[PATCH 6.18 091/122] rust: bits: always inline functions using build_assert with arguments

Greg Kroah-Hartman
2026-02-04T15:33:04Z

From: Alexandre Courbot <acourbot@nvidia.com>

commit 09c3c9112d71c44146419c87c55c710e68335741 upstream.

`build_assert` relies on the compiler to optimize out its error path.
Functions using it with its arguments must thus always be inlined,
otherwise the error path of `build_assert` might not be optimized out,
triggering a build error.

Cc: stable@vger.kernel.org
Fixes: cc84ef3b88f4 ("rust: bits: add support for bits/genmask macros")
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://patch.msgid.link/20251208-io-build-assert-v3-4-98aded02c1ea@nvidia.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
rust/kernel/bits.rs | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/bits.rs b/rust/kernel/bits.rs
index 553d50265883..2daead125626 100644
--- a/rust/kernel/bits.rs
+++ b/rust/kernel/bits.rs
@@ -27,7 +27,8 @@ pub fn [<checked_bit_ $ty>](n: u32) -> Option<$ty> {
///
/// This version is the default and should be used if `n` is known at
/// compile time.
- #[inline]
+ // Always inline to optimize out error path of `build_assert`.
+ #[inline(always)]
pub const fn [<bit_ $ty>](n: u32) -> $ty {
build_assert!(n < <$ty>::BITS);
(1 as $ty) << n
@@ -75,7 +76,8 @@ pub fn [<genmask_checked_ $ty>](range: RangeInclusive<u32>) -> Option<$ty> {
/// This version is the default and should be used if the range is known
/// at compile time.
$(#[$genmask_ex])*
- #[inline]
+ // Always inline to optimize out error path of `build_assert`.
+ #[inline(always)]
pub const fn [<genmask_ $ty>](range: RangeInclusive<u32>) -> $ty {
let start = *range.start();
let end = *range.end();
--
2.53.0