vmalloc,rcu: Convert call_rcu(rcu_free_va) to kfree_rcu()

The rcu callback rcu_free_va() just calls a kfree(),
so we use kfree_rcu() instead of the call_rcu(rcu_free_va).

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

mm/vmalloc.c

@@ -452,13 +452,6 @@ overflow:
 	return ERR_PTR(-EBUSY);
 }
 
-static void rcu_free_va(struct rcu_head *head)
-{
-	struct vmap_area *va = container_of(head, struct vmap_area, rcu_head);
-
-	kfree(va);
-}
-
 static void __free_vmap_area(struct vmap_area *va)
 {
 	BUG_ON(RB_EMPTY_NODE(&va->rb_node));
@@ -491,7 +484,7 @@ static void __free_vmap_area(struct vmap_area *va)
 	if (va->va_end > VMALLOC_START && va->va_end <= VMALLOC_END)
 		vmap_area_pcpu_hole = max(vmap_area_pcpu_hole, va->va_end);
 
-	call_rcu(&va->rcu_head, rcu_free_va);
+	kfree_rcu(va, rcu_head);
 }
 
 /*