rust: xarray: Add an abstraction for XArray

`XArray` is an efficient sparse array of pointers. Add a Rust
abstraction for this type.

This implementation bounds the element type on `ForeignOwnable` and
requires explicit locking for all operations. Future work may leverage
RCU to enable lockless operation.

Inspired-by: Maíra Canal <mcanal@igalia.com>
Inspired-by: Asahi Lina <lina@asahilina.net>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Link: https://lore.kernel.org/r/20250423-rust-xarray-bindings-v19-2-83cdcf11c114@gmail.com
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/rust/helpers/xarray.c b/rust/helpers/xarray.c
new file mode 100644
index 000000000000..60b299f11451
--- /dev/null
+++ b/rust/helpers/xarray.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/xarray.h>
+
+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);
+}
+
+void rust_helper_xa_lock(struct xarray *xa)
+{
+	return xa_lock(xa);
+}
+
+void rust_helper_xa_unlock(struct xarray *xa)
+{
+	return xa_unlock(xa);
+}