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[2003:d8:2f12:1b00:5d6b:db26:e2b7:12]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a6e80f2977sm5384651f8f.63.2025.06.25.11.24.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 25 Jun 2025 11:24:15 -0700 (PDT) Message-ID: Date: Wed, 25 Jun 2025 20:24:14 +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: rXJzmxkGFqWCDsc83l2gorjPMu4A43kxZ2IXdzDtJSA_1750875856 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: rspam12 X-Rspamd-Queue-Id: 644EE18000F X-Stat-Signature: xc1xiikwpmgcx9jc45wqzn5i6eyrktpo X-Rspam-User: X-HE-Tag: 1750875859-387328 X-HE-Meta: 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 1OR+Qrso 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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 25.06.25 20:00, Matthew Wilcox wrote: > On Wed, Jun 25, 2025 at 10:48:39AM -0700, Vishal Moola (Oracle) wrote: >> +++ b/mm/memory.c >> @@ -6820,9 +6820,10 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, >> } >> >> while (len) { >> - int bytes, offset, retval; >> + int bytes, folio_offset, page_offset retval; > > offset_in_folio() returns a size_t so that we can support folios larger > than 2GB (which is a real possibility here; hugetlbfs might end up with > a 16GB folio on some architectures). > >> @@ -6837,17 +6838,20 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, >> goto out; >> } >> >> + folio = page_folio(page); >> bytes = len; >> - offset = addr & (PAGE_SIZE - 1); >> - if (bytes > PAGE_SIZE - offset) >> - bytes = PAGE_SIZE - offset; >> + 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. Not special to anon memory I think ... :) Only the offset within a page is okay to derive (existing code). -- Cheers, David / dhildenb