NFS: Fix an NFS client lockdep issue

There is no reason to be freeing the delegation cred in the rcu callback,
and doing so is resulting in a lockdep complaint that rpc_credcache_lock
is being called from both softirq and non-softirq contexts.
Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org

fs/nfs/delegation.c

@@ -23,8 +23,6 @@
 
 static void nfs_do_free_delegation(struct nfs_delegation *delegation)
 {
-	if (delegation->cred)
-		put_rpccred(delegation->cred);
 	kfree(delegation);
 }
 
@@ -37,6 +35,10 @@ static void nfs_free_delegation_callback(struct rcu_head *head)
 
 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);
 }