NFSv4.1: Don't process the sequence op more than once.

mainline inclusion
from mainline-v5.0-rc1
commit c71c46f0
category: bugfix
bugzilla: NA
CVE: NA

--------------------------------

Ensure that if we call nfs41_sequence_process() a second time for the
same rpc_task, then we only process the results once.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: NZhang Xiaoxu <zhangxiaoxu5@huawei.com>
Reviewed-by: NZhang Yi <yi.zhang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/nfs/nfs4proc.c

@@ -770,7 +770,7 @@ static int nfs41_sequence_process(struct rpc_task *task,
 	if (slot == NULL)
 		goto out_noaction;
 	/* don't increment the sequence number if the task wasn't sent */
-	if (!RPC_WAS_SENT(task))
+	if (!RPC_WAS_SENT(task) || slot->seq_done)
 		goto out;
 
 	session = slot->table->session;