linux-kernel - [PATCH v2 05/11] rust: xarray: use `xas_load` instead of `xa

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Message-Id: <20260206-xarray-entry-send-v2-5-91c41673fd30@kernel.org>
Date: Fri, 06 Feb 2026 22:10:51 +0100
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Tamir Duberstein <tamird@...il.com>, Miguel Ojeda <ojeda@...nel.org>, 
 Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
 Gary Guo <gary@...yguo.net>, 
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
 Benno Lossin <lossin@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
 Vlastimil Babka <vbabka@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>, 
 Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>, 
 Roman Gushchin <roman.gushchin@...ux.dev>, Harry Yoo <harry.yoo@...cle.com>
Cc: Daniel Gomez <da.gomez@...nel.org>, rust-for-linux@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
 Andreas Hindborg <a.hindborg@...nel.org>
Subject: [PATCH v2 05/11] rust: xarray: use `xas_load` instead of `xa_load`
 in `Guard::load`

Replace the call to `xa_load` with `xas_load` in `Guard::load`. The
`xa_load` function takes the RCU lock internally, which we do not need,
since the `Guard` already holds an exclusive lock on the `XArray`. The
`xas_load` function operates on `xa_state` and assumes the required locks
are already held.

This change also removes the `#[expect(dead_code)]` annotation from
`XArrayState` and its constructor, as they are now in use.

Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
---
 rust/kernel/xarray.rs | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs
index d1246ec114898..eadddafb180ec 100644
--- a/rust/kernel/xarray.rs
+++ b/rust/kernel/xarray.rs
@@ -215,10 +215,8 @@ fn load<F, U>(&self, index: usize, f: F) -> Option<U>
     where
         F: FnOnce(NonNull<c_void>) -> U,
     {
-        // SAFETY: `self.xa.xa` is always valid by the type invariant.
-        let ptr = unsafe { bindings::xa_load(self.xa.xa.get(), index) };
-        let ptr = NonNull::new(ptr.cast())?;
-        Some(f(ptr))
+        let mut state = XArrayState::new(self, index);
+        Some(f(state.load()?))
     }

     /// Checks if the XArray contains an element at the specified index.
@@ -327,7 +325,6 @@ pub fn store(
 /// # Invariants
 ///
 /// - `state` is always a valid `bindings::xa_state`.
-#[expect(dead_code)]
 pub(crate) struct XArrayState<'a, 'b, T: ForeignOwnable> {
     /// Holds a reference to the lock guard to ensure the lock is not dropped
     /// while `Self` is live.
@@ -336,7 +333,6 @@ pub(crate) struct XArrayState<'a, 'b, T: ForeignOwnable> {
 }

 impl<'a, 'b, T: ForeignOwnable> XArrayState<'a, 'b, T> {
-    #[expect(dead_code)]
     fn new(access: &'b Guard<'a, T>, index: usize) -> Self {
         let ptr = access.xa.xa.get();
         // INVARIANT: We initialize `self.state` to a valid value below.
@@ -356,6 +352,13 @@ fn new(access: &'b Guard<'a, T>, index: usize) -> Self {
             },
         }
     }
+
+    fn load(&mut self) -> Option<NonNull<c_void>> {
+        // SAFETY: `state.state` is always valid by the type invariant of
+        // `XArrayState and we hold the xarray lock`.
+        let ptr = unsafe { bindings::xas_load(&raw mut self.state) };
+        NonNull::new(ptr.cast())
+    }
 }

 // SAFETY: `XArray<T>` has no shared mutable state so it is `Send` iff `T` is `Send`.

-- 
2.51.2