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Tue, 14 Oct 2025 21:03:25 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFRzf7FvM8OpEXrg7e1JvlWOpwl6hxFANdBMkZkYCR63zSreZUiUYv4PdbI0oENdYzK01tTDw== X-Received: by 2002:a17:90b:33cc:b0:338:3789:2e7b with SMTP id 98e67ed59e1d1-33b51118ee0mr34810857a91.13.1760501005275; Tue, 14 Oct 2025 21:03:25 -0700 (PDT) Received: from zeus ([2405:6580:83a0:7600:6e93:a15a:9134:ae1f]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-33b978607cfsm608006a91.9.2025.10.14.21.03.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Oct 2025 21:03:24 -0700 (PDT) From: Ryosuke Yasuoka To: arnd@arndb.de, gregkh@linuxfoundation.org, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, dakr@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz Cc: Ryosuke Yasuoka , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH rust-next v2 2/3] rust: miscdevice: add llseek support Date: Wed, 15 Oct 2025 13:02:42 +0900 Message-ID: <20251015040246.151141-3-ryasuoka@redhat.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251015040246.151141-1-ryasuoka@redhat.com> References: <20251015040246.151141-1-ryasuoka@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add the ability to write a file_operations->llseek hook in Rust when using the miscdevice abstraction. Signed-off-by: Ryosuke Yasuoka --- rust/kernel/miscdevice.rs | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs index d698cddcb4a5..2efd0847cde1 100644 --- a/rust/kernel/miscdevice.rs +++ b/rust/kernel/miscdevice.rs @@ -126,6 +126,16 @@ fn release(device: Self::Ptr, _file: &File) { drop(device); } + /// Handler for llseek. + fn llseek( + _device: ::Borrowed<'_>, + _file: &mut File, + _offset: i64, + _whence: i32, + ) -> Result { + build_error!(VTABLE_DEFAULT_ERROR) + } + /// Handle for mmap. /// /// This function is invoked when a user space process invokes the `mmap` system call on @@ -296,6 +306,27 @@ impl MiscdeviceVTable { } } + /// # Safety + /// + /// `file` must be a valid file that is associated with a `MiscDeviceRegistration`. + unsafe extern "C" fn llseek(file: *mut bindings::file, offset: i64, whence: c_int) -> i64 { + // SAFETY: The llseek call of a file can access the private data. + let private = unsafe { (*file).private_data }; + // SAFETY: This is a Rust Miscdevice, so we call `into_foreign` in `open` and + // `from_foreign` in `release`, and `fops_llseek` is guaranteed to be called between those + // two operations. + let device = unsafe { ::borrow(private) }; + // SAFETY: + // * The file is valid for the duration of this call. + // * There is no active fdget_pos region on the file on this thread. + let file = unsafe { File::from_raw_file_mut(file) }; + + match T::llseek(device, file, offset, whence) { + Ok(res) => res as i64, + Err(err) => i64::from(err.to_errno()), + } + } + /// # Safety /// /// `file` must be a valid file that is associated with a `MiscDeviceRegistration`. @@ -391,6 +422,11 @@ impl MiscdeviceVTable { const VTABLE: bindings::file_operations = bindings::file_operations { open: Some(Self::open), release: Some(Self::release), + llseek: if T::HAS_LLSEEK { + Some(Self::llseek) + } else { + None + }, mmap: if T::HAS_MMAP { Some(Self::mmap) } else { None }, read_iter: if T::HAS_READ_ITER { Some(Self::read_iter) -- 2.51.0