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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4538234b382sm222400965e9.9.2025.07.02.01.28.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Jul 2025 01:28:52 -0700 (PDT) Message-ID: Date: Wed, 2 Jul 2025 10:28:51 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] selftests/mm: pagemap_scan ioctl: add PFN ZERO test cases To: Muhammad Usama Anjum , Andrew Morton , Shuah Khan Cc: kernel@collabora.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250630102443.137809-1-usama.anjum@collabora.com> <20027e0c-f43b-4d10-a4d6-41dcc38145bd@redhat.com> <6846faf7-20b5-4f08-a8f0-9946f993b0e9@collabora.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <6846faf7-20b5-4f08-a8f0-9946f993b0e9@collabora.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 02.07.25 09:39, Muhammad Usama Anjum wrote: > On 7/1/25 7:51 PM, David Hildenbrand wrote: >> On 30.06.25 12:24, Muhammad Usama Anjum wrote: >>> Add test cases to test the correctness of PFN ZERO flag of pagemap_scan >>> ioctl. Test with normal pages backed memory and huge pages backed >>> memory. >> >> Just to verify: would this trigger on kernels before my fix? > Yes, it does trigger the bug without the fix. > >> >>> >>> Cc: David Hildenbrand >>> Signed-off-by: Muhammad Usama Anjum >>> --- >>> The bug has been fixed [1]. >>> >>> [1] https://lore.kernel.org/all/20250617143532.2375383-1-david@redhat.com >>> --- >>>   tools/testing/selftests/mm/pagemap_ioctl.c | 57 +++++++++++++++++++++- >>>   1 file changed, 56 insertions(+), 1 deletion(-) >>> >>> diff --git a/tools/testing/selftests/mm/pagemap_ioctl.c b/tools/ >>> testing/selftests/mm/pagemap_ioctl.c >>> index 57b4bba2b45f3..6138de0087edf 100644 >>> --- a/tools/testing/selftests/mm/pagemap_ioctl.c >>> +++ b/tools/testing/selftests/mm/pagemap_ioctl.c >>> @@ -1,4 +1,5 @@ >>>   // SPDX-License-Identifier: GPL-2.0 >>> + >>>   #define _GNU_SOURCE >>>   #include >>>   #include >>> @@ -1480,6 +1481,57 @@ static void transact_test(int page_size) >>>                     extra_thread_faults); >>>   } >>>   +void zeropfn_tests(void) >>> +{ >>> +    unsigned long long mem_size; >>> +    struct page_region vec; >>> +    int i, ret; >>> +    char *mem; >>> + >>> +    /* Test with page backed memory */ >> >> What is "page backed memory" ? :) > I mean, normal memory which isn't huge page backed. I've renamed it to > Test with normal memory. > >> >>> +    mem_size = 10 * page_size; >>> +    mem = mmap(NULL, mem_size, PROT_READ, MAP_PRIVATE | MAP_ANON, -1, >>> 0); >>> +    if (mem == MAP_FAILED) >>> +        ksft_exit_fail_msg("error nomem\n"); >>> + >>> +    /* Touch each page to ensure it's mapped */ >>> +    for (i = 0; i < mem_size; i += page_size) >>> +        (void)((volatile char *)mem)[i]; >>> + >>> +    ret = pagemap_ioctl(mem, mem_size, &vec, 1, 0, >>> +                (mem_size / page_size), PAGE_IS_PFNZERO, 0, 0, >>> PAGE_IS_PFNZERO); >>> +    if (ret < 0) >>> +        ksft_exit_fail_msg("error %d %d %s\n", ret, errno, >>> strerror(errno)); >>> + >>> +    ksft_test_result(ret == 1 && LEN(vec) == (mem_size / page_size), >>> +             "%s all pages must have PFNZERO set\n", __func__); >>> + >>> +    munmap(mem, mem_size); >>> + >>> +    /* Test with huge page */ >>> +    mem_size = 10 * hpage_size; >>> +    mem = memalign(hpage_size, mem_size); >>> +    if (!mem) >>> +        ksft_exit_fail_msg("error nomem\n"); >>> + >>> +    ret = madvise(mem, mem_size, MADV_HUGEPAGE); >>> +    if (ret) >>> +        ksft_exit_fail_msg("madvise failed %d %s\n", errno, >>> strerror(errno)); >> >> Might fail on older kernels, so we usually treat this as a skip. > I'll skip it in next version. > >> >>> + >>> +    for (i = 0; i < mem_size; i += hpage_size) >>> +        (void)((volatile char *)mem)[i]; >>> + >>> +    ret = pagemap_ioctl(mem, mem_size, &vec, 1, 0, >>> +                (mem_size / page_size), PAGE_IS_PFNZERO, 0, 0, >>> PAGE_IS_PFNZERO); >>> +    if (ret < 0) >>> +        ksft_exit_fail_msg("error %d %d %s\n", ret, errno, >>> strerror(errno)); >>> + >>> +    ksft_test_result(ret == 1 && LEN(vec) == (mem_size / page_size), >>> +             "%s all huge pages must have PFNZERO set\n", __func__); >> >> Wouldn't this be able to fail if /sys/kernel/mm/transparent_hugepage/ >> use_zero_page is set to false, > I wasn't aware of it. I'll check user_zero_page first as initial condition. > >> or if mmap() gave us a suboptimally- >> aligned range? > mem = memalign(hpage_size, mem_size) is being used to allocate this. So > aligment should be correct. > >> >> You'd have to read each and every page to get the ordinary shared >> zeropage in these configs instead without making the test too complicated. > In the above for loop, we are reading each new page already. Let's > resolve this and then I'll post the v2 which is ready. > >> >>> + >>> +    free(mem); >> >> >> Shouldn't this be an munmap() ? > free() is being used to free memory allocated by memalign(). Oh, I missed that detail. I'm afraid memalign+free that might not be what you want: there is no guarantee that what you are getting hasn't been used before and is not already filled with other pages? -- Cheers, David / dhildenb