linux.git/rust/kernel/sync/refcount.rs, branch v6.18.21 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git rust: sync: refcount: always inline functions using build_assert with arguments 2026-02-06T15:57:41+00:00 Alexandre Courbot acourbot@nvidia.com 2025-12-08T02:47:03+00:00 e82f822ed14723d536b23d446568d8098c3e1609 commit d6ff6e870077ae0f01a6f860ca1e4a5a825dc032 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: bb38f35b35f9 ("rust: implement `kernel::sync::Refcount`") Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com> Acked-by: Boqun Feng <boqun.feng@gmail.com> Link: https://patch.msgid.link/20251208-io-build-assert-v3-5-98aded02c1ea@nvidia.com Signed-off-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit d6ff6e870077ae0f01a6f860ca1e4a5a825dc032 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: bb38f35b35f9 ("rust: implement `kernel::sync::Refcount`")
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251208-io-build-assert-v3-5-98aded02c1ea@nvidia.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rust: block: convert `block::mq` to use `Refcount` 2025-09-15T07:38:36+00:00 Gary Guo gary@garyguo.net 2025-09-05T04:41:40+00:00 a307bf1db5448eccd72a1d7857f7661c6330d5ad Currently there's a custom reference counting in `block::mq`, which uses `AtomicU64` Rust atomics, and this type doesn't exist on some 32-bit architectures. We cannot just change it to use 32-bit atomics, because doing so will make it vulnerable to refcount overflow. So switch it to use the kernel refcount `kernel::sync::Refcount` instead. There is an operation needed by `block::mq`, atomically decreasing refcount from 2 to 0, which is not available through refcount.h, so I exposed `Refcount::as_atomic` which allows accessing the refcount directly. [boqun: Adopt the LKMM atomic API] Signed-off-by: Gary Guo <gary@garyguo.net> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Benno Lossin <lossin@kernel.org> Reviewed-by: Elle Rhumsaa <elle@weathered-steel.dev> Acked-by: Andreas Hindborg <a.hindborg@kernel.org> Tested-by: David Gow <davidgow@google.com> Link: https://lore.kernel.org/r/20250723233312.3304339-5-gary@kernel.org 
Currently there's a custom reference counting in `block::mq`, which uses
`AtomicU64` Rust atomics, and this type doesn't exist on some 32-bit
architectures. We cannot just change it to use 32-bit atomics, because
doing so will make it vulnerable to refcount overflow. So switch it to
use the kernel refcount `kernel::sync::Refcount` instead.

There is an operation needed by `block::mq`, atomically decreasing
refcount from 2 to 0, which is not available through refcount.h, so
I exposed `Refcount::as_atomic` which allows accessing the refcount
directly.

[boqun: Adopt the LKMM atomic API]
Signed-off-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: Elle Rhumsaa <elle@weathered-steel.dev>
Acked-by: Andreas Hindborg <a.hindborg@kernel.org>
Tested-by: David Gow <davidgow@google.com>
Link: https://lore.kernel.org/r/20250723233312.3304339-5-gary@kernel.org
rust: implement `kernel::sync::Refcount` 2025-09-15T07:38:35+00:00 Gary Guo gary@garyguo.net 2025-09-05T04:41:37+00:00 bb38f35b35f9de0cebc4d62ea73482454e38cef3 This is a wrapping layer of `include/linux/refcount.h`. Currently the kernel refcount has already been used in `Arc`, however it calls into FFI directly. [boqun: Add the missing <> for the link in comment] Signed-off-by: Gary Guo <gary@garyguo.net> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Boqun Feng <boqun.feng@gmail.com> Reviewed-by: Fiona Behrens <me@kloenk.dev> Reviewed-by: Benno Lossin <lossin@kernel.org> Reviewed-by: Elle Rhumsaa <elle@weathered-steel.dev> Link: https://lore.kernel.org/r/20250723233312.3304339-2-gary@kernel.org 
This is a wrapping layer of `include/linux/refcount.h`. Currently the
kernel refcount has already been used in `Arc`, however it calls into
FFI directly.

[boqun: Add the missing <> for the link in comment]
Signed-off-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Fiona Behrens <me@kloenk.dev>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: Elle Rhumsaa <elle@weathered-steel.dev>
Link: https://lore.kernel.org/r/20250723233312.3304339-2-gary@kernel.org