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b=VJJjaibsIHpdBm9Dc8E7uYrAZfg7FXmoqZrc0K/k2QtFykZticTsazwBOnHIMOhN1 JNCvpGF5V/91NM2XYkj7sAgNZOQwpYcROcU62wtvWRwwYud1tKC3dPpgZyWhC6xDDe aBy2rN//OuG017ao4sgjFjv91qhvkK/umSd8ktWl0mrGZ3fPqA376MyJ7PS6zIIA5U cjq13EaB6MG7z/08sa16NmgtqWzQv4TufYJMviM6VgRkYPNG0f/tEMQ/1aFqCzqvmq BBsb4kDo/0AFFiKGg6VTqQv99ZPgPo+BalmB9qbIUvIWc8TWurjbJaUW+39s6CF4C3 PxPNyi/cORVDg== Message-ID: <857be078-1464-4e29-979d-0459cad8508b@kernel.org> Date: Tue, 6 Jan 2026 21:03:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 1/2] mm/memory hotplug: fix zone->contiguous always false when hotplug To: Tianyou Li , Oscar Salvador , Mike Rapoport , Wei Yang Cc: linux-mm@kvack.org, Yong Hu , Nanhai Zou , Yuan Liu , Tim Chen , Qiuxu Zhuo , Yu C Chen , Pan Deng , Chen Zhang , linux-kernel@vger.kernel.org References: <20251222145807.11351-1-tianyou.li@intel.com> <20251222145807.11351-2-tianyou.li@intel.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 ZW5icmFuZCA8ZGF2aWRAa2VybmVsLm9yZz7CwY0EEwEIADcWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCaKYhwAIbAwUJJlgIpAILCQQVCgkIAhYCAh4FAheAAAoJEE3eEPcA/4Naa5EP/3a1 9sgS9m7oiR0uenlj+C6kkIKlpWKRfGH/WvtFaHr/y06TKnWn6cMOZzJQ+8S39GOteyCCGADh 6ceBx1KPf6/AvMktnGETDTqZ0N9roR4/aEPSMt8kHu/GKR3gtPwzfosX2NgqXNmA7ErU4puf zica1DAmTvx44LOYjvBV24JQG99bZ5Bm2gTDjGXV15/X159CpS6Tc2e3KvYfnfRvezD+alhF XIym8OvvGMeo97BCHpX88pHVIfBg2g2JogR6f0PAJtHGYz6M/9YMxyUShJfo0Df1SOMAbU1Q Op0Ij4PlFCC64rovjH38ly0xfRZH37DZs6kP0jOj4QdExdaXcTILKJFIB3wWXWsqLbtJVgjR YhOrPokd6mDA3gAque7481KkpKM4JraOEELg8pF6eRb3KcAwPRekvf/nYVIbOVyT9lXD5mJn IZUY0LwZsFN0YhGhQJ8xronZy0A59faGBMuVnVb3oy2S0fO1y/r53IeUDTF1wCYF+fM5zo14 5L8mE1GsDJ7FNLj5eSDu/qdZIKqzfY0/l0SAUAAt5yYYejKuii4kfTyLDF/j4LyYZD1QzxLC MjQl36IEcmDTMznLf0/JvCHlxTYZsF0OjWWj1ATRMk41/Q+PX07XQlRCRcE13a8neEz3F6we 08oWh2DnC4AXKbP+kuD9ZP6+5+x1H1zEzsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCgh Cj/CA/lc/LMthqQ773gauB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseB fDXHA6m4B3mUTWo13nid0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts 6TZ+IrPOwT1hfB4WNC+X2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiu Qmt3yqrmN63V9wzaPhC+xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKB Tccu2AXJXWAE1Xjh6GOC8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvF FFyAS0Nk1q/7EChPcbRbhJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh 2YmnmLRTro6eZ/qYwWkCu8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRk F3TwgucpyPtcpmQtTkWSgDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0L LH63+BrrHasfJzxKXzqgrW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4v q7oFCPsOgwARAQABwsF8BBgBCAAmAhsMFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmic2qsF CSZYCKEACgkQTd4Q9wD/g1oq0xAAsAnw/OmsERdtdwRfAMpC74/++2wh9RvVQ0x8xXvoGJwZ rk0Jmck1ABIM//5sWDo7eDHk1uEcc95pbP9XGU6ZgeiQeh06+0vRYILwDk8Q/y06TrTb1n4n 7FRwyskKU1UWnNW86lvWUJuGPABXjrkfL41RJttSJHF3M1C0u2BnM5VnDuPFQKzhRRktBMK4 GkWBvXlsHFhn8Ev0xvPE/G99RAg9ufNAxyq2lSzbUIwrY918KHlziBKwNyLoPn9kgHD3hRBa Yakz87WKUZd17ZnPMZiXriCWZxwPx7zs6cSAqcfcVucmdPiIlyG1K/HIk2LX63T6oO2Libzz 7/0i4+oIpvpK2X6zZ2cu0k2uNcEYm2xAb+xGmqwnPnHX/ac8lJEyzH3lh+pt2slI4VcPNnz+ vzYeBAS1S+VJc1pcJr3l7PRSQ4bv5sObZvezRdqEFB4tUIfSbDdEBCCvvEMBgoisDB8ceYxO cFAM8nBWrEmNU2vvIGJzjJ/NVYYIY0TgOc5bS9wh6jKHL2+chrfDW5neLJjY2x3snF8q7U9G EIbBfNHDlOV8SyhEjtX0DyKxQKioTYPOHcW9gdV5fhSz5tEv+ipqt4kIgWqBgzK8ePtDTqRM qZq457g1/SXSoSQi4jN+gsneqvlTJdzaEu1bJP0iv6ViVf15+qHuY5iojCz8fa0= In-Reply-To: <20251222145807.11351-2-tianyou.li@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: E402420015 X-Rspamd-Server: rspam10 X-Stat-Signature: jyxt3rmfrgnznfhk88s8cqq37oo6koge X-HE-Tag: 1767729843-456134 X-HE-Meta: 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 ehARlpPG WcsGvd8sZ/VvddZ+gHpz09DrcJzJH1w1jBw5hph0KGyyJTncg033iPcJVElFkc7yBH1xRwXjGhtcXAHXoSEj+DDxBgrdiybgdBqWS3kzO5p8U4OaLD5bPqviJCdTjXRTJZxQOkm8iZ46yQUZQRCmW7pNyO3buH4wjt7EYT3epMKseinvUjyVyCVaV5/tq1nLpAZACLKDeQbgbdiPWeAnelU9L/0oiGFTIcokS/+R3aqTh7Hyn0d0bAZO9bO+ibDhn+LFuJd8xYwkOjBtDWolN5QAgWYJ+ZjBYQDGj6FBk4hIhqs7VObCP1uN1xnx24ugqB14nfb/ZgLnyFqU= 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 12/22/25 15:58, Tianyou Li wrote: > Function set_zone_contiguous used __pageblock_pfn_to_page to > check the whole pageblock is in the same zone. One assumption is > the memory section must online, otherwise the __pageblock_pfn_to_page > will return NULL, then the set_zone_contiguous will be false. > When move_pfn_range_to_zone invoked set_zone_contiguous, since the > memory section did not online, the return value will always be false. > > To fix this issue, we removed the set_zone_contiguous from the > move_pfn_range_to_zone, and place it after memory section onlined. > > Function remove_pfn_range_from_zone did not have this issue because > memory section remains online at the time set_zone_contiguous invoked. The description is a bit hard to follow. Let me try: "set_zone_contiguous() uses __pageblock_pfn_to_page() to detect pageblocks that either do not exist (hole) or that do not belong to the same zone. __pageblock_pfn_to_page(), however, relies on pfn_to_online_page(), effectively always returning NULL for memory ranges that were not onlined yet. So when called on a range-to-be-onlined, it indicates a memory hole to set_zone_contiguous(). Consequently, the set_zone_contiguous() call in move_pfn_range_to_zone(), which happens early during memory onlining, will never detect a zone as being contiguous. Bad. To fix the issue, move the set_zone_contiguous() call to a later stage in memory onlining, where pfn_to_online_page() will succeed: after we mark the memory sections to be online" Now, there is no need to add the handling to mhp_init_memmap_on_memory(). Note how mhp_init_memmap_on_memory() in memory_block_online() is always followed by online_pages(). So, it's sufficient to move it after the online_pages_range(). I would also add a comment there saying something like: /* * Now that the ranges are indicated as online, check whether the whole * zone is contiguous. */ Can we find some Fixes: tag (which commit introduced the regression)? Likely we want to CC stable. -- Cheers David