Merge tag 'rust-6.13' of https://github.com/Rust-for-Linux/linux

Pull rust updates from Miguel Ojeda:
 "Toolchain and infrastructure:

   - Enable a series of lints, including safety-related ones, e.g. the
     compiler will now warn about missing safety comments, as well as
     unnecessary ones. How safety documentation is organized is a
     frequent source of review comments, thus having the compiler guide
     new developers on where they are expected (and where not) is very
     nice.

   - Start using '#[expect]': an interesting feature in Rust (stabilized
     in 1.81.0) that makes the compiler warn if an expected warning was
     _not_ emitted. This is useful to avoid forgetting cleaning up
     locally ignored diagnostics ('#[allow]'s).

   - Introduce '.clippy.toml' configuration file for Clippy, the Rust
     linter, which will allow us to tweak its behaviour. For instance,
     our first use cases are declaring a disallowed macro and, more
     importantly, enabling the checking of private items.

   - Lints-related fixes and cleanups related to the items above.

   - Migrate from 'receiver_trait' to 'arbitrary_self_types': to get the
     kernel into stable Rust, one of the major pieces of the puzzle is
     the support to write custom types that can be used as 'self', i.e.
     as receivers, since the kernel needs to write types such as 'Arc'
     that common userspace Rust would not. 'arbitrary_self_types' has
     been accepted to become stable, and this is one of the steps
     required to get there.

   - Remove usage of the 'new_uninit' unstable feature.

   - Use custom C FFI types. Includes a new 'ffi' crate to contain our
     custom mapping, instead of using the standard library 'core::ffi'
     one. The actual remapping will be introduced in a later cycle.

   - Map '__kernel_{size_t,ssize_t,ptrdiff_t}' to 'usize'/'isize'
     instead of 32/64-bit integers.

   - Fix 'size_t' in bindgen generated prototypes of C builtins.

   - Warn on bindgen < 0.69.5 and libclang >= 19.1 due to a double issue
     in the projects, which we managed to trigger with the upcoming
     tracepoint support. It includes a build test since some
     distributions backported the fix (e.g. Debian -- thanks!). All
     major distributions we list should be now OK except Ubuntu non-LTS.

  'macros' crate:

   - Adapt the build system to be able run the doctests there too; and
     clean up and enable the corresponding doctests.

  'kernel' crate:

   - Add 'alloc' module with generic kernel allocator support and remove
     the dependency on the Rust standard library 'alloc' and the
     extension traits we used to provide fallible methods with flags.

     Add the 'Allocator' trait and its implementations '{K,V,KV}malloc'.
     Add the 'Box' type (a heap allocation for a single value of type
     'T' that is also generic over an allocator and considers the
     kernel's GFP flags) and its shorthand aliases '{K,V,KV}Box'. Add
     'ArrayLayout' type. Add 'Vec' (a contiguous growable array type)
     and its shorthand aliases '{K,V,KV}Vec', including iterator
     support.

     For instance, now we may write code such as:

         let mut v = KVec::new();
         v.push(1, GFP_KERNEL)?;
         assert_eq!(&v, &[1]);

     Treewide, move as well old users to these new types.

   - 'sync' module: add global lock support, including the
     'GlobalLockBackend' trait; the 'Global{Lock,Guard,LockedBy}' types
     and the 'global_lock!' macro. Add the 'Lock::try_lock' method.

   - 'error' module: optimize 'Error' type to use 'NonZeroI32' and make
     conversion functions public.

   - 'page' module: add 'page_align' function.

   - Add 'transmute' module with the existing 'FromBytes' and 'AsBytes'
     traits.

   - 'block::mq::request' module: improve rendered documentation.

   - 'types' module: extend 'Opaque' type documentation and add simple
     examples for the 'Either' types.

  drm/panic:

   - Clean up a series of Clippy warnings.

  Documentation:

   - Add coding guidelines for lints and the '#[expect]' feature.

   - Add Ubuntu to the list of distributions in the Quick Start guide.

  MAINTAINERS:

   - Add Danilo Krummrich as maintainer of the new 'alloc' module.

  And a few other small cleanups and fixes"

* tag 'rust-6.13' of https://github.com/Rust-for-Linux/linux: (82 commits)
  rust: alloc: Fix `ArrayLayout` allocations
  docs: rust: remove spurious item in `expect` list
  rust: allow `clippy::needless_lifetimes`
  rust: warn on bindgen < 0.69.5 and libclang >= 19.1
  rust: use custom FFI integer types
  rust: map `__kernel_size_t` and friends also to usize/isize
  rust: fix size_t in bindgen prototypes of C builtins
  rust: sync: add global lock support
  rust: macros: enable the rest of the tests
  rust: macros: enable paste! use from macro_rules!
  rust: enable macros::module! tests
  rust: kbuild: expand rusttest target for macros
  rust: types: extend `Opaque` documentation
  rust: block: fix formatting of `kernel::block::mq::request` module
  rust: macros: fix documentation of the paste! macro
  rust: kernel: fix THIS_MODULE header path in ThisModule doc comment
  rust: page: add Rust version of PAGE_ALIGN
  rust: helpers: remove unnecessary header includes
  rust: exports: improve grammar in commentary
  drm/panic: allow verbose version check
  ...

4 files changed, 49 insertions, 40 deletions

diff --git a/rust/kernel/block/mq/operations.rs b/rust/kernel/block/mq/operations.rs
index 9ba7fdfeb4b2..c8646d0d9866 100644
--- a/rust/kernel/block/mq/operations.rs
+++ b/rust/kernel/block/mq/operations.rs
@@ -131,7 +131,7 @@ impl<T: Operations> OperationsVTable<T> {
     unsafe extern "C" fn poll_callback(
         _hctx: *mut bindings::blk_mq_hw_ctx,
         _iob: *mut bindings::io_comp_batch,
-    ) -> core::ffi::c_int {
+    ) -> crate::ffi::c_int {
         T::poll().into()
     }
 
@@ -145,9 +145,9 @@ impl<T: Operations> OperationsVTable<T> {
     /// for the same context.
     unsafe extern "C" fn init_hctx_callback(
         _hctx: *mut bindings::blk_mq_hw_ctx,
-        _tagset_data: *mut core::ffi::c_void,
-        _hctx_idx: core::ffi::c_uint,
-    ) -> core::ffi::c_int {
+        _tagset_data: *mut crate::ffi::c_void,
+        _hctx_idx: crate::ffi::c_uint,
+    ) -> crate::ffi::c_int {
         from_result(|| Ok(0))
     }
 
@@ -159,7 +159,7 @@ impl<T: Operations> OperationsVTable<T> {
     /// This function may only be called by blk-mq C infrastructure.
     unsafe extern "C" fn exit_hctx_callback(
         _hctx: *mut bindings::blk_mq_hw_ctx,
-        _hctx_idx: core::ffi::c_uint,
+        _hctx_idx: crate::ffi::c_uint,
     ) {
     }
 
@@ -176,9 +176,9 @@ impl<T: Operations> OperationsVTable<T> {
     unsafe extern "C" fn init_request_callback(
         _set: *mut bindings::blk_mq_tag_set,
         rq: *mut bindings::request,
-        _hctx_idx: core::ffi::c_uint,
-        _numa_node: core::ffi::c_uint,
-    ) -> core::ffi::c_int {
+        _hctx_idx: crate::ffi::c_uint,
+        _numa_node: crate::ffi::c_uint,
+    ) -> crate::ffi::c_int {
         from_result(|| {
             // SAFETY: By the safety requirements of this function, `rq` points
             // to a valid allocation.
@@ -203,7 +203,7 @@ impl<T: Operations> OperationsVTable<T> {
     unsafe extern "C" fn exit_request_callback(
         _set: *mut bindings::blk_mq_tag_set,
         rq: *mut bindings::request,
-        _hctx_idx: core::ffi::c_uint,
+        _hctx_idx: crate::ffi::c_uint,
     ) {
         // SAFETY: The tagset invariants guarantee that all requests are allocated with extra memory
         // for the request data.
diff --git a/rust/kernel/block/mq/raw_writer.rs b/rust/kernel/block/mq/raw_writer.rs
index 9222465d670b..7e2159e4f6a6 100644
--- a/rust/kernel/block/mq/raw_writer.rs
+++ b/rust/kernel/block/mq/raw_writer.rs
@@ -25,7 +25,7 @@ impl<'a> RawWriter<'a> {
     }
 
     pub(crate) fn from_array<const N: usize>(
-        a: &'a mut [core::ffi::c_char; N],
+        a: &'a mut [crate::ffi::c_char; N],
     ) -> Result<RawWriter<'a>> {
         Self::new(
             // SAFETY: the buffer of `a` is valid for read and write as `u8` for
diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs
index a0e22827f3f4..7943f43b9575 100644
--- a/rust/kernel/block/mq/request.rs
+++ b/rust/kernel/block/mq/request.rs
@@ -16,50 +16,55 @@ use core::{
     sync::atomic::{AtomicU64, Ordering},
 };
 
-/// A wrapper around a blk-mq `struct request`. This represents an IO request.
+/// A wrapper around a blk-mq [`struct request`]. This represents an IO request.
 ///
 /// # Implementation details
 ///
 /// There are four states for a request that the Rust bindings care about:
 ///
-/// A) Request is owned by block layer (refcount 0)
-/// B) Request is owned by driver but with zero `ARef`s in existence
-///    (refcount 1)
-/// C) Request is owned by driver with exactly one `ARef` in existence
-///    (refcount 2)
-/// D) Request is owned by driver with more than one `ARef` in existence
-///    (refcount > 2)
+/// 1. Request is owned by block layer (refcount 0).
+/// 2. Request is owned by driver but with zero [`ARef`]s in existence
+///    (refcount 1).
+/// 3. Request is owned by driver with exactly one [`ARef`] in existence
+///    (refcount 2).
+/// 4. Request is owned by driver with more than one [`ARef`] in existence
+///    (refcount > 2).
 ///
 ///
-/// We need to track A and B to ensure we fail tag to request conversions for
+/// We need to track 1 and 2 to ensure we fail tag to request conversions for
 /// requests that are not owned by the driver.
 ///
-/// We need to track C and D to ensure that it is safe to end the request and hand
+/// We need to track 3 and 4 to ensure that it is safe to end the request and hand
 /// back ownership to the block layer.
 ///
 /// The states are tracked through the private `refcount` field of
 /// `RequestDataWrapper`. This structure lives in the private data area of the C
-/// `struct request`.
+/// [`struct request`].
 ///
 /// # Invariants
 ///
-/// * `self.0` is a valid `struct request` created by the C portion of the kernel.
+/// * `self.0` is a valid [`struct request`] created by the C portion of the
+///   kernel.
 /// * The private data area associated with this request must be an initialized
 ///   and valid `RequestDataWrapper<T>`.
 /// * `self` is reference counted by atomic modification of
-///   self.wrapper_ref().refcount().
+///   `self.wrapper_ref().refcount()`.
+///
+/// [`struct request`]: srctree/include/linux/blk-mq.h
 ///
 #[repr(transparent)]
 pub struct Request<T: Operations>(Opaque<bindings::request>, PhantomData<T>);
 
 impl<T: Operations> Request<T> {
-    /// Create an `ARef<Request>` from a `struct request` pointer.
+    /// Create an [`ARef<Request>`] from a [`struct request`] pointer.
     ///
     /// # Safety
     ///
     /// * The caller must own a refcount on `ptr` that is transferred to the
-    ///   returned `ARef`.
-    /// * The type invariants for `Request` must hold for the pointee of `ptr`.
+    ///   returned [`ARef`].
+    /// * The type invariants for [`Request`] must hold for the pointee of `ptr`.
+    ///
+    /// [`struct request`]: srctree/include/linux/blk-mq.h
     pub(crate) unsafe fn aref_from_raw(ptr: *mut bindings::request) -> ARef<Self> {
         // INVARIANT: By the safety requirements of this function, invariants are upheld.
         // SAFETY: By the safety requirement of this function, we own a
@@ -84,12 +89,14 @@ impl<T: Operations> Request<T> {
     }
 
     /// Try to take exclusive ownership of `this` by dropping the refcount to 0.
-    /// This fails if `this` is not the only `ARef` pointing to the underlying
-    /// `Request`.
+    /// This fails if `this` is not the only [`ARef`] pointing to the underlying
+    /// [`Request`].
     ///
-    /// If the operation is successful, `Ok` is returned with a pointer to the
-    /// C `struct request`. If the operation fails, `this` is returned in the
-    /// `Err` variant.
+    /// If the operation is successful, [`Ok`] is returned with a pointer to the
+    /// C [`struct request`]. If the operation fails, `this` is returned in the
+    /// [`Err`] variant.
+    ///
+    /// [`struct request`]: srctree/include/linux/blk-mq.h
     fn try_set_end(this: ARef<Self>) -> Result<*mut bindings::request, ARef<Self>> {
         // We can race with `TagSet::tag_to_rq`
         if let Err(_old) = this.wrapper_ref().refcount().compare_exchange(
@@ -109,7 +116,7 @@ impl<T: Operations> Request<T> {
 
     /// Notify the block layer that the request has been completed without errors.
     ///
-    /// This function will return `Err` if `this` is not the only `ARef`
+    /// This function will return [`Err`] if `this` is not the only [`ARef`]
     /// referencing the request.
     pub fn end_ok(this: ARef<Self>) -> Result<(), ARef<Self>> {
         let request_ptr = Self::try_set_end(this)?;
@@ -123,13 +130,13 @@ impl<T: Operations> Request<T> {
         Ok(())
     }
 
-    /// Return a pointer to the `RequestDataWrapper` stored in the private area
+    /// Return a pointer to the [`RequestDataWrapper`] stored in the private area
     /// of the request structure.
     ///
     /// # Safety
     ///
     /// - `this` must point to a valid allocation of size at least size of
-    ///   `Self` plus size of `RequestDataWrapper`.
+    ///   [`Self`] plus size of [`RequestDataWrapper`].
     pub(crate) unsafe fn wrapper_ptr(this: *mut Self) -> NonNull<RequestDataWrapper> {
         let request_ptr = this.cast::<bindings::request>();
         // SAFETY: By safety requirements for this function, `this` is a
@@ -141,7 +148,7 @@ impl<T: Operations> Request<T> {
         unsafe { NonNull::new_unchecked(wrapper_ptr) }
     }
 
-    /// Return a reference to the `RequestDataWrapper` stored in the private
+    /// Return a reference to the [`RequestDataWrapper`] stored in the private
     /// area of the request structure.
     pub(crate) fn wrapper_ref(&self) -> &RequestDataWrapper {
         // SAFETY: By type invariant, `self.0` is a valid allocation. Further,
@@ -152,13 +159,15 @@ impl<T: Operations> Request<T> {
     }
 }
 
-/// A wrapper around data stored in the private area of the C `struct request`.
+/// A wrapper around data stored in the private area of the C [`struct request`].
+///
+/// [`struct request`]: srctree/include/linux/blk-mq.h
 pub(crate) struct RequestDataWrapper {
     /// The Rust request refcount has the following states:
     ///
     /// - 0: The request is owned by C block layer.
-    /// - 1: The request is owned by Rust abstractions but there are no ARef references to it.
-    /// - 2+: There are `ARef` references to the request.
+    /// - 1: The request is owned by Rust abstractions but there are no [`ARef`] references to it.
+    /// - 2+: There are [`ARef`] references to the request.
     refcount: AtomicU64,
 }
 
@@ -204,7 +213,7 @@ fn atomic_relaxed_op_return(target: &AtomicU64, op: impl Fn(u64) -> u64) -> u64
 }
 
 /// Store the result of `op(target.load)` in `target` if `target.load() !=
-/// pred`, returning true if the target was updated.
+/// pred`, returning [`true`] if the target was updated.
 fn atomic_relaxed_op_unless(target: &AtomicU64, op: impl Fn(u64) -> u64, pred: u64) -> bool {
     target
         .fetch_update(Ordering::Relaxed, Ordering::Relaxed, |x| {
diff --git a/rust/kernel/block/mq/tag_set.rs b/rust/kernel/block/mq/tag_set.rs
index f9a1ca655a35..d7f175a05d99 100644
--- a/rust/kernel/block/mq/tag_set.rs
+++ b/rust/kernel/block/mq/tag_set.rs
@@ -53,7 +53,7 @@ impl<T: Operations> TagSet<T> {
                     queue_depth: num_tags,
                     cmd_size,
                     flags: bindings::BLK_MQ_F_SHOULD_MERGE,
-                    driver_data: core::ptr::null_mut::<core::ffi::c_void>(),
+                    driver_data: core::ptr::null_mut::<crate::ffi::c_void>(),
                     nr_maps: num_maps,
                     ..tag_set
                 }