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[80.187.83.110]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46e619b86e1sm239387935e9.5.2025.10.06.01.20.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Oct 2025 01:20:05 -0700 (PDT) Message-ID: Date: Mon, 6 Oct 2025 10:20:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] mm: Consistently use current->mm in mm_get_unmapped_area() To: Ryan Roberts , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20251003155306.2147572-1-ryan.roberts@arm.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: <20251003155306.2147572-1-ryan.roberts@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: BeGvQbu2yXdDx_STBfFGAjn-zS8v27yi37Fj8dssLRM_1759738806 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 1BB8FC000A X-Stat-Signature: neqscfizrpmfpp9wsgah51zmd6c65xce X-HE-Tag: 1759738810-2473 X-HE-Meta: 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 oWVNqYB1 1vzjVrcJnsJ+PZoXBsde8YTxNx+NNgFqEWhudPwXkfqbUJi+SFq/EB1C0yPHv9gEBw5I9Ik23cbjlvZ6mFqXHjHJ4VWokv25NfVd5nZqN60hDHPEUSFLkh9mNxl0S7wCJMtKuAkU0fZEUrI5t2HJZb5ktiQdmK1nfWKBM38gD7rlvFhiRPA6iRIgRIx1wV/Mef02Hr+4qhMqeUuWKbdNyxLHHrQ== 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 03.10.25 17:53, Ryan Roberts wrote: > mm_get_unmapped_area() is a wrapper around arch_get_unmapped_area() / > arch_get_unmapped_area_topdown(), both of which search current->mm for > some free space. Neither take an mm_struct - they implicitly operate on > current->mm. > > But the wrapper takes an mm_struct and uses it to decide whether to > search bottom up or top down. All callers pass in current->mm for this, > so everything is working consistently. But it feels like an accident > waiting to happen; eventually someone will call that function with a > different mm, expecting to find free space in it, but what gets returned > is free space in the current mm. > > So let's simplify by removing the parameter and have the wrapper use > current->mm to decide which end to start at. Now everything is > consistent and self-documenting. > > Signed-off-by: Ryan Roberts Yeah, that looks better to me. Acked-by: David Hildenbrand -- Cheers David / dhildenb