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[2003:d8:2f4a:5800:f1ae:8e20:d7f4:51b0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a1f58eb9dfsm11689105f8f.31.2025.05.12.00.58.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 May 2025 00:58:55 -0700 (PDT) Message-ID: <3c4b6a50-f12d-467c-bb5f-e8afb5dc046a@redhat.com> Date: Mon, 12 May 2025 09:58:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/contig_alloc: fix alloc_contig_range when __GFP_COMP and order < MAX_ORDER To: Jinjiang Tu , Zi Yan Cc: Andrew Morton , yuzhao@google.com, linux-mm@kvack.org, wangkefeng.wang@huawei.com, sunnanyong@huawei.com References: <20250312084705.2938220-1-tujinjiang@huawei.com> <20250417195935.2ac19ac5f92add5931b6fa5a@linux-foundation.org> <6E553AA1-5B53-4E52-9940-3B8E0DE36FC1@nvidia.com> <80039e40-a518-a85b-b955-96fb048a2dd0@huawei.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 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: <80039e40-a518-a85b-b955-96fb048a2dd0@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: TtuxISyIwetjgOpE8mGfiuE9nnK-t-e3SDrt73TPauQ_1747036737 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 43693C0007 X-Rspam-User: X-Stat-Signature: rkat4ifh86ac1s5cmcxac13gb6d4n7yi X-HE-Tag: 1747036740-288524 X-HE-Meta: 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 gE9kji2X AGBgtKYzv1RY/IjmE/3TdBp7fpxJujxhhK+iwhjbxk/iTASGRwWe0sAX69YEmwy8D6Ve4DZjiCAEC6HLHl/HtYGKRwxe1kK+jV0IVMB6aVe8WL/ok1ktRTaqWE3c2M51OYMMr80VUD7hza7L6VnpKedwR9HT48nfL2rqDtELEyNSD5m+fCfMim7KKYSEcl6qgDg4oPN+Ugoshd1vtczRHRT0CVs4RHL4hdrn4GSN0qpqDYroZToENKd9VyQ== 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: >>> to a compound page. > > This is wrong. After split_free_pages(), these pages are order-0 pages with refcount 1. Call > prep_new_page(head) and set_page_refcounted(head) lead to VM_BUG_ON_PAGE(page_ref_count(page), page). > >> OK, got it. Since cc.freepages can be MAX_PAGE_ORDER and the requested >> PFN range is smaller than MAX_PAGE_ORDER. A more “right” way of handling >> this would be in the second if (the one shown below), you check order >> against the cc.freepages order and free out of requested range pages. >> But that might be too complicated. Your approach is simpler. > > For (outer_start != start) || (outer_end != end) case, We could split the pages to order-0 list, > and only call post_alloc_hook/set_page_refcounted for pages in [outer_start, start), [end, outer_end) range, > and call free_contig_range() for them. How about this approach? > As there is no in-tree user of this functionality, I'm wondering if we should simply fail the allocation if GFP_COMP is specified with a non-suitable range? -- Cheers, David / dhildenb