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Message-ID: <20251008124619.3160-3-work@onurozkan.dev>
Date: Wed, 8 Oct 2025 15:46:17 +0300
From: Onur Özkan <work@...rozkan.dev>
To: rust-for-linux@...r.kernel.org
Cc: ojeda@...nel.org,
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Onur Özkan <work@...rozkan.dev>
Subject: [PATCH v2 2/4] rust: xarray: abstract `xa_alloc`
Implements `alloc` function to `XArray<T>` that wraps
`xa_alloc` safely, which will be used to generate the
auxiliary device IDs.
Resolves a task from the nova/core task list under the "XArray
bindings [XARR]" section in "Documentation/gpu/nova/core/todo.rst"
file.
Signed-off-by: Onur Özkan <work@...rozkan.dev>
---
rust/kernel/xarray.rs | 41 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 40 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs
index 90e27cd5197e..0711ccf99fb4 100644
--- a/rust/kernel/xarray.rs
+++ b/rust/kernel/xarray.rs
@@ -10,7 +10,7 @@
ffi::c_void,
types::{ForeignOwnable, NotThreadSafe, Opaque},
};
-use core::{iter, marker::PhantomData, pin::Pin, ptr::NonNull};
+use core::{iter, marker::PhantomData, ops::Range, pin::Pin, ptr::NonNull};
use pin_init::{pin_data, pin_init, pinned_drop, PinInit};
/// An array which efficiently maps sparse integer indices to owned objects.
@@ -268,6 +268,45 @@ pub fn store(
Ok(unsafe { T::try_from_foreign(old) })
}
}
+
+ /// Allocates an empty slot within the given `limit` and stores `value` there.
+ ///
+ /// May drop the lock if needed to allocate memory, and then reacquire it afterwards.
+ ///
+ /// On success, returns the allocated index.
+ ///
+ /// On failure, returns the element which was attempted to be stored.
+ pub fn alloc(
+ &mut self,
+ limit: Range<u32>,
+ value: T,
+ gfp: alloc::Flags,
+ ) -> Result<u32, StoreError<T>> {
+ let new = value.into_foreign();
+ let mut id: u32 = 0;
+
+ let limit = bindings::xa_limit {
+ min: limit.start,
+ max: limit.end,
+ };
+
+ // SAFETY:
+ // - `self.xa.xa` is valid by the type invariant.
+ // - `new` came from `T::into_foreign`.
+ let ret =
+ unsafe { bindings::__xa_alloc(self.xa.xa.get(), &mut id, new, limit, gfp.as_raw()) };
+
+ if ret < 0 {
+ // SAFETY: `__xa_alloc` doesn't take ownership on error.
+ let value = unsafe { T::from_foreign(new) };
+ return Err(StoreError {
+ value,
+ error: Error::from_errno(ret),
+ });
+ }
+
+ Ok(id)
+ }
}
// SAFETY: `XArray<T>` has no shared mutable state so it is `Send` iff `T` is `Send`.
--
2.51.0
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