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(p200300d82f187500202eb0f176d6f9af.dip0.t-ipconnect.de. [2003:d8:2f18:7500:202e:b0f1:76d6:f9af]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a892e528a9sm12735286f8f.60.2025.07.01.01.17.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Jul 2025 01:17:16 -0700 (PDT) Message-ID: Date: Tue, 1 Jul 2025 10:17:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 04/29] mm/page_alloc: let page freeing clear any set page type To: Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux.dev, linux-fsdevel@vger.kernel.org, Andrew Morton , Jonathan Corbet , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Jerrin Shaji George , Arnd Bergmann , Greg Kroah-Hartman , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Alexander Viro , Christian Brauner , Jan Kara , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Minchan Kim , Sergey Senozhatsky , Brendan Jackman , Johannes Weiner , Jason Gunthorpe , John Hubbard , Peter Xu , Xu Xin , Chengming Zhou , Miaohe Lin , Naoya Horiguchi , Oscar Salvador , Rik van Riel , Harry Yoo , Qi Zheng , Shakeel Butt References: <20250630130011.330477-1-david@redhat.com> <20250630130011.330477-5-david@redhat.com> <8c5392d6-372c-4d5d-8446-6af48fba4548@lucifer.local> 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: <8c5392d6-372c-4d5d-8446-6af48fba4548@lucifer.local> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: qK7Np3WGDqXzJUVKzAg4AJM9GFqVWHnZCu7WgUcYi74_1751357837 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: rspam03 X-Rspamd-Queue-Id: A9164180008 X-Stat-Signature: twijsuc1j7rhjx9h98z995w36uxrabgc X-Rspam-User: X-HE-Tag: 1751357840-361292 X-HE-Meta: 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 u+AWvW6z 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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 30.06.25 17:27, Lorenzo Stoakes wrote: > On Mon, Jun 30, 2025 at 02:59:45PM +0200, David Hildenbrand wrote: >> Currently, any user of page types must clear that type before freeing >> a page back to the buddy, otherwise we'll run into mapcount related >> sanity checks (because the page type currently overlays the page >> mapcount). >> >> Let's allow for not clearing the page type by page type users by letting >> the buddy handle it instead. >> >> We'll focus on having a page type set on the first page of a larger >> allocation only. >> >> With this change, we can reliably identify typed folios even though >> they might be in the process of getting freed, which will come in handy >> in migration code (at least in the transition phase). >> >> In the future we might want to warn on some page types. Instead of >> having an "allow list", let's rather wait until we know about once that >> should go on such a "disallow list". > > Is the idea here to get this to show up on folio dumps or? As part of the netmem_desc series, there was a discussion about removing the mystical PP checks -- page_pool_page_is_pp() in page_alloc.c and replacing them by a proper page type check. In that case, we would probably want to warn in case we get such a netmem page unexpectedly freed. But, that page type does not exist yet in code, so the sanity check must be added once introduced. > >> >> Reviewed-by: Zi Yan >> Acked-by: Harry Yoo >> Signed-off-by: David Hildenbrand >> --- >> mm/page_alloc.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 858bc17653af9..44e56d31cfeb1 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -1380,6 +1380,9 @@ __always_inline bool free_pages_prepare(struct page *page, >> mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1); >> page->mapping = NULL; >> } >> + if (unlikely(page_has_type(page))) >> + page->page_type = UINT_MAX; > > Feels like this could do with a comment! /* Reset the page_type -> _mapcount to -1 */ -- Cheers, David / dhildenb