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(p200300d82f18f900e0ae65d58bf88cfd.dip0.t-ipconnect.de. [2003:d8:2f18:f900:e0ae:65d5:8bf8:8cfd]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e859a278c1sm10646171f8f.24.2025.09.15.06.58.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 15 Sep 2025 06:58:50 -0700 (PDT) Message-ID: Date: Mon, 15 Sep 2025 15:58:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv2] mm/khugepaged: Do not fail collapse_pte_mapped_thp() on SCAN_PMD_NULL To: Kiryl Shutsemau , Andrew Morton , Lorenzo Stoakes Cc: Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: From: David Hildenbrand 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: wgc084nZJ8Ig5_cEq3baMWmxk72-6nbnCUYYmrHou_c_1757944731 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: zhjy5cdny68hqdn9kkggzpjcjrzg5jjm X-Rspam-User: X-Rspamd-Queue-Id: 613DB20009 X-Rspamd-Server: rspam10 X-HE-Tag: 1757944734-856736 X-HE-Meta: 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 9cCmeifs 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 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 15.09.25 15:52, Kiryl Shutsemau wrote: > From: Kiryl Shutsemau > > MADV_COLLAPSE on a file mapping behaves inconsistently depending on if > PMD page table is installed or not. > > Consider following example: > > p = mmap(NULL, 2UL << 20, PROT_READ | PROT_WRITE, > MAP_SHARED, fd, 0); > err = madvise(p, 2UL << 20, MADV_COLLAPSE); > > fd is a populated tmpfs file. > > The result depends on the address that the kernel returns on mmap(). > If it is located in an existing PMD table, the madvise() will succeed. > However, if the table does not exist, it will fail with -EINVAL. > > This occurs because find_pmd_or_thp_or_none() returns SCAN_PMD_NULL when > a page table is missing, which causes collapse_pte_mapped_thp() to fail. > > SCAN_PMD_NULL and SCAN_PMD_NONE should be treated the same in > collapse_pte_mapped_thp(): install the PMD leaf entry and allocate page > tables as needed. > > Signed-off-by: Kiryl Shutsemau > --- Acked-by: David Hildenbrand -- Cheers David / dhildenb