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[2003:cb:c748:ba00:1c00:48ea:7b5a:c12b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4215c19e567sm174033245e9.1.2024.06.11.03.45.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Jun 2024 03:45:26 -0700 (PDT) Message-ID: <68292d2d-c1a4-46bf-a3a2-7fa37fe6b4f3@redhat.com> Date: Tue, 11 Jun 2024 12:45:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/6] fs/proc/task_mmu: don't indicate PM_MMAP_EXCLUSIVE without PM_PRESENT To: Oscar Salvador Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Jonathan Corbet References: <20240607122357.115423-1-david@redhat.com> <20240607122357.115423-3-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-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-Stat-Signature: 7864co6ymqzh96h8rhiijygefarak6d8 X-Rspamd-Queue-Id: BF7954001F X-Rspam-User: X-HE-Tag: 1718102731-957843 X-HE-Meta: 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 hWto+qDJ miK3ke1hWIWJuOuFhSrwtggNAVUogdTuct5h0j1ryIOQKZu87M78S96YtBKG6dmH6Uki7WF6gzcZ4zTZSp73bKLw6lHP3nqY7tqHo+s+5Vxey9cEEUCXWQLH2nVf1aPtIjxBVpvnE3cXBJcDKjUmF/7LJAdgqPJOULTTyU1Q5+qzUna1c7F4oP2/yEweecS5aCF8nu+wBN5mg6T4DFDluOJhjc0vFg8XWEZvSAhjQqDOic/cqdgl06R+sNCNp/Ehp4yHmiWrLGoQNXTWbXL1Dxz9rGwm4isnJK8dYs7+nRGyQy/Q/4xyQNmPWXDMpeiUIfHfVWQyU6RVKITq982cl/F/NzIW5I/q5YoK5fA8IAZp9y2AhtXXkS2TTganDY1MAP4xDP+ZvmzNULgAuqncOdf3ko70QVRRnzq33 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000018, 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 10.06.24 06:38, Oscar Salvador wrote: > On Fri, Jun 07, 2024 at 02:23:53PM +0200, David Hildenbrand wrote: >> Relying on the mapcount for non-present PTEs that reference pages >> doesn't make any sense: they are not accounted in the mapcount, so >> page_mapcount() == 1 won't return the result we actually want to know. >> >> While we don't check the mapcount for migration entries already, we >> could end up checking it for swap, hwpoison, device exclusive, ... >> entries, which we really shouldn't. >> >> There is one exception: device private entries, which we consider >> fake-present (e.g., incremented the mapcount). But we won't care about >> that for now for PM_MMAP_EXCLUSIVE, because indicating PM_SWAP for them >> although they are fake-present already sounds suspiciously wrong. >> >> Let's never indicate PM_MMAP_EXCLUSIVE without PM_PRESENT. > > Alternatively we could use is_pfn_swap_entry? It's all weird, because only device private fake swp entries are fake-present. For these, we might want to use PM_PRESENT, but I don't care enough about device private entries to handle that here in a better way :) Indicating PM_SWAP for something that is not swap (migration/poison/...) is also a bit weird. But likely nobody cared about that for now: it's either present (PM_PRESENT), something else (PM_SWAP), or nothing is there (no bit set). Thanks! -- Cheers, David / dhildenb