From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C96282F0673; Mon, 24 Aug 2026 09:20:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787563223; cv=none; b=V801l+vWWPlihS48zFfnvf7wlGe0Samoc6wZpLlhdsgZtlEuY2ZIfw+P+M6n1SK+7hJDZ+FRQaDrEUxW3GmYRjwdnz2zQJvtLIIOGjBjZjml47ozFJZnMmfteg/a56ODtmmNRFeOmUoQK+dHg0itfeZTopZ9oTUHx2LFD+SCnNo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787563223; c=relaxed/simple; bh=Rvtrha3WTwJfTW7AGl4KCnnuSmmFePp1BK56VobH9xE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CC2rteBZK1M3LqKyKcUW8W4hvTEC4cDlr/yB/bbS3LbFe760vwl6BXGHoHJ0xdX+ZMY1bF2V5dyQIr4qpIcTzPEeFN2vGtRQJrlMdl0LjUmNxEeKUJGOtGJUbabdRkYowz4v5oK+/EwCrMwYqjwUUEkP+al86EYnrQ9wDYmYINU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=e1eo9w/4; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="e1eo9w/4" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B333E1682; Mon, 24 Aug 2026 02:20:10 -0700 (PDT) Received: from [10.164.19.33] (unknown [10.164.19.33]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 48C8B3F66F; Mon, 24 Aug 2026 02:20:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1787563214; bh=Rvtrha3WTwJfTW7AGl4KCnnuSmmFePp1BK56VobH9xE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=e1eo9w/4F3aeUbP3ylOLqmXreb1gqC5tm96XNjAdlcRRSjG12eqVCqr3IJnEbgJBj zpqIXpj9Frupixb9kRecyrH22PZUEnc5PVqJ3almuz0qWkOKQqxnSuLmKAYYEYVveq fuZWLqK8DRJc3Yn3nCJu/7Cp3uvr/WhmOfajoEPQ= Message-ID: Date: Mon, 24 Aug 2026 14:50:06 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper To: Yeoreum Yun , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260820-fix_split-v1-0-ab430c58c7cf@arm.com> <20260820-fix_split-v1-2-ab430c58c7cf@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: <20260820-fix_split-v1-2-ab430c58c7cf@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 21/08/26 1:10 am, 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. Replying to this because I saw my malloc commit pop up :) So IIUC the test is dependent on VMA boundaries. Therefore we shouldn't rely on a glibc function like memalign() which can do anything internally. I think in this case memalign is using one of the heaps, which reuses VMAs. Because I would expect mmap() to internally align the VMA start to 2M, as we handle this as a special case in kernel mmap code. > > 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) > Signed-off-by: Yeoreum Yun > --- > 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; > + > + 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; > } > > 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 ea8fc8fdf0eb0..0a1627f36efc3 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) >