NFSv4: Avoid referencing the cred unnecessarily during NFSv4 I/O

Avoid unnecessary references to the cred when we have already referenced
it through the open context or the open owner.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs4proc.c

@@ -2346,7 +2346,7 @@ static int _nfs4_proc_open_confirm(struct nfs4_opendata *data)
 		.callback_ops = &nfs4_open_confirm_ops,
 		.callback_data = data,
 		.workqueue = nfsiod_workqueue,
-		.flags = RPC_TASK_ASYNC,
+		.flags = RPC_TASK_ASYNC | RPC_TASK_CRED_NOREF,
 	};
 	int status;
 
@@ -2511,7 +2511,7 @@ static int nfs4_run_open_task(struct nfs4_opendata *data,
 		.callback_ops = &nfs4_open_ops,
 		.callback_data = data,
 		.workqueue = nfsiod_workqueue,
-		.flags = RPC_TASK_ASYNC,
+		.flags = RPC_TASK_ASYNC | RPC_TASK_CRED_NOREF,
 	};
 	int status;
 
@@ -3651,7 +3651,7 @@ int nfs4_do_close(struct nfs4_state *state, gfp_t gfp_mask, int wait)
 		.rpc_message = &msg,
 		.callback_ops = &nfs4_close_ops,
 		.workqueue = nfsiod_workqueue,
-		.flags = RPC_TASK_ASYNC,
+		.flags = RPC_TASK_ASYNC | RPC_TASK_CRED_NOREF,
 	};
 	int status = -ENOMEM;
 
@@ -6350,7 +6350,7 @@ static int _nfs4_proc_delegreturn(struct inode *inode, const struct cred *cred,
 		.rpc_client = server->client,
 		.rpc_message = &msg,
 		.callback_ops = &nfs4_delegreturn_ops,
-		.flags = RPC_TASK_ASYNC | RPC_TASK_TIMEOUT,
+		.flags = RPC_TASK_ASYNC | RPC_TASK_CRED_NOREF | RPC_TASK_TIMEOUT,
 	};
 	int status = 0;
 
@@ -6933,7 +6933,7 @@ static int _nfs4_do_setlk(struct nfs4_state *state, int cmd, struct file_lock *f
 		.rpc_message = &msg,
 		.callback_ops = &nfs4_lock_ops,
 		.workqueue = nfsiod_workqueue,
-		.flags = RPC_TASK_ASYNC,
+		.flags = RPC_TASK_ASYNC | RPC_TASK_CRED_NOREF,
 	};
 	int ret;