rust: alloc: add Vec::insert_within_capacity

This adds a variant of Vec::insert that does not allocate memory. This
makes it safe to use this function while holding a spinlock. Rust Binder
uses it for the range allocator fast path.

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://lore.kernel.org/r/20250502-vec-methods-v5-7-06d20ad9366f@google.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/rust/kernel/alloc/kvec/errors.rs b/rust/kernel/alloc/kvec/errors.rs
index 06fe696e8bc6..348b8d27e102 100644
--- a/rust/kernel/alloc/kvec/errors.rs
+++ b/rust/kernel/alloc/kvec/errors.rs
@@ -36,3 +36,26 @@ impl From<RemoveError> for Error {
         EINVAL
     }
 }
+
+/// Error type for [`Vec::insert_within_capacity`].
+pub enum InsertError<T> {
+    /// The value could not be inserted because the index is out of bounds.
+    IndexOutOfBounds(T),
+    /// The value could not be inserted because the vector is out of capacity.
+    OutOfCapacity(T),
+}
+
+impl<T> Debug for InsertError<T> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            InsertError::IndexOutOfBounds(_) => write!(f, "Index out of bounds"),
+            InsertError::OutOfCapacity(_) => write!(f, "Not enough capacity"),
+        }
+    }
+}
+
+impl<T> From<InsertError<T>> for Error {
+    fn from(_: InsertError<T>) -> Error {
+        EINVAL
+    }
+}