[PATCH 10/10] rust: xarray: fix false positive lockdep warnings

[Andreas Hindborg <a.hindborg@kernel.org>]

Replace the `xa_init_flags` helper with direct initialization of XArray
structures using `__spin_lock_init`. This allows each XArray to have
its own lock class key for lockdep, preventing false positive warnings
about lock ordering violations.

Add a `new_xarray!` macro that automatically generates a unique lock
class key for each XArray instantiation site. The macro accepts an
optional name parameter and uses the `optional_name!` and
`static_lock_class!` macros to generate appropriate names and lock
classes.

Update the `XArray::new` method signature to accept explicit name and
lock class key parameters. This enables proper lockdep tracking while
maintaining flexibility for advanced use cases.

Remove `rust_helper_xa_init_flags` as it is now dead code.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/helpers/xarray.c       |  5 ---
 rust/kernel/xarray.rs       | 74 +++++++++++++++++++++++++++++++++------------
 rust/kernel/xarray/entry.rs | 55 ++++++++++++++++++---------------
 3 files changed, 86 insertions(+), 48 deletions(-)

diff --git a/rust/helpers/xarray.c b/rust/helpers/xarray.c
index 425a6cc494734..2852f63388eea 100644
--- a/rust/helpers/xarray.c
+++ b/rust/helpers/xarray.c
@@ -7,11 +7,6 @@ int rust_helper_xa_err(void *entry)
 	return xa_err(entry);
 }
 
-void rust_helper_xa_init_flags(struct xarray *xa, gfp_t flags)
-{
-	return xa_init_flags(xa, flags);
-}
-
 int rust_helper_xa_trylock(struct xarray *xa)
 {
 	return xa_trylock(xa);
diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs
index a405f2b6fdcad..c393d4c01af2a 100644
--- a/rust/kernel/xarray.rs
+++ b/rust/kernel/xarray.rs
@@ -29,6 +29,8 @@
         Result, //
     },
     ffi::c_void,
+    str::CStr,
+    sync::LockClassKey,
     types::{
         ForeignOwnable,
         NotThreadSafe,
@@ -48,6 +50,19 @@
 
 mod preload;
 
+/// Creates a [`XArray`] initialiser with the given name and a newly-created lock class.
+///
+/// It uses the name if one is given, otherwise it generates one based on the file name and line
+/// number.
+#[macro_export]
+macro_rules! new_xarray {
+    ($kind:expr $(, $name:literal)? $(,)?) => {
+        $crate::xarray::XArray::new(
+            $kind, $crate::optional_name!($($name)?), $crate::static_lock_class!())
+    };
+}
+pub use new_xarray;
+
 /// An array which efficiently maps sparse integer indices to owned objects.
 ///
 /// This is similar to a [`crate::alloc::kvec::Vec<Option<T>>`], but more efficient when there are
@@ -62,9 +77,10 @@
 ///
 /// ```rust
 /// use kernel::alloc::KBox;
-/// use kernel::xarray::{AllocKind, XArray};
+/// use kernel::xarray::{new_xarray, AllocKind, XArray};
 ///
-/// let xa = KBox::pin_init(XArray::new(AllocKind::Alloc1), GFP_KERNEL)?;
+/// let xa: Pin<KBox<XArray<KBox<u32>>>> =
+///     KBox::pin_init(new_xarray!(AllocKind::Alloc1), GFP_KERNEL)?;
 ///
 /// let dead = KBox::new(0xdead, GFP_KERNEL)?;
 /// let beef = KBox::new(0xbeef, GFP_KERNEL)?;
@@ -124,7 +140,11 @@ pub enum AllocKind {
 
 impl<T: ForeignOwnable> XArray<T> {
     /// Creates a new initializer for this type.
-    pub fn new(kind: AllocKind) -> impl PinInit<Self> {
+    pub fn new(
+        kind: AllocKind,
+        name: &'static CStr,
+        key: Pin<&'static LockClassKey>,
+    ) -> impl PinInit<Self> {
         let flags = match kind {
             AllocKind::Alloc => bindings::XA_FLAGS_ALLOC,
             AllocKind::Alloc1 => bindings::XA_FLAGS_ALLOC1,
@@ -133,8 +153,14 @@ pub fn new(kind: AllocKind) -> impl PinInit<Self> {
             // SAFETY: `xa` is valid while the closure is called.
             //
             // INVARIANT: `xa` is initialized here to an empty, valid [`bindings::xarray`].
-            xa <- Opaque::ffi_init(|xa| unsafe {
-                bindings::xa_init_flags(xa, flags)
+            xa <- Opaque::ffi_init(|xa: *mut bindings::xarray| unsafe {
+                bindings::__spin_lock_init(
+                    &raw mut (*xa).xa_lock,
+                    name.as_ptr().cast(),
+                    key.as_ptr(),
+                );
+                (*xa).xa_flags = flags;
+                (*xa).xa_head = null_mut();
             }),
             _p: PhantomData,
         })
@@ -236,8 +262,12 @@ fn load(&self, index: usize) -> Option<NonNull<c_void>> {
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{alloc::{flags::GFP_KERNEL, kbox::KBox}, xarray::{AllocKind, XArray}};
-    /// let xa = KBox::pin_init(XArray::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{
+    /// #     alloc::{flags::GFP_KERNEL, kbox::KBox},
+    /// #     xarray::{new_xarray, AllocKind, XArray},
+    /// # };
+    /// let xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     ///
     /// let mut guard = xa.lock();
     /// assert_eq!(guard.contains_index(42), false);
@@ -272,8 +302,9 @@ pub fn get_mut(&mut self, index: usize) -> Option<T::BorrowedMut<'_>> {
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray, Entry}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray, Entry}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// assert_eq!(guard.contains_index(42), false);
@@ -309,8 +340,9 @@ fn load_next(&self, index: usize) -> Option<(usize, NonNull<c_void>)> {
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// guard.store(10, KBox::new(10u32, GFP_KERNEL)?, GFP_KERNEL)?;
@@ -339,8 +371,9 @@ pub fn find_next(&self, index: usize) -> Option<(usize, T::Borrowed<'_>)> {
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// guard.store(10, KBox::new(10u32, GFP_KERNEL)?, GFP_KERNEL)?;
@@ -366,8 +399,9 @@ pub fn find_next_mut(&mut self, index: usize) -> Option<(usize, T::BorrowedMut<'
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// guard.store(10, KBox::new(10u32, GFP_KERNEL)?, GFP_KERNEL)?;
@@ -401,8 +435,9 @@ pub fn find_next_entry<'b>(&'b mut self, index: usize) -> Option<OccupiedEntry<'
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// guard.store(100, KBox::new(42u32, GFP_KERNEL)?, GFP_KERNEL)?;
@@ -505,8 +540,9 @@ pub fn store(
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// assert_eq!(guard.get(42), None);
diff --git a/rust/kernel/xarray/entry.rs b/rust/kernel/xarray/entry.rs
index 2d6ef4781f47d..6e370252309fc 100644
--- a/rust/kernel/xarray/entry.rs
+++ b/rust/kernel/xarray/entry.rs
@@ -26,8 +26,9 @@ impl<T: ForeignOwnable> Entry<'_, '_, T> {
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray, Entry}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray, Entry}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// let entry = guard.get_entry(42);
@@ -100,17 +101,17 @@ fn insert_internal(
     ///
     /// Returns a reference to the newly inserted value.
     ///
-    /// - This method will fail if the nodes on the path to the index
-    ///   represented by this entry are not present in the XArray and no memory
-    ///   is available via the `preload` argument.
+    /// - This method will fail if the nodes on the path to the index represented by this entry are
+    ///   not present in the XArray and no memory is available via the `preload` argument.
     /// - This method will not drop the XArray lock.
     ///
     ///
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray, Entry}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray, Entry}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// assert_eq!(guard.get(42), None);
@@ -139,16 +140,16 @@ pub fn insert(
 
     /// Inserts a value and returns an occupied entry representing the newly inserted value.
     ///
-    /// - This method will fail if the nodes on the path to the index
-    ///   represented by this entry are not present in the XArray and no memory
-    ///   is available via the `preload` argument.
+    /// - This method will fail if the nodes on the path to the index represented by this entry are
+    ///   not present in the XArray and no memory is available via the `preload` argument.
     /// - This method will not drop the XArray lock.
     ///
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray, Entry}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray, Entry}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// assert_eq!(guard.get(42), None);
@@ -182,8 +183,9 @@ pub fn insert_entry(
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray, Entry}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray, Entry}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// assert_eq!(guard.get(42), None);
@@ -221,8 +223,9 @@ pub(crate) fn new(guard: &'b mut Guard<'a, T>, index: usize, ptr: NonNull<c_void
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray, Entry}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray, Entry}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// guard.store(42, KBox::new(0x1337u32, GFP_KERNEL)?, GFP_KERNEL)?;
@@ -266,8 +269,9 @@ pub fn remove(mut self) -> T {
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray, Entry}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray, Entry}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// guard.store(42, KBox::new(0x1337u32, GFP_KERNEL)?, GFP_KERNEL)?;
@@ -287,8 +291,9 @@ pub fn index(&self) -> usize {
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray, Entry}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray, Entry}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// guard.store(42, KBox::new(0x1337u32, GFP_KERNEL)?, GFP_KERNEL)?;
@@ -334,8 +339,9 @@ pub fn insert(&mut self, value: T) -> T {
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray, Entry}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray, Entry}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// guard.store(42, KBox::new(0x1337u32, GFP_KERNEL)?, GFP_KERNEL)?;
@@ -361,8 +367,9 @@ pub fn into_mut(self) -> T::BorrowedMut<'b> {
     /// # Examples
     ///
     /// ```
-    /// # use kernel::{prelude::*, xarray::{AllocKind, XArray, Entry}};
-    /// let mut xa = KBox::pin_init(XArray::<KBox<u32>>::new(AllocKind::Alloc), GFP_KERNEL)?;
+    /// # use kernel::{prelude::*, xarray::{new_xarray, AllocKind, XArray, Entry}};
+    /// let mut xa: Pin<KBox<XArray<KBox<u32>>>> =
+    ///     KBox::pin_init(new_xarray!(AllocKind::Alloc), GFP_KERNEL)?;
     /// let mut guard = xa.lock();
     ///
     /// guard.store(42, KBox::new(100u32, GFP_KERNEL)?, GFP_KERNEL)?;

-- 
2.51.2