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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1767804539; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SkZj0dPY3n8EAH1cWcHwyk27DW9K23otGzxdykp1f6Y=; b=owX5FT5IZAWbz4yOkaMAbboQUss7tI1hWIPWQP4cJJTx//EyM/p+QelgiGjUjYujjgGyyD nhhbOMBpvTx+bmjByeA1glZXU8Mew68iu60dNQPyFcOr4X3pjpIj164dwZc0B1fA7lXz+D oe2tylR23LMu6KNUQP9lFQEZ5LtWevk= 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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 364F3100007 X-Stat-Signature: 9sepcb8u5nwg4sbsycp74ecbre81ixi5 X-Rspam-User: X-HE-Tag: 1767804539-685941 X-HE-Meta: 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 rUWQCg7b zg1+SmDBsNAinfnCovyxBiuc5i7Yi0K36L9on1ANunDCXVS9i9uDp0tjsiWmWa3oumi7qs5gUjV7J5O/s0gXfBXM0wb8S5dd5wWCTSVfqUuoAxiXM3HSOkckrEvIZJ0IKK9/2gqupdeKCYROiJ2Lig+XPVQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 --- 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/selftests/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_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_in_range(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..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); } -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; 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_in_range(addr, size); + if (signal(SIGSEGV, SIG_DFL) == SIG_ERR) return -EINVAL; @@ -138,7 +135,7 @@ FIXTURE_SETUP(pfnmap) SKIP(return, "Invalid file: '%s'. Not pfnmap'ed\n", file); /* ... 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); self->size2 = 0; @@ -243,8 +240,7 @@ TEST_F(pfnmap, fork) ASSERT_GE(pid, 0); 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); } diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/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 *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_in_range(*addr, fd_size); 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..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; } +static inline void force_read_pages_in_range(char *addr, size_t len) +{ + for (size_t i = 0; i < len; i += psize()) + FORCE_READ(addr[i]); +} + bool detect_huge_zeropage(void); /* -- 2.51.2