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[2003:d8:2f3c:2f00:8afc:23fe:3813:776c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4538a421434sm11660005e9.37.2025.06.26.01.14.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 26 Jun 2025 01:14:36 -0700 (PDT) Message-ID: <8e8058b7-9912-40c5-9bf8-571fee4d62a6@redhat.com> Date: Thu, 26 Jun 2025 10:14:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/3] mm/memory.c: convert __copy_remote_vm_str() to folios To: Matthew Wilcox , "Vishal Moola (Oracle)" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jordan Rome , Andrew Morton References: <20250625174841.1094510-1-vishal.moola@gmail.com> <20250625174841.1094510-2-vishal.moola@gmail.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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: rq8CVlA7vClGag5F_qtdMBtAI27KxWef6Zn3TALwJhs_1750925677 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspam-User: X-Rspamd-Queue-Id: 460F71C0005 X-Stat-Signature: qmetuyekri7skgu61ysncckptc9fnsg5 X-HE-Tag: 1750925682-88343 X-HE-Meta: U2FsdGVkX1/lZkzyL0UsLSlBVUXyrEysJfLn4oThyINNWicvsvau9MTKM5mAb2XVO2D2Q8QvnsYSlkD2y47bf7/jKd+ElpS88SxK+WPor/svsLcB5F2zwYRxKpXAcK3zDBNYPsQw7B1teo+21YxrQKRYqw9Ll7iOvg6x4JduZliR6rdXtyrF/a8tTZZCG4khGgQ6ZaNPJcqqd/GaN1ngFoGYd8ccUl3F3IU1Jmhy6CyTo5W/kCNtFUOe8oMOlx6zwoHRv2jQ00UNbzU7vuUpSlcNoS8t/TKv/7rr9m/Wn3YXBlLnB4LFFm9Qxf52LNXbcZRVFcMcGY06xS05HKD8PRf8BNyXZqeRVhTr9aTKj4esp873vlzeK0rysufgjif4TlOMvw7BXEAb8IAhfd/J4wMmnTsBmJsWiTQq4tEtLKHDkVGJbHKOcDNO86cuIQcyTWvwRySkwTg2FsQnLMohTVnkR8li5ePoYfk+7E5jnKK3H7XALQzfQh38LC3cH0fwNJOQnqZ9yo5nqkhQMVIC+QgWNX0DKuSy+2F8ej/WiLTBHHHPGqiwbV2+t3Pn0gxcqYVlzebxVtLVqGVhzIfezPVK50G3lSyklz1DsG9eMVdV8QmuPGjB8vPIrJYNDxryv4r7FoNR+Fvd3pT45WuONwGCn2lkoSxnRfqbcZG37rHN9KTgS/VCcKi4mEmnClNYmmKi4swikYX4uHdhzwPEam/tKct8yhTOyWR/mZT+qEkfune78oyh3E/1V5CClUCgc3vlPUld0fDArPWqdMWn3lWOr6OObts2uroVUOccPWZmPoBCbj1S8TgQLTxiehBCPvDUFjGBzo15Xch/BYVvLert6q4zCYrYAW9VUFxKeq7PkYkgFpjaOCIZg4Ogg5W49az7B6/GXhWVCUlO+Q8Q/9grm3wxy50zfiiSaPZqsaHblN1aMkAwniP68NNigN1XMh/giBMDkYEw0/j9Wwy sjDf8QBX 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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 26.06.25 05:02, Matthew Wilcox wrote: > On Wed, Jun 25, 2025 at 07:00:22PM +0100, Matthew Wilcox wrote: >>> + folio_offset = offset_in_folio(folio, addr); >> >> Umm. Not sure this is safe. A folio might be mapped misaligned, so >> 'addr' might not give you the right offset within the folio. I think >> you might need to use addr - (vma->vm_pgoff << PAGE_SHIFT). But I'd >> defer to others here ... particularly when it comes to anonymous folios. > > Sorry, this calculation is obviously wrong. It should be something like > the calculation in linear_page_index(), only without throwing away the > bottom PAGE_SHIFT bits. But that's for file VMAs only, and I'm not sure > what should be done for anon vmas. Possibly there is no way? In __folio_set_anon(), we set folio->index = linear_page_index(vma, address); and in __page_check_anon_rmap, we check VM_BUG_ON_PAGE(page_pgoff(folio, page) != linear_page_index(vma, address), So given the VMA, addr, folio, we should be able to figure out the offset into the folio. ... but I didn't have my second coffee yet. -- Cheers, David / dhildenb