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[2003:cb:c707:4f00:a44a:5ad6:765a:635]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43ec16f1a73sm158435015e9.24.2025.04.08.02.15.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Apr 2025 02:15:54 -0700 (PDT) Message-ID: Date: Tue, 8 Apr 2025 11:15:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/3] mm/gup: remove unneeded checking in follow_page_pte() To: Oscar Salvador , Baoquan He Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mingo@kernel.org, yanjun.zhu@linux.dev, linux-kernel@vger.kernel.org References: <20250407030306.411977-1-bhe@redhat.com> <20250407030306.411977-3-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: wiAScNMn0aEq_Muex8WFxW9vXmWJ4r29KuhMMZjNydA_1744103756 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-Rspamd-Queue-Id: E527240017 X-Stat-Signature: ttndjg1tzxms5wijf66cgwabg1k1sp88 X-Rspam-User: X-HE-Tag: 1744103758-356693 X-HE-Meta: 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 tLk0HTOe i1pLynj1JQaMn16Z5Eg+IMaXTXHJzixmtdL03W4FZpVWk6LdCb/YfpBdmE9EjqDSaOtxtxQKa22RS+jcj7W4HWhZHT8jyVwL2UiPlqX9CZdldG/anWj+ow2JdeEJc/qvWvIU+I7a0ACAbeCfQP1UyF/hl9l5l3aok9nrIbsslRQcJO9RNFgWwti5T0tCLti5/fjn85k9kMPtLMaOpMQPkZ4rn+QAUhdjhmTeotqTymth+N5OxksV2v+q2totPGhBYqFW/l+S4OvkA35LXD0FCdYgnyQTl0v4cWoMdwyolcrFamZARu6oeBBBa0xq+j2ZdSdX96UvXOW3XrjcJmjau4ORhSHjKybRN/+QyTloUgBTYEx4tmcp2t6VUBbLhiM8MQ0aIE3DneD8zqEmNXaTv/BzVNREqKxFIHO5kG3zvrROxgilKXAOn2ZI9Zsf5+66jt2+4qn/pMRWA9I5ylwjqM/Z5ICfmTdgss+Wk 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 08.04.25 11:04, Oscar Salvador wrote: > On Mon, Apr 07, 2025 at 11:03:05AM +0800, Baoquan He wrote: >> In __get_user_pages(), it will traverse page table and take a reference >> to the page the given user address corresponds to if GUP_GET or GUP_PIN >> is set. However, it's not supported both GUP_GET and GUP_PIN are set. >> Even though this check need be done, it should be done earlier, but not >> doing it till entering into follow_page_pte() and failed. >> >> Furthermore, this checking has been done in is_valid_gup_args() and all >> external users of __get_user_pages() will call is_valid_gup_args() to >> catch the illegal setting. We don't need to worry about internal users >> of __get_user_pages() because the gup_flags are set by MM code correctly. >> >> Here remove the checking in follow_page_pte(), and add VM_WARN_ON_ONCE() >> to catch the possible exceptional setting just in case. >> >> And also change the VM_BUG_ON to VM_WARN_ON_ONCE() for checking >> (!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))) because the checking >> has been done in is_valid_gup_args() for external users of __get_user_pages(). > > I will also note that you changed the flags check to VM_WARN_ON_ONCE. > I guess this is fine as we have the WARN_ON_ONCE version in > is_valid_gup_args(). > Yes, that was my reasoning when I proposed it. >> Signed-off-by: Baoquan He > > LGTM, > > Reviewed-by: Oscar Salvador > > Acked-by: David Hildenbrand -- Cheers, David / dhildenb