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[2003:cb:c74b:ca00:4ca2:ff2c:9092:f070]) by smtp.gmail.com with ESMTPSA id fm14-20020a05600c0c0e00b00407b93d8085sm19023933wmb.27.2023.12.12.05.55.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 Dec 2023 05:55:54 -0800 (PST) Message-ID: <62127195-468e-4059-8811-903846e130b0@redhat.com> Date: Tue, 12 Dec 2023 14:55:53 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/9] mm: Simplify the assertions in unuse_pte() To: Matthew Wilcox Cc: Andrew Morton , linux-mm@kvack.org References: <20231211162214.2146080-1-willy@infradead.org> <20231211162214.2146080-3-willy@infradead.org> <02d6d72a-334c-40c0-8490-b941d798d2dc@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-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: AED6118001F X-Rspam-User: X-Stat-Signature: aefwwwf4yays4oqg71eoqrf4chugjbbo X-Rspamd-Server: rspam01 X-HE-Tag: 1702389358-965823 X-HE-Meta: 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 sWOUNCj3 jbHoZHpYVqOcanMN9FNC3Qg6oRL2vKp1SaST9XMmr51ogA2Ei3HsTR0VgxLZEdMjn3DMWl9XpTWt04D0pRQqplqg8Hjx488JqguSl2BImAzQnbdf4lEgtwf/t7gMutA/q8/TEpCYl0gLEBr0WE2a+/IaotiIKZ3m5Jb+BsTIcfhtU94bceXMm3NpPHNZKfLr3QW4GQAzAG+OIDix88vY2YgzZiEjcL7u8IXFgrb9tlebBRstQQerltoGhBJHkovgYb+ayC0T5qgqAB7jZOywEBS/lxzmEC/8YriSwzHaw2MfZKJOssSQ+vu8G2MdpQlhctbNB3r9kx9tQgObWzWII/MVMJKJIyo11UhlH0yT60Vs+U66dNgQclWKYYk4LQLQy8HStm5qBohUwIoEX2jvaN1oxS50LWYi2G2gP2REU5YwCavR7Jkdc4XrExlBFk9HxiFr8jFft5F2S30XnuFeJTOeORw== 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 12.12.23 14:52, Matthew Wilcox wrote: > On Tue, Dec 12, 2023 at 01:26:35PM +0100, David Hildenbrand wrote: >> On 11.12.23 17:22, Matthew Wilcox (Oracle) wrote: >>> We should only see anon folios in this function (and there are many >>> assumptions of that already), so we can simplify these two assertions. >> >> If we swapped in a fresh page, it is not PageAnon before we do the >> page_add_anon_rmap() call. >> >> So I'm pretty sure this is wrong. > > Argh, yes. > > What do you think to just dropping the assertions altogether? You > added them in 78fbe906cc90 as part of general paranoia about using > an existing flag for a new purpose. I think they've now served their > purpose and can go away. At least the ones here, yes. I mean, unuse_pte() is a very corner case feature either way. > > Perhaps simply: > > VM_BUG_ON_PAGE(PageAnonExclusive(page), page); If we refault a page form the swapcache, it would already be PageAnon. Maybe just drop the assertions completely in unuse_pte(). -- Cheers, David / dhildenb