linux-kernel - [PATCH 2/3] rust fs: kiocb: take advantage from file::Offset

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Message-ID: <20251105002346.53119-2-dakr@kernel.org>
Date: Wed,  5 Nov 2025 01:22:49 +0100
From: Danilo Krummrich <dakr@...nel.org>
To: gregkh@...uxfoundation.org,
	rafael@...nel.org,
	ojeda@...nel.org,
	alex.gaynor@...il.com,
	boqun.feng@...il.com,
	gary@...yguo.net,
	bjorn3_gh@...tonmail.com,
	lossin@...nel.org,
	a.hindborg@...nel.org,
	aliceryhl@...gle.com,
	tmgross@...ch.edu,
	viro@...iv.linux.org.uk,
	brauner@...nel.org,
	jack@...e.cz,
	arnd@...db.de
Cc: rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH 2/3] rust fs: kiocb: take advantage from file::Offset

Make use of file::Offset, now that we have a dedicated type for it.

Suggested-by: Alice Ryhl <aliceryhl@...gle.com>
Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
 rust/kernel/fs/kiocb.rs          |  9 ++++++---
 samples/rust/rust_misc_device.rs | 10 +++++++---
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/rust/kernel/fs/kiocb.rs b/rust/kernel/fs/kiocb.rs
index 84c936cd69b0..3159b9ac2bf6 100644
--- a/rust/kernel/fs/kiocb.rs
+++ b/rust/kernel/fs/kiocb.rs
@@ -8,7 +8,10 @@
 
 use core::marker::PhantomData;
 use core::ptr::NonNull;
-use kernel::types::ForeignOwnable;
+use kernel::{
+    fs::file,
+    types::ForeignOwnable, //
+};
 
 /// Wrapper for the kernel's `struct kiocb`.
 ///
@@ -61,8 +64,8 @@ pub fn ki_pos(&self) -> i64 {
     }
 
     /// Gets a mutable reference to the `ki_pos` field.
-    pub fn ki_pos_mut(&mut self) -> &mut i64 {
+    pub fn ki_pos_mut(&mut self) -> &mut file::Offset {
         // SAFETY: We have exclusive access to the kiocb, so we can write to `ki_pos`.
-        unsafe { &mut (*self.as_raw()).ki_pos }
+        unsafe { file::Offset::from_raw(&raw mut (*self.as_raw()).ki_pos) }
     }
 }
diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
index d69bc33dbd99..6a9f59ccf71d 100644
--- a/samples/rust/rust_misc_device.rs
+++ b/samples/rust/rust_misc_device.rs
@@ -100,7 +100,11 @@
 use kernel::{
     c_str,
     device::Device,
-    fs::{File, Kiocb},
+    fs::{
+        file,
+        File,
+        Kiocb, //
+    },
     ioctl::{_IO, _IOC_SIZE, _IOR, _IOW},
     iov::{IovIterDest, IovIterSource},
     miscdevice::{MiscDevice, MiscDeviceOptions, MiscDeviceRegistration},
@@ -183,7 +187,7 @@ fn read_iter(mut kiocb: Kiocb<'_, Self::Ptr>, iov: &mut IovIterDest<'_>) -> Resu
 
         let inner = me.inner.lock();
         // Read the buffer contents, taking the file position into account.
-        let read = iov.simple_read_from_buffer(kiocb.ki_pos_mut(), &inner.buffer)?;
+        let read = iov.simple_read_from_buffer(&mut kiocb.ki_pos_mut().0, &inner.buffer)?;
 
         Ok(read)
     }
@@ -199,7 +203,7 @@ fn write_iter(mut kiocb: Kiocb<'_, Self::Ptr>, iov: &mut IovIterSource<'_>) -> R
         let len = iov.copy_from_iter_vec(&mut inner.buffer, GFP_KERNEL)?;
 
         // Set position to zero so that future `read` calls will see the new contents.
-        *kiocb.ki_pos_mut() = 0;
+        *kiocb.ki_pos_mut() = file::Offset::from(0);
 
         Ok(len)
     }
-- 
2.51.2