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(p200300d82f2c1e001e1e7a32e7986457.dip0.t-ipconnect.de. [2003:d8:2f2c:1e00:1e1e:7a32:e798:6457]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4532dea07e3sm19940355e9.9.2025.06.12.05.45.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Jun 2025 05:45:43 -0700 (PDT) Message-ID: <95b46a68-3461-4555-a168-df82d53efcf3@redhat.com> Date: Thu, 12 Jun 2025 14:45:41 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/pagewalk: split walk_page_range_novma() into kernel/user parts To: Lorenzo Stoakes , Andrew Morton Cc: Barry Song , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Muchun Song , Oscar Salvador , Huacai Chen , WANG Xuerui , Jonas Bonn , Stefan Kristiansson , Stafford Horne , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Jann Horn , loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, linux-openrisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-mm@kvack.org References: <20250605135104.90720-1-lorenzo.stoakes@oracle.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: <20250605135104.90720-1-lorenzo.stoakes@oracle.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: uzlGNtGY5vEfjoDUrQgMcHXk8CKwmYRqJrAkj8J5HFU_1749732344 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: rspam01 X-Stat-Signature: czsfhtdr7jsfmgk8cabkmhuwfx4yqjx9 X-Rspamd-Queue-Id: 753FB1C001C X-Rspam-User: X-HE-Tag: 1749732347-683368 X-HE-Meta: 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 TT/qWM2Q 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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 05.06.25 15:51, Lorenzo Stoakes wrote: > The walk_page_range_novma() function is rather confusing - it supports two > modes, one used often, the other used only for debugging. > > The first mode is the common case of traversal of kernel page tables, which > is what nearly all callers use this for. > > Secondly it provides an unusual debugging interface that allows for the > traversal of page tables in a userland range of memory even for that memory > which is not described by a VMA. > > It is far from certain that such page tables should even exist, but perhaps > this is precisely why it is useful as a debugging mechanism. > > As a result, this is utilised by ptdump only. Historically, things were > reversed - ptdump was the only user, and other parts of the kernel evolved > to use the kernel page table walking here. > > Since we have some complicated and confusing locking rules for the novma > case, it makes sense to separate the two usages into their own functions. > > Doing this also provide self-documentation as to the intent of the caller - > are they doing something rather unusual or are they simply doing a standard > kernel page table walk? > > We therefore establish two separate functions - walk_page_range_debug() for > this single usage, and walk_kernel_page_table_range() for general kernel > page table walking. > > The walk_page_range_debug() function is currently used to traverse both > userland and kernel mappings, so we maintain this and in the case of kernel > mappings being traversed, we have walk_page_range_debug() invoke > walk_kernel_page_table_range() internally. > > We additionally make walk_page_range_debug() internal to mm. > > Signed-off-by: Lorenzo Stoakes > Acked-by: Mike Rapoport (Microsoft) > Acked-by: Qi Zheng > Reviewed-by: Oscar Salvador > Reviewed-by: Suren Baghdasaryan > --- Acked-by: David Hildenbrand -- Cheers, David / dhildenb