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[80.187.83.110]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46fa9b622cdsm30801905e9.0.2025.10.08.02.55.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Oct 2025 02:55:40 -0700 (PDT) Message-ID: <519c13e0-6b68-4987-8602-7b9ba47daee0@redhat.com> Date: Wed, 8 Oct 2025 11:55:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] mm/compaction: some fix for the range passed to pageblock_pfn_to_page() To: Wei Yang , Michal Hocko Cc: Andrew Morton , vbabka@suse.cz, surenb@google.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, iamjoonsoo.kim@lge.com, linux-mm@kvack.org References: <20251002033140.24462-1-richard.weiyang@gmail.com> <20251007182922.4a254daff78633b1452bdcc3@linux-foundation.org> <20251008023218.g53gm33vmrdt5nw7@master> <20251008091301.44xerz33fmrgnjyt@master> 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: <20251008091301.44xerz33fmrgnjyt@master> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: M5EkiHHe-X9cEQACnq_24rm4fTd9Gh7HN9R5OgNEhRQ_1759917341 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: cjxt997r7y5mbrewpdd8d9qatc1jqdxx X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BD0C61C0006 X-HE-Tag: 1759917345-257035 X-HE-Meta: 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 hd1Y01lF 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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 08.10.25 11:13, Wei Yang wrote: > On Wed, Oct 08, 2025 at 09:52:51AM +0200, Michal Hocko wrote: >> On Wed 08-10-25 02:32:18, Wei Yang wrote: >>> On Tue, Oct 07, 2025 at 06:29:22PM -0700, Andrew Morton wrote: >>>> On Thu, 2 Oct 2025 03:31:38 +0000 Wei Yang wrote: >>>> >>>>> During the code reading of isolate_migratepages_range(), first spot the range >>>>> passed to pageblock_pfn_to_page() is different from that to >>>>> isolate_migratepages_block(). >>>>> >>>>> This implies there is a chance that pageblock_pfn_to_page() thinks the range >>>>> is in the same zone, but isolate_migratepages_block() will isolate range in >>>>> two different zones. This is not what we expect. >>>>> >>>>> Then I found pageblock_pfn_to_page() has an optimization if zone->contiguous, >>>>> this means even the range is across two different zones, it will think the >>>>> range is within the same zone. >>>>> >>>>> So introduce two patches to fix it: >>>> >>>> What do you think might be the worst-case userspace-visible effects >>>> of the bug? >>> >>> I don't see userspace-visible effect yet. >>> >>> Since I lack the knowledge of the consequence of isolating cross zone range, >>> currently I can't tell the effect accurately. >>> >>> The worst case in my mind is we put some page on a different zone's freelist. >>> But I don't totally understand the behavior now. >> >> Is there any actual problem to fix here then? > > I don't see an actual problem in practice yet. We should avoid talking about "fix" then. Let me take a look at the patches. -- Cheers David / dhildenb