linux-kernel - [PATCH] rust: debugfs: Implement Reader for Mutex<T> only when T is Unpin

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Message-ID: <20251022034237.70431-1-boqun.feng@gmail.com>
Date: Tue, 21 Oct 2025 23:42:37 -0400
From: Boqun Feng <boqun.feng@...il.com>
To: Peter Zijlstra <peterz@...radead.org>,
	Daniel Almeida <daniel.almeida@...labora.com>,
	Matthew Maurer <mmaurer@...gle.com>,
	Danilo Krummrich <dakr@...nel.org>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org,
	linux-next@...r.kernel.org,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	lossin@...nel.org,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	rust-for-linux@...r.kernel.org
Subject: [PATCH] rust: debugfs: Implement Reader for Mutex<T> only when T is Unpin

Since we are going to make `Mutex<T>` structurally pin the data (i.e.
`T`), therefore `.lock()` function only returns a `Guard` that can
dereference a mutable reference to `T` if only `T` is `Unpin`, therefore
restrict the impl `Reader` block of `Mutex<T>` to that.

Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
 rust/kernel/debugfs/traits.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/debugfs/traits.rs b/rust/kernel/debugfs/traits.rs
index ab009eb254b3..ba7ec5a900b8 100644
--- a/rust/kernel/debugfs/traits.rs
+++ b/rust/kernel/debugfs/traits.rs
@@ -50,7 +50,7 @@ pub trait Reader {
     fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result;
 }
 
-impl<T: FromStr> Reader for Mutex<T> {
+impl<T: FromStr + Unpin> Reader for Mutex<T> {
     fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
         let mut buf = [0u8; 128];
         if reader.len() > buf.len() {
-- 
2.51.0