nfs,rcu: convert call_rcu(nfs_free_delegation_callback) to kfree_rcu()

The rcu callback nfs_free_delegation_callback() just calls a kfree(),
so we use kfree_rcu() instead of the call_rcu(nfs_free_delegation_callback).
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/delegation.c

@@ -21,25 +21,13 @@
 #include "delegation.h"
 #include "internal.h"
 
-static void nfs_do_free_delegation(struct nfs_delegation *delegation)
-{
-	kfree(delegation);
-}
-
-static void nfs_free_delegation_callback(struct rcu_head *head)
-{
-	struct nfs_delegation *delegation = container_of(head, struct nfs_delegation, rcu);
-
-	nfs_do_free_delegation(delegation);
-}
-
 static void nfs_free_delegation(struct nfs_delegation *delegation)
 {
 	if (delegation->cred) {
 		put_rpccred(delegation->cred);
 		delegation->cred = NULL;
 	}
-	call_rcu(&delegation->rcu, nfs_free_delegation_callback);
+	kfree_rcu(delegation, rcu);
 }
 
 /**