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(p200300d82f38ca00ca3a83da653e0234.dip0.t-ipconnect.de. [2003:d8:2f38:ca00:ca3a:83da:653e:234]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-454dd466154sm129926275e9.12.2025.07.14.05.41.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Jul 2025 05:41:14 -0700 (PDT) Message-ID: <3db65a9c-4ee4-4bba-ba8b-f1171f942766@redhat.com> Date: Mon, 14 Jul 2025 14:41:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 08/14] mm/huge_memory: mark PMD mappings of the huge zero folio special To: Oscar Salvador Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, nvdimm@lists.linux.dev, Andrew Morton , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dan Williams , Alistair Popple , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , Zi Yan , Baolin Wang , Lorenzo Stoakes , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato References: <20250617154345.2494405-1-david@redhat.com> <20250617154345.2494405-9-david@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: D9W07ZqWYlityZNt6x44BGznTF8wYZPc2f54Oz7ji7M_1752496875 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 5B30712000E X-Stat-Signature: g75iwx99gts11owu35c4jzqf6hy5tkux X-HE-Tag: 1752496880-349116 X-HE-Meta: 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 +exueBEC 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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 10:32, Oscar Salvador wrote: > On Tue, Jun 17, 2025 at 05:43:39PM +0200, David Hildenbrand wrote: >> The huge zero folio is refcounted (+mapcounted -- is that a word?) >> differently than "normal" folios, similarly (but different) to the ordinary >> shared zeropage. >> >> For this reason, we special-case these pages in >> vm_normal_page*/vm_normal_folio*, and only allow selected callers to >> still use them (e.g., GUP can still take a reference on them). >> >> vm_normal_page_pmd() already filters out the huge zero folio. However, >> so far we are not marking it as special like we do with the ordinary >> shared zeropage. Let's mark it as special, so we can further refactor >> vm_normal_page_pmd() and vm_normal_page(). >> >> While at it, update the doc regarding the shared zero folios. >> >> Signed-off-by: David Hildenbrand > > Reviewed-by: Oscar Salvador > > While doing this, would it make sense to update vm_normal_page_pmd() > comments to refelect that pmd_special will also catch huge_zero_folio()? > It only mentions huge pfnmaps. > > It might not be worth doing since you remove that code later on, but > maybe if someone stares at this commit alone.. Yes, it should be removed in this patch, thanks! -- Cheers, David / dhildenb