linux-kernel - [PATCH 5/5] rust: fs: use READ_ONCE instead of read

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Message-ID: <20251231-rwonce-v1-5-702a10b85278@google.com>
Date: Wed, 31 Dec 2025 12:22:29 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Boqun Feng <boqun.feng@...il.com>, Will Deacon <will@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>
Cc: Richard Henderson <richard.henderson@...aro.org>, Matt Turner <mattst88@...il.com>, 
	Magnus Lindholm <linmag7@...il.com>, Catalin Marinas <catalin.marinas@....com>, 
	Miguel Ojeda <ojeda@...nel.org>, Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	FUJITA Tomonori <fujita.tomonori@...il.com>, Frederic Weisbecker <frederic@...nel.org>, 
	Lyude Paul <lyude@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Anna-Maria Behnsen <anna-maria@...utronix.de>, John Stultz <jstultz@...gle.com>, 
	Stephen Boyd <sboyd@...nel.org>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, linux-kernel@...r.kernel.org, 
	linux-alpha@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	rust-for-linux@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH 5/5] rust: fs: use READ_ONCE instead of read_volatile

Using `READ_ONCE` is the correct way to read the `f_flags` field.

Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
 rust/kernel/fs/file.rs | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs
index 23ee689bd2400565223181645157d832a836589f..6b07f08e7012f512e53743266096ce0076d29e1c 100644
--- a/rust/kernel/fs/file.rs
+++ b/rust/kernel/fs/file.rs
@@ -335,12 +335,8 @@ pub fn cred(&self) -> &Credential {
     /// The flags are a combination of the constants in [`flags`].
     #[inline]
     pub fn flags(&self) -> u32 {
-        // This `read_volatile` is intended to correspond to a READ_ONCE call.
-        //
-        // SAFETY: The file is valid because the shared reference guarantees a nonzero refcount.
-        //
-        // FIXME(read_once): Replace with `read_once` when available on the Rust side.
-        unsafe { core::ptr::addr_of!((*self.as_ptr()).f_flags).read_volatile() }
+        // SAFETY: The `f_flags` field of `struct file` is readable with `READ_ONCE`.
+        unsafe { kernel::sync::READ_ONCE(&raw const (*self.as_ptr()).f_flags) }
     }
 }
 

-- 
2.52.0.351.gbe84eed79e-goog