From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EB0BAF46102 for ; Mon, 23 Mar 2026 12:48:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 472A06B0005; Mon, 23 Mar 2026 08:48:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 44A116B008A; Mon, 23 Mar 2026 08:48:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 360996B008C; Mon, 23 Mar 2026 08:48:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 24B0E6B0005 for ; Mon, 23 Mar 2026 08:48:21 -0400 (EDT) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id D152D5BF44 for ; Mon, 23 Mar 2026 12:48:20 +0000 (UTC) X-FDA: 84577305960.06.7343DF6 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf14.hostedemail.com (Postfix) with ESMTP id B5C5410000D for ; Mon, 23 Mar 2026 12:48:18 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=PaQystNC; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774270099; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=IokPiS0CL2SnimYfixKxpfLEzjMGaCp6NQfNP7BKZag=; b=bkS+MAXfpGqAd/61wuYtSqhYEihXYw7fbvDr8iQ2HSgRpG/Rp/Vk0anEMU/QA3L1ssxU3Z R3b7lPO6QoTRCmL0ffyelsp7PRDmaa77/nvgFBbA2dTGFcLNjVju1YloHjIIVoZ2Gm1XUd Lu8UoEziWAXtgiIOpCL2D8zfcYGjLCs= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=PaQystNC; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774270099; a=rsa-sha256; cv=none; b=Sb+KRQVxN3m4VcWcQ0DqZAJactip/NBSGWTLMGZfpgwkSKKHKaDtJljcMY0DX0P8vdsxGH u5t5/D7FLvEPP6P23RwooEAuRae3ZFWev3Gpz4ujBXq0bHPP/WnUkXAqaX0B5JccnaQCQr ooxXXFEDO15H1whIC06Ac0wy/bgavLA= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 1D86560103; Mon, 23 Mar 2026 12:48:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D6E6C2BCB7; Mon, 23 Mar 2026 12:48:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774270097; bh=cS3/NknCLhK8WaSljXNkknygeOm2tTxLjOQjsgzkLNk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=PaQystNCi3tC9eeQ55SD2194neCmAcWHrQNqYEeBHGqp2HRInR1FE3LQKoMFqPD8n vH4CIQVeprMEHI/h7fN5jqkDBg2cizwnJ2XIVXLCBuNkNnBvdYhv03yyqEivYuJVd/ Oq/GoixmUMDYEY7TMREqB248SN/ZQFsKBlqYN8dw/elHJwAld3lbbpRNarcFWFMenf o/tvdpCvX6Hx/Plud55Ly1kAceg3Iq1xCTl+GcYC+2EwZWbbNYRHQvnJrfF809QOXg qC3pgOIldXNir+lrzdulBx8c9NWv2lUsO2B4k5nqie2at4LV0BuaED9mFQXl01QShb y9hlNoFqeaHQQ== Message-ID: Date: Mon, 23 Mar 2026 13:48:12 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] selftests/mm: add folio_split() and filemap_get_entry() race test To: Zi Yan , Andrew Morton Cc: Lorenzo Stoakes , Hugh Dickins , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Matthew Wilcox , Bas van Dijk , Eero Kelly , Andrew Battat , Adam Bratschi-Kaye , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20260320142219.375118-1-ziy@nvidia.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: <20260320142219.375118-1-ziy@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 1i3rr6pd8kcxgw11k71wzex5urnoo16j X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: B5C5410000D X-HE-Tag: 1774270098-578832 X-HE-Meta: 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 yjOdH3tt mLPgKaD1fCFOjObFvVUUlxMdWYskfd1Z6yZ6acFlLfzFtrx9xqNu/Bz1RlFF28+FhgZlZeR03bM6nsQs3CFu3P5WKbTxShO5CL7FjwbWDi7lWMzrfG+z93UNj4whji/kL5jyImkAeYa2bw7i/7JFqQiROWERFJuRmXOcG5zdcVtkqlXg2r4Lgi/fI9GLJXGy2W+/BYllMgRfq2pPPPfmZRjdRvZBzB/A98Y4+WC2LRl+20kkbiJ/pQ05Jh2YTa2eg/B3czJQMp0q62mCSVFCAM74/+WuF2gbX25eXYS4WzKZxKdqWijjhtch3/LPBq8+lmIE+Y6cQ8dK5Rd2CLAqb5BOAmCksIvcqKlDEDUM7IBQoljp4eeoG4+0Mjkati+fg1x6L++YHM3SvRipUKCjvNmbzpTTv9yz61lm3T7r9O3qpcpfByK97IEwz/64bph6kAdngXQrFep3VVOY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/20/26 15:22, Zi Yan wrote: > The added folio_split_race_test is a modified C port of the race condition > test from [1]. The test creates shmem huge pages, where the main thread > punches holes in the shmem to cause folio_split() in the kernel and > a set of 16 threads reads the shmem to cause filemap_get_entry() in the > kernel. filemap_get_entry() reads the folio and xarray split by > folio_split() locklessly. The original test[2] is written in rust and uses > memfd (shmem backed). This C port uses shmem directly and use a single > process. > > Note: the initial rust to C conversion is done by Cursor. > > Link: https://lore.kernel.org/all/CAKNNEtw5_kZomhkugedKMPOG-sxs5Q5OLumWJdiWXv+C9Yct0w@mail.gmail.com/ [1] > Link: https://github.com/dfinity/thp-madv-remove-test [2] > Signed-off-by: Bas van Dijk > Signed-off-by: Adam Bratschi-Kaye You are likely missing two Co-developed-by. See Documentation/process/submitting-patches.rst on how to handle such SOBs. > Signed-off-by: Zi Yan > --- > From V3: > 1. fixed for loop stepping issue > 2. used PRIu64 instead of %zu for uint64_t. > > From V2: > 1. simplied the program by removing fork. > > From V1: > 1. added prctl(PR_SET_PDEATHSIG, SIGTERM) to avoid child looping > forever. > 2. removed page_idx % PUNCH_INTERVAL >= 0, since it is a nop. Added a > comment. > 3. added a child process status check to prevent parent looping forever > and record that as a failure. > 4. used ksft_exit_skip() instead of ksft_finished() when the program is > not running as root. > 5. restored THP settings properly when the program exits abnormally. > tools/testing/selftests/mm/Makefile | 1 + > .../selftests/mm/folio_split_race_test.c | 293 ++++++++++++++++++ > tools/testing/selftests/mm/run_vmtests.sh | 2 + > 3 files changed, 296 insertions(+) > create mode 100644 tools/testing/selftests/mm/folio_split_race_test.c > > diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile > index 7a5de4e9bf520..cd24596cdd27e 100644 > --- a/tools/testing/selftests/mm/Makefile > +++ b/tools/testing/selftests/mm/Makefile > @@ -105,6 +105,7 @@ TEST_GEN_FILES += droppable > TEST_GEN_FILES += guard-regions > TEST_GEN_FILES += merge > TEST_GEN_FILES += rmap > +TEST_GEN_FILES += folio_split_race_test > > ifneq ($(ARCH),arm64) > TEST_GEN_FILES += soft-dirty > diff --git a/tools/testing/selftests/mm/folio_split_race_test.c b/tools/testing/selftests/mm/folio_split_race_test.c > new file mode 100644 > index 0000000000000..c264cc625a7cb > --- /dev/null > +++ b/tools/testing/selftests/mm/folio_split_race_test.c > @@ -0,0 +1,293 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * The test creates shmem PMD huge pages, fills all pages with known patterns, > + * then continuously verifies non-punched pages with 16 threads. Meanwhile, the > + * main thread punches holes via MADV_REMOVE on the shmem. > + * > + * It tests the race condition between folio_split() and filemap_get_entry(), > + * where the hole punches on shmem lead to folio_split() and reading the shmem > + * lead to filemap_get_entry(). > + */ > + > +#define _GNU_SOURCE > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include "vm_util.h" > +#include "kselftest.h" > +#include "thp_settings.h" [...] some comment son the main() part :) > +int main(void) > +{ > + struct thp_settings current_settings; > + bool failed = false; > + size_t failures; > + size_t iter; Why are iterations a "size_t" ? Similarly for "failures". Just use int / unsigned long? > + > + ksft_print_header(); > + > + if (!thp_is_enabled()) > + ksft_exit_skip("Transparent Hugepages not available\n"); Is checking thp_is_enabled() the right thing to do when you perform your own setup below either way? I think you should just use thp_available(). Then, configure THP accordingly below? > + > + if (geteuid() != 0) > + ksft_exit_skip("Please run the test as root\n"); > + > + thp_save_settings(); > + /* make sure thp settings are restored */ > + if (atexit(thp_settings_cleanup) != 0) > + ksft_exit_fail_msg("atexit failed\n"); > + > + signal(SIGINT, thp_cleanup_handler); > + signal(SIGTERM, thp_cleanup_handler); > + > + thp_read_settings(¤t_settings); > + current_settings.shmem_enabled = SHMEM_ADVISE; > + thp_write_settings(¤t_settings); > + > + ksft_set_plan(1); > + > + page_size = getpagesize(); > + pmd_pagesize = read_pmd_pagesize(); I wonder whether we should check for 0 here and skip the test (older kernels?). > + > + ksft_print_msg("folio split race test\n"); > + ksft_print_msg("===================================================\n"); > + ksft_print_msg("Shmem size: %" PRIu64 " MiB\n", FILE_SIZE / 1024 / 1024); > + ksft_print_msg("Total pages: %" PRIu64 "\n", TOTAL_PAGES); > + ksft_print_msg("Child readers: %d\n", NUM_READER_THREADS); > + ksft_print_msg("Punching every %dth to %dth page\n", PUNCH_INTERVAL, > + PUNCH_INTERVAL + PUNCH_SIZE_FACTOR); > + ksft_print_msg("Iterations: %d\n", NUM_ITERATIONS); I don't think printing static test information is that helpful. Do we need all that at all? > + > + for (iter = 1; iter <= NUM_ITERATIONS; iter++) { Why not start at 0? You know, to confuse less people :) for (iter = 0; iter < NUM_ITERATIONS; iter++) { > + failures = run_iteration(); "corrupted_pages" ? > + if (failures > 0) { > + failed = true; Do you really need that variable? > + ksft_print_msg( > + "FAILED on iteration %zu: %zu pages corrupted by MADV_REMOVE!\n", > + iter, failures); Can that simply be printed below? Like if (iter < NUM_ITERATIONS) { ksft_test_result_fail("Test failed on iterations %zu: %zu pages ...\n", iter + 1, corrupted_pages); } else { ksft_test_result_pass ... } > + break; > + } > + } > + > + if (failed) { > + ksft_test_result_fail("Test failed\n"); > + ksft_exit_fail(); > + } else { > + ksft_test_result_pass("All %d iterations passed\n", > + NUM_ITERATIONS); > + ksft_exit_pass(); > + } > + > + return 0; -- Cheers, David