From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DAB123815E4; Fri, 2 Oct 2026 08:44:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790930644; cv=none; b=k1ovLIZmYM7pTkElWOkS73rqh0QguOuVYdpJj4yMowoC61JpJK+GooJg58A/DziE62z0g+Q/qO7DEgC20bjhkQWyeOKQtvoRDGW9WfXzFGPVvSb/H5hpb50UzySyET7uLBUyr/LE4ZBjBVu4qVsB9FY42IJLbGTAMHezCfQ0Abg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790930644; c=relaxed/simple; bh=WMXtorft3yFSsxaaQVsOoB9M+UsRVtahEneyXQcysGY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=n/o0uDU7Rsgu63ai5xx0KvZWJCVpWKAOhEbJikeVIxO0bgevHej3FpPtf0xpRLrcMbzD1QFYjvTk7ew4RoBUms2nTEt30Ijl5wenj3ygThWfR5CVrEBVDakNtzyormJpPbzh6opMNf3UvqIfHYqaOYDoPbusSnc/lx1Eq3RED9w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Vwe8P+39; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Vwe8P+39" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 858461F000FF; Fri, 2 Oct 2026 08:43:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790930642; bh=QaW3NvlDbie2nX8q04QLao6HBP5b6PgxRU/jNxrvHlo=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Vwe8P+39JCuHBizogmo2GNh1ALOKZtDQnio60+ojHg0sgpeiqScLp79z3mbw02V8F EYxN83kKfoU1dBWiYlTSNvqPO1sv2qLGQOHtGQ88RqyFySjslidqooaKnggLK/gJKG IWC5bqdlh9R7rDJ83vR8KTnnawGa9boU4Lb7HKydbTNBsoXeXWf2WMnkMILp6bICUN iHO/PMicuO4lycVHpnBubmnWdEzmOyVRE765syr056W+9jA4+6LnbRxAw4zEa6ohWa 6CAE+VUsdlJvbi6bS41ZcL7w0M7FG61svR56MHeK92o8dhMmvZCsTExm2N2AYdnoxH W1EwRBuRDq0NQ== Date: Fri, 2 Oct 2026 09:43:55 +0100 From: "Lorenzo Stoakes (ARM)" To: Yeoreum Yun Cc: Andrew Morton , David Hildenbrand , Zi Yan , Baolin Wang , "Liam R. 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, Sarthak Sharma Subject: Re: [PATCH v9 2/4] kselftest: mm: replace usage of /proc/self/smaps for __check_pmd_huge() Message-ID: References: <20261001-fix_split-v9-0-0f4ba8bbdbdf@arm.com> <20261001-fix_split-v9-2-0f4ba8bbdbdf@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20261001-fix_split-v9-2-0f4ba8bbdbdf@arm.com> On Thu, Oct 01, 2026 at 10:17:52PM +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_pmd_huge() > helpers incorrectly require the address returned by memalign() to > match the VMA start address reported in /proc/self/smaps. > > Instead of relying on /proc/self/smaps, use /proc/self/pagemap and > /proc/kpageflags to detect huge-page mappings checking PAGE_IS_HUGE > and PAGE_IS_FILE according to type of huge page. > > Since shmem pages are also file-backed, simply check whether the page > is file-backed. > > Fixes: 642bc52aed9c ("selftests: vm: bring common functions to a new file") > Suggested-by: David Hildenbrand (Arm) > Reviewed-by: Sarthak Sharma > Reviewed-by: Baolin Wang > Acked-by: David Hildenbrand (Arm) > Tested-by: Baolin Wang > Signed-off-by: Yeoreum Yun LGTM so: Acked-by: Lorenzo Stoakes (ARM) Thanks for doing this! :) > --- > tools/testing/selftests/mm/vm_util.c | 78 ++++++++++++++++++++++-------------- > 1 file changed, 49 insertions(+), 29 deletions(-) > > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > index a0ab78ceedb1..a3c3a2706c22 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -351,24 +351,6 @@ 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) > { > @@ -410,20 +392,51 @@ static bool check_large_folios(void *addr, size_t len, int nr_hpages, > return ret; > } > > -bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > +enum check_huge_type { > + CHECK_HUGE_ANON, > + CHECK_HUGE_FILE, > +}; > + > +static bool check_huge_type(uint64_t categories, enum check_huge_type type) > { > - uint64_t pmd_pagesize = read_pmd_pagesize(); > + const bool file = categories & PAGE_IS_FILE; > > - if (!pmd_pagesize) > - ksft_exit_fail_msg("reading PMD pagesize failed\n"); > + switch (type) { > + case CHECK_HUGE_ANON: > + return !file; > + case CHECK_HUGE_FILE: > + return file; > + } > > - if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "AnonHugePages: ", nr_hpages, hpage_size); > + return false; > +} > > - return check_large_folios(addr, len, nr_hpages, hpage_size); > +static bool __check_pmd_huge(void *addr, size_t len, int nr_hpages, > + uint64_t hpage_size, enum check_huge_type type) > +{ > + int pagemap_fd; > + int nr_pmd_mappings = 0; > + uint64_t categories; > + char *start = addr; > + char *end = start + len; > + > + pagemap_fd = open(PAGEMAP_PATH, O_RDONLY); > + if (pagemap_fd < 0) > + ksft_exit_fail_perror("open pagemap"); > + > + for (; start < end; start += hpage_size) { > + categories = pagemap_scan_get_categories(pagemap_fd, start); > + if (!(categories & PAGE_IS_HUGE)) > + continue; > + if (check_huge_type(categories, type)) > + nr_pmd_mappings++; > + } > + close(pagemap_fd); > + > + return nr_hpages == nr_pmd_mappings; > } > > -bool check_huge_file(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(); > > @@ -431,12 +444,13 @@ bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > ksft_exit_fail_msg("reading PMD pagesize failed\n"); > > if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "FilePmdMapped:", nr_hpages, hpage_size); > + return __check_pmd_huge(addr, len, nr_hpages, hpage_size, > + CHECK_HUGE_ANON); > > 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) > +bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size) > { > uint64_t pmd_pagesize = read_pmd_pagesize(); > > @@ -444,11 +458,17 @@ bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size > ksft_exit_fail_msg("reading PMD pagesize failed\n"); > > if (hpage_size == pmd_pagesize) > - return __check_pmd_huge(addr, "ShmemPmdMapped:", nr_hpages, hpage_size); > + return __check_pmd_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_file(addr, len, nr_hpages, hpage_size); > +} > + > int64_t allocate_transhuge(void *ptr, int pagemap_fd) > { > uint64_t ent[2]; > > -- > 2.43.0 > -- Cheers, Lorenzo