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[2003:cb:c73a:3a00:a025:9b06:549e:c16b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4212b84ae09sm143652095e9.18.2024.06.04.00.57.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Jun 2024 00:57:34 -0700 (PDT) Message-ID: Date: Tue, 4 Jun 2024 09:57:33 +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: xu.xin16@zte.com.cn, akpm@linux-foundation.org, ziy@nvidia.com Cc: v-songbaohua@oppo.com, mhocko@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yang.yang29@zte.com.cn References: <20240604134738264WKaKYb3q_YTE32hNAy2lz@zte.com.cn> 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: <20240604134738264WKaKYb3q_YTE32hNAy2lz@zte.com.cn> 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-Stat-Signature: gf7pnwjaao4wnqsndqac6ioqwmazz9ar X-Rspamd-Queue-Id: BBF83A0008 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1717487858-128364 X-HE-Meta: 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 Nj7LehyN 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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 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. > > In split_huge_page_to_list_to_order(), the folio passed to > mapping_large_folio_support() maybe anonmous folio. The > folio_test_anon() check is missing. So the split of the anonmous THP > is failed. This is also the same for shmem_mapping(). We'd better add > a check for both. But the shmem_mapping() in __split_huge_page() is > not involved, as for anonmous folios, the end parameter is set to -1, so > (head[i].index >= end) is always false. shmem_mapping() is not called. > > Using /sys/kernel/debug/split_huge_pages to verify this, with this > patch, large anon THP is successfully split and the warning is ceased. > > Signed-off-by: Ran Xiaokai > Cc: xu xin > Cc: Yang Yang > --- > mm/huge_memory.c | 38 ++++++++++++++++++++------------------ > 1 file changed, 20 insertions(+), 18 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 317de2afd371..4c9c7e5ea20c 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3009,31 +3009,33 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, > if (new_order >= folio_order(folio)) > return -EINVAL; > > - /* Cannot split anonymous THP to order-1 */ > - if (new_order == 1 && folio_test_anon(folio)) { > - VM_WARN_ONCE(1, "Cannot split to order-1 folio"); > - return -EINVAL; > - } > - > if (new_order) { > /* Only swapping a whole PMD-mapped folio is supported */ > if (folio_test_swapcache(folio)) > return -EINVAL; > - /* Split shmem folio to non-zero order not supported */ > - if (shmem_mapping(folio->mapping)) { > - VM_WARN_ONCE(1, > - "Cannot split shmem folio to non-0 order"); > - return -EINVAL; > - } > - /* No split if the file system does not support large folio */ > - if (!mapping_large_folio_support(folio->mapping)) { > - VM_WARN_ONCE(1, > - "Cannot split file folio to non-0 order"); > - return -EINVAL; > + > + if (folio_test_anon(folio)) { > + /* Cannot split anonymous THP to order-1 */ > + if (new_order == 1) { > + VM_WARN_ONCE(1, "Cannot split to order-1 folio"); > + return -EINVAL; > + } > + } else { > + /* Split shmem folio to non-zero order not supported */ > + if (shmem_mapping(folio->mapping)) { > + VM_WARN_ONCE(1, > + "Cannot split shmem folio to non-0 order"); > + return -EINVAL; > + } > + /* No split if the file system does not support large folio */ > + if (!mapping_large_folio_support(folio->mapping)) { > + VM_WARN_ONCE(1, > + "Cannot split file folio to non-0 order"); > + return -EINVAL; > + } > } > } What about the following sequence: if (folio_test_anon(folio)) { if (new_order == 1) ... } else if (new_order) { if (shmem_mapping(...)) ... ... } if (folio_test_swapcache(folio) && new_order) return -EINVAL; Should result in less churn and reduce indentation level. -- Cheers, David / dhildenb