linux-kernel - [PATCH 3/3] rust: iov: take advantage from file::Offset

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Message-ID: <20251105002346.53119-3-dakr@kernel.org>
Date: Wed,  5 Nov 2025 01:22:50 +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 3/3] rust: iov: 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/iov.rs               | 13 +++++++++----
 samples/rust/rust_misc_device.rs |  2 +-
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/rust/kernel/iov.rs b/rust/kernel/iov.rs
index 43bae8923c46..a3b1233441b6 100644
--- a/rust/kernel/iov.rs
+++ b/rust/kernel/iov.rs
@@ -10,6 +10,7 @@
 use crate::{
     alloc::{Allocator, Flags},
     bindings,
+    fs::file,
     prelude::*,
     types::Opaque,
 };
@@ -292,8 +293,12 @@ pub fn copy_to_iter(&mut self, input: &[u8]) -> usize {
     /// that the file will appear to contain `contents` even if takes multiple reads to read the
     /// entire file.
     #[inline]
-    pub fn simple_read_from_buffer(&mut self, ppos: &mut i64, contents: &[u8]) -> Result<usize> {
-        if *ppos < 0 {
+    pub fn simple_read_from_buffer(
+        &mut self,
+        ppos: &mut file::Offset,
+        contents: &[u8],
+    ) -> Result<usize> {
+        if ppos.is_negative() {
             return Err(EINVAL);
         }
         let Ok(pos) = usize::try_from(*ppos) else {
@@ -306,8 +311,8 @@ pub fn simple_read_from_buffer(&mut self, ppos: &mut i64, contents: &[u8]) -> Re
         // BOUNDS: We just checked that `pos < contents.len()` above.
         let num_written = self.copy_to_iter(&contents[pos..]);
 
-        // OVERFLOW: `pos+num_written <= contents.len() <= isize::MAX <= i64::MAX`.
-        *ppos = (pos + num_written) as i64;
+        // OVERFLOW: `pos+num_written <= contents.len() <= isize::MAX <= file::Offset::MAX`.
+        *ppos += num_written as isize;
 
         Ok(num_written)
     }
diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
index 6a9f59ccf71d..edbcc761b4a2 100644
--- a/samples/rust/rust_misc_device.rs
+++ b/samples/rust/rust_misc_device.rs
@@ -187,7 +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(&mut kiocb.ki_pos_mut().0, &inner.buffer)?;
+        let read = iov.simple_read_from_buffer(kiocb.ki_pos_mut(), &inner.buffer)?;
 
         Ok(read)
     }
-- 
2.51.2