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 AA0C83A782F; Thu, 22 Jan 2026 17:02:46 +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=1769101371; cv=none; b=o7JZK1dim6Loy4zinaAPpxLVCWP4SuJgzgxYNcHXwwceJKKUV/9NoVDumecqkXGv+clLTQ9Tq6XdxZGoqniR7EGx6XK8hb0IVjK7v6YPFiVhafH0Gn/J6dKVviMpKLo942TldMcZMsMQ5SWuOL7eVUj+xF1wp217Bny0/b0AYEE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769101371; c=relaxed/simple; bh=3Zp9oZUvOKoIljBvArIWni49Effe1tdg49MfcrjnnJ0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=D1WhDO6JD0j3tI2ApJAVcGJx5O5Y9d46Q8EnRfSAIHY2XRjavwU5JhAhlaAZu5x2cd3JJgHny+lcwrWcSChkLhhiiTeDY69hCHeFen0Il7X8mylVSQTb2fxdKKsDCE8p96qs3GZ22tY+o/Mh6VrG9ZPkOVufbU0p8QZ+8y9D7a4= 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; 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 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 1813D1476; Thu, 22 Jan 2026 09:02:38 -0800 (PST) Received: from e123572-lin.arm.com (e123572-lin.cambridge.arm.com [10.1.194.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4F9203F632; Thu, 22 Jan 2026 09:02:43 -0800 (PST) From: Kevin Brodsky To: linux-mm@kvack.org, linux-kselftest@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Kevin Brodsky , Andrew Morton , David Hildenbrand , Dev Jain , Lorenzo Stoakes , Mark Brown , Ryan Roberts , Shuah Khan Subject: [PATCH v3 6/9] selftests/mm: introduce helper to read every page Date: Thu, 22 Jan 2026 17:02:21 +0000 Message-ID: <20260122170224.4056513-7-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20260122170224.4056513-1-kevin.brodsky@arm.com> References: <20260122170224.4056513-1-kevin.brodsky@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit FORCE_READ(*addr) ensures that the compiler will emit a load from addr. Several tests need to trigger such a load for a range of pages, ensuring that every page is faulted in, if it wasn't already. Introduce a new helper force_read_pages() that does exactly that and replace existing loops with a call to it. The step size (regular/huge page size) is preserved for all loops, except in split_huge_page_test. Reading every byte is unnecessary; we now read every huge page, matching the following call to check_huge_file(). Reviewed-by: Dev Jain Signed-off-by: Kevin Brodsky --- tools/testing/selftests/mm/hugetlb-madvise.c | 9 +-------- tools/testing/selftests/mm/pfnmap.c | 9 +++------ tools/testing/selftests/mm/split_huge_page_test.c | 6 +----- tools/testing/selftests/mm/vm_util.h | 7 +++++++ 4 files changed, 12 insertions(+), 19 deletions(-) diff --git a/tools/testing/selftests/mm/hugetlb-madvise.c b/tools/testing/selftests/mm/hugetlb-madvise.c index 05d9d2805ae4..5b12041fa310 100644 --- a/tools/testing/selftests/mm/hugetlb-madvise.c +++ b/tools/testing/selftests/mm/hugetlb-madvise.c @@ -47,14 +47,7 @@ void write_fault_pages(void *addr, unsigned long nr_pages) void read_fault_pages(void *addr, unsigned long nr_pages) { - unsigned long i; - - for (i = 0; i < nr_pages; i++) { - unsigned long *addr2 = - ((unsigned long *)(addr + (i * huge_page_size))); - /* Prevent the compiler from optimizing out the entire loop: */ - FORCE_READ(*addr2); - } + force_read_pages(addr, nr_pages, huge_page_size); } int main(int argc, char **argv) diff --git a/tools/testing/selftests/mm/pfnmap.c b/tools/testing/selftests/mm/pfnmap.c index f546dfb10cae..45b5f1cf6019 100644 --- a/tools/testing/selftests/mm/pfnmap.c +++ b/tools/testing/selftests/mm/pfnmap.c @@ -35,18 +35,15 @@ static void signal_handler(int sig) static int test_read_access(char *addr, size_t size, size_t pagesize) { - size_t offs; int ret; if (signal(SIGSEGV, signal_handler) == SIG_ERR) return -EINVAL; ret = sigsetjmp(sigjmp_buf_env, 1); - if (!ret) { - for (offs = 0; offs < size; offs += pagesize) - /* Force a read that the compiler cannot optimize out. */ - *((volatile char *)(addr + offs)); - } + if (!ret) + force_read_pages(addr, size/pagesize, pagesize); + if (signal(SIGSEGV, SIG_DFL) == SIG_ERR) return -EINVAL; diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c index 40799f3f0213..e0167111bdd1 100644 --- a/tools/testing/selftests/mm/split_huge_page_test.c +++ b/tools/testing/selftests/mm/split_huge_page_test.c @@ -652,11 +652,7 @@ static int create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, } madvise(*addr, fd_size, MADV_HUGEPAGE); - for (size_t i = 0; i < fd_size; i++) { - char *addr2 = *addr + i; - - FORCE_READ(*addr2); - } + force_read_pages(*addr, fd_size / pmd_pagesize, pmd_pagesize); if (!check_huge_file(*addr, fd_size / pmd_pagesize, pmd_pagesize)) { ksft_print_msg("No large pagecache folio generated, please provide a filesystem supporting large folio\n"); diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h index 6ad32b1830f1..522f7f9050f5 100644 --- a/tools/testing/selftests/mm/vm_util.h +++ b/tools/testing/selftests/mm/vm_util.h @@ -54,6 +54,13 @@ static inline unsigned int pshift(void) return __page_shift; } +static inline void force_read_pages(char *addr, unsigned int nr_pages, + size_t pagesize) +{ + for (unsigned int i = 0; i < nr_pages; i++) + FORCE_READ(addr[i * pagesize]); +} + bool detect_huge_zeropage(void); /* -- 2.51.2