diff --git a/lib/idr.c b/lib/idr.c
index ed055b2..12499ba 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -595,8 +595,10 @@
  * Returns pointer to registered object with id, which is next number to
  * given id. After being looked up, *@nextidp will be updated for the next
  * iteration.
+ *
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
  */
-
 void *idr_get_next(struct idr *idp, int *nextidp)
 {
 	struct idr_layer *p, *pa[MAX_LEVEL];
@@ -605,11 +607,11 @@
 	int n, max;
 
 	/* find first ent */
-	n = idp->layers * IDR_BITS;
-	max = 1 << n;
 	p = rcu_dereference_raw(idp->top);
 	if (!p)
 		return NULL;
+	n = (p->layer + 1) * IDR_BITS;
+	max = 1 << n;
 
 	while (id < max) {
 		while (n > 0 && p) {