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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Kiryl Shutsemau , Hugh Dickins , Vlastimil Babka , Jann Horn , Pedro Falcato , Jane Chu , linux-mm@kvack.org, stable@vger.kernel.org References: <20250921232709.1608699-1-harry.yoo@oracle.com> <6e4f6a37-2449-4089-8b3d-234ba86878e2@redhat.com> <9b05b974-7478-4c99-9c4f-6593e0fd4f93@redhat.com> <9f3e4031-9e13-4f8b-a7fb-8db4166c47f0@redhat.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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 0V1TCwD_5w5jDc6KI0132GAjq-2IBxSojpDE2vIrX8c_1760969248 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: nkmbz3p1r1uig4mpicz1iji1kkdq4653 X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 1A9041C000D X-HE-Tag: 1760969250-491122 X-HE-Meta: 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 hR8T1EN6 zGPLrxSscJ/NSpgmSKl5UUvs8aq2ivaSccFY5JoIdr6BhJd7Td3/fI83jNzLPSqD6d4LkO9al9OTNrqw403FO+hGNnSAJ/KJ2GOxTvA6cAjup8SwM0L5e0Ibwhj0BS4NgSguh2mnxYVfSbM9EuvQsr34sTho0qYjF6gdxIiBqbV9Wv6UrAqUyQJbUBzbOfKfNZHIKOBSnXXxe1/VC0YxBu5Du9pupdWjCPsZG26bTU6WNE9uCi57A5jjSIxn3BujZ/ZRHId/ChnxeThf1R+dKDB3LTmCZy61MU2em36hmAppeedN3Jsul55tNWyrRZcSCykNt5EBJme+6Ece8bkvo+QqxbrswTIEFazHbloCteZRxCqLa+0atzjoM6udj++wzeEFJkjV21G+axwdu8ufEvkK//LQaEM0QAYqoqKFXheG375Fa5BXLVCgKfyjQ3PG2qSiu3xAEK4D4Yx9bSGHMFFcrCDbkB/kW5x2W 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: >> >>>>>>> It'd be more robust to do something like: >>>>>> >>>>>> That's also what I had in mind. But all this lockless stuff makes me a bit >>>>>> nervous :) >>>>> >>>>> Yeah the code is not very straightforward... :/ >>>>> >>>>> But technically the diff that I pasted here should be enough to fix >>>>> this... or do you have any alternative approach in mind? >>>> >>>> Hopefully, I'm not convinced this code is not buggy, but at least regarding >>>> concurrent migration it should be fine with that. >>> >>> I've been thinking about this... >>> >>> Actually, it'll make more sense to open-code what pte_map_offset_lock() >>> does in the mainline: >>> >>> 1. do not remove the "bad pte" checks, because pte_offset_map() in pre-6.5 >>> kernels doesn't do the check for us unlike the mainline. >>> 2. check is_swap_pmd(), pmd_trans_huge(), pmd_devmap() without ptl, but >>> atomically. >>> 3. after acquiring ptl in change_pte_range(), check if pmd has changed >>> since step 1 and 2. if yes, retry (like mainline). if no, we're all good. >>> >>> What do you think? > > Apologies for late reply... > >> Only for -stable, right? > > Right! > >> Does not sound too wrong for me, but I would have >> to take a closer look at the end result! > > FYI I'll test these two patches and see if they survive for a week, > and then submit them to -stable. Thanks. > > The first patch is also going to be backported since change_pte_range() > cannot return negative values without it. That sound reasonable to me! -- Cheers David / dhildenb