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[2003:cb:c722:3700:6501:8925:6f9:fcdc]) by smtp.gmail.com with ESMTPSA id u8-20020a05600c19c800b004030e8ff964sm19635029wmq.34.2023.12.04.09.59.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 04 Dec 2023 09:59:38 -0800 (PST) Message-ID: <1120cff5-df34-47ab-86ca-d73887fcba2e@redhat.com> Date: Mon, 4 Dec 2023 18:59:37 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 34/39] mm/rmap: introduce folio_try_dup_anon_rmap_[pte|ptes|pmd]() To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , "Matthew Wilcox (Oracle)" , Hugh Dickins , Ryan Roberts , Yin Fengwei , Mike Kravetz , Muchun Song , Peter Xu References: <20231204142146.91437-1-david@redhat.com> <20231204142146.91437-35-david@redhat.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: <20231204142146.91437-35-david@redhat.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-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3F9F0180025 X-Stat-Signature: x7dyg7s79bur8n6oeaartgpaa3k34nud X-HE-Tag: 1701712782-798403 X-HE-Meta: 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 Jp2WE8TN DTc/sxKCemF6Ip1yUoZJxyF22yeckyjqErxwAB4pmbhCwow3bmeXr+P1CKrvdKsayaJ20/joLQP8s8csUQyJHrtTTYOiT9C1UnNdFKBi4J/J1hMjFcpDvU+plr9AGB6DT97ogBstZpsaLMxiNzhpj9WuVO0TYMH8y2BLfMkOH0o0n9RyVDXARQpjTuiWkJ9C4FN9dlIRMzxLULzcacifjVrUj05kKYBxRV4WLsai/iwsy8XImHmQhDJqADT7GaR2uLkPagB+oP9fME3qt2qAubqJdMkAaagi3cLcayPB05tt2Zf4nf80g7t+7Pe1g2+bEAgGKdyeeEgAid01G4T6zgyGuWQJYm8CLKnpcJeQt00kPiF6bT925IB9gO27DxQyJ3dwLuwabnb+LAWsshH08mBsWA8nS5kWOqRRW/L8IqIGieBM2/pbiSGGeXfU+nGK8nFZ6/PIEzO+HtQ+QvDxzLnx5kg== 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: > -static inline void __page_dup_rmap(struct page *page, bool compound) > +static inline int __folio_try_dup_anon_rmap(struct folio *folio, > + struct page *page, unsigned int nr_pages, > + struct vm_area_struct *src_vma, enum rmap_mode mode) > { > - VM_WARN_ON(folio_test_hugetlb(page_folio(page))); > + int i; > > - if (compound) { > - struct folio *folio = (struct folio *)page; > + VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); > > - VM_BUG_ON_PAGE(compound && !PageHead(page), page); > - atomic_inc(&folio->_entire_mapcount); > - } else { > - atomic_inc(&page->_mapcount); > + /* > + * No need to check+clear for already shared PTEs/PMDs of the folio. > + * This includes PTE mappings of (order-0) KSM folios. > + */ > + if (likely(mode == RMAP_MODE_PTE)) { > + for (i = 0; i < nr_pages; i++) { > + if (PageAnonExclusive(page + i)) > + goto clear; > + } > + } else if (mode == RMAP_MODE_PMD) { > + if (PageAnonExclusive(page)) > + goto clear; > } > + goto dup; > + > +clear: > + /* > + * If this folio may have been pinned by the parent process, > + * don't allow to duplicate the mappings but instead require to e.g., > + * copy the subpage immediately for the child so that we'll always > + * guarantee the pinned folio won't be randomly replaced in the > + * future on write faults. > + */ > + if (likely(!folio_is_device_private(folio) && > + unlikely(folio_needs_cow_for_dma(src_vma, folio)))) > + return -EBUSY; > + > + if (likely(mode == RMAP_MODE_PTE)) { > + for (i = 0; i < nr_pages; i++) > + ClearPageAnonExclusive(page + i); > + } else if (mode == RMAP_MODE_PMD) { > + ClearPageAnonExclusive(page); > + } > + > +dup: > + __folio_dup_rmap(folio, page, nr_pages, mode); > + return 0; Playing with this, I think it can be implemented more efficiently by only looping once and optimizing for the common case that PAE is set. Will have to do some more measurements. -- Cheers, David / dhildenb