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 47FCE3B05B2; Thu, 10 Sep 2026 10:21:04 +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=1789035665; cv=none; b=JdtD+9aQft0RRVN3a7YnluVXG25xlj2F+d/3Xk5g9iy2/IYiUEi0PiwNN6lqFW0a99BpGTO9UIDxbTvBpWD1HLXKBTnkb1Vt9A7FVPXugEopK8bCxDOGkSKNeRuqXzJcrWtwU9EkbFBn1KPbQdomIr9IB/VGtTkXQBF+tnKbo4g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789035665; c=relaxed/simple; bh=wM9NfSZD6O3T04Mhq9A1yZn+d/3E9jbY1u4IYz/CxeI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jjpU+K+vTo7ivmrf25JpjAHgcYMgoZFcE1QSEOTlfb13KJhRwNBEA33dHUPEJ6fudWiEF9xZlFlkjULZs2T2A1S3uIGZZIUmWDEdIIZUlVRC8VguZdDytRUHWFtTSTA4IkLqzhxR5De5kXD6ScS/LcVfgc2mqc6k5xCdrNAeU9k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XiLgP0iU; 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="XiLgP0iU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E81CA1F00898; Thu, 10 Sep 2026 10:20:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789035663; bh=VNqAmjn7vwuecUWun/yj3LWAkYuAP3u7AHtle9TvBmY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=XiLgP0iUsnOLzVKKvCt33C/duL0ZjMqv/RyWaXpMwHO+aUoP3TNxa2utHfFlAODHu DmOlmNl6rKZvn1EaUHf0D/ouerBwA1AdWaUok4+mrCeLEf88PbMTDWr6sOzQBi4D17 ngQpqWiIp0cCiHPiLsMNKo3NHa7W4e31E+X3Y7yfbi+83u3xxqYBxmJZW39jnuODZj kmCw6xTWUioYw3/CbjSkxdML86R6nAwyJ0EX4DvV718lQTaCFTgAArINxrA4iMPYxp EqUFHNB3AN/f4jNsnaH6S3ZILEK6UbH0GvZrJH86wy7xS7dVO/bDSKQiYRK1Wr4XU0 VRoAiXqnr9tEA== Message-ID: <956df69d-8c0a-420f-889e-7df2842605dc@kernel.org> Date: Thu, 10 Sep 2026 12:20:56 +0200 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 v5 2/3] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper To: Yeoreum Yun , Andrew Morton , Lorenzo Stoakes , 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 Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260907-fix_split-v5-0-822b810458bc@arm.com> <20260907-fix_split-v5-2-822b810458bc@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260907-fix_split-v5-2-822b810458bc@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 9/7/26 10:19, 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. > > Instead of relying on /proc/self/smaps, use /proc/self/pagemap and > /proc/kpageflags to detect huge-page mappings and large folios: > > 1. If hpage_size == pmd_pagesize, check PAGE_IS_HUGE instead of > using check_large_folios(), since only the mapping type matters. > This identifies PMD-mapped huge pages. > 2. Otherwise, use check_large_folios() to detect large folios. This > covers mTHP cases. > 3. Check the folio flags according to the type of huge page. > > Suggested-by: David Hildenbrand (Arm) > Suggested-by: Zi Yan > Reviewed-by: Zi Yan > Reviewed-by: Baolin Wang > Tested-by: Baolin Wang > Acked-by: Lorenzo Stoakes (ARM) > Signed-off-by: Yeoreum Yun > --- > 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..dc62ce84e143 100644 [...] > > - 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) > +{ > + const bool file = categories & PAGE_IS_FILE; > + const bool swapbacked = kpageflags & KPF_SWAPBACKED; > + > + switch (type) { > + case CHECK_HUGE_ANON: > + return !file; > + case CHECK_HUGE_FILE: > + return file && !swapbacked; > + case CHECK_HUGE_SHMEM: > + return file & swapbacked; > + } Why do we even need CHECK_HUGE_SHMEM? That's really just a legacy thing for using smaps to identify huge pages. It's sufficient to identify CHECK_HUGE_FILE if you know that you have shmem mapping. You will not arbitrarily have non-shmem folios in a shmem mapping :) > > - 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); No need to cleanup when exiting. > + 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; > } -- Cheers, David