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[2003:cb:c707:4d00:6ac5:30d:1611:918f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39c0b66277dsm14462400f8f.24.2025.04.01.09.44.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Apr 2025 09:44:07 -0700 (PDT) Message-ID: <0a636dd6-3d19-4a3b-8645-21c7b85a4aff@redhat.com> Date: Tue, 1 Apr 2025 18:44:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory_hotplug: fix call folio_test_large with tail page in do_migrate_range To: Andrew Morton Cc: Jinjiang Tu , osalvador@suse.de, nao.horiguchi@gmail.com, zi.yan@cs.rutgers.edu, linux-mm@kvack.org, wangkefeng.wang@huawei.com, sunnanyong@huawei.com References: <20250324131750.1551884-1-tujinjiang@huawei.com> <899807c3-931f-43e6-bf3e-188787a4205a@redhat.com> <68ab727b-dc3d-327f-33b6-25bbfce8530e@huawei.com> <20250328163700.82c9b426bf199102f3d90dcd@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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20250328163700.82c9b426bf199102f3d90dcd@linux-foundation.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: -cHv1uGjZYRXNQVdhLLtQzB4m7BCJ2fHnvXNs_pstl0_1743525849 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: rspam09 X-Rspamd-Queue-Id: 8F9F81C000B X-Stat-Signature: sp8i15wa3osr3jbwf5c4r577cms5gxar X-HE-Tag: 1743525853-18974 X-HE-Meta: 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 MDcgaxKv 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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 29.03.25 00:37, Andrew Morton wrote: > On Tue, 25 Mar 2025 20:05:50 +0100 David Hildenbrand wrote: > >> On 25.03.25 04:02, Jinjiang Tu wrote: >>> >>>> Moving that will not make it able to skip the large frozen >>>> (refcount==0, e.g., free hugetlb) folio in the continue/put_folio case >>>> above. Hmmmm .. >>> For free hugetlb, pfn is increased by 1 in each loop. This leads to skip >>> free hugetlb slower. >> >> Yes. But now I realize that we have the same issue with free buddy pages >> already (folio_try_get of each individual page :( ). >> >>>> >>>> We could similarly to dumping folios, snapshot them, so we can read >>>> stable data. >>> extract the code in __dump_page()? But snapshot may lead to >>> do_migrate_range() slower too. >> >> There is a patch series on the list to do that, but it might take a >> while to clean that up. Ideally, we'd also jump over free buddy pages. >> In the future we might have better ways to do that. >> >> I don't consider this change here really important, but if all it >> affects is free hugetlb folios, it's not really worth it to have this >> code around. >> >> Acked-by: David Hildenbrand >> >> But: I suspect 8135d8926c08 is not the introducing commit. Please re-verify. >> >> We should not CC stable. > Sorry for the late reply. > Why shouldn't we cc:stable? A userspace-triggerable BUG? My reasoning was that it's a VM_BUG_ON_PAGE, and nothing is actually broken on !CONFIG_DEBUG_VM systems ... combined with hugetlb allocation and memory offlining usually being rare and usually privileged operations. It would be a different story if the VM_BUG_ON_PAGE revealed an actual issue; but this is a well documented race. One might argue that unplugging a DIMM could automatically trigger it (rare operation ..), and as we discovered in the meantime, THPs are also affected. But again, CONFIG_VM_DEBUG ... which even Fedora stopped setting. So I don't think CC stable is warranted here, but I wouldn't object if there are good reasons to do it: like assuming that there are CONFIG_VM_DEBUG stable users out there that rely on these features. -- Cheers, David / dhildenb