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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-70da717df65sm81671596d6.30.2025.08.27.04.56.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Aug 2025 04:56:12 -0700 (PDT) Message-ID: <11a5d391-3a13-4376-98f1-34b529d3c583@redhat.com> Date: Wed, 27 Aug 2025 13:56:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] huge_mm.h: is_huge_zero_folio(NULL) should return false To: Max Kellermann Cc: Andrew Morton , lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, shikemeng@huaweicloud.com, kasong@tencent.com, nphamcs@gmail.com, bhe@redhat.com, chrisl@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250826231626.218675-1-max.kellermann@ionos.com> <20250826185515.7fbe1821713195b170ac1b31@linux-foundation.org> 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: 8AD0uAJX03X7bT5EMa0nGNB6HJTk33m8byR-HjxtxBI_1756295774 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 971A640003 X-Stat-Signature: tkkems9omq9dhc5xj66whf3ud63biwkg X-HE-Tag: 1756295776-327939 X-HE-Meta: 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 R/nvJpt6 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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 27.08.25 12:13, Max Kellermann wrote: > On Wed, Aug 27, 2025 at 11:36 AM David Hildenbrand wrote: >> Why should it be allowed to pass in garbage (folio == NULL) into a >> function that operates on valid folios? > > This patch isn't about the function parameter but about the global > variable being NULL. > (Don't mix up with my other patch.) Huh? "Calling is_huge_zero_folio(NULL) should not be legal - it makes no sense, and a different (theoretical) implementation may dereference the pointer." And then "But currently, lacking any explicit documentation, this call is legal." No. It isn't. It never was. -- Cheers David / dhildenb