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[2003:cb:c70d:fb00:d3ed:5f44:1b2d:12af]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43994f0c10csm12319315e9.26.2025.02.18.02.29.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Feb 2025 02:29:29 -0800 (PST) Message-ID: Date: Tue, 18 Feb 2025 11:29:28 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/7] Add folio_mk_pte() and simplify mk_pte() To: "Matthew Wilcox (Oracle)" , linux-mm@kvack.org Cc: linux-arch@vger.kernel.org, x86@kernel.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org References: <20250217190836.435039-1-willy@infradead.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: <20250217190836.435039-1-willy@infradead.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ZELRq8CAs6_Ym0hG11BnzEdV3xEGRknJ_RCrI1FaNNM_1739874570 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: D1CE8100009 X-Stat-Signature: q9mtqyns3kmau6wixg814cd4cnwws7xo X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1739874573-101497 X-HE-Meta: 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 12JmWsnx 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.014546, 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 17.02.25 20:08, Matthew Wilcox (Oracle) wrote: > The intent is to add folio_mk_pte() to remove the conversion from folio > to page necessary to call mk_pte(). Eventually we might end up removing > mk_pte(), but that's not what's being proposed today. > > I didn't want to add folio_mk_pte() to each architecture, and I didn't > want to lose any optimisations that architectures have from their own > implementation of mk_pte(). Fortunately, most architectures have by > now turned their mk_pte() into a fairly bland variant of pfn_pte(), > but s390 is different. > > So patch 1 hoists the optimisation of calling pte_mkdirty() from s390 > to generic code. I'd appreciate some eyes on this from mm people who > understand this better than I do. I originally had > > - if (write) > + if (write || folio_test_dirty(folio)) > entry = maybe_mkwrite(pte_mkdirty(entry), vma); > > and I think that broke COW under some circumstances that 01.org could > reproduce and I couldn't. If it's an anon folio that logic would be broken, yes (anon CoW). We do have can_change_pte_writable() that tells you when it is safe to upgrade write permissions for a PTE. Looking at can_change_pte_writable(), I don't know if filesystems with writenotify might have a problem when setting the PTE dirty and allowing for write access, just because the folio is dirty. So I assume that it would break fs-level CoW indeed. -- Cheers, David / dhildenb