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[2003:cb:c706:3100:19a8:d898:8e69:6aff]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-35dd04cc0b6sm13597124f8f.44.2024.06.05.01.33.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Jun 2024 01:33:03 -0700 (PDT) Message-ID: <62c19f0d-4dfe-4bc8-99b6-c84583747093@redhat.com> Date: Wed, 5 Jun 2024 10:33:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH linux-next] mm: huge_memory: fix misused mapping_large_folio_support() for anon folios To: ran xiaokai Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, ran.xiaokai@zte.com.cn, v-songbaohua@oppo.com, xu.xin16@zte.com.cn, yang.yang29@zte.com.cn, ziy@nvidia.com References: <05e50d0c-4222-4c1f-b051-c7249f04c661@redhat.com> <20240605083008.891170-1-ranxiaokai627@163.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: <20240605083008.891170-1-ranxiaokai627@163.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A00298000A X-Stat-Signature: fow3pf3gxqwcj1ua87phe3mfi3bz4dck X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1717576389-349945 X-HE-Meta: U2FsdGVkX1+tUTebO1Wy+h5ku549orDkaTvRhhV7z5o4oVtrLkQ/yG2gtlQGUvFsaJKZ69F6w1/gNtJZbS8sJYc02V1RWXYBWZQdi0zxsaC79Q+khLsHY6/5cBrqCNODtbILxM51xKvtzSSVHd8dwO17SLUxb5ObGdT7Myftrn/6/fqz/xSd3bvYROF4nbYHuzp8C13WxzOoQHF7EKhCaUZx8oc6d+rwIn2qjX7zgg6f1feoX7C/isyoogqunR7pZCBXjKS5ZWd5Ewq3hq7fQnnryDU11qY4itlCTIX7apwD7eBiJGxr0YLEszgej7po+HXYqFdDagHJ+Ds421EAWatvfcc5XuwVBQHk4E4A+El3ZeV175WdDjVciyPYLJDUkKRwYkEmsFCjIoO5xmcH+dchQw7uue5BAXqLsXlXi3EgOaoRPjx5hycehGYdDXdmI5rRsVfUCETD5PXmzqJauP7d1XmJCDYTfpLZ31adKhVXpkvvzmgomi1a9cyZF26GREejBWa/ZYCLrWM7ZE7kC4HqVRdA6IFxCBiLyKTC9VkglVi8DB/QwcXO5deMhwLWMpnf3gqKD+lG0jWOnlDSPjcrgISyWEM9GZhIfIsitR6HGs1WH5a1QeTo7kOjLwCfcZ1YUmKJ4PTfxhKr+dtGs+XqdrlG/xfgjtVXnszIuKyM4gANPA48WFnPJ7XBj6HaZl8YpKWfRd2wGWzm6ZqmllyNm+o+nJG0aiaR6bskVP1V3g3ptALAgsfq7/XLT80MThRZTX4kD1oEbL4z+UPybnJyQl3b1/AS/9Mq5lY1vhFACkf2IkIFMypdOHc+k2bt0F+nfvwLVA2rebnBD4IQoogz9iTV1OI17RAvyuF0Mwa9pv4zEYo72P8Mrw4ffPnP8b/StNbwgFk6HyYdncFWl8XcSgXX8WbCF9wDKyQBqnsUe45VxhYywCZxiMF6fhwLSlY9SMh23UJYiX5c0vn ooRhF+Be 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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 05.06.24 10:30, ran xiaokai wrote: >> On 05.06.24 04:20, ran xiaokai wrote: >>>> On 04.06.24 07:47, xu.xin16@zte.com.cn wrote: >>>>> From: Ran Xiaokai >>>>> >>>>> When I did a large folios split test, a WARNING >>>>> "[ 5059.122759][ T166] Cannot split file folio to non-0 order" >>>>> was triggered. But my test cases are only for anonmous folios. >>>>> while mapping_large_folio_support() is only reasonable for page >>>>> cache folios. >>>> >>>> Agreed. >>>> >>>> I wonder if mapping_large_folio_support() should either >>>> >>>> a) Complain if used for anon folios, so we can detect the wrong use more >>>> easily. (VM_WARN_ON_ONCE()) >>> >>>> b) Return "true" for anonymous mappings, although that's more debatable. >>>> >>> >>> Hi, David, >>> Thanks for the review. >>> I think a) is better. >>> But we have to add a new parameter "folio" to mapping_large_folio_support(), right ? >>> something like mapping_large_folio_support(struct address_space *mapping, struct folio *folio) ? >>> But in the __filemap_get_folio() path, >>> >>> __filemap_get_folio() >>> no_page: >>> .... >>> if (!mapping_large_folio_support(mapping)) >>> >>> the folio is not allocated yet, yes ? >>> Or do you mean there is some other way to do this ? >> >> If we really pass unmodified folio->mapping, you can do what >> folio_test_anon() would and make sure PAGE_MAPPING_ANON is not set. > > I think I just misunderstood your suggestion. Likely my use of "folio" was confusing. > How about this ? > > static inline bool mapping_large_folio_support(struct address_space *mapping) > { > VM_WARN_ONCE((unsigned long)mapping & PAGE_MAPPING_ANON, > "Anonymous mapping always supports large folio"); > > return IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && > test_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags); > } Yes, and we should likely document that this is not supposed to be used with mappings from anonymous folios. -- Cheers, David / dhildenb