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[2003:cb:c726:6800:7ddf:5fc:2ee5:f08a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39eae9807b7sm1776611f8f.60.2025.04.11.04.41.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Apr 2025 04:41:15 -0700 (PDT) Message-ID: <332ce477-59f6-47f9-9687-10b642b86230@redhat.com> Date: Fri, 11 Apr 2025 13:41:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 4/4] mm/gup: clean up codes in fault_in_xxx() functions To: Baoquan He Cc: linux-mm@kvack.org, akpm@linux-foundation.org, osalvador@suse.de, yanjun.zhu@linux.dev, linux-kernel@vger.kernel.org References: <20250410035717.473207-1-bhe@redhat.com> <20250410035717.473207-5-bhe@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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 4bPVPkhvUeveMi2TsmdvPp3yRT0whMDv1nUirwFxEe4_1744371677 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: 232811C0011 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 5x3u5mg7swn6yexzfnpu93uyhytj9xnq X-HE-Tag: 1744371681-720802 X-HE-Meta: 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 G3MnIbBn jv5nzYai9INzLfFbPOAjG6qgo3UguqmN7vuwz7LuOtcKwFWP8/kFHKmcSo7AWJZXu/vcFszjwCoYVA8OE6+e0ydX25lITIws6+XJfEgZBE/rKiFniIdUuHXuOpRecbfnZQcl3mY6tgWpjrSGSRkD2X0MeZS52rZpT3JUyQcXd10W+8R4y8Hg3OBaLSSFCjBk91DLrIzGtd7WH97vdw0wzehr0HOGxR+u7lMyFsAyuPorTQGKgvRLOjXkvdxwB2gZTI1BLi+pk+AD2pZ9CvpC9tbHj65QHzcwexL3rgNhxagkBSJI5WClWDFes61R/dxTWQID4aVWrxzYL/FjC4U21rWeJdtLX4OT+OMk++6dAdiTWn9AATSq1WcF0/fROQXP0V4xUSBII+yZsYudvoDE1YRpQ6uR3qNFea/Rgs0a7SNYxZoict2ZXWs4KKrLJkSeVDIe6kC8OiHhdf7uHpLj6emE0Ag== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, 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 11.04.25 13:15, Baoquan He wrote: > On 04/11/25 at 10:54am, David Hildenbrand wrote: >> On 10.04.25 05:57, Baoquan He wrote: >>> The code style in fault_in_readable() and fault_in_writable() is a >>> little inconsistent with fault_in_safe_writeable(). In fault_in_readable() >>> and fault_in_writable(), it uses 'uaddr' passed in as loop cursor. While >>> in fault_in_safe_writeable(), local variable 'start' is used as loop >>> cursor. This may mislead people when reading code or making change in >>> these codes. >>> >>> Here define explicit loop cursor and use for loop to simplify codes in >>> these three functions. These cleanup can make them be consistent in >>> code style and improve readability. >>> >>> Signed-off-by: Baoquan He >>> --- >>> mm/gup.c | 65 +++++++++++++++++++++++--------------------------------- >>> 1 file changed, 26 insertions(+), 39 deletions(-) >>> >>> diff --git a/mm/gup.c b/mm/gup.c >>> index 77a5bc622567..a76bd7e90a71 100644 >>> --- a/mm/gup.c >>> +++ b/mm/gup.c >>> @@ -2113,28 +2113,24 @@ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start, >>> */ >>> size_t fault_in_writeable(char __user *uaddr, size_t size) >>> { >>> - char __user *start = uaddr, *end; >>> + const unsigned long start = (unsigned long)uaddr; >>> + const unsigned long end = start + size; >>> + unsigned long cur = start; >> >> I would initialize cur in the for loop header, makes the loop easier to >> read. > > Both is fine to me. It's to satisfy checkpatch.sh which complains about > exceeding 80 char in the line. Did checkpatch.sh actually complain? You might be happy to learn that the new limit is 100. :) [...] >> /* Stop once we overflow to 0. */ >> end = PAGE_ALIGN(end) >> if (start < end) >> end = 0; >> >> for (cur = start; cur != end; cur = PAGE_ALIGN_DOWN(cur + PAGE_SIZE)) >> unsafe_put_user(0, (char __user *)cur, out); >> >> Essentially, removing the "cur" check from the loop condition. Not sure if >> that is better. > > The current code is simpler. Your now saying may save the CPU execution > instructions a little bit. Both is fine to me. > > I don't have strong preference, I can make v4 to address these concerns > if decided. Thanks for careful checking. Whatever you prefer! -- Cheers, David / dhildenb