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Thu, 11 Jul 2024 10:27:29 -0700 (PDT) Received: from [10.35.209.243] ([208.115.86.77]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fbb6ab75ffsm53099335ad.175.2024.07.11.10.27.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Jul 2024 10:27:29 -0700 (PDT) Message-ID: <54b6de32-f127-4928-9f4a-acb8653e5c81@redhat.com> Date: Thu, 11 Jul 2024 19:27:27 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v22 1/4] mm: add MAP_DROPPABLE for designating always lazily freeable mappings From: David Hildenbrand To: "Jason A. Donenfeld" , Linus Torvalds Cc: linux-kernel@vger.kernel.org, patches@lists.linux.dev, tglx@linutronix.de, linux-crypto@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, Greg Kroah-Hartman , Adhemerval Zanella Netto , Carlos O'Donell , Florian Weimer , Arnd Bergmann , Jann Horn , Christian Brauner , David Hildenbrand , linux-mm@kvack.org References: <20240709130513.98102-1-Jason@zx2c4.com> <20240709130513.98102-2-Jason@zx2c4.com> <378f23cb-362e-413a-b221-09a5352e79f2@redhat.com> <9b400450-46bc-41c7-9e89-825993851101@redhat.com> <98798483-dfcd-451e-94bb-57d830bf68d8@redhat.com> 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: <98798483-dfcd-451e-94bb-57d830bf68d8@redhat.com> 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: 092798001E X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 3gkq95usu1hyw74578e7qwyqf6u956yy X-HE-Tag: 1720718853-59491 X-HE-Meta: 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 OK12zp6q y8DDk+Rk2aPQTUxx65cdV8jomLpwGGBqPBYbNRUf47T+WF4cPY6jtRWJQ3EirMl8QnB8SbpW2osvErl2wq5Mq07s7UXd3rsR0ssCyCaud45qiGOB60rtWvcVKlc+Xi5eX9jIgBXWUU2NUcht85oC5k003rI1g7A0rL2wYF7Pgzw5fB2q+ldaRJDsKuvJbuUVwjWPkl2ZF2dbfrBcjfNHi1L1tgHb6nC+7xTXP7MwF3Cmp/P8vi4Nvul9OPgPTy763enjZQnVjiQj+DyZ4/qeMfoPd+vbY8CwCr4qroE/rs75/SPTvHFFFOrMb8Pq0C44HiQ0r8aY4WWjmaPt76jbZ+RTxC+L2mr6jKyNTaLpL2ESZLr6BoT1xxtptGD+X1gVZq3CfdCrtwaVgSKw= 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 11.07.24 19:24, David Hildenbrand wrote: > On 11.07.24 19:17, Jason A. Donenfeld wrote: >> On Thu, Jul 11, 2024 at 07:09:36PM +0200, Jason A. Donenfeld wrote: >>> So, hmm... The swapbacked thing really seemed so simple... I wonder if >>> there's a way of recovering that. >> >> Not wanting to introduce a new bitflag, I went looking and noticed this: >> >> /* >> * Private page markings that may be used by the filesystem that owns the page >> * for its own purposes. >> * - PG_private and PG_private_2 cause release_folio() and co to be invoked >> */ >> PAGEFLAG(Private, private, PF_ANY) >> PAGEFLAG(Private2, private_2, PF_ANY) TESTSCFLAG(Private2, private_2, PF_ANY) >> PAGEFLAG(OwnerPriv1, owner_priv_1, PF_ANY) >> TESTCLEARFLAG(OwnerPriv1, owner_priv_1, PF_ANY) >> >> The below +4/-1 diff is pretty hacky and might be illegal in the state >> of California, but I think it does work. The idea is that if that bit is >> normally only used for filesystems, then in the anonymous case, it's >> free to be used for this. >> >> Any opinions about this, or a suggestion on how to do that in a less >> ugly way? >> >> Jason >> >> >> diff --git a/mm/rmap.c b/mm/rmap.c >> index 1f9b5a9cb121..090554277e4a 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1403,6 +1403,8 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma, >> */ >> if (!(vma->vm_flags & VM_DROPPABLE)) >> __folio_set_swapbacked(folio); >> + else >> + folio_set_owner_priv_1(folio); > > > PG_owner_priv_1 maps to PG_swapcache? :) Maybe the combination !swapbacked && swapcache could be used to indicate such folios. (we will never set swapbacked) But likely we have to be a bit careful here. We don't want folio_test_swapcache() to return for folios that ... are not in the swapcache. -- Cheers, David / dhildenb