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Howlett" , Miguel Ojeda , Boqun Feng , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Trevor Gross , Danilo Krummrich , Will Deacon , Mark Rutland , linux-mm@kvack.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] rust: page: add byte-wise atomic memory copy methods Message-ID: <20260213095557.GS2995752@noisy.programming.kicks-ass.net> References: <20260212-page-volatile-io-v2-1-a36cb97d15c2@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260212-page-volatile-io-v2-1-a36cb97d15c2@kernel.org> X-Rspamd-Server: rspam12 X-Stat-Signature: 3wmjudu56b978otgs4gkxpehd8n1rgi6 X-Rspamd-Queue-Id: B9510140003 X-Rspam-User: X-HE-Tag: 1770976565-975409 X-HE-Meta: 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 oXGJ6WYo eKD4HSX8KKcpm3eqf3ROLrgGKKHqyAQwNK/445LkNtHrC5ZboU37rWIIr1b7vYTSNNPEGjtCnPwCgTmjc4M/P0HeV9nGX0VdHfaY3LwPopm6BwCcA5RWm1rlBONgoJWyj2oitbZ8M2f0hMBVLPzNl3JcoP2QI+I5qJyNnwxiqXrgTxVxk4GgLh3ZfKNgWmVlHdwUU4tdfBOhSdka9ZJGuhCGWh7psIRNSOvxol9qEP+G1rcTCFzN+08S+hsPTnDvljVzELw6vIC++4w4AI5OfqRALVwWp0sUGO1/gnvK2V7R5387+6VBSqE+KmA== 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 Thu, Feb 12, 2026 at 03:51:24PM +0100, Andreas Hindborg wrote: > When copying data from buffers that are mapped to user space, it is > impossible to guarantee absence of concurrent memory operations on those > buffers. Copying data to/from `Page` from/to these buffers would be > undefined behavior if no special considerations are made. > > Add methods on `Page` to read and write the contents using byte-wise atomic > operations. I'm completely failing to understand. What!? There is no such thing as an 'atomic' byte load, nor does it help one whit against concurrent modification of the memory you're copying.