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 <[email protected]>
Inspired-by: Asahi Lina <[email protected]>
Reviewed-by: Andreas Hindborg <[email protected]>
Reviewed-by: Alice Ryhl <[email protected]>
Signed-off-by: Tamir Duberstein <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Andreas Hindborg <[email protected]>

2 files changed, 29 insertions, 0 deletions

diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 1e7c84df7252..80785b1e7a63 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -38,3 +38,4 @@
 #include "vmalloc.c"
 #include "wait.c"
 #include "workqueue.c"
+#include "xarray.c"
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);
+}