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(p200300cbc70dfb00d3ed5f441b2d12af.dip0.t-ipconnect.de. [2003:cb:c70d:fb00:d3ed:5f44:1b2d:12af]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f258b4314sm15212358f8f.9.2025.02.18.08.01.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Feb 2025 08:01:18 -0800 (PST) Message-ID: <6500a93f-aad1-4b21-a94e-feb493c344a3@redhat.com> Date: Tue, 18 Feb 2025 17:01:16 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] mm: allow guard regions in file-backed and read-only mappings To: Lorenzo Stoakes , Andrew Morton Cc: Suren Baghdasaryan , "Liam R . Howlett" , Matthew Wilcox , Vlastimil Babka , "Paul E . McKenney" , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Shuah Khan , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, John Hubbard , Juan Yescas , Kalesh Singh References: 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: zXdVMsPSy0jNh2sluGTcs5umC5rRSAcxM5hGyBCElDg_1739894481 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: CBF1814000B X-Stat-Signature: jpjgpzo3s37tifsr616n6utff1fkacdo X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1739894486-229011 X-HE-Meta: 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 0xam8JFG +v0EKQcFL0MHLPip+hRV/9hQfd/44mDzEvhzKwsie+MMNU2iDAYuXvRn6V1zvSFL/m5Rz7RopVggiUZFrm5fSZtWFCLq+goe1Ys+rPUMhTTjlFTemhyrLNqoLJ64IkbPoPSMrqNGYJzxPm8orVOi2BZmh2ZFjXZfqOGUVltLyHSTObmNXKVhTwiOVpWM05MvsHv4puZ1pps3h9W4uji349d/o8yPjvAvK/YRWzgHXUzYkgT80U7qid9YAgqA2aYof3/anNneYAc+MiVcL0Ta+AhN0E5rEangv7fD14sjSMkNa3apzNxW8BQJgYosIUsjcoH6KTvV5LCR9jRRSVoAXZ5B7TZLChy3hYxaQv6u9N12eIXbtKImcdXuetRk+OO18ZjdDqCKpeyjiCcH27RMAmoO10bo/vo7rh7J/NkUBQUoX/5s0YqhrhSEUu6h6VJY4tqrt 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 13.02.25 19:17, Lorenzo Stoakes wrote: > There is no reason to disallow guard regions in file-backed mappings - > readahead and fault-around both function correctly in the presence of PTE > markers, equally other operations relating to memory-mapped files function > correctly. > > Additionally, read-only mappings if introducing guard-regions, only > restrict the mapping further, which means there is no violation of any > access rights by permitting this to be so. > > Removing this restriction allows for read-only mapped files (such as > executable files) correctly which would otherwise not be permitted. > > Signed-off-by: Lorenzo Stoakes > --- > mm/madvise.c | 8 +------- > 1 file changed, 1 insertion(+), 7 deletions(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index 6ecead476a80..e01e93e179a8 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -1051,13 +1051,7 @@ static bool is_valid_guard_vma(struct vm_area_struct *vma, bool allow_locked) > if (!allow_locked) > disallowed |= VM_LOCKED; > > - if (!vma_is_anonymous(vma)) > - return false; > - > - if ((vma->vm_flags & (VM_MAYWRITE | disallowed)) != VM_MAYWRITE) > - return false; > - > - return true; > + return !(vma->vm_flags & disallowed); > } > > static bool is_guard_pte_marker(pte_t ptent) Acked-by: David Hildenbrand I assume these markers cannot completely prevent us from allocating pages/folios for these underlying file/pageache ranges of these markers in case of shmem during page faults, right? -- Cheers, David / dhildenb