XArray tests: Add RCU locking

0day picked up that I'd forgotten to add locking to this new test.

Signed-off-by: Matthew Wilcox <[email protected]>
diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index 4676c0a..a885afd 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -839,6 +839,7 @@ static noinline void check_find_3(struct xarray *xa)
 
 	for (i = 0; i < 100; i++) {
 		for (j = 0; j < 100; j++) {
+			rcu_read_lock();
 			for (k = 0; k < 100; k++) {
 				xas_set(&xas, j);
 				xas_for_each_marked(&xas, entry, k, XA_MARK_0)
@@ -847,6 +848,7 @@ static noinline void check_find_3(struct xarray *xa)
 					XA_BUG_ON(xa,
 						xas.xa_node != XAS_RESTART);
 			}
+			rcu_read_unlock();
 		}
 		xa_store_index(xa, i, GFP_KERNEL);
 		xa_set_mark(xa, i, XA_MARK_0);