diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 656c22b8e07e..785ddcb17e9e 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -2968,7 +2968,9 @@ bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect)
 		return false;
 
 	tree_index = r5c_tree_index(conf, sect);
+	rcu_read_lock();
 	slot = radix_tree_lookup(&log->big_stripe_tree, tree_index);
+	rcu_read_unlock();
 	return slot != NULL;
 }