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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/2] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper Message-ID: References: <20260828-fix_split-v3-0-374022586a4b@arm.com> <20260828-fix_split-v3-2-374022586a4b@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260828-fix_split-v3-2-374022586a4b@arm.com> X-Stat-Signature: ejziq39gh8ess47szxa4ixrnizgidpbp X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 98E0018000C X-Rspam-User: X-HE-Tag: 1787909428-905855 X-HE-Meta: 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 k7m6fIui AgLyjZHYb0M/RrVeGgUWjHzTwLxBkp0uvlAWki7H+znXt45FRbymXQZcKZt0FxfJ8lnxlM/uUHNtY+Z3BbIwYFvtVwHZEd3++Ij+Jg8/4NRQVZ5QuV9oWNqZUn7Mjg5EtaekyHHy/5JtAW6xOlr3s0Qr4jYhAZFlXDeWrrS7CFBI7isHdVTBPcHVlkD+aOGeefJBdoULppvqC/BKr2FKplgF5rqM0lp39NDok332QR9mPkeS0PSWTzoR/3reJjdySyRZ2gPISDj9I9+Gvchbj8ZU2h0YVhZtEzDsosCK8Z9r3WNSnzeVWZGlIJKi8YQ2FTYAlmuLMudn6cI2Qwixn/+32LkWUVZefxouy5eQV7oqhCd23FMuq3GRhWr+LASl4+5H9fO90beCPei90pnWqmNknLtGjlZece4QRcOcypgIV76PK84kJqziDgA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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) Should always have a Closes: tag if Reported-by: ideally. > Suggested-by: Zi Yan > Signed-off-by: Yeoreum Yun Generally looks reasonable to me, some nits above and below though :) Acked-by: Lorenzo Stoakes (ARM) > --- > 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