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(p200300d82f1f3f00731af5e5774ed40c.dip0.t-ipconnect.de. [2003:d8:2f1f:3f00:731a:f5e5:774e:d40c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45b661d87a7sm163776295e9.2.2025.09.02.01.43.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Sep 2025 01:43:21 -0700 (PDT) Message-ID: <1acb705c-4846-4a12-9e90-f7853da8a295@redhat.com> Date: Tue, 2 Sep 2025 10:43:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] huge_memory: return -EINVAL in folio split functions when THP is disabled To: "Pankaj Raghav (Samsung)" , Ryan Roberts , Lorenzo Stoakes , Baolin Wang , Dev Jain , Barry Song , Andrew Morton , Nico Pache , Zi Yan , "Liam R . Howlett" Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org, mcgrof@kernel.org, gost.dev@samsung.com, Pankaj Raghav References: <20250902084036.208921-1-kernel@pankajraghav.com> 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: <20250902084036.208921-1-kernel@pankajraghav.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: JS_uonP5FTOoTFcUH-B9U5Lw7IJTpWFHTy8vFL0sXss_1756802602 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: E5D0B40009 X-Stat-Signature: 4zdzznzktcwzsm8j8jsgmys6pzfo4ohm X-Rspam-User: X-HE-Tag: 1756802604-167763 X-HE-Meta: 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 khq9hv4P 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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 02.09.25 10:40, Pankaj Raghav (Samsung) wrote: > From: Pankaj Raghav > > split_huge_page_to_list_[to_order](), split_huge_page() and > try_folio_split() return 0 on success and error codes on failure. > > When THP is disabled, these functions return 0 indicating success even > though an error code should be returned as it is not possible to split a > folio when THP is disabled. > > Make all these functions return -EINVAL to indicate failure instead of > 0. > > This issue was discovered while experimenting enabling large folios > without THP and found that returning 0 in these functions is resulting in > undefined behavior in truncate operations. This change fixes the issue. Currently large folios that could be split are impossible without THP, so why should this be a fix? -- Cheers David / dhildenb