[PATCH v5] rust: aref: make `AlwaysRefCounted::inc_ref` an associated function
From: Trevor Chan <hidden>
Date: 2026-06-28 09:29:19
Also in:
dri-devel, driver-core, linux-block, linux-fsdevel, linux-mm, linux-pci, lkml, rust-for-linux
Subsystem:
auxiliary bus driver, block layer device driver api [rust], credentials, driver core, kobjects, debugfs and sysfs, drm drivers, drm drivers and common infrastructure [rust], filesystems (vfs and infrastructure), i2c subsystem [rust], memory management - rust, namespaces:, pci subsystem [rust], rust, rust [sync], the rest, usb subsystem · Maintainers:
Greg Kroah-Hartman, "Rafael J. Wysocki", Danilo Krummrich, Andreas Hindborg, Paul Moore, David Airlie, Simona Vetter, Alice Ryhl, Alexander Viro, Christian Brauner, Igor Korotin, Miguel Ojeda, Boqun Feng, Gary Guo, Linus Torvalds
`AlwaysRefCounted::inc_ref` is a function that shouldn't be called lightly. To prevent accidentally calling it, change `inc_ref` to be an associated function. Modify all `AlwaysRefCounted` implementors to work with this change. Suggested-by: Benno Lossin <lossin@kernel.org> Link: https://github.com/Rust-for-Linux/linux/issues/1177 Reviewed-by: Alice Ryhl <aliceryhl@google.com> Signed-off-by: Trevor Chan <redacted> --- Changes in v2: - Don't word wrap the patch Changes in v3: - Make argument name of `Empty::inc_ref` consistent with `Empty::dec_ref` Changes in v4: - Rebase to new rust-next, change new implementors - Reword explanation for change in `AlwaysRefCounted::inc_ref` doc comment Changes in v5: - Change commit message to be imperative --- rust/kernel/auxiliary.rs | 4 ++-- rust/kernel/block/mq/request.rs | 4 ++-- rust/kernel/cred.rs | 4 ++-- rust/kernel/device.rs | 4 ++-- rust/kernel/device/property.rs | 4 ++-- rust/kernel/drm/device.rs | 4 ++-- rust/kernel/drm/gem/mod.rs | 4 ++-- rust/kernel/fs/file.rs | 8 ++++---- rust/kernel/i2c.rs | 8 ++++---- rust/kernel/mm.rs | 8 ++++---- rust/kernel/mm/mmput_async.rs | 4 ++-- rust/kernel/pci.rs | 4 ++-- rust/kernel/pid_namespace.rs | 4 ++-- rust/kernel/platform.rs | 4 ++-- rust/kernel/sync/aref.rs | 9 ++++++--- rust/kernel/task.rs | 4 ++-- rust/kernel/usb.rs | 8 ++++---- 17 files changed, 46 insertions(+), 43 deletions(-)
diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index c42928d5a239..75a61b51cf79 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs@@ -345,9 +345,9 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for Device<Ctx> // SAFETY: Instances of `Device` are always reference-counted. unsafe impl crate::sync::aref::AlwaysRefCounted for Device { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. - unsafe { bindings::get_device(self.as_ref().as_raw()) }; + unsafe { bindings::get_device(obj.as_ref().as_raw()) }; } unsafe fn dec_ref(obj: NonNull<Self>) {
diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs
index ce3e30c81cb5..f41d01ea4595 100644
--- a/rust/kernel/block/mq/request.rs
+++ b/rust/kernel/block/mq/request.rs@@ -234,8 +234,8 @@ unsafe impl<T: Operations> Sync for Request<T> {} // keeps the object alive in memory at least until a matching reference count // decrement is executed. unsafe impl<T: Operations> AlwaysRefCounted for Request<T> { - fn inc_ref(&self) { - self.wrapper_ref().refcount().inc(); + fn inc_ref(obj: &Self) { + obj.wrapper_ref().refcount().inc(); } unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
diff --git a/rust/kernel/cred.rs b/rust/kernel/cred.rs
index ffa156b9df37..d53cbc792fa3 100644
--- a/rust/kernel/cred.rs
+++ b/rust/kernel/cred.rs@@ -78,9 +78,9 @@ pub fn euid(&self) -> Kuid { // SAFETY: The type invariants guarantee that `Credential` is always ref-counted. unsafe impl AlwaysRefCounted for Credential { #[inline] - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. - unsafe { bindings::get_cred(self.0.get()) }; + unsafe { bindings::get_cred(obj.0.get()) }; } #[inline]
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index 645afc49a27d..ec44dcc405d5 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs@@ -449,9 +449,9 @@ pub fn name(&self) -> &CStr { // SAFETY: Instances of `Device` are always reference-counted. unsafe impl crate::sync::aref::AlwaysRefCounted for Device { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. - unsafe { bindings::get_device(self.as_raw()) }; + unsafe { bindings::get_device(obj.as_raw()) }; } unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
diff --git a/rust/kernel/device/property.rs b/rust/kernel/device/property.rs
index 5aead835fbbc..c39ccc1458b9 100644
--- a/rust/kernel/device/property.rs
+++ b/rust/kernel/device/property.rs@@ -361,10 +361,10 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { // SAFETY: Instances of `FwNode` are always reference-counted. unsafe impl crate::sync::aref::AlwaysRefCounted for FwNode { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference guarantees that the // refcount is non-zero. - unsafe { bindings::fwnode_handle_get(self.as_raw()) }; + unsafe { bindings::fwnode_handle_get(obj.as_raw()) }; } unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index 477cf771fb10..0c70ec010bd9 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs@@ -363,9 +363,9 @@ fn deref(&self) -> &Self::Target { // SAFETY: DRM device objects are always reference counted and the get/put functions // satisfy the requirements. unsafe impl<T: drm::Driver, C: DeviceContext> AlwaysRefCounted for Device<T, C> { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. - unsafe { bindings::drm_dev_get(self.as_raw()) }; + unsafe { bindings::drm_dev_get(obj.as_raw()) }; } unsafe fn dec_ref(obj: NonNull<Self>) {
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index c8b66d816871..ee9e412066ab 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs@@ -52,10 +52,10 @@ unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::AlwaysRefCounted for $ Self: IntoGEMObject, $( $( $bind_param : $bind_trait ),+ )? { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference guarantees that the refcount is // non-zero. - unsafe { bindings::drm_gem_object_get(self.as_raw()) }; + unsafe { bindings::drm_gem_object_get(obj.as_raw()) }; } unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs
index 23ee689bd240..8e5967afcd11 100644
--- a/rust/kernel/fs/file.rs
+++ b/rust/kernel/fs/file.rs@@ -199,9 +199,9 @@ unsafe impl Sync for File {} // makes `ARef<File>` own a normal refcount. unsafe impl AlwaysRefCounted for File { #[inline] - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. - unsafe { bindings::get_file(self.as_ptr()) }; + unsafe { bindings::get_file(obj.as_ptr()) }; } #[inline]
@@ -235,9 +235,9 @@ pub struct LocalFile { // makes `ARef<LocalFile>` own a normal refcount. unsafe impl AlwaysRefCounted for LocalFile { #[inline] - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. - unsafe { bindings::get_file(self.as_ptr()) }; + unsafe { bindings::get_file(obj.as_ptr()) }; } #[inline]
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index 624b971ca8b0..1a9882a64c4b 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs@@ -425,9 +425,9 @@ pub fn get(index: i32) -> Result<ARef<Self>> { // SAFETY: Instances of `I2cAdapter` are always reference-counted. unsafe impl AlwaysRefCounted for I2cAdapter { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. - unsafe { bindings::i2c_get_adapter(self.index()) }; + unsafe { bindings::i2c_get_adapter(obj.index()) }; } unsafe fn dec_ref(obj: NonNull<Self>) {
@@ -501,9 +501,9 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for I2cClient<C // SAFETY: Instances of `I2cClient` are always reference-counted. unsafe impl AlwaysRefCounted for I2cClient { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. - unsafe { bindings::get_device(self.as_ref().as_raw()) }; + unsafe { bindings::get_device(obj.as_ref().as_raw()) }; } unsafe fn dec_ref(obj: NonNull<Self>) {
diff --git a/rust/kernel/mm.rs b/rust/kernel/mm.rs
index 4764d7b68f2a..c955cbd884b8 100644
--- a/rust/kernel/mm.rs
+++ b/rust/kernel/mm.rs@@ -57,9 +57,9 @@ unsafe impl Sync for Mm {} // SAFETY: By the type invariants, this type is always refcounted. unsafe impl AlwaysRefCounted for Mm { #[inline] - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The pointer is valid since self is a reference. - unsafe { bindings::mmgrab(self.as_raw()) }; + unsafe { bindings::mmgrab(obj.as_raw()) }; } #[inline]
@@ -93,9 +93,9 @@ unsafe impl Sync for MmWithUser {} // SAFETY: By the type invariants, this type is always refcounted. unsafe impl AlwaysRefCounted for MmWithUser { #[inline] - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The pointer is valid since self is a reference. - unsafe { bindings::mmget(self.as_raw()) }; + unsafe { bindings::mmget(obj.as_raw()) }; } #[inline]
diff --git a/rust/kernel/mm/mmput_async.rs b/rust/kernel/mm/mmput_async.rs
index b8d2f051225c..7df40777654c 100644
--- a/rust/kernel/mm/mmput_async.rs
+++ b/rust/kernel/mm/mmput_async.rs@@ -36,9 +36,9 @@ unsafe impl Sync for MmWithUserAsync {} // SAFETY: By the type invariants, this type is always refcounted. unsafe impl AlwaysRefCounted for MmWithUserAsync { #[inline] - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The pointer is valid since self is a reference. - unsafe { bindings::mmget(self.as_raw()) }; + unsafe { bindings::mmget(obj.as_raw()) }; } #[inline]
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 5071cae6543f..0f16cf0da3d7 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs@@ -482,9 +482,9 @@ impl<'a> crate::dma::Device<'a> for Device<device::Core<'a>> {} // SAFETY: Instances of `Device` are always reference-counted. unsafe impl crate::sync::aref::AlwaysRefCounted for Device { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. - unsafe { bindings::pci_dev_get(self.as_raw()) }; + unsafe { bindings::pci_dev_get(obj.as_raw()) }; } unsafe fn dec_ref(obj: NonNull<Self>) {
diff --git a/rust/kernel/pid_namespace.rs b/rust/kernel/pid_namespace.rs
index 979a9718f153..381c9f980b1f 100644
--- a/rust/kernel/pid_namespace.rs
+++ b/rust/kernel/pid_namespace.rs@@ -43,9 +43,9 @@ pub unsafe fn from_ptr<'a>(ptr: *const bindings::pid_namespace) -> &'a Self { // SAFETY: Instances of `PidNamespace` are always reference-counted. unsafe impl AlwaysRefCounted for PidNamespace { #[inline] - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. - unsafe { bindings::get_pid_ns(self.as_ptr()) }; + unsafe { bindings::get_pid_ns(obj.as_ptr()) }; } #[inline]
diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 9b362e0495d3..85068ae5a405 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs@@ -519,9 +519,9 @@ impl<'a> crate::dma::Device<'a> for Device<device::Core<'a>> {} // SAFETY: Instances of `Device` are always reference-counted. unsafe impl crate::sync::aref::AlwaysRefCounted for Device { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. - unsafe { bindings::get_device(self.as_ref().as_raw()) }; + unsafe { bindings::get_device(obj.as_ref().as_raw()) }; } unsafe fn dec_ref(obj: NonNull<Self>) {
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index b721b2e00b98..2ae2130d5bb1 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs@@ -44,7 +44,10 @@ /// alive.) pub unsafe trait AlwaysRefCounted { /// Increments the reference count on the object. - fn inc_ref(&self); + /// + /// This function should not be called accidentally; a type might declare their own `inc_ref` + /// function and it shouldn't be confused with this one. + fn inc_ref(obj: &Self); /// Decrements the reference count on the object. ///
@@ -145,7 +148,7 @@ pub fn into_raw(me: Self) -> NonNull<T> { impl<T: AlwaysRefCounted> Clone for ARef<T> { fn clone(&self) -> Self { - self.inc_ref(); + T::inc_ref(self); // SAFETY: We just incremented the refcount above. unsafe { Self::from_raw(self.ptr) } }
@@ -162,7 +165,7 @@ fn deref(&self) -> &Self::Target { impl<T: AlwaysRefCounted> From<&T> for ARef<T> { fn from(b: &T) -> Self { - b.inc_ref(); + T::inc_ref(b); // SAFETY: We just incremented the refcount above. unsafe { Self::from_raw(NonNull::from(b)) } }
diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
index 38273f4eedb5..a7711e1558c2 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs@@ -349,9 +349,9 @@ pub fn group_leader(&self) -> &Task { // SAFETY: The type invariants guarantee that `Task` is always refcounted. unsafe impl crate::sync::aref::AlwaysRefCounted for Task { #[inline] - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. - unsafe { bindings::get_task_struct(self.as_ptr()) }; + unsafe { bindings::get_task_struct(obj.as_ptr()) }; } #[inline]
diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
index 7aff0c82d0af..c039059c1891 100644
--- a/rust/kernel/usb.rs
+++ b/rust/kernel/usb.rs@@ -393,11 +393,11 @@ fn as_ref(&self) -> &Device { // SAFETY: Instances of `Interface` are always reference-counted. unsafe impl AlwaysRefCounted for Interface { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The invariants of `Interface` guarantee that `self.as_raw()` // returns a valid `struct usb_interface` pointer, for which we will // acquire a new refcount. - unsafe { bindings::usb_get_intf(self.as_raw()) }; + unsafe { bindings::usb_get_intf(obj.as_raw()) }; } unsafe fn dec_ref(obj: NonNull<Self>) {
@@ -444,11 +444,11 @@ fn as_raw(&self) -> *mut bindings::usb_device { // SAFETY: Instances of `Device` are always reference-counted. unsafe impl AlwaysRefCounted for Device { - fn inc_ref(&self) { + fn inc_ref(obj: &Self) { // SAFETY: The invariants of `Device` guarantee that `self.as_raw()` // returns a valid `struct usb_device` pointer, for which we will // acquire a new refcount. - unsafe { bindings::usb_get_dev(self.as_raw()) }; + unsafe { bindings::usb_get_dev(obj.as_raw()) }; } unsafe fn dec_ref(obj: NonNull<Self>) {
--
2.47.3