hpage_size < len; > > - return check_large_folios(addr, len, nr_hpages, hpage_size); > + pagemap_fd = open(PAGEMAP_PATH, O_RDONLY); > + if (pagemap_fd < 0) > + ksft_exit_fail_msg("open pagemap fail\n"); > + > + kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY); > + if (kpageflags_fd < 0) { > + close(pagemap_fd); > + ksft_exit_fail_msg("open kpageflags fail\n"); > + } > + > + if (!check_pmd_mapping && > + !check_large_folios(pagemap_fd, kpageflags_fd, > + addr, len, nr_hpages, hpage_size)) > + goto out; > + > + for (; start < end; start += scan_mapping_size) { > + categories = pagemap_scan_get_categories(pagemap_fd, start); > + pfn = pagemap_get_pfn(pagemap_fd, start); > + if (pfn == -1UL) { > + if (!allow_nonpresent) > + goto out; > + else > + continue; > + } > + if (pageflags_get(pfn, kpageflags_fd, &kpf)) > + ksft_exit_fail_msg("read kpageflags: %s\n", > strerror(errno)); > + if (check_pmd_mapping && (categories & PAGE_IS_HUGE)) > + nr_pmd_mappings++; > + if (kpf & KPF_COMPOUND_TAIL) > + continue; > + if (!check_huge_type(categories, kpf, type)) > + goto out; > + } > + > + if (check_pmd_mapping && (nr_pmd_mappings != nr_hpages)) > + goto out; > + ret = true; > + > +out: > + close(pagemap_fd); > + close(kpageflags_fd); > + return ret; > } > > -bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t > hpage_size) > +bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t > hpage_size) > { > - uint64_t pmd_pagesize = read_pmd_pagesize(); > - > - if (!pmd_pagesize) > - ksft_exit_fail_msg("reading PMD pagesize failed\n"); > + return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_ANON); > +} > > - if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "ShmemPmdMapped:", nr_hpages, > hpage_size); > +bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t > hpage_size) > +{ > + return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_FILE); > +} > > - return check_large_folios(addr, len, nr_hpages, hpage_size); > +bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t > hpage_size) > +{ > + return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_SHMEM); > } > > int64_t allocate_transhuge(void *ptr, int pagemap_fd) > diff --git a/tools/testing/selftests/mm/vm_util.h > b/tools/testing/selftests/mm/vm_util.h > index 9a49af88702e..f19bd17817e5 100644 > --- a/tools/testing/selftests/mm/vm_util.h > +++ b/tools/testing/selftests/mm/vm_util.h > @@ -18,6 +18,7 @@ > #define PM_SWAP BIT_ULL(62) > #define PM_PRESENT BIT_ULL(63) > > +#define KPF_SWAPBACKED BIT_ULL(14) > #define KPF_COMPOUND_HEAD BIT_ULL(15) > #define KPF_COMPOUND_TAIL BIT_ULL(16) > #define KPF_HWPOISON BIT_ULL(19) > > -- > 2.43.0 > -- Cheers, Lorenzo
