rust: debugfs: Replace the usage of Rust native atomics

Rust native atomics are not allowed to use in kernel due to the mismatch
of memory model with Linux kernel memory model, hence remove the usage
of Rust native atomics in debufs.

Reviewed-by: Matthew Maurer <mmaurer@google.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Tested-by: David Gow <davidgow@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251022035324.70785-4-boqun.feng@gmail.com

rust/kernel/debugfs/traits.rs

@@ -4,14 +4,11 @@
 //! Traits for rendering or updating values exported to DebugFS.
 
 use crate::prelude::*;
+use crate::sync::atomic::{Atomic, AtomicBasicOps, AtomicType, Relaxed};
 use crate::sync::Mutex;
 use crate::uaccess::UserSliceReader;
 use core::fmt::{self, Debug, Formatter};
 use core::str::FromStr;
-use core::sync::atomic::{
-    AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicIsize, AtomicU16, AtomicU32, AtomicU64,
-    AtomicU8, AtomicUsize, Ordering,
-};
 
 /// A trait for types that can be written into a string.
 ///
@@ -66,37 +63,21 @@ fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
     }
 }
 
-macro_rules! impl_reader_for_atomic {
-    ($(($atomic_type:ty, $int_type:ty)),*) => {
-        $(
-            impl Reader for $atomic_type {
-                fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
-                    let mut buf = [0u8; 21]; // Enough for a 64-bit number.
-                    if reader.len() > buf.len() {
-                        return Err(EINVAL);
-                    }
-                    let n = reader.len();
-                    reader.read_slice(&mut buf[..n])?;
+impl<T: AtomicType + FromStr> Reader for Atomic<T>
+where
+    T::Repr: AtomicBasicOps,
+{
+    fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
+        let mut buf = [0u8; 21]; // Enough for a 64-bit number.
+        if reader.len() > buf.len() {
+            return Err(EINVAL);
+        }
+        let n = reader.len();
+        reader.read_slice(&mut buf[..n])?;
 
-                    let s = core::str::from_utf8(&buf[..n]).map_err(|_| EINVAL)?;
-                    let val = s.trim().parse::<$int_type>().map_err(|_| EINVAL)?;
-                    self.store(val, Ordering::Relaxed);
-                    Ok(())
-                }
-            }
-        )*
-    };
+        let s = core::str::from_utf8(&buf[..n]).map_err(|_| EINVAL)?;
+        let val = s.trim().parse::<T>().map_err(|_| EINVAL)?;
+        self.store(val, Relaxed);
+        Ok(())
+    }
 }
-
-impl_reader_for_atomic!(
-    (AtomicI16, i16),
-    (AtomicI32, i32),
-    (AtomicI64, i64),
-    (AtomicI8, i8),
-    (AtomicIsize, isize),
-    (AtomicU16, u16),
-    (AtomicU32, u32),
-    (AtomicU64, u64),
-    (AtomicU8, u8),
-    (AtomicUsize, usize)
-);

samples/rust/rust_debugfs.rs

@@ -32,14 +32,12 @@
 //! ```
 
 use core::str::FromStr;
-use core::sync::atomic::AtomicUsize;
-use core::sync::atomic::Ordering;
 use kernel::c_str;
 use kernel::debugfs::{Dir, File};
 use kernel::new_mutex;
 use kernel::prelude::*;
+use kernel::sync::atomic::{Atomic, Relaxed};
 use kernel::sync::Mutex;
-
 use kernel::{acpi, device::Core, of, platform, str::CString, types::ARef};
 
 kernel::module_platform_driver! {
@@ -59,7 +57,7 @@ struct RustDebugFs {
     #[pin]
     _compatible: File<CString>,
     #[pin]
-    counter: File<AtomicUsize>,
+    counter: File<Atomic<usize>>,
     #[pin]
     inner: File<Mutex<Inner>>,
 }
@@ -109,7 +107,7 @@ fn probe(
     ) -> Result<Pin<KBox<Self>>> {
         let result = KBox::try_pin_init(RustDebugFs::new(pdev), GFP_KERNEL)?;
         // We can still mutate fields through the files which are atomic or mutexed:
-        result.counter.store(91, Ordering::Relaxed);
+        result.counter.store(91, Relaxed);
         {
             let mut guard = result.inner.lock();
             guard.x = guard.y;
@@ -120,8 +118,8 @@ fn probe(
 }
 
 impl RustDebugFs {
-    fn build_counter(dir: &Dir) -> impl PinInit<File<AtomicUsize>> + '_ {
-        dir.read_write_file(c_str!("counter"), AtomicUsize::new(0))
+    fn build_counter(dir: &Dir) -> impl PinInit<File<Atomic<usize>>> + '_ {
+        dir.read_write_file(c_str!("counter"), Atomic::<usize>::new(0))
     }
 
     fn build_inner(dir: &Dir) -> impl PinInit<File<Mutex<Inner>>> + '_ {

samples/rust/rust_debugfs_scoped.rs

@@ -6,9 +6,9 @@
 //! `Scope::dir` to create a variety of files without the need to separately
 //! track them all.
 
-use core::sync::atomic::AtomicUsize;
 use kernel::debugfs::{Dir, Scope};
 use kernel::prelude::*;
+use kernel::sync::atomic::Atomic;
 use kernel::sync::Mutex;
 use kernel::{c_str, new_mutex, str::CString};
 
@@ -62,7 +62,7 @@ fn create_file_write(
     let file_name = CString::try_from_fmt(fmt!("{name_str}"))?;
     for sub in items {
         nums.push(
-            AtomicUsize::new(sub.parse().map_err(|_| EINVAL)?),
+            Atomic::<usize>::new(sub.parse().map_err(|_| EINVAL)?),
             GFP_KERNEL,
         )?;
     }
@@ -109,7 +109,7 @@ fn init(device_dir: Dir) -> impl PinInit<Self> {
 
 struct DeviceData {
     name: CString,
-    nums: KVec<AtomicUsize>,
+    nums: KVec<Atomic<usize>>,
 }
 
 fn init_control(base_dir: &Dir, dyn_dirs: Dir) -> impl PinInit<Scope<ModuleData>> + '_ {