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imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=U5HR1K7C; spf=pass (imf15.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=1768820159; a=rsa-sha256; cv=none; b=LZrIJ582D5Ahiu7DlTV8jPnZI7cw2b0zS2nhS1taBT8aB0Z86eFAReBTfCGnL31y7G7fiK OpVcdjFDEn2f0NdECfi4+SBOhD2kTcluKCkFtQ//5wh6M0sxsrRPV++qMRDjfLrEW/ME1n TYKl/smFTeb0kNO3TlgJdU2q5CWqMhI= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 08C1760140; Mon, 19 Jan 2026 10:55:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7F7E2C116C6; Mon, 19 Jan 2026 10:55:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768820158; bh=bsXo26KZ+K1aH/HZ8wolPUoG9a2d4fNHkR3P0zLa+8g=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=U5HR1K7Cjv0Cp+7YA9y3rZzYh3llbIkfZP8dDEoV9I93qC40yuDZuPbkDtUVAE8Xg W7/u0Dc4zylWNGHI2B/csqj7mS8kuwdP6elJFVLdx6UbEdH6hy7LNPodk4rb2UvPku PRsyafmBOay1dqnXvPNE9mACu05Ir5P33XWVzP8Bc91mrb8vmXgUkQqrGf1DRxq/Nb 9MdLKrAaR2r//UIh9a4FhU6Nq64ghVu9kwpROwSidCRdJtB2M2Xbz/SlUJqMImyGP4 ouTywClMcWbwMw59omh7dCa2luVHaowpKS6lyNbYgozqnWikaAZQprzz+3UpK3ecTj yUcKnCrZxwa4g== Message-ID: Date: Mon, 19 Jan 2026 11:55:54 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 5/8] selftests/mm: introduce helper to read every page in range To: Kevin Brodsky , linux-mm@kvack.org, linux-kselftest@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Lorenzo Stoakes , Mark Brown , Ryan Roberts , Shuah Khan References: <20260107164842.3289559-1-kevin.brodsky@arm.com> <20260107164842.3289559-6-kevin.brodsky@arm.com> From: "David Hildenbrand (Red Hat)" 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAa2VybmVsLm9yZz7CwY0EEwEIADcWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCaKYhwAIbAwUJJlgIpAILCQQVCgkIAhYCAh4FAheAAAoJEE3eEPcA/4Naa5EP/3a1 9sgS9m7oiR0uenlj+C6kkIKlpWKRfGH/WvtFaHr/y06TKnWn6cMOZzJQ+8S39GOteyCCGADh 6ceBx1KPf6/AvMktnGETDTqZ0N9roR4/aEPSMt8kHu/GKR3gtPwzfosX2NgqXNmA7ErU4puf zica1DAmTvx44LOYjvBV24JQG99bZ5Bm2gTDjGXV15/X159CpS6Tc2e3KvYfnfRvezD+alhF XIym8OvvGMeo97BCHpX88pHVIfBg2g2JogR6f0PAJtHGYz6M/9YMxyUShJfo0Df1SOMAbU1Q Op0Ij4PlFCC64rovjH38ly0xfRZH37DZs6kP0jOj4QdExdaXcTILKJFIB3wWXWsqLbtJVgjR YhOrPokd6mDA3gAque7481KkpKM4JraOEELg8pF6eRb3KcAwPRekvf/nYVIbOVyT9lXD5mJn IZUY0LwZsFN0YhGhQJ8xronZy0A59faGBMuVnVb3oy2S0fO1y/r53IeUDTF1wCYF+fM5zo14 5L8mE1GsDJ7FNLj5eSDu/qdZIKqzfY0/l0SAUAAt5yYYejKuii4kfTyLDF/j4LyYZD1QzxLC MjQl36IEcmDTMznLf0/JvCHlxTYZsF0OjWWj1ATRMk41/Q+PX07XQlRCRcE13a8neEz3F6we 08oWh2DnC4AXKbP+kuD9ZP6+5+x1H1zEzsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCgh Cj/CA/lc/LMthqQ773gauB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseB fDXHA6m4B3mUTWo13nid0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts 6TZ+IrPOwT1hfB4WNC+X2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiu Qmt3yqrmN63V9wzaPhC+xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKB Tccu2AXJXWAE1Xjh6GOC8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvF FFyAS0Nk1q/7EChPcbRbhJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh 2YmnmLRTro6eZ/qYwWkCu8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRk F3TwgucpyPtcpmQtTkWSgDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0L LH63+BrrHasfJzxKXzqgrW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4v q7oFCPsOgwARAQABwsF8BBgBCAAmAhsMFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmic2qsF CSZYCKEACgkQTd4Q9wD/g1oq0xAAsAnw/OmsERdtdwRfAMpC74/++2wh9RvVQ0x8xXvoGJwZ rk0Jmck1ABIM//5sWDo7eDHk1uEcc95pbP9XGU6ZgeiQeh06+0vRYILwDk8Q/y06TrTb1n4n 7FRwyskKU1UWnNW86lvWUJuGPABXjrkfL41RJttSJHF3M1C0u2BnM5VnDuPFQKzhRRktBMK4 GkWBvXlsHFhn8Ev0xvPE/G99RAg9ufNAxyq2lSzbUIwrY918KHlziBKwNyLoPn9kgHD3hRBa Yakz87WKUZd17ZnPMZiXriCWZxwPx7zs6cSAqcfcVucmdPiIlyG1K/HIk2LX63T6oO2Libzz 7/0i4+oIpvpK2X6zZ2cu0k2uNcEYm2xAb+xGmqwnPnHX/ac8lJEyzH3lh+pt2slI4VcPNnz+ vzYeBAS1S+VJc1pcJr3l7PRSQ4bv5sObZvezRdqEFB4tUIfSbDdEBCCvvEMBgoisDB8ceYxO cFAM8nBWrEmNU2vvIGJzjJ/NVYYIY0TgOc5bS9wh6jKHL2+chrfDW5neLJjY2x3snF8q7U9G EIbBfNHDlOV8SyhEjtX0DyKxQKioTYPOHcW9gdV5fhSz5tEv+ipqt4kIgWqBgzK8ePtDTqRM qZq457g1/SXSoSQi4jN+gsneqvlTJdzaEu1bJP0iv6ViVf15+qHuY5iojCz8fa0= In-Reply-To: <20260107164842.3289559-6-kevin.brodsky@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: fqx94b3o5idmpqtjrye8ozwi6geg4qbo X-Rspamd-Queue-Id: A538CA0009 X-Rspamd-Server: rspam04 X-HE-Tag: 1768820159-306086 X-HE-Meta: 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 bSYt7TFD Yzy6EzRiuAvUGQJvTo1VqC7+nzqoXDAr89hCZcU7Vgx0+SjPp3ltMXuSgJF4ScuUJy9rSSPuJE3no5skX4FC+X6/RcvT7CZVeAdnnR5gc7GJO4sluFqkQte5E7RcZpNXzV54Z4WGnJYBtIB5URCJE5r9wUECGspEgW3OTyr/oEuN2dS4GsRy6fruG73zCZlfysYZDnuG+dIzZt5hxNnlRAa85DilGWON4FTV4yL4mervpdc0edxnAnA3lKuH3DfXDaof+3OIFprgfRAS8DBIh/skq7f6EI03iZhsLVA6lAfPfwarcJLTKSum9NA== 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: On 1/7/26 17:48, Kevin Brodsky wrote: > 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]); > +} > + Of course, we could also just pass the pagesize static inline void force_read_pages_in_range(char *addr, size_t len, size_t pagesize) { for (size_t i = 0; i < len; i += pagesize) FORCE_READ(addr[i]); } Or alternatively even better: static inline void force_read_pages(char *addr, unsigned int nr_pages, size_t pagesize) { for (size_t i = 0; i < nr_pages; i++) FORCE_READ(addr[i * pagesize]); } Then there is no change at all and we avoid the repeated psize() naturally. Thoughts? -- Cheers David