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[2003:cb:c726:6800:7ddf:5fc:2ee5:f08a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39eae977a7fsm1367091f8f.45.2025.04.11.01.54.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Apr 2025 01:54:10 -0700 (PDT) Message-ID: Date: Fri, 11 Apr 2025 10:54:09 +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 , linux-mm@kvack.org Cc: 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: <20250410035717.473207-5-bhe@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: i8Ga4C_ErBnrBQuDaqotQEKcsXE57aWSoF1bHvRapIQ_1744361651 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: 0C34E140004 X-Rspamd-Server: rspam05 X-Rspam-User: X-Stat-Signature: ru5wddfazgngjyhpoojyq14hamfkatbw X-HE-Tag: 1744361653-149507 X-HE-Meta: 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 UnJruxlt tF9CmTVHvXeB7p0DFs1wlltezdR4K6EqPc7rgQ1NabFMSeJaKhzlz0ido+nECyInrNWktB9BIAhYHffb7EPRd46PeQftGkROk1OQSn3lZmpqLVx7ovMWB/9n9ghjuVtXNzdzu4yy0lzRPGsWTGB4temYt9dSyxY8mGm2D9Xqtx0ZqehQGnWVN1S77g+udeSscHNw2eN+An7sOZ24etF9kxXA4Qj+OA0I6qOARmh3eBbG1trvrwHjXmSDP28Z/aEZpbd+aZoYtmEeMn/8o587uBk6mc6bZNdGj6I6iVPQlp4NJF3xCSANvRnit+IqtRkibLfpcoH/B9rlWJ4HAFczxtEH5JFM5huReeHJN4Jr1vC4uENPbHprRqc6rNH1r6FY1hnr1TtuDFYMr+pqzZmT72kXWuTYWpYW2jZMEzhAfR6i35ikDnyOjtPMnRHXW+yEoFVcEpmZCkZ6sie45Y/AqPIXCwA== 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 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. > > if (unlikely(size == 0)) > return 0; > + Would not add that line to keep it like fault_in_readable() below. > if (!user_write_access_begin(uaddr, size)) > return size; > - if (!PAGE_ALIGNED(uaddr)) { > - unsafe_put_user(0, uaddr, out); > - uaddr = (char __user *)PAGE_ALIGN((unsigned long)uaddr); > - } > - end = (char __user *)PAGE_ALIGN((unsigned long)start + size); > - if (unlikely(end < start)) > - end = NULL; > - while (uaddr != end) { > - unsafe_put_user(0, uaddr, out); > - uaddr += PAGE_SIZE; > - } > + > + /* Stop once we overflow to 0. */ > + for (; cur && cur < end; cur = PAGE_ALIGN_DOWN(cur + PAGE_SIZE)) > + unsafe_put_user(0, (char __user *)cur, out); > Staring at fault_in_safe_writeable(), we could also do /* 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. In any case, if all functions later look similar and clearer it's a big win. -- Cheers, David / dhildenb