linux-kernel - [PATCH] rust: task: mark Task methods inline

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Message-Id: <20250310-inline-c-wrappers-v1-1-d726415e6332@posteo.net>
Date: Mon, 10 Mar 2025 09:39:15 +0000
From: Panagiotis Foliadis <pfoliadis@...teo.net>
To: 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 <benno.lossin@...ton.me>, 
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Nathan Chancellor <nathan@...nel.org>, 
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
 llvm@...ts.linux.dev, Panagiotis Foliadis <pfoliadis@...teo.net>
Subject: [PATCH] rust: task: mark Task methods inline

When you build the kernel using the llvm-18.1.3-rust-1.85.0-x86_64
toolchain provided by kernel.org, the following symbols are generated:

$ nm vmlinux | grep ' _R'.*Task | rustfilt
ffffffff817b2d30 T <kernel::task::Task>::get_pid_ns
ffffffff817b2d50 T <kernel::task::Task>::tgid_nr_ns
ffffffff817b2c90 T <kernel::task::Task>::current_pid_ns
ffffffff817b2d00 T <kernel::task::Task>::signal_pending
ffffffff817b2cc0 T <kernel::task::Task>::uid
ffffffff817b2ce0 T <kernel::task::Task>::euid
ffffffff817b2c70 T <kernel::task::Task>::current
ffffffff817b2d70 T <kernel::task::Task>::wake_up
ffffffff817b2db0 T <kernel::task::Task as kernel::types::AlwaysRefCounted>::dec_ref
ffffffff817b2d90 T <kernel::task::Task as kernel::types::AlwaysRefCounted>::inc_ref

Most of these Rust symbols are trivial wrappers around the C functions
signal_pending, uid, euid, wake_up, dec_ref and inc_ref.It doesn't
make sense to go through a trivial wrapper for these functions, so
mark them inline.

After applying this patch, the above command will produce this output:

ffff8000805aa004 T <kernel::task::Task>::get_pid_ns
ffff8000805aa01c T <kernel::task::Task>::tgid_nr_ns
ffff8000805a9fe8 T <kernel::task::Task>::current_pid_ns
ffff8000805a9fd0 T <kernel::task::Task>::current

Signed-off-by: Panagiotis Foliadis <pfoliadis@...teo.net>
Link: https://github.com/Rust-for-Linux/linux/issues/1145
---
 rust/kernel/task.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
index 07bc22a7645c0c7d792a0a163dd55b8ff0fe5f92..996d7c96e48689a5752817f9ca196c021865291d 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs
@@ -273,18 +273,21 @@ pub fn pid(&self) -> Pid {
     }
 
     /// Returns the UID of the given task.
+    #[inline]
     pub fn uid(&self) -> Kuid {
         // SAFETY: It's always safe to call `task_uid` on a valid task.
         Kuid::from_raw(unsafe { bindings::task_uid(self.as_ptr()) })
     }
 
     /// Returns the effective UID of the given task.
+    #[inline]
     pub fn euid(&self) -> Kuid {
         // SAFETY: It's always safe to call `task_euid` on a valid task.
         Kuid::from_raw(unsafe { bindings::task_euid(self.as_ptr()) })
     }
 
     /// Determines whether the given task has pending signals.
+    #[inline]
     pub fn signal_pending(&self) -> bool {
         // SAFETY: It's always safe to call `signal_pending` on a valid task.
         unsafe { bindings::signal_pending(self.as_ptr()) != 0 }
@@ -319,6 +322,7 @@ pub fn tgid_nr_ns(&self, pidns: Option<&PidNamespace>) -> Pid {
     }
 
     /// Wakes up the task.
+    #[inline]
     pub fn wake_up(&self) {
         // SAFETY: It's always safe to call `signal_pending` on a valid task, even if the task
         // running.
@@ -328,11 +332,13 @@ pub fn wake_up(&self) {
 
 // SAFETY: The type invariants guarantee that `Task` is always refcounted.
 unsafe impl crate::types::AlwaysRefCounted for Task {
+    #[inline]
     fn inc_ref(&self) {
         // SAFETY: The existence of a shared reference means that the refcount is nonzero.
         unsafe { bindings::get_task_struct(self.as_ptr()) };
     }
 
+    #[inline]
     unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
         // SAFETY: The safety requirements guarantee that the refcount is nonzero.
         unsafe { bindings::put_task_struct(obj.cast().as_ptr()) }

---
base-commit: 7f0e9ee5e44887272627d0fcde0b19a675daf597
change-id: 20250308-inline-c-wrappers-da83ec1c2a77

Best regards,
-- 
Panagiotis Foliadis <pfoliadis@...teo.net>