diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 92c0160b3352..a91e3d90df8a 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -229,9 +229,10 @@ static inline int xa_err(void *entry)
  *
  * This structure is used either directly or via the XA_LIMIT() macro
  * to communicate the range of IDs that are valid for allocation.
- * Two common ranges are predefined for you:
+ * Three common ranges are predefined for you:
  * * xa_limit_32b	- [0 - UINT_MAX]
  * * xa_limit_31b	- [0 - INT_MAX]
+ * * xa_limit_16b	- [0 - USHRT_MAX]
  */
 struct xa_limit {
 	u32 max;
@@ -242,6 +243,7 @@ struct xa_limit {
 
 #define xa_limit_32b	XA_LIMIT(0, UINT_MAX)
 #define xa_limit_31b	XA_LIMIT(0, INT_MAX)
+#define xa_limit_16b	XA_LIMIT(0, USHRT_MAX)
 
 typedef unsigned __bitwise xa_mark_t;
 #define XA_MARK_0		((__force xa_mark_t)0U)
diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index 8294f43f4981..8b1c318189ce 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -1530,24 +1530,24 @@ static noinline void check_store_range(struct xarray *xa)
 
 #ifdef CONFIG_XARRAY_MULTI
 static void check_split_1(struct xarray *xa, unsigned long index,
-							unsigned int order)
+				unsigned int order, unsigned int new_order)
 {
-	XA_STATE(xas, xa, index);
-	void *entry;
-	unsigned int i = 0;
+	XA_STATE_ORDER(xas, xa, index, new_order);
+	unsigned int i;
 
 	xa_store_order(xa, index, order, xa, GFP_KERNEL);
 
 	xas_split_alloc(&xas, xa, order, GFP_KERNEL);
 	xas_lock(&xas);
 	xas_split(&xas, xa, order);
+	for (i = 0; i < (1 << order); i += (1 << new_order))
+		__xa_store(xa, index + i, xa_mk_index(index + i), 0);
 	xas_unlock(&xas);
 
-	xa_for_each(xa, index, entry) {
-		XA_BUG_ON(xa, entry != xa);
-		i++;
+	for (i = 0; i < (1 << order); i++) {
+		unsigned int val = index + (i & ~((1 << new_order) - 1));
+		XA_BUG_ON(xa, xa_load(xa, index + i) != xa_mk_index(val));
 	}
-	XA_BUG_ON(xa, i != 1 << order);
 
 	xa_set_mark(xa, index, XA_MARK_0);
 	XA_BUG_ON(xa, !xa_get_mark(xa, index, XA_MARK_0));
@@ -1557,14 +1557,16 @@ static void check_split_1(struct xarray *xa, unsigned long index,
 
 static noinline void check_split(struct xarray *xa)
 {
-	unsigned int order;
+	unsigned int order, new_order;
 
 	XA_BUG_ON(xa, !xa_empty(xa));
 
 	for (order = 1; order < 2 * XA_CHUNK_SHIFT; order++) {
-		check_split_1(xa, 0, order);
-		check_split_1(xa, 1UL << order, order);
-		check_split_1(xa, 3UL << order, order);
+		for (new_order = 0; new_order < order; new_order++) {
+			check_split_1(xa, 0, order, new_order);
+			check_split_1(xa, 1UL << order, order, new_order);
+			check_split_1(xa, 3UL << order, order, new_order);
+		}
 	}
 }
 #else
diff --git a/lib/xarray.c b/lib/xarray.c
index 5fa51614802a..f5d8f54907b4 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -987,7 +987,7 @@ static void node_set_marks(struct xa_node *node, unsigned int offset,
  * xas_split_alloc() - Allocate memory for splitting an entry.
  * @xas: XArray operation state.
  * @entry: New entry which will be stored in the array.
- * @order: New entry order.
+ * @order: Current entry order.
  * @gfp: Memory allocation flags.
  *
  * This function should be called before calling xas_split().
@@ -1011,7 +1011,7 @@ void xas_split_alloc(struct xa_state *xas, void *entry, unsigned int order,
 
 	do {
 		unsigned int i;
-		void *sibling;
+		void *sibling = NULL;
 		struct xa_node *node;
 
 		node = kmem_cache_alloc(radix_tree_node_cachep, gfp);
@@ -1021,7 +1021,7 @@ void xas_split_alloc(struct xa_state *xas, void *entry, unsigned int order,
 		for (i = 0; i < XA_CHUNK_SIZE; i++) {
 			if ((i & mask) == 0) {
 				RCU_INIT_POINTER(node->slots[i], entry);
-				sibling = xa_mk_sibling(0);
+				sibling = xa_mk_sibling(i);
 			} else {
 				RCU_INIT_POINTER(node->slots[i], sibling);
 			}
@@ -1041,9 +1041,10 @@ EXPORT_SYMBOL_GPL(xas_split_alloc);
  * xas_split() - Split a multi-index entry into smaller entries.
  * @xas: XArray operation state.
  * @entry: New entry to store in the array.
- * @order: New entry order.
+ * @order: Current entry order.
  *
- * The value in the entry is copied to all the replacement entries.
+ * The size of the new entries is set in @xas.  The value in @entry is
+ * copied to all the replacement entries.
  *
  * Context: Any context.  The caller should hold the xa_lock.
  */
diff --git a/tools/testing/radix-tree/idr-test.c b/tools/testing/radix-tree/idr-test.c
index 3b796dd5e577..ca24f6839d50 100644
--- a/tools/testing/radix-tree/idr-test.c
+++ b/tools/testing/radix-tree/idr-test.c
@@ -296,21 +296,34 @@ static void *idr_throbber(void *arg)
 	return NULL;
 }
 
+/*
+ * There are always either 1 or 2 objects in the IDR.  If we find nothing,
+ * or we find something at an ID we didn't expect, that's a bug.
+ */
 void idr_find_test_1(int anchor_id, int throbber_id)
 {
 	pthread_t throbber;
 	time_t start = time(NULL);
 
-	pthread_create(&throbber, NULL, idr_throbber, &throbber_id);
-
 	BUG_ON(idr_alloc(&find_idr, xa_mk_value(anchor_id), anchor_id,
 				anchor_id + 1, GFP_KERNEL) != anchor_id);
 
+	pthread_create(&throbber, NULL, idr_throbber, &throbber_id);
+
+	rcu_read_lock();
 	do {
 		int id = 0;
 		void *entry = idr_get_next(&find_idr, &id);
-		BUG_ON(entry != xa_mk_value(id));
+		rcu_read_unlock();
+		if ((id != anchor_id && id != throbber_id) ||
+		    entry != xa_mk_value(id)) {
+			printf("%s(%d, %d): %p at %d\n", __func__, anchor_id,
+				throbber_id, entry, id);
+			abort();
+		}
+		rcu_read_lock();
 	} while (time(NULL) < start + 11);
+	rcu_read_unlock();
 
 	pthread_join(throbber, NULL);
 
@@ -577,6 +590,7 @@ void ida_tests(void)
 
 int __weak main(void)
 {
+	rcu_register_thread();
 	radix_tree_init();
 	idr_checks();
 	ida_tests();
@@ -584,5 +598,6 @@ int __weak main(void)
 	rcu_barrier();
 	if (nr_allocated)
 		printf("nr_allocated = %d\n", nr_allocated);
+	rcu_unregister_thread();
 	return 0;
 }
diff --git a/tools/testing/radix-tree/linux/compiler_types.h b/tools/testing/radix-tree/linux/compiler_types.h
deleted file mode 100644
index e69de29bb2d1..000000000000
diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index 9eae0fb5a67d..e00520cc6349 100644
--- a/tools/testing/radix-tree/multiorder.c
+++ b/tools/testing/radix-tree/multiorder.c
@@ -224,7 +224,9 @@ void multiorder_checks(void)
 
 int __weak main(void)
 {
+	rcu_register_thread();
 	radix_tree_init();
 	multiorder_checks();
+	rcu_unregister_thread();
 	return 0;
 }
diff --git a/tools/testing/radix-tree/xarray.c b/tools/testing/radix-tree/xarray.c
index e61e43efe463..f20e12cbbfd4 100644
--- a/tools/testing/radix-tree/xarray.c
+++ b/tools/testing/radix-tree/xarray.c
@@ -25,11 +25,13 @@ void xarray_tests(void)
 
 int __weak main(void)
 {
+	rcu_register_thread();
 	radix_tree_init();
 	xarray_tests();
 	radix_tree_cpu_dead(1);
 	rcu_barrier();
 	if (nr_allocated)
 		printf("nr_allocated = %d\n", nr_allocated);
+	rcu_unregister_thread();
 	return 0;
 }