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[87.94.132.183]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-53dd2481e86sm270678e87.129.2024.11.22.00.09.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 22 Nov 2024 00:09:51 -0800 (PST) Message-ID: <1cb1a118-7cc2-4ba5-bf56-b51bfd84cd63@gmail.com> Date: Fri, 22 Nov 2024 10:09:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/2] rust: page: Extend support to existing struct page mappings To: Jann Horn Cc: rust-for-linux@vger.kernel.org, Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Wedson Almeida Filho , Valentin Obst , open list , Andrew Morton , "open list:MEMORY MANAGEMENT" , airlied@redhat.com References: <20241119112408.779243-1-abdiel.janulgue@gmail.com> <20241119112408.779243-3-abdiel.janulgue@gmail.com> <43a07c04-2985-4999-b6d6-732794906a36@gmail.com> Content-Language: en-US From: Abdiel Janulgue In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 82B2980005 X-Stat-Signature: 5o4q6r6jgyhhgi9q63kzm4cgjmx4dsyo X-Rspam-User: X-HE-Tag: 1732262893-304801 X-HE-Meta: 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 EgJfrZyw 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.068526, 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 21/11/2024 22:17, Jann Horn wrote: > > Does Rust also prevent safe code from invoking inc_ref() on the > returned Page reference? Normally, the AlwaysRefCounted trait means > that safe code can create an owned reference from a shared reference, > right? While it is possible for someone to *manually* convert the Page reference returned in page_slice_to_page() to a refcounted Page (one could wrap it in an ARef). However, by design, page_slice_to_page() explicitly returns just an ordinary Page reference. We could add an invariant in page_slice_to_page() to warn against such usage just in case. Anyway seems like the consensus from the other thread is to avoid refcounting the rust Page abstraction. If we go with that, then that moots this issue. Regards, Abdiel