From nobody Tue Feb 10 10:54:07 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 1DC3134B425; Wed, 7 Jan 2026 16:49:05 +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=1767804555; cv=none; b=dqMMoQEa6f5z8BpegjVZvQRR9MpoMBblhN+D4U7sxjNxsRdMaqtSUD914Gol6py6Y1ZvU3BqOYe0dEP5THLhxOwgy3Ys9JSZhJaNwE2kQdKI0X90XbvmJO8xMADIa3ezGDZqiQc7vXzrQNo0siTrZeJHCvABBzAfxNvGM0IVsx4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767804555; c=relaxed/simple; bh=hVcrYx1PlEIf89awYzQhAdw/HoIMx6RpxVSkN+eaEgA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mJ2YIm7UXUuCXM7CeS/2sP1AZPjzHoKPSrxTszKM8NHziCNQWExkKv+6RUr4TBS2WdwzDWqhmd3eQM6ARfo4vJ5inDZmBb4dHDW5QC2zdAx6JQ55j17ioPq2OaEVWKEC7lK4GeV0esTe1w/W9JON3bSsPfDYMnL/2KpQ/+V7a3I= 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 094C11684; Wed, 7 Jan 2026 08:48:52 -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 986943F5A1; Wed, 7 Jan 2026 08:48:57 -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 , Lorenzo Stoakes , Mark Brown , Ryan Roberts , Shuah Khan Subject: [PATCH v2 5/8] selftests/mm: introduce helper to read every page in range Date: Wed, 7 Jan 2026 16:48:39 +0000 Message-ID: <20260107164842.3289559-6-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20260107164842.3289559-1-kevin.brodsky@arm.com> References: <20260107164842.3289559-1-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: quoted-printable Content-Type: text/plain; charset="utf-8" FORCE_READ(*addr) ensures that the compiler will emit a load from addr. Several tests need to trigger such a load for every page in the range [addr, addr + len), ensuring that every page is faulted in, if it wasn't already. Introduce a new helper force_read_pages_in_range() that does exactly that and replace existing loops with a call to it. Some of those loops have a different step size, but reading from every page is appropriate in all cases. Signed-off-by: Kevin Brodsky Reviewed-by: Dev Jain Reviewed-by: SeongJae Park --- tools/testing/selftests/mm/hugetlb-madvise.c | 9 +-------- tools/testing/selftests/mm/pfnmap.c | 16 ++++++---------- .../testing/selftests/mm/split_huge_page_test.c | 6 +----- tools/testing/selftests/mm/vm_util.h | 6 ++++++ 4 files changed, 14 insertions(+), 23 deletions(-) diff --git a/tools/testing/selftests/mm/hugetlb-madvise.c b/tools/testing/s= elftests/mm/hugetlb-madvise.c index 05d9d2805ae4..1f82568ae262 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_page= s) =20 void read_fault_pages(void *addr, unsigned long nr_pages) { - unsigned long i; - - for (i =3D 0; i < nr_pages; i++) { - unsigned long *addr2 =3D - ((unsigned long *)(addr + (i * huge_page_size))); - /* Prevent the compiler from optimizing out the entire loop: */ - FORCE_READ(*addr2); - } + force_read_pages_in_range(addr, nr_pages * huge_page_size); } =20 int main(int argc, char **argv) diff --git a/tools/testing/selftests/mm/pfnmap.c b/tools/testing/selftests/= mm/pfnmap.c index f546dfb10cae..35b0e3ed54cd 100644 --- a/tools/testing/selftests/mm/pfnmap.c +++ b/tools/testing/selftests/mm/pfnmap.c @@ -33,20 +33,17 @@ static void signal_handler(int sig) siglongjmp(sigjmp_buf_env, -EFAULT); } =20 -static int test_read_access(char *addr, size_t size, size_t pagesize) +static int test_read_access(char *addr, size_t size) { - size_t offs; int ret; =20 if (signal(SIGSEGV, signal_handler) =3D=3D SIG_ERR) return -EINVAL; =20 ret =3D sigsetjmp(sigjmp_buf_env, 1); - if (!ret) { - for (offs =3D 0; offs < size; offs +=3D pagesize) - /* Force a read that the compiler cannot optimize out. */ - *((volatile char *)(addr + offs)); - } + if (!ret) + force_read_pages_in_range(addr, size); + if (signal(SIGSEGV, SIG_DFL) =3D=3D SIG_ERR) return -EINVAL; =20 @@ -138,7 +135,7 @@ FIXTURE_SETUP(pfnmap) SKIP(return, "Invalid file: '%s'. Not pfnmap'ed\n", file); =20 /* ... and want to be able to read from them. */ - if (test_read_access(self->addr1, self->size1, self->pagesize)) + if (test_read_access(self->addr1, self->size1)) SKIP(return, "Cannot read-access mmap'ed '%s'\n", file); =20 self->size2 =3D 0; @@ -243,8 +240,7 @@ TEST_F(pfnmap, fork) ASSERT_GE(pid, 0); =20 if (!pid) { - EXPECT_EQ(test_read_access(self->addr1, self->size1, - self->pagesize), 0); + EXPECT_EQ(test_read_access(self->addr1, self->size1), 0); exit(0); } =20 diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/test= ing/selftests/mm/split_huge_page_test.c index 40799f3f0213..65a89ceca4a5 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 *tes= tfile, size_t fd_size, } madvise(*addr, fd_size, MADV_HUGEPAGE); =20 - for (size_t i =3D 0; i < fd_size; i++) { - char *addr2 =3D *addr + i; - - FORCE_READ(*addr2); - } + force_read_pages_in_range(*addr, fd_size); =20 if (!check_huge_file(*addr, fd_size / pmd_pagesize, pmd_pagesize)) { ksft_print_msg("No large pagecache folio generated, please provide a fil= esystem supporting large folio\n"); diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests= /mm/vm_util.h index 6ad32b1830f1..74bdf96161d7 100644 --- a/tools/testing/selftests/mm/vm_util.h +++ b/tools/testing/selftests/mm/vm_util.h @@ -54,6 +54,12 @@ static inline unsigned int pshift(void) return __page_shift; } =20 +static inline void force_read_pages_in_range(char *addr, size_t len) +{ + for (size_t i =3D 0; i < len; i +=3D psize()) + FORCE_READ(addr[i]); +} + bool detect_huge_zeropage(void); =20 /* --=20 2.51.2